monocea gb 5/04/06 15:30 page 3 commissariat à...

e-den

Commissariat à l’énergie atomique

A monograph of the Nuclear Energy Directorate

Nuclear energy of the future:what research

for which objectives?

Éditions techniques

MonoCEA GB 5/04/06 15:30 Page 3

DEN monographs

A monograph of the Nuclear Energy DirectorateCommissariat à l’énergie atomique, 31-33, rue de la Fédération75752 Paris Cedex 15 Tél. : +33-1 40 56 10 00

Scientific comitee Michel Alexandre, Michel Beauvy, Georges Berthoud, Mireille Defranceschi, Gérard Ducros, Yannick Guérin, Yves Limoge, Charles Madic, Gérard Santarini, Jean-Marie Seiler,Pierre Sollogoub, Étienne Vernaz, Research Directors.

The following people participated in this work:Fanny Bazile, Patrice Bernard, Bernard Bonin, Jacques Bouchard,Jean-Claude Bouchter, Bernard Boullis, Franck Carré, Jean Cazalet, Alain Marvy, Valérie Moulin, Emmanuel Touron, Yves Terrien.

Publishing Supervisor: Philippe Pradel.

Editorial Board: Bernard Bonin (Managing Editor), Bernard Bouquin, Martine Dozol, Michel Jorda, Jean-Pierre Moncouyoux, Alain Vallée.

Administrator: Fanny Bazile.

Editor: Jean-François Parisot.Graphic concept: Pierre Finot.Cover illustration: Véronique Frouard.

Correspondence: all correspondence can be addressed to the Editor or to CEA / DEN Direction scientifique, CEA Saclay 91191 Gif-sur-Yvette Cedex.Tél. : + 33-1 69 08 16 75.

© CEA Saclay and Groupe Moniteur (Éditions du Moniteur), Paris, 2006

The information contained in this document can be freelyreproduced, with the agreement of the Editorial Boardand due mention of its origin.

MonoCEA GB 5/04/06 15:30

5Nuclear energy of the future: what research for which objectives?

Preface

After a dazzling start in the 1950s as a promising, inexhaustible, cost-effective energysource, nuclear energy was rejected by majority opinion in several countries in NorthAmerica and Western Europe three to four decades later, suddenly bringing its developmentto a halt.

Although the 1973 and 1979 oil crises marked the beginning of massive construction pro-grammes in the countries most heavily penalized by oil imports, France and Japan in par-ticular, they were paradoxically followed by a gap in nuclear spending, first in the UnitedStates and then in Western Europe. However, more recent oil market tensions and emerg-ing concerns over non-renewable natural resources should have increased such spending.

There are surely many reasons for this pause, which can in part be explained by the acci-dents in Three Mile Island in 1979 and Chernobyl in 1986, which deeply impacted publicopinion. On top of this, ecological movements and Green parties made their (highly publi-cized) fight against nuclear energy a key part of their platform.

In France, whose population, with the exception of one case, had never disputed nuclearplant construction, negative attitudes began to surface in the late 1980s concerning thenuclear waste issue. Given Andra’s growing difficulties in finding an underground laboratorysite, the Government decided to suspend work in favour of a one-year moratorium and sub-mitted the issue to the OPECST (French parliamentary evaluation office for scientific andtechnological choices).

The Act of 30 December 1991 on nuclear waste management implemented the essenceof the OPECST’s recommendations, in particular its definition of a diversified research pro-gramme and the basis for democratic discussion, thus helping calm the debate.That said,although it is now an accepted fact that long-term nuclear waste management is a neces-sity, there is still no guarantee that France will continue its electronuclear programme: forthis reason, the recent energy act of 13 July 2005 merely aimed to “keep nuclear optionsopen through 2020”.

However, this century should be marked by renewed collective awareness that our gener-ation’s energy needs cannot be met without concern for the environment and without pre-serving future generations’ rights to satisfy these same needs.This concept of sustainabledevelopment is an inevitable challenge to our society.

Today, it goes unquestioned that global warming due to increasing greenhouse gas emis-sions is a human-caused problem.The only remaining debate concerns the consequencesof this climate change. Industrialized nations, which are for the most part responsible for thecurrent situation, should feel particularly obliged to voluntarily take steps towards reducingemissions of these gases. Nuclear energy should gain considerable ground since, by nature,it does not produce this type of emissions and yet is an abundant, reliable and cost-effec-tive energy source.

The situation varies from country to country. On one hand, European countries such asGermany and Belgium have chosen to progressively stop using nuclear energy, even with-out making plans for reversibility. On the other hand, countries like China, South Korea, or,


closer to home, Finland, are making huge investments in developing this technology.Furthermore, according to a recent statement by President Bush, the United States hasdecided to launch new nuclear power plant construction projects over the next ten years,picking up a process that had been on hold for over a quarter-century.

Following France’s national energy debate that took place in the first half of 2003, the par-liamentary bill on energy adopted in June 2005 established the decision to build a demon-strator EPR in preparation for the switchover when currently operating plants will be shutdown.

Several signs lead us to believe that there could soon be a nuclear energy "renaissance",especially if the barrel of crude stays at or above the 70 USD mark. Nevertheless, the futureof nuclear energy in our country, as in many others, will depend largely on its capacity toproperly address the following two concerns:- First, its social acceptability: nuclear energy must be deployed under stringent safety andsecurity conditions, generating as little final waste as possible, with perfect control of thewaste that is produced in terms of its possible impact on human health and the environment.- Secondly, the availability of nuclear resources: it is important to guarantee a long-termsupply of fuel, by preparing to resort to more economical natural fissile material systemswhich are less dependent on market fluctuations.

These topics are a key part of the CEA Nuclear Energy Division’s work. Indeed, this divi-sion is a major player in the research that aims to support the nuclear industry’s efforts toimprove reactor safety and competitiveness, providing the Public Authorities with the ele-ments necessary for making decisions on the long-term management of nuclear waste,and, finally, developing the nuclear systems of the future, essentially fast neutron reactors,which offer highly promising innovations in waste management and raw material use.

As a fervent partisan of sharing as much scientific and technical knowledge as possible toa broad public, I believe that this research work, which calls upon a diverse array of scien-tific disciplines often at top worldwide level, should be presented and explained in priorityto anyone who would like to form their own opinion on nuclear energy. For this reason, it iswith great satisfaction that I welcome the publication of these DEN monographs. Throughclose reading of these works, they can become an invaluable source of information for the,I hope, many readers.

I would like to thank all the researchers and engineers who, by contributing to this project,helped share their experience and knowledge.

Bernard BIGOT

High Commissioner for Atomic Energy



Introduction

There are two conditions for this: firstly that we know how torespond to public opinion concerns.Then that we are capableof proposing new nuclear systems, even more effective interms of safety or economy, but, above all, that will place inhighest priority the sustainable development and non-pro-liferation criteria.

But, making nuclear power acceptable is above all demonstrat-ing it “with proof”. From this point of view, the exemplary oper-ation of nuclear reactors for over 15 years, throughout theworld, is an invaluable advantage. The availability rates areexcellent, incidents, even minor, are decreasing and thisenables public confidence to be gained.

In the last few years waste management has been seen asthe main problem of nuclear power for public opinion. It aloneprobably explains part of the defiance regarding nuclear powerso well that it may have no future if we do not provide solutionsfor it. That said, contrary to the idea often spread, technicalsolutions do exist…

In France, as in other countries in fact, the management ofless active waste and of that which has a shorter lifetime, is a

reality already implemented in industrial disposalcentres. It must be remembered that this repre-sents more than 90% of the overall volume ofnuclear waste.

The question of high level and long lived waste,that which, with a few percent of the volumes, con-centrates most of the radioactivity, remains. Forthis waste, the R&D employed in France, as out-lined by law, has enabled numerous results to beobtained. This R&D will allow, by the legal dead-line, in 2006, various technical solutions to be pro-posed to the French Parliament for the manage-ment of this waste.

Our first objective is to reduce the quantity of waste producedat source.

Fig. 1. A global production of energy with 87% of fossile origin!…

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, Wor

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Renewables

Hydrogen

Nuclear

Gas

Oil

Coal

Mtep16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

1971 1997 2010 2020

These studies also show that beyond 2020, even more thantoday, the environmental impacts will have to be studied withgreat urgency.

Nuclear energy has many advantages for being a satisfactoryenergy response, in the long-term, from the resources andenvironmental point of view. We believe that it will have in thefuture, its place in an energy “mix”, even more than today.

Today energy problems are global problems. It is on theinternational scale that we share resources and risks, in par-ticular those linked to climate changes caused by greenhousegas emissions.

For this reason any new generation* of nuclear energy pro-duction must be thought out based on serious projections onthe international scale.

Recent studies carried out by the World Energy Council or bythe International Energy Agency of the OECD provide us withthe following trends:

• An energy demand which will increase by 50 to 60% before2020;

• A demand which will increase predominately in developingcountries;

• Fossil energy which will continue to provide for the majorityof our needs;

• Finally, in spite of national efforts, CO2 emissions which willprobably be greater than the Kyoto objectives.


8 Introduction

This involves evaluating and establishing the feasibility ofprocesses enabling the waste to be separated, then the quan-tity and the noxiousness to be significantly reduced: this is par-titioning* and transmutation*.The objective is to reduce theradiotoxicity of waste by a factor 100 by recycling plutoniumand transmuting minor actinides.

France has already chosen to recycle plutonium. Firstlybecause it is a recyclable energy material. Also, over time, it isthe main element responsible for the radiotoxicity of waste.When exiting the reactor, spent fuel contains only 4% bonafide waste and 96% uranium and plutonium. In constantprogress, the processing of spent fuel, then its recycling aresolutions already implemented industrially in France.

In this field of recycling, the research in progress targets thedevelopment of new fuel assemblies which will enable pluto-nium to be multiple-recycled, either in current water reactorsor in EPR reactors, the deployment of which is envisaged inFrance.This would enable the stocks of plutonium with the cur-rent reactors to be stabilized, or even reduced.

Once the plutonium recycled, a logical follow-up consists ofpartitioning then transmuting minor actinides (Np, Am and Cm)which are, after plutonium, the main contributors of wasteradiotoxicity.The partitioning processes, developed in the wakeof that which is currently being carried out for plutonium, willenable these minor actinides to be partitioned from fissionproducts, thus considered as the sole final waste to be vitri-fied. As for the transmutation, its scientific feasibility isacquired, but its technical feasibility remains to be demon-strated and CEA is working on it, in an international, mainlyEuropean and American, collaboration.

The advantages of this partition-ing/transmutation strategy arevery clear: it enables considerablereduction of waste radiotoxicityover the long-term. Thus, if theradiotoxicity of uranium used toproduce fuel is taken as a refer-ence, the same level of radiotoxi-city is reached:• After several hundreds of thou-

sands of years if the fuels are not reprocessed;• After 10,000 years if Pu is reprocessed/recycled according

to the current solutions;• After some hundreds of years if only fission products are left

in the glasses and if the actinides are recycled.

1. For the meaning of all technical terms, refer to the developed glossarysituated at the end of work. The terms in fat accompanied with an aster-isk send back to the glossary (pp. 103-106). [Note of the Editor.]

Fig. 2. A major stake… and realistic solutions.

Objective: To assure waste

Directions selected Technical solutions Results

1. Conditioning Matrices and containers 1. Intact glass at 99,9 %after 10,000 years

2. Storage • Durability 2. First storage conceptsand/or • Reversibility

3. Disposal • Flexibility of the solutions 3. ANDRA researchlaboratory in construction

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This then involves, for final waste, proposing technical solu-tions, which enable long-term waste management, either bystorage, or by permanent disposal.

The work carried out on conditioning* must enable processesto be proposed guaranteeing sustainable containment and thepossibility of reusing the waste in complete safety, within along-term storage* or deep geological formation disposal*perspective.

Finally studies are being carried out on the long-term storageprocesses or on the disposal in deep geological formationsintegrating reversibility requirements.

There again, we are starting to gather results: intact glass at99.9% after 10,000 years, new storage concepts or even anew research laboratory for deep geological disposal.

In France, these studies are carried out in compliance with thelegal ethics and decisions which were made in 1991, in orderto clarify by 2006 the Parliamentary and Governmental deci-sions.

It is therefore up to the politicians to decide. But on a techni-cal note, we will know how to deal with the small quantities ofwaste in question, and their low volumes originating fromenergy production, in safe conditions, in disposal or storageareas, for extremely long periods and assuring the traceabil-ity of any necessary information.

At present, various waste management strategies may beimplemented complementarily. Reversible direct disposal, aswill be the case in the USA with Yucca Mountain, storage inview of recycling at a later date, for example to give the sys-tem flexibility, or even immediate reprocessing and recycling,as is the case in France.

From now on, the recycling of all actinides seems to be astrong specification for reducing waste and proceeding towardsustainable development in nuclear energy. This criterion for



reducing waste is furthermore widely repeated in the defini-tions for the designs of nuclear systems of the future.

Today’s challenge is imagining the nuclear systems of thefuture.

With a first question: what future are we talking about? Theobjective is to develop systems that can be deployed from theindustrial point of view by 2030-2040. There are two reasonsfor this: firstly time is needed in order to propose truly innova-tive systems. If improvements in safety and competitivenessare expected, it is in fact technological ruptures that we arespeaking of in terms of fuel, cycle and reactor core*. Then, itis the date on which the studies show an increased inflectionof a requirement to use nuclear power with in particular theresponse to the electricity requirement but also the productionof hydrogen*, the desalination* of seawater, etc.

There already seems to be a convergence of opinions on theinternational level regarding the criteria the nuclear systemsof the future must meet. These criteria, which privilege sus-tainable development, determine the order in which it will benecessary to try and decide on the research priorities.

The CEA undertakes to work on three of them in particular:

• The sodium-cooled fast neutron concept, on which CEAalready has a great deal of experience regarding reactors butwhich requires improvements regarding fuel cycles;

• The very high temperature gas-cooled and thermal neutronsystem for the production of hydrogen (VHTR);

• The gas-cooled and fast neutron system (FNR-G), whichoffers a promising alternative in relation to the sodium,regarding both reactor and cycle.

On sodium reactors, the CEA has an important R&D pro-gramme in partnership with countries such as Japan andRussia. We are attempting to take advantage of the experi-ence gained and the advantages of sodium, whilst improvingthe system on the difficult points.

Various concepts of gas reactors were studied in the 70s-80s.Since, considerable progress has been accomplished in par-ticular in the field of high temperature materials. Our ability toobtain high temperatures, and therefore high yields, placethese reactors at the forefront.

The R&D in progress concerns the materials, helium technolo-gies, and the modelling supporting the developments.

One part, mostly dedicated to the VHTRs, concerns the mate-rials for the high temperatures, the exchangers and thethermo-chemical cycles.

The research centred on FNR-Gs will focus on the highly inno-vative fuels for these reactors.

Nuclear energy will without a doubt play an important role inthe future in order to meet international energy requirements.This, however, presupposes that the decision-makers knowhow to find and implement the correct responses to the ques-tion of waste, and to best take account of the sustainabledevelopment criteria.

It will be necessary to innovate and redouble efforts in order topropose new concepts. This is carried out in a totally newframework which seeks to promote international cooperation,the sharing of tasks and results, and this within the group ofcountries who believe in the future of sustainable nuclearpower…

Fig. 3. Nuclear systems of the future: the 5 basic criteria.

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Economy

Safety

Reductionof waste

Economyof naturalresources Reduction risk

of proliferation

Research on this nuclear power of the future is developingwithin a largely international framework. For example, tencountries plus the European Union are participating in theAmerican Generation IV initiative. This international work hasalready defined by consensus the most promising nuclear sys-tems and drafted a common research and development planfor these systems.

Among the six concepts which have been selected after twoyears of preliminary work, the majority have a closed fuelcycle* and most have a fast neutron* core. This is the resultof the sustainable development, waste reduction and optimisa-tion and use of natural resources criteria.



The origins of current civilian nuclear power

Fifty years ago, in December 1953, right in the middle of thecold war, the “Atoms for Peace” speech by the AmericanPresident Eisenhower before the United Nations, prompted adeep mutation in the role of nuclear energy, until then limitedto military usage.The president promoted its development forcivil and peaceful use in order to “serve the needs rather thanthe fears of humanity”. The following year marked the start ofthe commercial generation of nuclear electricity in Russia.These initiatives have influenced energy policies because overthese past fifty years, nuclear energy hasdeveloped widely throughout the world: 440reactors were in operation at the end of2004, representing approximately 360 GWeinstalled in more than 30 countries.The pro-portion of nuclear power in the generationof electricity is 16% (30% in countries of theOECD), which also represents 7% of theprimary energy.

The first generation of reactors includes firstprototypes constructed mainly in the UnitedStates, Russia, France and Great Britain.This first generation, developed in the1950s-1960s, operated with natural ura-nium as enriched uranium was not yet com-mercially available. This is why during thisperiod France developed the system calledNatural Uranium Graphite Gas.

It was then the Generation II of reactorswhich was deployed in the 1970s to the1990s and which corresponded to most of the fleet currentlyin operation throughout the world.This generation arose fromthe need occurring in the ’70s to make nuclear energy compet-itive and to reduce the energy dependence of certain coun-tries at a time when considerable tensions were felt on the fos-sil energy market.

This period was that of the deployment of pressurized waterreactors (PWR) and boiling water reactors (BWR), whichtogether currently constitute over 85% of the global electro-nuclear fleet.

Ordinary water reactors, dominantspeciesIt is necessary to underline the industrial feedback, duringthese past decades, from all of these second generation reac-tors, which currently capitalize over ten thousand years ofoperation: it has in particular enabled the performances of thenuclear energy production to be demonstrated with a verycompetitive kilowatt-hour cost in relation to that of fossil energy.

Overall, this industrial maturity, this satisfactory competitive-ness and this favourable feedback have contributed consider-ably to renewing the electricians’ confidence in nuclear energy.The ready availability of their power plants and the possibility,for some of them, to see their lifetime extended up to 50, even60 years, strengthens this trend.

0

50

100

150

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BWR Boiling water Heavy water Graphite-Gas Water-Graphite Fast Total(HWR) GCR (Chernobyl) neutrons

GW in 1990 138.7 48.0 9.9 7.2 10.7 0.61 215.1GW in 1997 167.7 61.6 12.4 9.2 7.8 0.44 259.1

Cap

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GW

Fig. 4. Two main types of water reactor coexist: pressurized waterreactors (PWR) and boiling water reactors (BWR). In the first, waterfrom the primary circuit is under high pressure, which maintains itbelow boiling point although the temperature is significantly above100°C; in the second, the pressure is lower, and the water boils oncontact with the fuel.


The neutrons produced by a fissionreaction may induce new fissions ofother fissile nuclei present within theirvicinity, and thus contribute to maintain-ing the chain reaction.

In a PWR, the water is both a coolantand neutron retarder.

The water circulates across a forest offuel assemblies, long bundles of thinzirconium alloy metal tubes, where theuranium oxide or plutonium ceramicpellets are stacked.

This water which circulates in a verythick steel closed circuit, yields its calo-ries by making the water of a second-

ary circuit boil into a steam generator. The steam thus pro-duced will activate the turbo-alternator.

After being distributed in the turbines, the steam is condensedby way of a new water circuit, itself in thermal contact with acold source, atmosphere, river or sea.

12 The origins of current civilian nuclear power

Gravelines

Penly

Chooz

Cattenom

Fessenheim

Nogent-sur-Seine

PaluelFlamanvile

Plants installed

1 plant in construction(execution orderrrr given)

Units permanentlyshutdown (11 units)

Reactor system

Natural Uranium Graphite-Gas

Gaz-Heavy water

Breeder reactor

PWR* open circuitcooled

PWR closed/looped circuit cooler

*Pressurised ordinary Water Reactors

Mont d’Arrée

Chinon

0 100 km

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Civaux

Le Blayais

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Given the lifetime of the reactors and the time necessary fordeveloping new systems, water reactors will certainly remainpreponderant in the global nuclear fleet up to 2030, and prob-ably during all of the first half of the 21st century.

The operation of a pressurizedwater nuclear reactorA pressurized water reactor is none other than a developeddevice designated to heat water, with inside the boiler a pres-sure of 150 bars and a temperature of 300°C.The principle ofsuch a reactor is to permanently maintain fission reactions ofthe uranium or plutonium nuclei within an environment, calledreactor core*. Each fission, induced by the neutrons presentin the core, releases energy in the order of 200 MeV*, and pro-duces two or three additional neutrons, one of which servesto maintain the chain reaction*, the others being absorbed in(the water or) the structures or lost outside of the core.

A pressurized water reactor is from the group of reactors,called thermal neutron, that is the high energy neutrons pro-duced by the fission are slowed down by successive shocks inan environment that is called a moderator*, in order to obtainthermal equilibrium with this environment.They therefore havea much higher probability of inducing new fissions.

Fig. 5. There are 59 reactors in France, producing a capacity of 63GWe. France has replaced all of its first generation “graphite gas”reactors with PWRs.

Freeneutron Freed

neutron

Fissileatom

Fissionproduct

Fission product

γ radiation

γ radiation

Fig. 6. Nuclear fission: under the impact of a neutron, a heavynucleus such as uranium 235 may fission, and provide two lighternuclei (fission products) and a few neutrons. The reaction releasesenergy 200 million times higher than that typically called into play ina chemical reaction between atoms or molecules.



Fig. 7.The neutrons produced by a fission reaction may induce newfissions of other fissile nuclei present within their vicinity, and thuscontribute to maintaining the chain reaction.

Primary circuit

Secondary circuit

Generator

Turbine

Condenser

water

Vapour generator

Pressurizer

Cluster commandmechanisms

primarypump

Reactorcore

Vessel

Water supplypump

ReheaterCollant water

vapour

Fig. 8. Diagram of a pressurized water reactor (PWR).



The fuel and the fuel cycle

Nuclear fuel is designed to supply the power expectedfrom the reactor, by best using the fissile material.The designof the fuel element must in addition allow a certain flexibility inthe reactor operation, in order to enable it to adapt to the vari-ations in power imposed by the system. This must be carriedout without releasing radionuclides* from the nuclear reac-tions into the reactor’s primary circuit.These constraints com-bine in fact to give the nuclear fuel leaktightness, robustnessand reliability qualities.

The fuel assembly of an ordinary water reactor is always madeup of “fuel rods*” containing the nuclear materials, arrangedin a square lattice array in a “structure” assuring in particularthe mechanical maintenance of the rods.

The fuel rod is made up of pellets of uranium oxide or mixeduranium and plutonium oxide (diameter and height in the orderof 1 cm) stacked in metal tubes (cladding* in zirconium alloy)sealed at the ends (leaktight).

Fig. 9. UO2 fuel pellets.

Fig. 10. Fuel rod for a PWR reactor.

Fig. 11. 17 x 17 Fuel Assembly and control cluster.

PlugOrifice for pressurisation

Controlcluster

Upperend fitting

Guide-tube

Mixing grid

Fuel rod

Lower end fitting

Upper plug

Lower plug

Spring

UO2 pellet

Zircaloycladding

remain leaktight in incidental or accidental situations, even atthe end of the fuel rod’s life. That said:

• Some fission products are gaseous: their production pro-gressively increases the pressure inside the cladding;

• The chemical composition of the pellets is modified by theappearance of fission products and actinides;

The robustness and reliability of the fuel must enable a longstay in the reactor (currently 4 years, with an objective of 6years towards 2010 for French reactors).

The integrity of the cladding is very important because this iswhat constitutes the first barrier* between the radioactiveproducts and the environment. The fuel rod’s cladding must


Most of the radiotoxicity of the spent fuel comes from pluto-nium.This is an additional reason for recycling it and not leav-ing it in the waste.

16 The fuel and the fuel cycle

Fig. 12. Reactions within the standard fuel assemblies in the PWRs(45,000 MWd/t).

Uranium 238

Uranium 235

Plutonium

Minoractinides

Fissionproducts

U 235U 238

Pu

REP UOX

PF

496

U 23893

3

3

2

5 0,11 1

• The fuel ceramic swells under irradiation and imposes astress on the cladding which contains it (pellet-claddinginteraction).

Only the odd Pu and U 235 isotopes are fissile to thermalneutrons. The irradiation of the U 238 form of Pu.

In a water reactor, a certain number of neutrons are absorbedby the water: it would therefore be impossible to maintain thechain reaction if natural uranium, which only contains 0.7% fis-sile 235 isotope, was used for fuel. It is therefore necessaryto enrich the uranium, up to a content of approximately 4%of U 235 (see inset).

Fig. 13. Composition of a 500 kg enriched uranium assembly after itspassage in a reactor.

U 470 kg(94 %)

Pu 5 kg(1 %)

A.M. 0,7 kg(0,15 %)

P.F. 25 kg(5 %)

The fuel is taken out of the reactor when it no longer containsenough fissile nuclei in order to maintain the chain reaction(typically at the end of four years in a water reactor).

After its stay in the reactor, the fuel no longer contains enoughfissile material to maintain the chain reaction, but it is not nec-essarily exhausted. As shown in the diagram above, it still con-tains a large quantity of fissile and fertile* material, which isimportant to recover. It also contains fission products andminor actinides which make it extremely radioactive and diffi-cult to handle.

The finality of the reprocessing is double:

• Recovering the recyclable energy materials;• Separating these materials from the true waste, and condi-

tioning* the latter in an inert and safe form (vitrification*).

In France, these operations are carried out in the Cogemaplant IN La Hague.

The combined play of fissions and neutron captures in the fuelof the water reactor may be summarized as follows (see figurebelow): we start with 100 uranium atoms, four of which are iso-tope 235 (fissile) and 96 isotope 238. Of the four, only one willsurvive, and three will undergo fission.

Of the initial 96 U 238, three will be transformed into Pu and93 will survive. Of the three Pu formed, two will undergo the fis-sion and only one will survive. In total, there will have been 3+2 = 5 fissions: only 5% of the heavy metal will therefore beconsumed in a water reactor. In a fast neutron reactor*, theschema would be very different with a greater consumption ofthe fertile isotope U 238.

Fig. 14. The COGEMA reprocessing plant in La Hague, in which thespent fuel reprocessing and waste conditioning operations are car-ried out.

Recyclable materials Final residue



The nuclear fuel cycleIt is not the uranium ore directly which constitutes the nuclearfuel. So that the heavy nuclei can be used in a reactor, theymust follow a “fuel cycle*” which combines numerous indus-trial stages:• Extraction of the uranium ore;• Concentration of the ore;• Conversion of the uranium concentrates into gaseous ura-

nium hexafluoride (UF6);• Isotopic enrichment* of the uranium in the UF6 form, in order

to increase the proportion of U 235 fissile nuclei, too low innatural uranium;

• Manufacturing of the fuel (conversion of the fluoride intoenriched uranium oxide UO2, making into pellets, pellet sin-tering*, rodding, assembly of rodsinto bundles).

The fuel produces energy for approxi-mately four years in the reactor. Thelast stages are therefore:• Interim storage, under water, of the

spent fuel;• Management of the spent fuel. This

stage differs according to what isconsidered as a “closed” or “open”cycle.

The open cycle, which is not really acycle, ends by the final disposition ofthe spent fuel, therefore considered inblock as waste*.The open cycle is cur-rently practized in the United States,Sweden, etc.

Fig. 15. The streams through the reprocessing plant.

Reprocessing plant

Reprocessing

Vitrifiedresidue

Compactedwaste

Structurewaste

Depleteduranium

Enricheduranium

Manufactureof fuel

Naturaluranium Concentration

Extractionminerai Permanent

disposal

Conversion

Storage

UO2 fuel

MOX fuelNewUO2 fuel

New MOX fuel

Spent MOX fuel

Final residues

SpentUO2 fuel

Reactor

Plutonium

Recyclableuranium

Enrichment

Technologicalwaste

Final waste

Recyclablematerials

UraniumUraniumUranium

Plutonium

Cementedwaste

PF

U

Pu

AM

Fig. 16. The nuclear fuel cycle.

The closed fuel cycle is the one practized in France, Germany,Switzerland and Japan. The following substages are found:• Chemical reprocessing of spent fuel in order to recover the

fissile and fertile materials that it still contains, in view of recy-cling them;

• Recycling of the plutonium in the form of MOX* fuel (acronymfor Mixed OXide fuel);

• Conditioning of the waste, and, in particular, vitrification ofhighly radioactive waste resulting from the fission;

• Final disposition of the conditioned waste.

Each cycle facility, enrichment, manufacturing, or reprocessingplant is dimensioned is in order to supply several dozens oflarge reactors.


18 The fuel and the fuel cycle

The enrichment of uranium

An important stage of the cycle is uranium enrichment. Isotopicpartitioning is a very difficult undertaking because the isotopesto be separated have the same chemical properties andalmost the same physical properties.

Two main enrichment techniques are industrially implementedthroughout the world:Gaseous diffusion, which consists of passing uranium, in thegaseous UF6 form, into a porous medium by exploiting the factthat the light isotope diffuses a little more quickly than theheavy isotope. The elementary process enriches very little,which obliges the operation to be repeated a great number oftimes in succession in order to obtain the suitable level ofenrichment.

Expensive in energy, gaseous diffusion is currently beingreplaced by ultracentrifugation, which consists of making theUF6 gas circulate in a centrifuge rotating at very high speed.The heaviest molecules concentrate on the periphery, whichenables the two isotopes to be partitioned. As each centrifugehas a low materialflow rate, this tech-nology thereforerequires many cen-trifuges to be work-ing at the sametime.

Fig. 17. The Georges Besse enrichment plant, in Pierrelatte.

Fig. 18. A successionof centrifuges for theenrichment of uranium.

Why recycle plutonium? MOX fuelToday, plutonium is recycled in water reactors, PWRs andBWRs which constitute the main part of the global electro-nuclear fleet.This enables saving enriched uranium, for whichplutonium is substituted in part, and preventing the plutoniumending up in final waste or only accumulating “on shelf” afterhaving been partitioned during the reprocessing of spent fuel.This recycling is carried out in MOX fuel. The reprocessing/recycling combination also enables the quantities of spent fuelstored in pools to be significantly reduced.

A MOX fuel, made up of a solid solution of plutonium and ura-nium oxides, is outwardly in every way identical to the enricheduranium fuel that it replaces.The pellets which fill the claddinghave identical dimensions: only their composition and theirmanufacturing process change.

In the core of a water reactor, due particularly to the presenceof non fissile plutonium isotopes, it is necessary to placeapproximately twice as much plutonium in order to obtain theenergy equivalence of an assembly enriched with U 235: inorder to replace the uranium enriched to 4%, a mixture con-taining approximately 8% of plutonium and 92% of depleteduranium will be necessary. At the end of its life, the MOX fuelwill contain no more than approximately 4% of plutonium.There is thus a net consumption of plutonium: the use of MOXenables the increase in the plutonium inventory to be limitedin the fleet of reactors.

The recycling of spent fuel in the form of MOX began experi-mentally in Belgium at the beginning of the 60s. It was thenindustrialized in this country, in Germany and in Switzerland,then in France from 1985. Today, Japan is preparing, in turn,to “MOX” BWRs and PWRs, and the United States is seriouslythinking about it.

In France, EDF decided to recycle its plutonium progressivelyin some of the reactors of its fleet.The 20 MOX reactors recy-cle all of the plutonium effectively extracted by reprocessingEDF fuel at the UP2-800 plant in La Hague. The “plutoniuminventory” of an MOX PWR is balanced: as much plutonium isproduced in the enriched uranium fuel bundles as is con-sumed in the MOX bundles.

The economic profitability of MOX depends a great deal onthe authorized irradiation rate, that is the overall quantity ofenergy that a given fuel may supply, hence the research, cur-rently carried out, which aims to increase this rate. No funda-mental obstacle opposes a long irradiation time for the MOX,because the behaviour of MOX assemblies in reactors is verysimilar to that of uranium fuels.



Radioactive waste and its current management

Origin of radioactive wasteWhen a neutron causes the fission of a heavy nucleus, it splitsinto two unequal pieces. These fission fragments are rarelystable nuclei. Apart from fission products, the neutrons inducethe formation of actinides and activation products, originatingfrom their neutron capture by non-fissile nuclei, radioactivespecies that are partly found in waste. The radioactive decayof these various species may be, according to the case, fast,slow or very slow, from fractions of microseconds up to billionsof years.These various species, partitioned during reprocess-ing, constitute the main source of high level and long livedwaste.

However, throughout the fuel cycle and during the operation ofthe reactor, inert materials are contaminated by radionuclidesresulting from nuclear reactions in reactors. These are care-fully isolated and conditioned and constitute another categoryof waste, called “low or intermediate level”, much less radioac-tive but more abundant. In this category, waste contaminatedby radionuclides but which has another origin than the elec-tro-nuclear industry and which are caused by conventionalindustry, research or medicine are also found.

The various categories of radioactive wasteFor its daily management, radioactive waste isclassified according to two criteria:• The level of activity*, that is the intensity of

the radiation that it emits, which conditionsthe importance of protections to be estab-lished, in order to protect ourselves fromradioactivity;

• The radioactive half-life* of the products contained, whichenable the duration of its potential harmfulness to be defined.

Thus in general three categories of radioactive waste are dis-tinguished.

Category A: low and intermediate level short lived waste(radioactive half-life less than 30 years). Its radioactivity (β andγ) will be reduced to a level comparable with natural radioac-tivity between now and 300 years. It may come from powerstations and fuel cycle plants, but also from hospitals, labora-tories, industry, etc.

Short lived Long lived

Very low level VLL Disposal at Morvilliers Secured for(Aube) since 2003 mine tailings

Low level LL Centre de stockage Dedicated disposalde l’Aube under review

Intermediate level IL “A” waste “B” waste

High level HL “C” waste “C” waste

What quantities?

In France, where three quarters of electricity is neverthelessproduced by nuclear energy, the quantities concerned repre-sent less than 1 kg of radioactive waste per inhabitant andper year, that is 0.04% of the industrial waste (2,500 kg/inhab-itant/year). This quantity is distributed as follows:

• 900 grams of “A” waste, which however only contains 5% of the overall radioactivity;

• 90 grams of “B” waste;• 10 grams of “C” type.

Category B: low and intermediate level (A) long lived waste(several thousands of years and more). Example: the spentfuel rod cladding segments, after dissolution of the fuel itselfduring reprocessing.

Category C: long lived waste and high level waste, emitters ofα, β and γ radiation, release heat for several hundreds of yearsand remaining radioactive much longer. It concerns eitherunprocessed spent fuel (four countries having renounced“reprocessing”), or glass containers from the reprocessing andwhich incorporate fission products and minor actinides.

In France, rather than speak of A, B or C, ANDRA* and theNuclear Safety authority thus classified waste, according tothe system implemented for their long-term management:


2. A deep disposal site of long lived intermediate military waste wasopened and commissioned in the USA, in 1999 on the WIPP site (NewMexico).

20 Radioactive waste and its current management

The overall production of A waste (packages included) isapproximately 15,000 m3/year, a volume which regularlydecreases thanks to the efforts of the producers. After condi-tioning, the packages are sent to the Centre de Stockage del’Aube (CSA). ANDRA stacks these packages in reinforcedconcrete cells which, after filling and packing out the spaceswith gravel or mortar, are sealed with a concrete slab andcoated with a waterproofing polymer. Lastly, a leaktight coverwill be placed and the site covered with a few metres of earth.The overall capacity of the CSA is 1 million m3, which, at thecurrent rate of production of this waste, assures it an operationat least until 2050.

The annual production of “B” and “C” waste, from the repro-cessing in La Hague of spent fuel from French reactors, is inthe order of 700 m3 per year, of which less than 200 m3/yearfor glass. “B” and “C” waste is currently stored in La Hague (butthe waste from the reprocessing of foreign fuel is sent back toits owners).

The ultimate future of long livedwaste (“B” and “C”)

A seemingly necessary solution

From the beginning of nuclear power up to the 80s, most spe-cialists shared a common vision of the final management, thedisposal of highly radioactive waste in deep geological strata:in order to permanently isolate it from the human environment(today known as the biosphere), it would be buried in a leak-tight way, deep enough, in a fairly stable geological stratum,isolated by judiciously arranged “engineered barriers”. Underthese conditions, the time necessary for the radionuclides con-tained in the waste to migrate up to the surface, after corro-sion of the packages by ground water, would largely exceedthe time necessary for the radioactivity to decay and return toa natural radioactivity level.

Almost all of the countries equipped with reactors have stud-ied variants of this same solution, according to the geologi-cal nature of their subsoil and the respective qualities of thestratum envisaged: salt, clay, granite, basalt, etc.Throughoutthe entire world, approximately fifteen underground laborato-ries have been installed to study on site the characteristics of

the stratum which would host the waste andthe behaviour of the geological barrier. Themain topics of study concerned and still con-cern the mechanical resistance of rocks, thenetwork of faults, the physical chemistry andthe flow rate of the ground water, the mech-anisms and the degradation kinetics of thepackages, etc.

However, in spite of this research, no longlived and high level waste disposal hasyet been implemented in the Westernworld 2. In France, a law enacted on the 30December 1991 prescribed the continuationof research on the long-term management oflong lived and high level radioactive waste.

Fig. 19. The centre de stockage de l’Aube, for category “A” waste(short lived).

Fig. 20. The volume of conditioned waste regularly decreases thanksto the efforts of producers.

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The steering of the research relating to lines 1 and 3 is entrusted to CEA, that of the researchfor line 2 is a matter for ANDRA.

Line 1 programmes have permitted the defini-tion and experimentation on the laboratory scaleof enhanced partitioning processes, as well asa certain number of experimental demonstra-tions of the physical feasibility of the transmuta-tion of certain long lived radionuclides.Partitioning/transmutation offers the prospect of

considerably reducing the quantities to be disposed of, andtherefore the cost of disposal, but final waste will alwaysremain.This leads to the belief that geological disposal will benecessary.

Research on disposal results in the digging of an undergroundlaboratory in a clay formation in the Parisian Region, on theBure site, at the edge of Meuse and Haute-Marne, underAndra’s responsibility. CEA is also associated with thisresearch, in the capacity of main contractor or service providerfor some experiments.

Studies on the long-term conditioning of waste are being con-tinued, with a large knowledge base between disposal andstorage.

A Commission Nationale d’Évaluation (CNE) – NationalEvaluation Commission –, consisting of experts appointed bythe government, follows the progress of this research andreports annually to the Parliament and the Government.

In 2006, at the end of these 15 years of research and accord-ing to their results, the national representation will once againtake hold of the subject and will make the necessary decisions.

Enhanced partitioning Conditioning and storage

Reversible disposal

Fig. 21. Storage of vitrified waste on the COGEMA site at La Hague.

Fig. 22. The three main lines of research on waste management.

Line1

Line 2

Line 3

This research has mobilized the entire French nuclear scien-tific community and takes advantage of internationally accu-mulated knowledge. It is declined according to three mainpoints:

• Line 1 concerns the methods of enhanced partitioning ofwaste from very long lived radionuclides and the possibilitiesof their transmutation by nuclear reactions into shorter livedspecies, or even, ideally, stable nuclides*.The reprocessingof spent fuel is a mandatory prerequisite for any partitioning/transmutation;

• Line 2 concerns geological disposal and involves the con-struction of underground laboratories to study on site the for-mations presumed as favourable;

• Line 3 concentrates on the conditioning of waste in view ofenabling, if necessary, its storage in complete safety overlong periods.



The decommissioning and dismantling of nuclear installations

The issues Nuclear installations, whatever their nature – laboratories, con-trol or production plants, experimental or electricity producingreactors, radioactive waste reprocessing installations, etc. –have a limited operating time.When their nuclear installationsbecome old, many countries are led to shut down operation,decommission them and dismantle them. The end of life of anuclear installation may be caused by the completion of exper-imental programmes planned in the installation, the obsoles-cence of materials and processes, economic (optimization ofmeans, cost of maintenance) or safety and security (change inthe regulations) considerations.

Decommissioning and dismantling* (D-D) aims to enablethe partial or total liberation of a nuclear site.

Three stages may be distinguished for the decommissioningof a nuclear installation: the permanent closure, the deconta-mination-dismantling, then the demolition and liberation of thesite.

In the case of a reactor, the spent fuel is removed from thecore and stored or reprocessed. The circuits are drained, theoperating systems switched off and the openings to the exte-rior locked and sealed. The containment atmosphere ischecked and the access to this containment is restricted; mon-itoring systems are installed. In general, permanent closureintervenes very shortly after the permanent shutdown of thereactor.

Then the decontamination of the surfaces of the buildings andthe material takes place. Decontamination techniques serveto reduce the installation’s radioactivity, to clean up the metalsand the concrete in the aim of facilitating the access to thework areas and the handling of the elements and material tobe dismantled, to enable the cutting work and to meet the stan-dards regulating the evacuation of waste. All of the operatingequipment is dismantled and, after checking its residualradioactivity, recycled or temporarily stored. Only the reactor’sstructures, in particular, the vessel and its protective shielding,are left on site.

To finish, in a third stage, all of the remaining materials andthe installation itself will be dismantled then the site decom-missioned and liberated for other uses. In some cases, a verylong timeframe may pass, which may reach several decadesafter the shutdown of the installation, up to this final stage.This

long timeframe enables radioactive decay and therefore eas-ier protection of the workers who proceed with the deconstruc-tion operations. It also facilitates the storage then the final dis-posal of the radioactive waste.

Decommissioning-dismantling: one of CEA’s important issuesA historical player in nuclear research in France, the CEA mustmanage the heritage of the past. It first involves the recoverywork and conditioning of old waste. CEA also has numerousinstallations of various types to dismantle in its own centres.Cleanup and dismantling actions from now on constitute oneof the important requirements of CEA’s policy.

Since the beginning of 2002, the part of the actions that canbe attributed to “catching up with the past” is covered by a ded-icated fund taken from CEA’s participation in the Areva group.In particular, this concerns the management of old waste (theproduction of which is prior to 1992), spent fuel and uselessradioactive sources, the dismantling of installations placed inpermanent shutdown, the cleaning up of the environment, theconstruction of service installations and the manufacturing oftransportation packaging relating to these actions.The use ofthe dedicated fund is controlled by a Monitoring Committee,whose members represent in particular CEA’s sponsoringdepartments.

The R&D requirements in the nuclear field and the orientationstaken in order to meet them lead CEA to grouping the major-ity of the experimental nuclear installations in operation inCadarache and Marcoule in the not so distant future (in theorder of 10 years). The number of installations to be treated(approximately thirty installations from 2001 to 2010) meansthat CEA’s decommissioning-dismantling programme is verylarge in volume.

In 2012, CEA will have completed the dismantling and radioac-tive cleanup of the Fontenay-aux-Roses site and in 2015 thatof the Grenoble site installations.

Only the LECI* hot laboratory, for the programmes concerningmaterials and structures, and the Orphée reactor, for basicresearch programmes, will remain in Saclay.


24 The decommissioning and dismantling of nuclear installations

Cadarache, which will group between now and ten years alarge part of the experimental nuclear installations, must beable to manage all of the waste produced on the site locallyand offer its capabilities to other Centres, for waste which isnot their own. It is therefore at Cadarache that investmentefforts regarding service installations are concentrated.

The decommissioning-dismantling:an important emerging marketDecommissioning practices are realizing their full potential andmay be considered from now on as a controlled phase of anuclear installation’s life cycle.

A few figures illustrate the scope of the commercial D-Dissues: more than 500 nuclear power plants have already beenconstructed and operated throughout the world, among which108 were decommissioned in January 2005. In addition to thepower plants, there are also plants connected to the manufac-turing of fuel and reprocessing of spent fuel, a part of whichhas already been or will soon be decommissioned.

As a general indication of the overall level of the D-D costs,the United States regulating body demands that operatorshave at least 164 million dollars (2000 value) in order todecommission and dismantle a conventional pressurisedwater reactor.

The average age of nuclear power plants in OECD countriesis approximately fifteen years, in relation to an average effec-tive lifetime of at least 30 years. The decommissioning rateshould peak around 2015.

France is characterized by the large number (six) of graphite-gas reactors which have been shut down, and by the numberof R&D and demonstration power plants currently shut down.

Fig. 24. Institut national des radioéléments –Fleurus/Belgium: decontamination by gel of theC2 cell (XEMO I chain). Final status.

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Existing and future technologiesDismantling techniques already exist and installation designand decommissioning projects benefit from large amounts offeedback.

In general, decontamination techniques call upon chemical,mechanical or thermal processes, or a combination of these.In order to decontaminate concrete or metal surfaces, the veryhigh-speed projection of dry ice granules and the use of chem-ical gels or decontaminating foams are used for example.

Dismantling calls upon cutting techniques for metal or concretestructures. Mechanical (such as sawing or high pressure waterjet) or thermal (plasma torch) processes are used for example.

Radiological measurement techniques are used to addressthe inventory of radioactive stocks in the installation, sort thematerials and waste according to their category, and to takethe necessary provisions to protect the workers.

Dismantling uses various techniques: removable shielding,temporary airlocks and cells, mobile filtering and ventilationsystems, special clothing, ventilated protective suits andmasks.

Dismantling also uses lifting andhandling equipment, and makesextensive use of remote controltechniques: remote handlers,semi-automatic tools enablingthe employees to work at a cer-tain distance from the sources ofradiation.

Fig. 23. Projection of pressurized foam.



Dismantling wasteThe dismantling of nuclear installations produces a large quan-tity of waste, mainly of low level. The European Commissionestimates that the decommissioning of an “average” nuclearpower plant produces up to 10,000 m3 of radioactive waste.Concrete and other construction materials only containing avery low radioactivity represent, in volume, the main part ofthis waste.

The effective management and evacuation of radioactivewaste is an essential condition of the success of the D-D ofnuclear installations and represents the main part of the over-all cost (in the order of 60%, or installations together, accord-ing to a German estimate).

The large quantity of dismantling waste containing only verysmall concentrations of radionuclides requires special care inthe reduction to the minimum of the constraints linked to theirevacuation as radioactive waste. This leads to “waste zoning”of the installation being carefully carried out, by accuratelydefining the border between conventional waste areas andradioactive waste areas.

Dismantling waste currently has, in France, a specific disposalcentre (VLL centre, Very Low Level) in Morvilliers.

Decommissioning-dismantlingfeedback Numerous nuclear installations have already been success-fully decommissioned and dismantled. Here is the list of instal-lations dismantled or in the process of dismantling in France:

• Power reactors

- The Monts d’Arrée power plant (EL4).- Natural uranium graphite gas (NUGG) system reactors.- The Chooz A D reactor (Ardennes nuclear power plant).- The Superphénix reactor.

• Research reactors

- The Rapsodie reactor.- The Harmonie reactor.- The Mélusine and Siloé reactor.- The Strasbourg University reactor.

• CEA laboratories and workshops

- The AT1 pilot reprocessing workshop.- The caesium 137 and strontium 90 source manufactur-

ing workshop (ELAN IIB).- The enriched uranium reprocessing workshops (ATUE).- The fuel assembly cutting laboratory (LDAC).- The plutonium chemistry laboratory (LCPu).- The plutonium based fuel laboratory.- The Saturne accelerator.- The Saclay linear accelerator (ALS).

• The other installations

- The FBFC plant at Pierrelatte.- The irradiator of the Société normande de conserve et

stérilisation (SNCS).

The assessment of the operations carried out show that untilnow, only small research reactors have been the subject of atotal dismantling with complete deconstruction of the build-ings. Medium-sized reactors (G1, G2, G3, EL3, Rapsodie)have only been subjected to partial dismantling, due to theabsence of associated waste (graphite, sodium) disposal sys-tems. Several laboratories, workshops or pilot plants havebeen completely dismantled. Finally, an ore reprocessinginstallation, which produced almost 10,000 tonnes of uraniumin metal and oxide form, as well as thorium*, was completelydismantled.

The analysis of these operations leads to the observation thatthe dismantling of reactors and fuel manufacturing installations(hot cells and plutonium laboratories) is considerably shorterthan that of installations involving chemistry (ore processing,reprocessing) and contaminated by fission products. It has

Fig. 25. Cutting an auxiliary boiler in a ventilated flame resistant suit.Dismantling of the Brennilis’ EL4 power plant.

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been noted on the operations carried out that the volumes ofwaste generated, of a few hundreds to several thousandsof m3, can be properly managed.

Dismantlings in progress at CEA are good examples. Theexperience which will thus be acquired on small or medium-sized installations will certainly be very useful for the disman-tling of large nuclear power plants or certain plants of the frontor back-end of the civilian nuclear cycle.



Nuclear safety and security

The design, construction and operation of nuclear installa-tions must take account of the safety requirements, and theirimpact on Mankind and the Environment must be controlled.It is an essential link for the public’s acceptance of nuclearenergy.

The risks associated with nuclearpower are perceived by the publicas importantThe acceptance of the nuclear risk poses a problem for soci-ety. In the medical field, the risk is accepted because it is bal-anced with estimated benefits. This is rarely the case whenone becomes interested in energy production. That said, theFrench Académie nationale de médecine3 observed that “themost serious health risk is a lack of energy (link betweenhealth status and energy expenditure in developing countries,health consequences from supply shortages, etc.)” and rec-ommends “maintaining the nuclear system in so far as itproves to have the lowest impact per kWh produced in rela-tion to the systems using fossil fuels, biomasses or the incin-eration* of waste, or even when it is compared to wind andphotovoltaic energies”.

The comparison of factual data between nuclear risks, otherindustrial risks, risks arising from other human activities (trans-port, tobacco, etc.), natural risks, etc. is instructive. But con-cerns regarding accidents, long lived waste and the impact onfuture generations cannot simply be dissipated.The perceptionof risks is eminently subjective; those that result from choice(e.g. rock-climbing), and those which result from equipmentimposed by the community (nuclear power plants) are not per-ceived in the same way.

The acceptance of nuclear power by the society passes in anycase by a permanent communication and transparency effort(in particular regarding accidents and incidents), and by theindependence of a strong supervisory authority for operators.

3. Report concluding a colloquium held on June 25th, 2003 on the rela-tionship between health and the energy choices.

4. The La Hague reprocessing plant discharged in 1997 approximately12,000 terabecquerels (Tera = x 1012, ie multiplied by a million of millions)in the form of liquid waste (11,900 TBq of tritium and 1.8 TBq of iodine 129)and 300,000 terabecquerels in gaseous form (mainly krypton 85).

Nuclear power and environmentRadioactivity is found throughout the environment. But mostof this radioactivity is of natural origin. It comes from cosmicrays, radon* from minerals from the earth and exhaled intothe air that we breath, terrestrial radiation coming from the iso-topes from the uranium and thorium chains present in theground, and carbon 14 and potassium 40 present in our organ-ism and in our food. However, we also find in certain compart-ments of the environment, artificial radioactive isotopes, orig-inating from the atmospheric nuclear tests carried out duringthe Cold War, fallout from Chernobyl, and finally, for a verysmall part, from industrial nuclear activities.

In normal operation, the environmental impact of nuclearinstallations is low: power plant emissions (tritium) are barelydetectable (and yet, we know how to detect radioactivity atvery low levels, but natural radioactivity easily masks thehuman induced contribution); emissions from the La Haguereprocessing plant are much higher and much easier to detect4

(iodine 129 and tritium are discharged into the sea, kryptonand tritium into the atmosphere).They also include a chemicaldischarge element (nitrates, marginal compared to the “agri-cultural” contribution). However, the effects of dilutions and dis-persion in marine or atmospheric environments render theradioactive contribution from the plant insignificant comparedto the natural contribution a few kilometres away from theinstallation.

All radionuclides do not behave in the same way.Their behav-iour depends on their chemical properties. In most cases, adispersion and dilution of the contaminants is observed. In oth-ers, conversely, a concentration in certain compartments ofthe biosphere is observed. Reconcentration phenomena maybe of biological origin (case of caesium in mushrooms) or haveany physical or chemical cause (contamination* marksobserved in Mercantour are caused by runoff phenomena).


28 Nuclear safety and security

Nuclear power and health risksWe are all exposed to natural radioactivity, and the effects ofradioactivity on the organism are no different depending onwhether the radioactivity is of natural or artificial origin.

The control of the exposure to radiation is the subject of radi-ation protection. Current French regulation imposes a dose*limit of 20 milliSievert (mSv)* over 12 consecutive months(decree of March 2003) for worker exposure, and 1 mSv/year

(decree of March 2001) for public expo-sure. As a guide, the average naturalirradiation is 2.5 mSv/year, but it is nec-essary to specify that the abovemen-tioned dose limits concern doses inaddition to human activity.

In comparison to natural doses, thedosimetric impact of nuclear installa-tions is low. A nuclear power plant dis-charges into the environment ten timesless radioactivity than a coal or fuelpower plant of the same power: the col-lective dose is between 1.6 and 2.6man-sievert per gigawatt-year for anuclear power plant, compared to 20 fora coal power plant.The impact of cycleplants (reprocessing, mines) is muchgreater: according to the last reportfrom the Nord-Cotentin Commission,the dose induced by discharges fromthe La Hague plant on the most

exposed population is 0.06 milliSievert per year, that is 20times less than the dose caused by natural radioactivity.

If the effect of high doses resulting from serious accidental sit-uations is well-known, the problem of low doses of radiationremains a subject of biological and medical research (relation-ship between the risk and the dose, threshold effect), with anepidemiological section. The same goes for the hereditaryeffects of radiation.

Fig. 26. The analysis of the transfer of radioactive contaminants intothe biosphere is the subject of radioecology*. Different compart-ments of the biosphere are considered: soils, lakes, rivers, atmos-phere, plants, animals and humans.

Fig. 27. Components of the annual radioactive dose (in mSv).Fig. 28. Scale corresponding to the levels of exposure and healtheffects.

Rain

Rain

Atmosphere

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Cosmic raysTerrestrial gamma rays

Inhalation (mainly radon)Ingestion

Medical origin (diagnostic needs)

Aerial nuclear weapon testsChernobylNuclear industry

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Internalexposure

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Inhalation (1,2)

Medical origin (0,4) Nuclear industry (0,0002)

Nuclear tests (0,08) Chernobyl (0,002)

Cosmic rays (0,4)

Terrestrialgamma rays(0,5)

Ingestion (0,3)

Artificial origin

Inhalation

Externalexposure

Ingestion

Ingestion

Toward drinking water

Atmospheric diffusiontransfers

Hydrological/hydrogeological diffusiontransfers

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Drinking water

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Stream

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Low health risk

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Major health risk

Insignificanthealth risk

zero or practicallyno health risk

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+ 10 mSv/year

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- µSv/year

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1 mSv/year

10 mSv/year

+ 20 mSv/yearRange of naturalexposure the mostoftenencountered

Reminder:20 mSv workers’ limit1 mSv public limit

Normal situation

Scale of risk relating to effective annual dose

*AND = average natural dose

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Safety and demonstration of safetyIn the nuclear industry as in any human activity, zero risk doesnot exist. The objectives of the safety procedure is thereforenot to entirely eliminate the risks associated with nuclear activ-ities. In a less ambitious but more realistic way, it is to pre-emptthe risks of accident, and to mitigate their consequences in thehypothesis where the accident would nevertheless occur.Thenotion of safety is taken into account very early on, as of theinstallations’design phase.The specificity of the nuclear indus-try arises from the use of radioactive materials, which are likelyto be dispersed into the environment or even to affect thehuman being, and which are at the origin of ionising radiationswith multiple effects (irradiation, thermal energy, radiolysis,etc.).

Risk analysis is the subject of aconventional procedure:• Technical analysis of the instal-

lation’s safety and reliability;• Evaluation of the risks linked to

the dispersion of radioactive orchemical materials (impact onmankind and the environ-ment), and to the exposure ofworkers and the public to radi-ation (this is the entire field ofradiation protection);

• Risk management, comprizingboth compliancy with the regu-lations relating to radiation pro-tection and the development ofdecontamination processes forsoils and sites contaminatedfollowing an accident.

French regulation mainlyrequires deterministic calcula-tions (incidents or accidents arepostulated). With the safetyobjectives defined, possible fail-ures are imagined, which maybe of external or internal origin,(earthquake, fire, power cut,pump shutdown, etc.), thebehaviour of the installation issimulated, and it is made sure that the consequences areacceptable. All of the difficulty resides in the exhaustivenessof the list of scenarios envisaged. A set of principles, conceptsand methods has been developed, both at the design stage,and at the construction or operation stage. Thus defence in-depth* consists of interposing several “lines of defence” (fol-

low-up of actions, equipment or procedures, grouped in levelseach one of which has the purpose of pre-empting degrada-tions likely to lead to the next level and to limiting the conse-quences of the failure of the preceding level) in relation toaggressions that may affect the safety functions. This is gen-erally assured by the redundancy and the diversity of barriers(successive and leaktight multiple-barrier system). Severalmeans of stopping the chain reaction, redundant and diversi-fied residual power evacuation systems, several barriersbetween the radioactive products and the environment, thusexist. It is endeavoured to make these various means as inde-pendent as possible from one another, and to plan for each ofthem permanent or periodical monitoring used to guaranteetheir availability.

Containment(3rd barrier)

Core – fuel(cladding:1st barrier)

Primary circuit(2nd barrier)

Vessel(2nd barrier)

Steam generator

Sprinklingdevice

Control bars

Pressurizer

Pump

Sand filter

Fig. 29. The three containment barriers of a PWR.

The three safety functions for reactors• Control of the chain reaction• Evacuation at any moment of the energy produced in the core, production

which continues at the level of a few % after stopping the chain reaction (wethen speak of residual power).

• Containment of radioactivity, the main part of this relating to the fission prod-ucts formed in the fuel.

Increasingly, this approach is completed by a probabilisticsafety assessment (PSA), which aims to evaluate the prob-ability of the barriers’ destruction, the associated radioactivewaste and the consequences on the surrounding population.Here we come up against the difficulty of assessing the prob-ability of extremely rare events. Thanks to the probabilisticsafety studies carried out in the years which followed the ThreeMile Island (United States) accident, operators have made pro-visions having effectively reduced the probability of a coremelting* accident by factor 10 to 100.


30 Nuclear safety and security

Another point of view is the acknowledgment of the humanfactor as a progress point of safety, and this from the designstage up to the dismantling, cleanup and waste managementphases of nuclear installations.The analysis of significant inci-dents and accidents shows, in effect, that a significant part oferrors likely to have an impact on the safety of the installationsis linked to activities other than the conduct in control rooms(maintenance, tests, loading operations).

Risks linked to nuclear proliferationThe issue consists of developing civil uses of nuclear energy,without thereby lessening the world’s safety by enabling cer-tain countries or organisations to equip themselves more eas-ily with nuclear weapons7. The corresponding risks must beexamined from two angles…

The technical means that can be used to acquire fissile material needed for the construction of a bomb

The easiest means of acquiring the necessary material forconstructing a bomb is the enrichment of uranium. A shortcutconsists of recovering highly enriched uranium used in fuels forresearch reactors: this is why the Americans have decided toplace an embargo on fuel enriched by more than 20%, a rulegenerally applied today (there are however a few exceptions).A more difficult means is that implemented by the UnitedKingdom and France in the 1950s: to produce plutonium inreactors “burning” natural uranium at very low irradiation lev-els, enabling military quality plutonium to be produced. Theextraction of plutonium requires complex reprocessing instal-lations. Large power reactors using enriched uranium arepoorly suited to the production of military plutonium, becauseit would be necessary to very greatly limit the irradiation of thefuel and to reprocess it.This would not be impossible, but thiswould be a large-scale, very expensive and difficult to hideoperation.

The technical means and control policies

The keystone of the battle against nuclear proliferation is theNon-Proliferation Treaty (NPT), signed by most countries (butnot all). The signatory countries commit to accepting controlby the International Atomic Energy Agency of their nuclearinstallations and fissile materials in their possession (only 5permanent members of the UN Security Council8, who alreadyhad nuclear weapons in 1968, maintain the right to not submittheir military programmes to international control). The con-trols led by the IAEA are without a doubt difficult when theyconcern small installations such as small uranium enrichmentunits. On the other hand, they are effective for large fuel repro-cessing installations and power reactors. More worrying is thecase of countries who have not signed the NPT or who decideto leave it. But the corresponding risks of proliferation are notdirectly linked to the civilian use of nuclear energy. The fewcountries which have developed their own nuclear weaponshave moreover done it via specific means, and not by hijack-ing civilian installations.

5.Three Mile Island (USA), the 28th of March 1979; Chernobyl (ex-USSR),the 26th of April 1986; Tokaï Mura (Japan), the 30th of September 1999(Note of the Editor).6. International Agency for Atomic Energy.

Fig. 30. The INES gravity scale* of nuclear incidents or accidents.Between 1995 and 2005, the French electro-nuclear fleet was thesubject of thousands of level 1 incident declarations, of approximatelyforty level 2 incidents, and no higher level incident or accident.

INES gravity scale

7. Major Accidents (Chernobyl type )

6. Accidents having limitedconsequences around the site

5. Accidents presenting risks outsideof the site (T.M.I. type)

4. Accidents on the installations(Tokaï Mura type)

3. Incidents affecting safety

2. Incidents likely to developlater

1. Operating anomaly

Feedback constitutes a major element in the progression ofthe nuclear installation safety culture. The systematic record-ing and analysis of incidents, and all the more so, of accidents(Three Mile Island, Chernobyl, Tokaï-Mura5) must enable theoperation and the safety to be improved. But serious accidentsare generally and fortunately few, which does not enable themto be analyzed reliably by the existing mathematical tools. It istherefore important to pay attention to incidents as well as tonear incidents, defined as events which could have led to anaccident, or even to events in which human intervention hasenabled a potential incident to be caught in time. Equallynuclear operators have undertaken to exchange their bestpractices and to inform each other regarding any significantincident, within the World Association of Nuclear Operators(WANO); the safety authorities of various countries have alsoestablished close relationships which were lacking prior to theChernobyl disaster; and the IAEA6 has had adopted by all ofthe nuclear countries a set of common safety rules and prin-ciples.

7. Only the risks of nuclear weapon proliferation are mentioned here.“Dirty” bombs, associating radionuclides with a chemical explosive, pres-ent very real risks, but it would be infinitely easier for terrorists to seizeindustrial or medical radioactive sources, currently used and less pro-tected than fissile materials from the nuclear industry.8. Representing the United Kingdom, United States of America, France,China and Russia (Note of the Editor).



Risks linked to terrorist attacksThis subject is frequently talked about, more particularly sincethe 11 September 2001 attacks. Generally, nuclear installa-tions figure among the international installations which are thebest protected against terrorist risks, due to both their mas-sive and stocky character, and the in-depth defence provisionsmentioned above.

Risks linked to the transportation of nuclear materialsNuclear materials are subjected to many transformations: con-version, enrichment, manufacturing of fuel, irradiation in reac-tors, reprocessing, etc., all operations generally carried out indifferent locations, which require a great deal of transporta-tion*, by rail, road, air or sea.

Approximately 300,000 radioactive material packages aretransported each year in France for the requirements of indus-try, the medical sector and scientific research, which repre-sents less than 2% of all dangerous material packages trans-ported.

The tonnages to be transported are low, which does notexempt us from taking precautions in order to limit the risk ofdissemination of radioactivity during these transportations.There are four types of risks linked to transportation: irradia-tion, contamination, criticality concerning the protection ofpeople, property and the environment, theft or hijacking con-cerning the safety of materials.

An important part of the precautions concerns the robustnessof the containers. No major accident due to transportation is tobe deplored from the beginning of the nuclear era.

Risks linked to the disposal of nuclear wasteAttention has been focused for a decade on the risks linked tostorage (temporary by definition) and to the disposal (perma-nent or reversible) of high level and (or) long lived nuclearwaste.

Technically, four periods are to be considered:

• For several decades (a century in the case of the storage ofMOX spent fuel), nuclear waste is characterized by a veryhigh level of radioactivity originating from both relatively shortlived fission products and actinides (curium in glass, curiumand plutonium 241 in spent fuel). In parallel, there is a heatrelease which requires cooling; here we are in the field ofindustrial techniques currently used in the storage of highlevel waste.

• The beginning of disposal coincides with the beginning of thesecond period, when it is no longer necessary to cool thewaste. The radioactivity of fission products decreases to alow value, and it is the actinides present (neptunium, ameri-cium and curium in the glass, neptunium, americium, curiumand plutonium in the spent fuel) which release the heat.Thisrelease determines the dimensions, both of the waste pack-ages (the thermal load of each package being limited) andof the disposal site (the thermal load per unit of surfacearea being limited).

• In the third period, which lasts several tens of thousands ofyears, even 100,000 years, the main part of the radiotoxicityinventory of waste comes from minor actinides* (for themain part, in glass, neptunium and, at the beginning of thisperiod, americium and curium) and plutonium when the lat-ter is incorporated into it (case of spent fuel). The potentialradiotoxicity* of waste only becomes lower than that of theoriginal uranium ore towards the end of this period. Inbetween, the safety of a geological disposal site must beassured above all via the containment of the waste placed indisposal containers, themselves surrounded by engineeredbarriers; the geological barrier only intervenes in the case offailure of the latter. The work in progress on the containers,the engineered barriers and in underground laboratoriesaims to validate the safety analyses relating to this period.

• Beyond 100,000 to 200,000 years, the safety analysis con-siders that close containment is lost and that it is thereforethe geological barrier which plays the main role of protection.A large number of behaviour models over a very long term ofthese radionuclides, carried out in various countries andcompared in international programmes, have concluded thatthe doses received by man would amount to low fractions ofthose attributable to natural radioactivity.

During the first two periods, the problems posed will mainly benational. They concern the security and safety of the storageor the passive safety of the disposal.

Over a longer term, the accumulation of radionuclides in thedisposal sites, however, should be considered as a legacy tothe planet’s future generations9. The waste-related environ-mental risk may be considerable if it is badly managed (exam-ple of certain former Soviet sites such as Chelyabinsk). If theyare well-managed, the impact of the waste will probably beminimal, local and delayed. No demonstration of safety couldever be provided directly, due to the time scales at stake. Therole of science must probably be a little more modest: build

9. Final nuclear waste stored in well selected locations and carbon gasemissions should not be placed on the same level. For nuclear waste therisks will remain local because they would only concern at any momentthe geographical neighbourhood of the disposal site, therefore in any caseonly a limited number of people, whereas carbon gas emissions are notcontrolled and their effects concern the planet’s overall climate.


confidence, via a corroborating stream of indications showingthat all of the mishaps likely to affect the disposal have beenenvisaged including their consequences, etc. In short, that thelatter is a robust and controlled design.

Building confidenceControlling risks is not only technical and scientific: it also hasa strong social component.The confidence building proceduremust not stop once the conviction of experts is acquired. It isthen necessary to pass from scientific uncertainty to the nego-tiation of the risk. Nuclear safety calls on political decisionsmade democratically, that is with the opinion of citizens, whoseintellectual logic is different from that of scientists. Scientistsand citizens have a lot to say to each other!



Energy in the world

Since the discovery of fire, human development has beenaccompanied by increased energy consumption. Still today thelevel of energy consumption in general, electricity consumptionin particular, are indicators – fairly rough – of development.

have to compete with synthetic fuels manufactured from coal,the reserves of which are still significant.The use of hydrogenalone, without passing by a fuel cell is also a channel whichmust not be neglected, for land vehicles but also air or mar-itime vehicles.

A particular form of energy:electricityElectricity occupies a growing part in the energy consump-tion of all of the developed countries, due to its privileged usein the lighting, information and communication fields, andthanks to specific advantages linked to its flexibility of use inengines and switches. Electricity is a clean energy in thephases of transportation, distribution, and end use: no pollu-tion, and no greenhouse gases, with the exception of ozone.It is also clean in the production phase, if it is produced vianuclear, hydraulic, solar or wind power.

Apart from these advantages, electricity has a significantweakness: it can practically not be stored, except in minimalquantities and at a high costs in accumulators. It can be storedindirectly (pumping stations, flywheels), but this remains mar-ginal. Therefore it is necessary to produce it at any momentaccording to the immediate demand: the absolute example of“tight flow”!

The consequence of the difficulty of storing electricity: if the net-work is powered by an intermittent and random source, whichis the case of many renewable energies, it is necessary to planin reserve an equivalent power source ready to replace it.

The international consumption of primary energyIt is fairly certain that energy consumption will increase in thenext fifty years due to the increase in the world population andthe increase in the standard of living in developing countries.Fossil fuels (coal, oil and gas) will still be dominant. The pro-duction of oil should, between now and around ten to twentyyears, first peak then decrease. As requirements are increas-ing, the question will be to know how to fill this lack by moreenvironmentally friendly energy sources. The problem is notto oppose energy sources, but to find the best use for eachone of them in order to reach the most effective energy mix.

Fig. 31.The various uses of energy, during the ages, expressed in“tonne of oil equivalent” (toe) per year and per person.

0

1

2

3

4

5

6

7

8

9Transport

Industriy + agriculture

Domestique + tertiaire

Food

Prehistory

- 30 000 yearsAntiq

uity

- 2700 / - 1700 years

XVIIIth century

XXth century

United-States

XXth century

Toe / year

Energy useThe habitat represents approximately a third of the humanenergy consumption. This sector is likely to progress a greatdeal: the massive use of thermal solar energy would enableproduction of a large part of hot running water and residentialand service sector heating. Unfortunately, the very slow rate ofhabitat renewal is slowing down the progress which might becarried out in this energy sector.

Transportation represents a large part of the global energyconsumption, and a major source of pollution. In this sector,liquid hydrocarbons seem difficult to replace in the short term,even though hybrid vehicles, combining a thermal engine andan electric engine powered by batteries, have already startedto see the day fairly quickly. Hydrogen and fuel cells will reachtheir full potential probably in a more distant future and will


34 Energy in the world

Today, the Earth’s inhabitants consume on average 2.3 toeper person each year, which leads to a cumulated annualconsumption of primary energy, all sources together, of 9 bil-lion toe, 9 Gtoe/year.

This average of 2.3 toe/year per person hides a very largeregional disparity, which reflects the great North-South divi-sion in terms of development: whereas an American con-sumes 8 toe every year, a European or a Japanese personmakes do with 4 toe, and an Indian citizen lives with only 0.4toe per year.

Units

It is important to specify at which stage of use energy iscounted.When the assessment is made at source (coal mine,oil well, hydraulic dam, etc.) we speak of primary energy,which is what we will do in the rest of this text. Useful or finalenergy can also be counted. Due to the yields from transforma-tion and various losses, almost three times more primaryenergy is needed than useful energy, directly linked to theservice sought.

When we talk about the energy consumption of the country,we generally count it in tonne oil equivalent (toe).Approximately, 1 tonne of coal equals 0.667 toe and 1 MWh ofgas equals 0.077 toe.

Things become complicated when it involves expressing in toethe energy produced by a “primary” electricity source, whichdoes not come from the conversion of a fossil fuel (hydraulic,nuclear, wind electricity, etc.). In 2002, France rallied to theInternational Energy Agency conventions:

• The nuclear (or geothermal) MWh “equals” 0.26 toe, quan-tity of oil that it would be necessary to burn to produce oneMWh in a thermal power plant.

210020502000195019001850

0

10

20

30

40

50

A

B

C

12

10

8

6

4

2

01850 1900 1950 2000 2050 2100

Gtoe / year

A: Steady growthB: Average growth C: Eco-friendly growth

World population in billions

0 2 4 6 8 10

India

China

Emerging countries

World

Japan

France

Germany

EU

United States

0,2

0,7

0,8

1,6

3,9

4,0

4,1

3,8

8,1

Fig. 32. The world’s population approached half a billion individualsat the beginning of the christian era. It reached a billion towards themiddle of the 19th century then, by a fantastic acceleration of demog-raphy, the current figure of 6 billion in only 150 years. The world population is now increasing at a more moderate rate, but, at thepresent rate, we will without a doubt reach 10 billion during this century.

Sou

rce:

Etu

de II

AS

A/W

EC

“G

loba

l Ene

rgy

Per

spec

tives

”, 1

998.

Energy consumption per inhabitant (TOE)

Fig. 33. Can these inequalities last?

Distribution per source

The table below provides the distribution of the world energyconsumption between the various primary sources, in 2000,according to the International Energy Agency:

Coal

Oil

Gas

Nuclear

Hydroelectric

NRE

Fig. 34. The world energy consumption between the various primarysources.

Source Million toe %

Solid fuel 2,341 25.7

Oil 3,700 40.7

Gas 2,100 23.1

Nuclear 676 7.4

Hydroelectric 226 2.5

New Renewable Energies (NRE) 51 0.6

Total (commercial) 9,015 100



It can be seen that fossil fuels amount to 90% of the commer-cial primary energy used on the planet, and still over 80% ifnon-commercial energy is taken into account. The figuresspeak for themselves: there is no way that the increase in thecontribution of new renewable energies (NRE) can alone coverthe increase in requirements – or replace nuclear power aswished by certain people. In any case, not in the decades tocome.

Even if the OECD countries made spectacular strides inincreasing energy efficiency, the requirements of developingcountries are such that the energy consumption could notincrease less quickly than the population itself. All the morebecause the OECD countries and those of the former USSRhave now stabilized, and the 4 billion human beings which willincrease the world population during this century will originatefrom current developing countries. In order to face these gigan-tic requirements, we will not have too much of all of theenergy sources that mankind knows how to master!

Fossil energiesThe proportion of fossil energies should remain largely pre-ponderant in future decades. It should represent, according tothe International Energy Agency, 90% of the commercialenergy supply by 2030, hydrocarbons (oil and gas) represent-ing approximately 65%.

Oil

The proven reserves of oil currently represent approximatelyaround forty years of production at its current rate of consump-tion.

The rate of discovering new exploitable oil fields hasdecreased since the 60s, which implies a rapid exhaustion ofconventional resources if the current rate of consumption ismaintained.

Thanks to new discoveries and also a better recovery of oil onsite, it should be possible to exploit much larger resources.Thelatter will nevertheless be much more expensive than thoserecovered today. By lowering the costs, technical progressshould enable the development of deep sea production andthe exploitation of very deep deposits. Beyond that, theresources in non-conventional oil, and in particular, the extraheavy crudes, asphaltic sands and kerogen shale are consid-erable.

Natural gas

The proportion of natural gas in the world’s energy inventorycontinues to increase, given its advantages: lower impact onthe environment than coal or oil (no dust, better efficiency forthe generation of electricity with combined cycles, turbines,etc.), its flexibility of use, the importance of its reserves greaterthan that of oil (it currently represents more than 60 years ofconsumption at the current rate).There are also considerablereserves of methane hydrates (without a doubt more than dou-ble the quantities of fossil fuels which are yet to be exploited)that are trapped at the bottom of the sea or permanently infrozen ground. We still however do not know how to recoverthe latter technically. There are also uncertainties regardingthe energy efficiency and the economic cost of this recovery.

Coal

Coal, after a period of decline, may return in force, given theimportance of its reserves, which represent several centuriesof consumption at the current rate, in particular by implement-ing gasification systems, which enable it to be used in acleaner way. A good illustration of this is the “Futuregen” proj-ect, which was started in the United States of America in orderto lead to the industrial demonstration of a system of electric-ity production from “clean coal” with sequestering of CO2.

Gach SaranTia Juana

BurganZuana

Ghawar

Annual discover

Smooth on 5 years

Production

Fig. 35. The rate of discovery of new exploitable oil fields hasdecreased since the 60s, which implies a rapid exhaustion of con-ventional resources if the current rate of consumption is maintained.


36 Energy in the world

Fossil energies, CO2 and climatechangeIn the future, we must be able to answer to two major ques-tions: how to best manage the finite reserves of fossil fuels andhow, moreover, to respond to the risks of climate change, byrestricting greenhouse gas emissions.The increase in the con-tent of these gases in the atmosphere is due, without doubt,to human activities, and mainly to the use of fossil fuels, coal,oil and gas. If the phenomenon is not controlled very quickly,the global climate of the planet will be affected for a long time,with potentially catastrophic effects.

The relative contribution of the various sources of electricityto the production of GreenhouseGases (GHG)Among the various figures of the literature, here are the resultsfrom the LCA (Life Cycle Analysis, ISO 14040 standard) car-ried out by EDF, in CO2 gram equivalent per electric kilowatthour:

1000

0

100

1000 1200 1400 1600 1800 2000 2100

200

300

400

500

600

700

800

900

1000

0

100

200

300

400

500

600

700

800

900

Fig. 36. The concentrations of CO2 expected during the 21st centuryare two to four times that of the pre-industrial era.

ProjectionsDirect measurements

Ice core datappm

The sequestering of CO2 is an actively pursued avenue ofresearch. The options which seem to be the most interestingare those which consist of storing CO2 in exhausted hydrocar-bon deposits or in deep aquifers10.Work is yet to be carried outin order to reduce the costs, which are currently in the order of€ 50-100 per tonne of CO2 avoided, and to ensure the long-term security and longevity of the disposal site. Variousdemonstration projects are in progress or planned (Sleipner,Weyburn, In Salah, etc. deposit). Importance R&D pro-grammes have also been undertaken, in particular on theEuropean level. However the capture and disposal of CO2 mayonly provide a partial response to the problem posed: indeed,this solution can only currently be envisaged in large scalestatic systems, which excludes it from the transportation andhabitat sectors which represent a very large part of the emis-sions. A possible way out would be a large-scale use of hydro-gen produced without CO2 emission, but this cannot be envis-aged in the short-term.

System Operation Remaining Total life cycle g/kWhe

Coal 600 MWe 892 111 1003

Fuel-oil 839 149 988

Gas (turbine combustion) 844 68 912

Diesel 726 159 895

Hydraulic pumping 127 5 132

Photovoltaic/solar 0 97 97

Hydroelectric 0 5 5

Nuclear 0 5 5

Wind 0 3 3

As seen, it is not entirely true to say that nuclear, hydraulic orwind power does not produce any greenhouse gases,because the construction of power plants, dams or windmillsrequires concrete and steel, the production of which itselfreleases GHGs. But their contribution remains truly marginal!

Renewable energies The history of humanity is dominated by the use of renewableenergy, because the latter started to be used when humansdiscovered fire, approximately 500,000 years ago. Renewableresources are immense; the most abundant, solar radiation,represents 7.2 1017 kWh annually, that is to say more than5,000 times the entire global consumption of primary energy.But these resources are generally intermittent and manyrequire disposal in order to respond to the demand of modernsocieties, where the consumer wants energy when and wherehe needs it and not when it is available. The biomass and theaccumulation of water in reservoirs represents an energy stor-age which improves availability, and geothermy diffuses a heatflux fairly continuously.

In comparison to modern resources, often highly concen-trated, renewable resources have the disadvantage of a lowdensity; therefore they must rather be transformed there wherenature delivers them. Finally, even though the resource is free,the cost of many renewables is still too high in relation to otherenergy sources.This is mainly due to the additional investmentcosts for conversion systems.These additional costs resultingeither from the too low density of energy, or from the marketwhich is still too little developed, or from the technology which10. Permeable rocks with a high water content (Note of the Editor).

Past and future concentrations of CO2in the atmosphere



has not yet reached its asymptote of minimal cost.The limita-tion of non-renewable resources and their impact on the envi-ronment results in renewable energies experiencing increasedinterest. But, at this moment in time, hydraulics for producingelectricity, and biomass for producing heat, easily dominatethe renewable energies market, thanks to their competitivecost. They alone represent almost 20% of the primaryresources exploited.

A European political intent has led to supporting the mecha-nism of restricting greenhouse gas emissions; the Kyoto pro-tocol is the first step towards this. Oneof the aspects of this intent is securedby the European directive of the 27September 2001. The latter specifiesthat the generation of electricity fromrenewable sources must pass from13% to 22% in Europe in 2010, from15% to 21% in France.

The energy challengeThe 20th century has bequeathed us adouble challenge in the field of energy:

• To confront the energy requirementsof a world population multiplied by 10between 1750 and 2050, consuming10 times more per inhabitant;

• To control local, regional and plane-tary pollution (climate).

It has left us the means, but mobilisa-tion must be complete in order to riseto these challenges.

Although the increase in requirements and the aggravation ofrisks originates from poor countries, rich countries can andmust provide their contribution: controlling energy, technologytransfer, reduction of their GHG emissions.

The answers to be provided are not necessarily the same inevery country because priorities depend on the state ofdevelopment, the domestic resources, financial capabil-ities and the cultural context, but the challenge is to be meton a global scale because the effects on the environment areglobal.

The short and medium-term avenues are energy savings, thereplacement of coal by natural gas, the development of renew-able energies, and, last but not least, that of nuclear power.

The field of energy is a coveted field, the country which willfind and develop good technologies will reap an enormouscompetitive edge. It is therefore important that Europe be inthe race for the highest international level of innovation.

100

200

300

400

500

600

1 000

2 000

2550

Fig. 37. An illustration of the disparity of electric energy sources invarious European countries.

Fig. 38. The choice of energies: CO2 emissions per kWh throughout

the world (gC/kWh).

Electricity production in Europe (in 2000) per country and per source

Nuclear

Billions of Kwh (gross) Billions of Kwh (gross)

Hydroelectric Wind Coal Gas Fuel

D B E F I S Total EuropeanUnion

NLU-K

0 100 200 300

Denmark

United-States

Germany

UK

Japan

Sweden

France



The economy of nuclear power

The cost per kWh produced by high power water nuclearreactors has been the subject of numerous studies, the mostcomplete of which are probably those conducted by the FrenchMinistry of Industry, which is based on a very important andwell-known programme, and that carried out by the ProfessorTarjanne for the Finnish government and which supported itsrecent decision to build a new reactor.

The DGEMP study notes that all of the nuclear power costsare in fact taken into account, contrary to that which occurs forother energies: in particular the provisions for waste manage-ment and for the dismantling of installations.This overall costis evaluated at approximately € 30/MWh, of the same order ofmagnitude as the internal cost of the kWh in a combinedcycle gas power plant.

The Finnish study compares the costs of the kWh of a 1,250MW nuclear power plant and those of fossil fuel and windpower plants, with the conventional hypotheses regarding thelifetime of the power plants (40 years) and the availability ofthe installations (90% for thermal power plants, 2,200

22.8 24.1

32.1 30.532.5

39.6

3.0

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7.613.8

23.7

1.55.3

10.2

6.5

13.0

8.2

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18.4

10.0

50.1

40.1

man/year for wind turbines). As its French counterpart, theFinnish study gives the advantage to nuclear power.

Between 1974 and 1985, in France in particular, nuclear powerenjoyed a comfortable margin of competitiveness. Then, theoil counter-shock very rapidly brought the price of fossil ener-gies back down to the level that they were prior to 1974, andthis situation lasted until 1998, profoundly changing outlook.On the other hand, gas turbines, benefiting from technologi-cal effects from the aeronautical industry, achieved spectacu-lar progress in efficiency, unit size and thus price, whereas thestrengthening of safety and the increase in regulations hassomewhat increased the nuclear investment.

Since 2003, the scale has once again tipped in favour ofnuclear power and this trend should last and be accentuatedwith the inexorable rise in the price of hydrocarbons, accom-panied by the progressive growing scarcity of resources.

The evaluation of the competitiveness of nuclear energy mustbe made over a long time period, comparable to the lifetimeof nuclear plants. The comparison depends on the price per-formance of other primary energies during this time period.For hydrocarbons, this evaluation is very uncertain.

What is certain is that the nuclear power costs are stable andpredictable.The price of uranium raw material only intervenesfor a very small part in the price of the nuclear kWh.This favor-able situation protects nuclear energy from fluctuations in theraw materials market. Moreover, 90% of the expenditure takesplace on the national territory, with the location correspondingto the use, and with favorable consequences on the balanceof payments.

Today, existing nuclear power plants, partly amortized, consti-tute important sources of profit.

On the other hand, the initial investment necessary for con-structing new ones is high and difficult to assemble. It will prob-ably be necessary to resort to new financing structures in orderto finance such heavy investments in a largely deregulatedeconomy focussed on the short-term. Evidence of feasibilityis starting to emerge: for example, a consortium of Finnishpaper manufacturers is financing one part of the new PWRreactor recently ordered in this country.These credit arrange-ments must take account of the fact that the heavy investmentsof the nuclear power industry, combined long-term with the

Fig. 39. Cost of electricity (€/MWh) for various sources of primaryenergy, compared to the ELSPOT price, the Scandinavian kilowatt-hour market. The Finnish study from March 2002 concludes thatnuclear power is the most economical energy source when powerplants operate more than 6,000 hours per year. Only the internalcosts have been taken into account. A possible eco-tax on carbonwould further improve the competitiveness of nuclear power.

Fuel

Euro / MWh

ELSPOT ELSPOT Nuclear Coal Gas Peat Wood Wind

60

50

40

30

20

10

0

Maintenance and operation

Cost of thecapital

Price max 2000

Price in November 2001 - Interest rate = 5.0 %

Generation cost excluding subsidies and tax benefits

Pricemaxi. 2001

Cost of electricity generation


40 The economy of nuclear power

return on investment, makes the profitability of nuclear powerparticularly sensitive to the interest rate for necessary loans.

We will not enter into the debate here regarding the value allo-cated to plutonium, which may be considered as waste or asa precious resource, according to the recycling policy chosen.Recent studies suggest that the economy of fissile materialpermitted by the recycling of plutonium barely compensatesthe costs associated with recycling. The elements of choiceare furthermore not only economical but also, and above all,political, because considerations regarding the radiotoxicity offinal waste, the possible continuation of the nuclear pro-gramme with fast neutron reactors or the proliferation ofnuclear materials influences strategic choices.

0

10

20

30

40

50

60

3 52

6

15

46

53

€/MWh

Coal Oil Gas Bio Nuclear Solar Wind

Fig. 41. Health and environmental costs, called “external costs” forvarious energy sources.

Sou

rce:

Ext

ernE

, J.

Wei

sse,

Mar

ch 1

999.Nuclear Gas combined Wind

cycle

Real interest rate 5% 24.1 30.5 50

Real interest rate 8% 30.1 32.2 60

Real interest rate 5%and carbon tax €20/t 24.1 37.6 50

Fig. 40. The results of the Finnish study compare the price in € ofthe electric Megawatt-hour for various production modes. Two realinterest rates are taken into consideration: 5 and 8%. The competi-tiveness of nuclear power is indisputable for the low capitalisationrate (5%). Nuclear power remains competitive compared to gas up toa real interest rate of 8%, which leaves a fairly comfortable margin.

In normal operation, energy production systems impact ourenvironment and our health, which should be taken intoaccount if we want to compare them. For some activities, itconcerns liquid or gaseous waste, for others it is a noise dis-turbance or simply the degradation of a tourist site. They alsoinvolve possible accidents, the consequences of which mustbe taken into account. The “ExternE” study, carried out in col-laboration between the European Commission and the USDepartment of Energy, aims to identify and even quantifyexternal costs and profits, that is the positive or negativeeffects of various energy systems, not taken into account inthe direct economic assessment. It emerges from these stud-ies, carried out within a European framework, that the externalcosts of nuclear energy are particularly low.



Nuclear power throughout the world

Several events have recently reminded us of the advantagesof nuclear power and open new prospects to the sector…

Firstly, there is the European Commission Green Book 11,which recognizes in nuclear power a competitive energysource capable of responding to the double issue of the safetyof the energy supply and the reduction of greenhouse gases.In the same way as controlling the energy demand and devel-oping renewable energies, nuclear power is currently recog-nized as an essential component of a more balancedEuropean energy mix, privileging energies that do not emitgreenhouse gases.

An equivalent document, the “Report of the National EnergyPolicy Group”, published in the United States in May 2001,delivered a similar message.

Awareness of the sharp increase of the demand for primaryenergy throughout the world leads to the recognition that allenergy sources will be necessary in order to match theneeds, including nuclear power, which produces practi-cally no greenhouse gases.

Most countries thus currently integrate nuclear power into theirreflection on the short and medium term (up to 2020) and longterm (2020 and beyond) energy policy.

This is actually the case of the United States: between newrequirements and the replacement of aging installations, theAmerican administration thus evaluates the number of elec-tric power plants between 1,300 and 1,900 (that is power onthe order of 400 GWe) which must be installed between nowand 2020, all sources together.

The availability of American nuclear power plants has spec-tacularly improved, which constitutes the main reason for therenewal of their appeal in the United States. A large number ofthe 104 American reactors have obtained from the safetyauthority the extension of their operation beyond the initialexpected duration, and these “second-hand” reactors areresold between electricians at the price of new reactors.

Even if all of the conditions have not been met for significantinvestments in new nuclear power plants over the very shortterm, the use of nuclear power for the medium-term remainsunavoidable in order to satisfy part of the high demand.Several tens of GWe of nuclear origin will without doubt benecessary by this time.

It is in this context of vulnerability of hydrocarbon supply andenvironmental constraints, that the “National Energy Policy”report, submitted to the President of the United States in May2001, concludes with the need to resume the development ofnuclear power in this country. At the same time, the “NuclearPower 2010” initiative was launched in order to accelerate theprocess of granting authorisations in view of the deploymentof advanced reactors from 2010.The decision-making processregarding the opening of the Yucca Mountain nuclear wastedisposal sites has been initiated with the positive vote fromCongress in 2002 regarding this project, which had alreadyobtained President Bush’s support.The Department of Energy(DOE) is moreover very active within the scope of theInternational Forum on the fourth generation.The importanceof closed fuel cycles (“Advanced Fuel Cycle Initiative”) is alsobeing largely reconsidered, beyond the past position of oppo-sition to any reprocessing. Finally, it is important to point outthe propositions of research programmes from several nationallaboratories aiming to relaunch R&D and the related budgets.

11. Published in November 2000.

16

2

2

59104

27 30136

214

8

19

536

11

11

2

22

4

444

9

1118

Fig. 42. Nuclear power plants operating worldwide.


42 Nuclear power throughout the world

Russia, in spite of its economic difficulties, seeks to partici-pate in the global reflection on nuclear power and has takenseveral initiatives in this direction, in particular the launch of aglobal concertation, with the IAEA, regarding nuclear powerof the future (INPRO exercise) and the vote for a law onaccepting foreign nuclear waste on Russian territory enablingnuclear fuels to be offered on a lease basis.

Re-establishing strong economic growth, Russia is now show-ing a willingness to succeed with its civilian nuclear develop-ment programme with the completion, then the commercialcommissioning of power plants, the construction of which wasstopped following the Chernobyl accident in 1986. The coun-try is also very active with its fast neutron reactor developmentprogramme.

The United States and Russia are moreover making specificefforts, within the framework of nuclear disarmament, to con-vert and use fissile materials of military origin. This has createda common reflection, with a high involvement from France,regarding the cycle of these materials (including in the UnitedStates) and on reactors best suited to reach this objective.

In Asia, China, whose GDP has seen near 10% annual growthover the last few years, estimates the needs for new electricalcapacities at approximately 20 GWe per year during the next20 years.This huge figure indicates how important it is for thiscountry to increase its production capacities. In the 1980s,China launched itself, up to now within the framework of a

privileged relationship with France, into a nuclear equipmentpolicy with a willingness to control all of the technologies asso-ciated with the construction of reactors. Even though nuclearpower only represents 1.5% of its capacity with 8 reactorsoperating commercially, China projects having by 2020 acapacity in the order of 35 GWe of nuclear origin, that is theequivalent of 20 to 30 new reactors. The nuclear proportioncould therefore reach 4 to 5% of the capacity, thermal andhydraulic power remaining largely in the majority. The recentsoaring oil prices and the awareness of the energy depend-ence regarding exterior supplies nevertheless leaves open thepossibility of an acceleration of the development of theChinese nuclear programme.

Japan, which owns little natural energetic resources, hasadopted a strategy similar to France’s in the 70-80s. It alreadyhas 53 reactors which generate 45 GWe, ie approximately34% of the national electricity. Four reactors are in the processof being built and around ten additional units are active proj-ects. The next report from the Japanese Atomic EnergyCommission will update the deployment projections of theelectro-nuclear fleet by 2030. The previous report took intoaccount a need in the order of 20 new reactors between nowand 2030. Japan, whose population is declining, is neverthe-less currently beset by political and institutional difficultiesregarding nuclear power: the latter is struggling to regain pub-lic confidence after numerous matters which have punctuatedthe life of the sector during the last few years.The country maytherefore downsize its ambitious programme.

USA + 1500 Power Plants by2020 including nuclear

(> 50 GWe)

FINLAND 5th reactor

FRANCE new EPR reactor

KOREAnuclear capacityincrease + 9 GWe

by ~ 2015

JAPAN nuclear capacity

increase + 21 GWe by 2012

CHINA nuclear capacity

increase > 30 GWe by 2020

INDIA nuclear capacity

increase from 2.5 to 20 GWe by 2020

Fig. 43. There are currently 34 nuclear reactors being built throughoutthe world, and nearly as many projected.



In South Korea, 19 nuclear reactors represent approximately38% of the national electricity generation. This country is cur-rently constructing 2 nuclear reactors and is planning toincrease its capacities by constructing an additional 8 reactorsin the next 12 years. In the longer term, Korea, which is poorin energy resources, plans to double its capacity installed in2000.

India, with its one billion inhabitants and in spite of its low percapita consumption (0.5 toe/inhab/year), already figuresamong the largest energy consumers and is faced with impor-tant energy deficits. Fourteen nuclear reactors, of low powerand mainly CANDU* technology, are currently in operation andthe Indian government hopes to increase the nuclear capac-ity of the country for it to pass from approximately 3 GWe todayto 20 GWe between now and 2020. In order to do this, Indiaintends to increase its production capacity partly from reac-tors developed locally and partly by turning to foreign partnersin order to have access to light water reactors*. It should benoted that the country is actively pursuing its fast system andthorium system development programme, given its nationalreserves.

Brazil relies heavily on its hydroelectricity but has alreadycommissioned two PWRs, the first ordered fromWestinghouse and the second from Siemens. Framatome-ANP is expecting the decision to complete the construction ofthe third reactor ordered, at the time, from Siemens. TheBrazilian Ministry of Science and Technology has furthermoredeclared itself in favour of the development by its country ofresearch on nuclear technology.

South Africa, with 2 powerful reactors in operation, is devel-oping a 100 MWe high temperature reactor, of the Pebble BedModular Reactor (PBMR) type, in partnership with BNFL12

(GB) and a future partner yet to be defined. This concept ofsmall reactor, based on the German pebble technology andcooled with helium, mainly targets a faster return on invest-ment than that of the PWRs and would also present the inter-est of being accessible to small countries, given the smallerinitial investment.The ESKOM consortium announced in 2003that it was now ready to pass to the development and con-struction of a PBMR demonstration reactor.

And in Europe?Each European country is sovereign in the choice of its energyoptions, which leads to a panorama of very different options fornuclear power. Some countries make great use of nuclearpower (nearly 80% of the French electricity generation is ofnuclear origin; others have none at all (Ireland, Austria,Norway, Denmark, Italy).

Italy and Austria have declared themselves against nuclearenergy since the 1980s; in the same decade, Sweden decidedto pull out of nuclear power by 2010 but up to now has shut-down only one power plant; Germany decided to pull out ofnuclear power in 2000 and Belgium in 2001; the UnitedKingdom deferred the decision to renew its reactors to a laterdate... Conversely, in May 2003 Switzerland refused to pullout of nuclear power, and Finland ordered a PWR nuclearreactor on 18 December 2003. France has just decided toconstruct a PWR reactor on the Flamanville site.

This common absence of vision between the European Unioncountries creates an unfavourable global political environmentfor nuclear power, and yet this energy currently occupies animportant place in Europe:

• It contributes 35% of electricity production;

• It represents an important industrial sector on the interna-tional scene, for the supply in reactors (in particular those of3rd generation such as the PWR and the SWR 1000 fromAreva), for operating power plants, and for the fuel cycle;

• The European research on radioactive waste management,in particular that conducted in France since 1991, is amongthe most advanced in the world and from 2006 will enable anew management strategy to be decided regarding all of thewaste produced by nuclear power plants;

• European community R&D programmes also dedicate sig-nificant resources to thermonuclear fusion.

On 1st May 2004, the European Union passed from 15 to 25members: thus 5 nuclear countries out of 10 joined Europewith 23 reactors in commercial service. The importance ofthese countries’ integration extends to the nuclear energy sec-tor, in particular in terms of safety and waste management.The prospects of collaboration, in particular with the CzechRepublic, Slovenia and Hungary are numerous.

Signs of renewed interest are appearing:

• The European Commission “Green Book”, published in 2001concludes, of course in very cautious terms, on the need toreconsider the nuclear option in order to face energy supplyproblems and to respect the Kyoto commitments;

• Through private investors, Finland confirmed its choice ofconstruction of a fifth reactor by placing an order at the endof 2003 for a PWR reactor with the Areva group;

• Sweden, after closing Barsebäck 1 at the end of 1999, post-poned sine die the shutdown of its nuclear plants becausethey could only be replaced by a Danish electricity import(with coal) with the consequence, well perceived by publicopinion, of acid rain. Opinion polls are currently in favour of12. British Nuclear Fuels (Note of the Editor).


44 Nuclear power throughout the world

pursuing the nuclear activity in this country which20 years ago opposed it by referendum;

• Switzerland consulted its population by referen-dum in May 2003 regarding popular initiativeswhich should have led to eventually pulling out ofnuclear power: A quite clear refusal of renouncingthis energy emerged, even though in 1990 a mora-torium banned the construction of any new powerplant of this type;

• Germany concluded a political contract, well in thesocial consensus tradition of this country, to post-pone the real choices to a later date, whilst protect-ing the main thing, that is the operation of existingpower plants and thus the country’s safe supply inelectricity;

• Belgium more recently turned to a similar track,but changes in its political landscape could even-tually lead to a revision of its position and a possi-ble repeal of the law for pulling out of nuclearpower;

• Great Britain is conscious that with the foreseenshutdown of its ageing Magnox reactors betweennow and the end of the decade and the exhaus-tion of North Sea pools within 25 years (in 2004the country had just crossed its “peak oil”), theelectricity supply will be entirely dependent onimports in the not too distant future. A re-examina-tion of the energy policy is in progress and a WhiteBook came out in 2003. The latter certainly indi-cates a marked willingness to significantly reduce CO2 emis-sions by 2020 but did not clearly define the British positionregarding the nuclear option.

Finally, in France, the Parliamentary Bill regarding energy con-firms the major contribution of nuclear energy in the futurenational energy mix and the importance of launching the firstPWR reactor in order to guarantee the renewal of the currentfleet in due course. EDF has entered into the process oflaunching the EPR by selecting the Flamanville (Manche) sitefor the first reactor.

In this context favourable to a rebirth of nuclear powerthroughout the world, the current objective is to enhanceall of the European potential in the development of futurenuclear systems, with a just return of the profits to come.

This objective implies the different types of issues for whichresearch laboratories and their industrial partners are prepar-ing themselves:

• Research issues to develop the key technologies for sus-tainable nuclear power, an issue which presumes a willing-ness from political and industrial players to continue invest-ing in the R&D for the nuclear power of the future;

• Industrial issues to enhance the experience acquired in theprevious development of prototype reactors or advancedprocesses regarding the fuel cycle and to commercialize it;

% 0 10 20 30 40 50 60 70 80

Lithuania

France

Belgium

Ukraine

Sweden

Bulgaria

Slovakia

Switzerland

Hungary

Slovenia

Japan

Taiwan

South Korea

Germany

Finland

Spain

United-Kingdom

Armenia

United States

Czech

Canada

Russia

Argentina

Romania

South Africa

Mexico

Netherlands

India

Brazil

China

Pakistan

Kazakhstan

Coal (39 %)

Hydroelectricity (19 %)

Nuclear (16 %)

Gas (15 %)

Oil (10 %)

Fig. 44. The nuclear proportion in global electricity generation.

Fig. 45. World electricity generation.


• Industrial issues also to be recorded in international con-sortiums called upon to market the systems of the future;

• Also issues of development training in international co-operation, which would lead to sharing R&D whilst research-ing the reduction effects of national efforts by synergies, andco-financing opportunities for large research tools or proto-type installations.


46

Nuclear power: the main avenues of research

• To support the current nuclearindustry;

• To provide effective and acceptable

solutions to the problem

of long-lived and high level

waste management,

and to better understand

the impact of nuclear activities

on humans and the environment;

• To design and evaluate

new generations of nuclear

systems (reactors and cycles).



The near future: research supporting the existing nuclear power

The nuclear industry has reached its full potential. However,the margins of competitiveness can still be improved:

• By improving the profitability of the fleet through more effi-cient use of nuclear fuel;

• By extending the lifetime of existing reactors.The global fleetof reactors is aging rather well, and many electriciansthroughout the world envisage operating these existing reac-tors longer than the lifetime for which they were initiallydesigned. It is still necessary to obtain authorisations, andfor this, demonstrate that the aging of reactor components isforeseeable and controlled;

• By preparing the replacement of the fleet of current PWRreactors with evolutionary third generation reactors, endowedwith an improved efficiency and a (further) increased level ofsafety13.

These three avenues of improvement for the near futurerequire R&D. CEA takes on a large part, in close partnershipwith the French nuclear industrialists, Areva and EDF.

Using nuclear fuel more efficiently

Industrial issues

At the time of the start up of the programme for the construc-tion of PWR power plants for electricity production, in the 70s,one of the arguments put forward (apart from the energy inde-pendence) was linked to the relatively low cost of the fuelcycle. Indeed, the fuel cycle proportion in the cost of the kWh(30% including the “upstream” and “downstream” sections ofthe cycle), did not bring about particular optimisation effortsfor the fuel performances.

Today, given the updated economic reports between the vari-ous energy production systems, there are important produc-tivity gains to be achieved thanks to nuclear fuel and to itsmanagement means.

For electricians it involves increasing the overall efficiency ofits nuclear fleet in order to be competitive in an open market:

• By increasing the burn-up rate* of fuel assemblies;

• By extending the irradiation campaigns;

• By reducing the number of assemblies on each reloading(flexibility of the reloadings);

• By reducing the operating constraints, in particular duringtransient periods imposed by the monitoring of grid loading(these transient periods in fact test the fuel, and the devel-opment of a fuel capable of resisting rapid changes in reac-tor speed is an important issue);

• By controlling the equilibrium of the fuel cycle over the entirefleet, a policy of matching the reprocessing – recycling flux.

R&D objectives and challenges regarding PWR fuel

The maximum irradiation (average per assembly) is currently52 GWd/t whereas it was 33 GWd/t in the 80s.This importantincrease was obtained mainly thanks to:

• A better knowledge (associated with comprehension andmodelling) of the behaviour of the fuel in irradiation providedby the R&D and the feedback from standard or experimen-tal fuel irradiated in PWR cores, enabling optimised dimen-sioning;

• Progress on fuels themselves (cladding material, pellet,importance of the fuel ceramic microstructure). At present,the burnup rate is restricted by the strength of the cladding(the fuel is removed from the reactor before the claddingbreaks, or rather, before it risks breaking in incidental situa-tions).

With the objective of reaching burnup rates exceeding70 GWd/t within the next decade, a certain number of devel-opments and/or confirmations are necessary.These develop-ments concern numerous, often combined, phenomena (cor-rosion of the cladding, internal pressure, mechanicalbehaviour of the assembly and rods in incidental and acciden-tal situations, etc.).

13. Third generation reactors will be dealt with in the following chapter.


48 The near future: research supporting the existing nuclear power

CEA, in close collaboration with its industrial partners, has setup R&D programmes regarding fuel, based on its experimen-tal means and on its expert capacity.

R&D programmes regarding fuel

Responding to industrial needs

In the short and medium-term, the R&D needs expressed byindustrialists require a follow-up or even an increase in R&Defforts in the following fields:

• The behaviour and reliability of the mechanical structures offuel assemblies for high burnup rates.The progress targetedconsists of a reduction of the mechanical wear and tear ofrods thanks to a better control of their vibratory behaviour inthe reactor core.They undergo particular tests carried out inrepresentative situations (temperature conditions, pressure,chemistry and geometry of the reactor cores). These tests,carried out on the CEA/Cadarache Hermès installation serveto validate the modelling and simulation of the behaviour ofassemblies, and to demonstrate that the main phenomenaat stake are understood and controlled;

• One of the R&D objectives in particular regarding MOX fuelis to increase its competitiveness by increasing its burn-uprate. The aim is to produce a ceramic capable of effectively

retaining fission gases. It has been recently demonstratedthat the use of additives introduced into the oxide powderprior to sintering enables the homogeneity to be improvedand the size of the surrounding grains to be significantlyincreased, two important conditions for minimising itsgaseous release under irradiation. The current irradiationexperiments in progress on these new ceramics will enablethe gain obtained in burnup rate to be quantified.The exper-iments mainly consist of instrumented irradiations (for anexample in the Osiris reactor in Saclay), followed or not bythermal annealing associated to measurements of the fis-sion gas release (in hot laboratories, for exampleLECA/STAR in Cadarache). Post experimental examinationsuse the following conventional tools: electron microscopy,microprobe, mass spectrometry of secondary ions, with theparticularity that the corresponding devices are adapted forthe examination of highly radioactive objects;

• In the field of cladding, even with current materials or inprocess of deployment (such as the zirconium-niobium M5alloy), the behaviour of the claddings in more demandingconditions (high temperature oxidation with steam, hydrida-tion, fragilisation, etc.) must be explored further particularlyfor the safety demonstrations of new modes of fuel manage-ment;

Fig. 46. Microstructural analysis of advanced MOX fuel ceramics.The photo opposite compares the local content in plutonium of the MOX pelletssintered respectively with and without chromium additive. The second are much more homogenous.

MIC0F1

MIC02F1

MIC03F1

Addition of Cr2O3before dilution

Addition of Cr2O3

during dilution



• By 2010, the qualification of a fuel much less sensitive to thepellet-cladding interaction is a main objective of the EPR proj-ect, in particular in order to improve the reactor’s perform-ances, simplify its design and to minimise the constraintslinked to the monitoring of the power grid loading.

Fig. 47. Example of current progress regarding the fuel cladding: thezirconium alloys used for the cladding are subjected, in the presenceof water, to corrosion which tends to spiral out of control as the oxidelayer grows, which limits the time that the fuel stays in the reactorand the temperature of the fuel and coolant. Recent progress in thecomposition of cladding alloys enables corrosion to be considerablyreduced and these limitations to be postponed.

0

20

40

60

80

100

120

0 10 000 20 000 30 000 40 000 50 000 60 000 70 000

1990 1995 2000 2005 2010 2015

Oxide thickness (µm)

YearZy4

M 5

39,000 MWd/t

47,000 MWd/t

Garance (900)

52,000 MWd/t

Cyclades (900)Gemmes (1,300)Alcade (N4)

62,000 MWd/t

Galice (1,300)

70,000 MWd/t

HTC (900 / 1,300)

Burn-up

Burn-up rate

In order to carry out these studies correctly, CEA possesses“heavy” facilities: the LECA and LEFCA laboratories enableexperimental fuel elements to be manufactured; the Osirisreactor (Saclay) enables the irradiation; the PELECI (Saclay),LECA (Cadarache) and ATALANTE* (Marcoule) hot cellsenable these irradiated elements to be analyzed.

Some of these heavy facilities are recent, others are aging.This is the case of the Osiris reactor, which must be replacedby 2014 with a powerful and multipurpose research reactorintended to cover most of the European experimental irradia-tion needs: the Jules Horowitz reactor*.

Fig. 48. Changes in core management involves research on thebehaviour of fuel with high burn-up rates.Progress carried out on the strength of the cladding enables muchhigher burn-up rates and a better use of the fuel to be envisaged.Thanks to this type of progress and to this “small steps” policy, theburn-up rate of nuclear fuel passed from 39 GWd/t to 52 GWd/t in ten years and progress is still going on: 70 GWd/t is targeted in2010.

Fig. 49 and 50. The Osiris reactor. Experiments on fuel mainly con-sist of irradiations in experimental reactors such as Osiris. These arelong experiments, they are intended to validate the modelling, and toprovide confidence in its predictive capabilities. They also serve toqualify advanced fuels, prior to their use on an industrial scale.



Offices

Orisis reactor

“Electronic-control” building

Ventilation chimney

Hot cells hall

Isis reactor

Isis laboratories

Cooling towers

Waste containers

“Crown” building

Fig. 50.

Fig. 53. The Atalante facility, in Marcoule.Fig. 51 et 52. The future Jules Horowitz reactor should diverge inCadarache in 2014.

Another objective for CEA is to upgrade R&D methods, in par-ticular in the sectors where heavy experimentation is widelyused. This involves either taking best advantage of the entireexperimentation or substituting it, where possible, with a moreanalytical experimentation based on a more cognitiveapproach of phenomena and sizes which govern them. Thismust be done in complementarity with modelling develop-ment.



Developing modelling and simulation

CEA has modelling tools and continues to develop calculationcodes, continuously improving the predictions on the behav-iour of reactors and of their components. Apart from theCathare thermal-hydraulic* code, the future EDF/CEADescartes (neutronics*), Neptune (thermal-hydraulic) andPléiades (fuel) platforms must be mentioned.

The fuel modelling effort consists of extending the field of valid-ity of fuel behaviour models and to assure their qualificationby a specific experimentation.This field in particular covers themodelling of the thermomechanical behaviour of the rod, thedescription of the microscopic mechanisms of the fission gasrelease on the microstructure level, the pellet-cladding inter-action and the irradiation-induced swelling. All of these mod-els are introduced in the Pléiades software application co-developed by CEA and its industrial partners.

Extending the lifetime of existingreactorsPlanned initially to last for approximately forty years, nuclearpower plants age rather well, as the feedback on the globalfleet shows.That said, nuclear power plants see their profitabil-ity increase considerably once the initial investment is amor-tized. The extension of the lifetime of reactors is therefore amajor issue for electricians. This is why many nuclear opera-tors throughout the world are currently requesting that theircountry’s Safety Authority authorize extension of their facilities’lifetime.The French fleet of reactors is younger than the worldaverage, but EDF also wishes to extend the lifetime of its reac-tors. It is still necessary to demonstrate that the system’s safetyis preserved.

The extension of nuclear power plants’ lifetime requires a verygood knowledge and very good mastery of the aging mecha-nisms of all of their components. It is also necessary to havereliable diagnosis and control means. CEA carries outresearch in these two fields.

The aging mechanism of a nuclear reactor’s components arevery diverse. Some such as material fatigue, corrosion understress, corrosion-erosion, and wear and tear by friction areabsolutely conventional and are found in many other installa-tions or industrial objects. Other mechanisms are more nuclearspecific, in particular the fragilisation and swelling of steels dueto irradiation and corrosion due to radiation.The various mech-anisms do not act in isolation: it is their combined action whichcontributes to accelerating the aging of a nuclear power plant’scomponents, and which is to be controlled.

The aging of the power plant’s components

The vessel* of the primary circuit of water reactors is one ofthe elements presumed to being non-replaceable. It consti-tutes part of the second containment barrier: its mechanicalstrength must be kept, even in accidental conditions. It is alsothe subject of a specific lifetime monitoring and evaluation pro-gramme.Thus, on each ten-year visit, EDF presents the SafetyAuthority with a vessel maintenance file justifying its ability tofulfill this safety function for the next ten years.

The main phenomenon of vessel aging is of course linked toirradiation damages: The main influencing factors are thedegree of irradiation of the vessel and the loadings sustainedduring power transients.

The operator minimises the irradiation* of the vessel by usingfuel loading plans optimised from the neutronic point of view.Knowledge of the condition of the vessel material, in particu-lar on the internal side is essential because existing defectsmay, depending on their size, favour the propagation of cracks.Experimentally, the irradiation of the vessel is monitored bymeans of dose measurements on test specimens. Also, the

Fig. 54. Modelling of the pellet-clad interaction.Subject to irradiation, the fuel ceramic pellet tends to swell, due todisorders of the crystal lattice caused by the irradiation, and due tointerstitial atoms generated by the nuclear reactions (in particular fis-sion gases). This swelling, combined with pressures inside and out-side of the zirconium alloy cladding, places the latter under stress. Itis important to correctly model these stresses and their evolution intime, in order to control the risk of breaking the cladding and releas-ing radioactivity into the primary circuit of the reactor.



vessel’s condition is checked by ultrasounds, which enable thesize of the defects linked to cold fissuring and those resulting

from intergranular deco-hesions caused by heat-ing to be detected andevaluated.

The CEA is deeplyinvolved in a large R&Dprogramme which accom-panies this programme onthe vessel’s lifetime. It cov-ers the main influencingfactors regarding the eval-uation of the vessel’sstrength and its lifetime.

The main R&D pro-gramme concerns thephysical criteria justify-ing the strength of ves-

sels. Apart from the evaluation of the fluence* sustained bythe vessel, the programme comprizes amongst other things:• Irradiations of steel test specimens in experimental reactor

vessels (Osiris);• The development of methods for the determination of

mechanical properties;• The development of advanced methods in fracture mechan-

ics (probabilistic methods), aiming to better evaluate avail-able margins of resistance.

The monitoring of the condition of the vessel material vianon-destructive testing methods is the subject of R&D actions,in particular regarding the improvement and the qualificationof the ultrasonic processes implemented.

The operating return from reactors shows a few aging phe-nomena that must be taken into account in order to be able toassure the lifetime of the containment. It constitutes the lastbarrier for the retention of radioactive materials in the event ofa serious accident. In order to justify an increase in the lifetimeof the containment, it is necessary to show that it would stillplay its role in an accidental situation. The various aging phe-nomena observed or envisaged are corrosion of the internalmetallic skin and the degradation of the concrete containment,by fissuring or corrosion of the reinforcements. CEA con-tributes via its R&D programmes to the improvement of knowl-edge regarding these subjects.

The aging of replaceable components

CEA does not carry out specific programmes on the aging ofall of the replaceable components from reactors. However,given their importance, some components are the subject ofspecial attention.This is the case of steam generator tubes,the rupture of which may have serious consequences. TheR&D programmes carried out at CEA concern non-destruc-tive testing methods applicable to these tubes, and the twomain aging mechanisms identified: corrosion under stress andwear and tear by friction due to flow-induced vibrations.

The vessel internal components are also the subject of spe-cial attention, with the study of the hardening of steels due toirradiation, and the corrosion under stress accelerated by irra-diation. R&D programmes on the subject result, in particular,in the irradiation of internal materials in fast neutron reactors.

The wear and tear of control clusters, cluster guides and con-trol mechanisms has been noted on the fleet, and is alsoclosely monitored. The mechanism identified is tribo-corro-sion, which associates wear and tear and passivation – depas-sivation cycle of the oxidized metal surfaces. This programmeassociating the physical chemistry and the mechanics mustlead to the understanding of these phenomena, their model-ling and the production of rules to evaluate the aging and thecontrol cluster replacement policy.

In conclusion, it is important to specify that the calculationmethods in solid mechanics, in particular in the field of frac-ture mechanics, have made such progress following the com-puter and digital revolution (finite element analysis) that we arecurrently better equipped to predict the detailed behaviour ofthe installation without having to resort to unfavourable sim-plistic hypotheses. If, at the present time, we find ourselvesable to foresee a longer component lifetime, it is largely dueto the modern techniques of digital computing.

Fig. 55. Vessel defect inspectionmachine.



Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors

Firstly let’s briefly recall the various generations of reactorssince the 50s:

The first generation of reactorsThe first generation of reactors was strongly influenced by fuelcycle constraints, particularly in the 50s and 60s, with theabsence of uranium enrichment industrial technology, and onthe other hand with the willingness of some nations to equipthemselves with a nuclear deterrence tool requiring the pro-duction of fissile materials. In this context, reactors had to beable to operate with natural uranium (non-enriched, requiringthe use of moderators such as graphite or heavy water*.Thisis why family of Natural Uranium Gas-Graphite reactors(GGR), was developed in France.Three reactors, intended forproducing plutonium (G1, G2 and G3) were created first, thensix others intended for generating electricity (Saint-Laurent14,Bugey15 and Chinon 16).

CEA was very strongly involved in the development of this sys-tem, in the capacity of process supplier. The Magnox typereactors in Great Britain belong to the same generation.Thesereactors presented interesting characteristics (thermodynamicefficiency, optimised use of uranium in the reactor core, etc.),but also limitations linked to the technology of these types ofreactors, in view of development on a much larger scale: highinvestment cost, difficulty in improving the safety and theextrapolation to a much higher capacity, which penalized theireconomic performances as compared to light water reactors.

This first phase saw a rise in concerns developed relating tothe fuel cycle, regarding both the rational and sustainable useof natural resources (recycling of energy materials, in particu-lar plutonium) and the question of waste management. Thisled to the development of processes and installations for theback-end of the fuel cycle: reprocessing of spent fuel, recy-cling of plutonium. From the beginning, France thus adoptedthe fuel cycle based on reprocessing-recycling, enabling onthe one hand a better use of resources, by recycling plutoniumin the reactors, and on the other hand, the reduction in the

quantity and the long-term harmfulness of final waste, condi-tioned in order to ensure safe and sustainable containment ofthe radionuclides. The first UP1 reprocessing plant inMarcoule, for the reprocessing of GGR fuels, was commis-sioned in 1958, followed by the UP1 plant in La Hague in 1966,itself equipped in 1976 with a new workshop (HAO) for thereprocessing of pressurized water reactor fuel. They are nowreplaced by the two UP3 (1989) and UP2-800 (1994) plants inLa Hague. MOX fuel manufacturing installations have likewisebeen developed and commissioned: CFCa Cadarache (1968-2003), Dessel in Belgium (MOX fuels produced from 1986)and Melox in Marcoule (1995).

The second generation of reactorsThe second generation of reactors which corresponds to themajority of the global fleet currently in operation originatedfrom the need to render nuclear energy more competitive andfrom the willingness to reduce the level of energy dependencyof certain countries at a time where a great deal of tension onthe fossil energy market was being felt. The production of fis-sile materials for defence purposes was no longer a priority,enriched uranium produced by gaseous diffusion was com-mercially available (Eurodif plant in France). This period wasthat of the deployment of water reactors, pressurized waterreactors PWR and boiling water reactors BWR, which consti-tute more than 85% of the current global electro-nuclear fleetof approximately 450 reactors.

Industrial feedback from the last few decades has enabledeconomical as well as environmental performances of the pro-duction of nuclear energy to be demonstrated, with a highlycompetitive cost of the nuclear kWh in relation to that of fossilenergies and a continuous reduction of waste and effluents,well below the authorized limits. The cumulated operation ofmore than 10,000 reactor-years proves the industrial maturityof this technology.

14. Municipality of Saint-Laurent-Nouan (Loir-et-Cher). Nuclear power sta-tion on the Loire (Note of the Editor).15. Municipality of Saint-Vulbas (Ain). [Note of the Editor.]16. Indre-et-Loire (Note of the Editor).


54 Preparing the replacement of current reactors with more efficient and safer 3rd generation reactors

The third generationThe third generation represents the most advanced con-structible industrial state-of-the-art. It involves reactors knownas “evolutionary”: They benefit from the feedback and theindustrial maturity of second generation water reactors, whilstintegrating the most advanced specifications in terms of safety,knowing that the second generation already shows a very highlevel of safety.

3rd generation reactors are the subject of a large internationaloffer. These reactors are already being constructed in partic-ular in Asia, but also in Finland and soon in France

The types of 3rd generation reactors

• Advanced water pressurized reactorsAP 600, AP 1000, APR1400, APWR+, EPR

• Advanced boiling water reactorsABWR II, ESBWR, HC-BWR, SWR-1000

• Advanced heavy water reactorsACR-700 (Advanced CANDU Reactor 700)

• Small and medium power integrated reactors CAREM, IMR, IRIS, SMART

• Modular high temperature gas reactorsGT-MHR, PBMR

0

10 000

20 000

30 000

40 000

50 000

60 000

70 000

1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060

Average fleet lifetime: 48 years

Inst

alle

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ower

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e)

Fig. 56. The renewal schedule of the French nuclear reactor fleet, ascurrently envisaged by EDF.The operator will without a doubt wish to extend the lifetime of theexisting reactors as much as reasonably and legally possible. It isplanned to start the replacement of one part of the fleet “in bevel” asof 2020 in order to smooth out the financial effort, firstly with third,then fourth generation reactors.

France is extensively equipped with nuclear power and its fleet ofreactors is relatively young.Yet, the construction of a demonstrationEPR has just been decided. Why is this step being taken now? Thedevelopment of a new system is a long-drawn-out operation: in orderto introduce third generation reactors in 2020, it is necessary toorder an EPR prototype now.

The schedule envisaged for the EPR deployment in France is asfollows:

2005 Decision for an EPR demonstrator 2003-6 Regulatory authorisation process and preparation

for construction2007-2011 Construction and commissioning of the EPR

demonstrator2012-2014 Acquisition of the operating feedback (minimum 3 years)2015 Decision to construct an EPR series (number and rate

to be defined)2020 Commissioning of the first reactor of the series2021... Commissioning of the following reactors

Current fleet40 years lifetime

Extension beyond40 years

Generation 4

Generation 3+

Renewal at 50,000 MW spread over 30 years (2020-2050)

Rate of nuclear construction: 1,667 MW/year



CEA is associated with the EPR*, pressurized water reactor,prototype studies which represent the fruit of approximately10 years of collaboration between Framatome and Siemens.The two industrialists designed a reactor which uses the bestof the technologies from French N4 and German KONVOIreactors.

Industrial issues The EPR meets two main objectives:

• To make nuclear energy more competitive in relation to fos-sil energies;

• To further strengthen the reactor safety.

• A technical lifetime of 60 years, compared to 40 years in gen-eral for current power plants. The reactor should be able tooperate for 40 years without important rejuvenating opera-tions;

• Reduced operating costs: increased availability approaching92% compared to 82% today, partly due to shorter shut-downs for reloading (in the order of 16 days) and to designchoices (simplified maintenance of components is made pos-sible during operation with the aid of the redundancy of safetycircuits), reduction of the collective radiation doses for themaintenance staff (0.5 compared to 1 m.Sv/year currently);

• An optimised construction time (approximately 57 months);

• Strengthened safety combinedwith a more forgiving systemregarding possible controlfaults, a significantly improvedin-depth defence regarding theresistance to possible seriousaccidents (core fusion). Thebenefits provided by thisstrengthened safety results inthe non-necessity of evacuatingpopulations, even in the eventof a serious accident.

R&D objectivesand challenges The EPR enables optimisedreactor operation managementand a higher degree of flexibility

of use of the fuel resulting directly in a better competitiveness.In terms of safety, an important effort has been carried out inorder to minimize the consequences of possible core meltingaccidents thus contributing to better public acceptance.Thesetwo topics relating to the fuel and the safety are still importantR&D challenges in order to improve the concept and make ityet more competitive. In the near future, CEA will mainly inter-vene in the field of physics and core management and in thefield of safety.

Core physics and EPR core management

EPR reactor cores are made of the same standard fuel ele-ments as pressurized water reactors.They mainly differ in size,a slightly lower fuel rating and a more economical fuel man-agement in fissile material.

Containment designedto resist a hydrogenexplosion

Water tank

Molten core (corium)retention device in the event of an accident

Heat evacuation system

4 independentareasfor the redundantsafety systems

Main characteristics of the EPRThe characteristics of the EPR, enacted by an omnipresentconcern to improve performances and economy, may be sum-marized as follows:• A net electrical capacity of approximately 1,600 MWe (com-

pared with 1,450 MWe of the N4), well-suited for regions withmany well-linked power grids.This increase in capacity down-scales the costs per KWh;

• An energy efficiency of approximately 36% (10% better thanreactors from the previous generation) mainly due toincrease in performances of steam generators and turbines;

• A possible use of various types of fuel (UOX* or MOX, oreven 100% MOX) thus allowing a flexible and more econom-ical management of resources and waste (15% reduction ofthe quantity of uranium needed to produce the same quan-tity of electricity);

Fig. 57. The EPR project: a pressurized water reactor design whichtakes into account a large amount of feedback from second genera-tion PWRs, with increased safety requirements.



CP1 – CP2 P4 – P’4 N4 EPR

Electric power 900 MW 1,300 MW 1,450 MW 1,600 MW

Core thermal power 2,785 MW 3,817 MW 4,250 MW 4,450 MW

Type of assembly 17*17 17*17 17*17 17*17

Number of fuel rodsper assembly 264 264 264 265

Fuel rod height (m) 4 4.3 4.3 4.6

Number of assemblies 157 193 205 241

Average linear power density (kW/m) 18.4 18.9 19.8 16.3

A heavy reflector, made of a steel plate surrounding the core,enables a better neutonic economy. Thus the core is morereactive and will require a lesser investment in fissile materialin order to produce the same quantity of energy.This gain alsoshows in cycle length.

The heavy reflector also enables a reduction of the highenergy neutron flux* on the vessel.This reduction of fluenceauthorizes as of today a vessel lifetime of 60 years.

An experimental as well as theoretical R&D programme isrequired to increase the accuracy of the industrial calculationschemas and save the maximum amount of fuel. In parallel,it is also necessary to further qualify the “neutron transport cal-culations” of the fluence on the vessel.

The large size of the EPR’s core requires three-dimensionalcalculation methods with local reconstruction of the power.They require a specific qualification from the neutronic pointof view (for the accurate evaluation of strong gradients of neu-tron flux in the fuel bundles), and from the thermal-hydraulicpoint of view (in order to correctly evaluate the local develop-ment of the moderation by the water which causes the neu-tron transient.

EPR fuel management modes

UOX managements

For UOX cores, the standard management mode projects astay time of the fuel in the reactor of 72 months, with renewalof a quarter of the fuel every 18 months, the final burnup ratebeing 60 GWd/t.

MOX management modes

The benchmark management modes for the use of MOX fuelare 50% MOX hybrid modes with renewal by a quarter of theUOX bundles and by a third of the MOX bundles. The lengthof the cycles is 18 months, the respective burnup rate reachedby these two types of fuels are 60 and 55 GWd/t.

The fuel management modes in the reactor are chosen tosave fuel, by guaranteeing reactor shutdown times as short aspossible, by assuring a long lifetime to the various reactor com-ponents, all this in compliance with safety rules. These man-agement modes therefore result in a complex optimisation, theresult of which narrowly depends on the characteristics andperformances of the fuel and the components of the core itself.The continuous improvement of these performances alreadyleads to innovative management modes being researched forthe EPR reactor.

Apart from the conventional studies carried out and necessaryfor the neutronic qualification of the desired burnup rate cal-culation schemas, which consist of:• Analysing the isotopic composition of the irradiated rods;• Evaluating by oscillation in the Minerve reactor the integral

cross sections in order to evaluate the uncertainty of the cal-culation schemas and to minimise it;

• Optimising and validating the neutronic calculation schemasfor these burnup rates;

The specific design of the EPR core requires a certain num-ber of additional qualification elements.

This core can accomodate various reflector concepts andexact evaluations of their influence are carried out there asmuch on the core’s neutronic properties, as on the fission dis-tributions in the core’s rods, in particular in the periphery. Inaddition, this programme must enable the measurement of theneutron flux and in particular fast neutrons beyond the core inorder to be able to validate the calculation of the vessel’s flu-ence.

Fig. 58. Positioning the UOX fuel bundles in theEPR core.

Heavyreflector

Water

Coreenvelope

WaterNew1 cycle2 cycles3 cycles



The fuel without PCI

A main objective is to eliminate the constraints due to the class2 “PCI” (pellet-clad interaction) by 2010. Candidate productsexist (in particular the UOX fuel doped with chromium).Threestudy points were retained:

• The implementation of irradiation tests in more demandingtransient operating conditions (power transients simulatingthe load monitoring) for the qualification of the fuel;

• The 3D fine modelling aiming to obtain a better understand-ing of the PCI phenomenon. A relevant physical modellingmust enable the evaluation of the damage leading to thecladding’s loss of integrity, the impact of the design’s devel-opments, and the impact of the operating and transient his-tory;

• The “1.5D” “industrial” modelling copied both on the tests andon the above calculations.

The EPR’s safety

The evaluation of the consequences of a serious accident onthe EPR is placed within the framework of the in-depthdefence safety procedure and the joint recommendationsissued by the French and German Safety Authorities publishedin 1993. The procedure established as of the design studiesaccording to a deterministic method complemented by prob-abilistic studies targeted the following objectives:

• Elimination in practice of the accidental conditions which maylead to important discharges of fission products in the short-term;

• Elimination of the need to displace the population in seriousaccident situations, without the emergency evacuation of theclose neighbourhood and without long-term restriction for theconsumption of food products.

In serious accident situations on the EPR, the abovemen-tioned objectives may be obtained using a strategy enablingthe integrity of the containment to be assured. The strategymainly relies on the possibility of reliably depressurizing theprimary circuit, on the establishment of hydrogen recombin-ers in the containment, on the installation of a double-wall con-tainment with filtration in order to reduce the risks of radiationleakage and finally on the design of a corium catcher respon-sible for assuring stabilisation of the corium over the long term.

To study the accidents which must inevitably be taken intoaccount with the new core managements and new fuels (forexample, rupture of steam piping system) thermal-hydraulic-neutronic-fuel coupled calculations are necessary.These stud-ies are carried out with the current calculation codes, Cathareand Flica for the thermal-hydraulics, Meteor for the fuel andCronos for the neutronics. For the future (by 2010), theseanalyses will be conducted more easily with the calculationtools in process of co-development by CEA and its industrialpartners: Neptune for the thermal-hydraulics, Descartes for theneutronics and Pléiades for the fuel, tools integrated into aunique software platform.

Fig. 59. Over the past approximately twenty years, CEA, EDF,IRSN 17 and Framatome-ANP 18 have developed the Cathare acci-dental thermal-hydraulics code. This tool enables any type of acci-dent that may occur on light water reactors to be simulated. Moreparticularly, the Cathare code presents a wide validation field forPWR accidents; it is used intensively in France by industrialists andthe Safety Authority for all of the case studies relating to the safetyand control of reactors. With reference to the development of theEPR, the code was used as a benchmark tool for the design and foraccident studies.

17. Institute for nuclear radioprotection and safety (Note of the Editor).18. Framatome ANP stems from merging of the nuclear activities ofFramatome and Siemens. Framatome ANP has built more than 90 reac-tors, more than one third of the world’s nuclear capacity (Note of theEditor).

For the EPR, primary coolant loss accidents of the large breaktype (APRP-GB) are in principle excluded by design; indeed,leak detection devices on the primary piping enable them to beavoided.

In serious accident situations with important degradation ofthe reactor’s core, the mixture of molten materials (corium)would eventually attack the bottom of the vessels and couldpierce the wall. In order to collect and stabilize the corium overthe long-term, a “spreading” type of retention device has been



planned underneath the vessel (Figure opposite).This coriumcatcher system is an innovation with respect to current reac-tors. It should be noted that numerous studies in the fields ofhigh temperature metallurgy, physical chemistry of materialsand rheology* were conducted in France and Germany inorder to design and test the EPR’s retention device.

Fig. 60. Framatome ANP has designed a corium catcher outside ofthe vessel based on a concept of spreading over a large surfacearea with long-term cooling and stabilization of the corium. Theretention device is located in a dedicated compartment in the con-tainment so as not to sustain important stress during the vessel’srupture. This compartment is separated from the reactor pit by a melt

door. In order to deal with the long-term situation, it is necessary tobe able to evacuate the residual power (in the order of 35 MW) for acorium mass of approximately 200 tonnes. The cooling efficiency - inthe upper part thanks to the corium flooding, and in the lower partthanks to the metal cooling structure - will enable all of the corium tobe stabilized within a few hours and solidified within a few days.

-7.80m

Sacrificial material

Sacrificial material

Spreading compartment

Protective layer:

Melt plugMelt dischargechannel

Basemat cooling Zirconia layer

The EPR’s corium catcher



Research regarding waste management

Whereas large volumes of short lived radioactive wasteare currently managed industrially in surface disposal sites,the long-term management of long-lived high level radioactivewaste is the subject of important research in the countries gen-erating nuclear electricity in significant quantities, such asFrance, Japan and the United States. What should be donewith this waste has remained a conflicting question for manyyears. Yet, scientific knowledge is advancing and technicalsolutions are taking shape. Nevertheless, science and tech-nology largely interfere with the social dimensions of the prob-lem posed. People’s fears remain strong and difficult toappease, especially when the danger persists on time scaleswhich defy common comprehension. In addition, the geopolit-ical context, the energy crisis which has followed and the fearsof consequences of climate warming open ideological debatesregarding the energy choices to be made and the very natureof the economic development to be privileged for a sustain-able exploitation of the planet’s resources. Nuclear energy andradioactive waste management play a large part in thesedebates.

What is the future for this long lived radioactive waste? InFrance, the Bataille Act, voted in 1991, clearly posed this ques-tion to the scientific community by requiring that all options beexamined, and by proposing several research avenues.

What are the results of these effortsand what prospects do they offer? The orientations of this research are mainly concerned withreducing the volume and dangerousness of the waste by sort-ing and recycling. These are the same principles as thoseretained for the management of other household and industrialwaste. They have been implemented for several decades withthe industrial reprocessing of spent fuel in La Hague, whichenables energy materials that can be upgraded, such as pluto-nium and uranium to be recycled.Can we do better? This is thequestion posed to scientists.

The radioactivity of waste, which for some may persist for longperiods, requires the use of effective containment systems aslong as the danger subsists. The cost of these diverse meas-ures, evaluated by the yardstick of their effectiveness, will ofcourse have a decisive impact with regard to decisions and tothe schedule which will be implemented resulting from the law.

Several lessons are currentlyconfirmed• The very nature of final radioactive waste, which cannot be

recycled or reused, depends on the available technology: thefinal waste in 30 years may differ from that produced today.Thus B and C (glass) waste, already produced, is final wastefor our generation. Eventually, it will without a doubt be pos-sible to further reduce the radiotoxicity* of vitrified C wasteby eliminating some of the radionuclides (minor actinides)that it still contains today. This is the subject of the researchon enhanced partitioning and transmutation.The eliminationof these radionuclides would also reduce their thermal power.Nevertheless it will be necessary to be able to make themdisappear by transmutation if a net gain in the radiotoxicinventory is to be produced. Prior to becoming an industrialpractice, these technologies require complementaryresearch and development in order to enable their integra-tion into a viable economic contex;

• A permanent host location must also be found for the finalwaste. Deep geological disposal seems to be the only verylong-term management solution where the safety measuresdo not require continuous control by the society. An interna-tional consensus was established on this question, agreedon by the International Atomic Energy Agency (IAEA), theNuclear Energy Agency (NEA) or the Organisation forEconomic Co-operation and Development (OECD). No otherequivalent solution has appeared, neither in France, nor else-where in the world;

• A geological disposal facility will always be a rare, thereforeexpensive, resource. It should be used as effectively as pos-sible, by further reducing the volume and the thermal powerof the final waste which will be stored, two parameters whichlargely condition its capacity, therefore its utilisation period,and its cost. The reprocessing of spent fuel, practiced inFrance, is already going in this direction because it enablesthe extraction of uranium representing more than 90% of itsmass, and the recycling of plutonium, the highest contributorto its overall radiotoxicity;

• Therefore, the American AFCI (Advanced Fuel CycleInitiative) initiative is exemplary. After twenty years of effortsleading to the decision of creating the spent fuel disposal siteof Yucca Mountain, the Americans are now considering theoptimization of its usage, and therefore the very nature of theobjects which will be placed there;


60 Research regarding waste management

• In addition, waste conditioning studies will be continued byresearching an even better containment and a volumereduced as much as possible. The space thus saved in thedisposal site will help to make the industrial practice ofincreased spent fuel reprocessing profitable;

uncertainties associated with long timescales.This option willonly be practicable when we have the ability to separate andtransmute radionuclides.

Enhanced partitioning: what are theconsequences regarding long-termwaste management?The issue of enhanced partitioning, that is the additionalextraction of radionuclides other than plutonium and uranium,is the reduction of the radiotoxicity of the future high-levelwaste.

Figures 63 and 64 illustrate the decrease in radiotoxicity ofUOX spent fuel as a function of time, as well as the relativecontribution of each category of radionuclide to the overallradiotoxicity.

Fig. 61. The underground laboratory operated in Bure by the FrenchNational Radioactive Waste Management Agency (ANDRA).

• The safety of the disposal site relies on its capacity to con-tain radionuclides in geological formation until their radioac-tivity has sufficiently decayed. Finally, the demonstration ofthe safety of a disposal site will rely on the firm conviction ofthe correct operation of the installation. Studies must be pur-sued in order to better understand the evolution of the wastepackages in disposal situations over time and the migrationof radionuclides into the geosphere. Eventually, removingfrom the vitrified waste packages the long lived radionuclideswhich contribute the most to their long-term radioactivity, willsignificantly reduce the time during which they remain dan-gerous and will also have the effect of reducing the scientific

1 10 100 1 000 10 000 100 000 1 000 0000

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Fig. 62.The concept of the underground disposal site at YuccaMountain (Nevada), developed by the United States Department of Energy.

Fig. 63. Radiotoxicity of spent fuel.

Fig. 64. Distribution of contributions to the spent fuel radiotoxicity.

Time in years

Time in years

108 Sv / tonne

108 Sv / tonne

U

Other

Other

Pu

Pu

AmNp

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PF

U

North portal

Main tunnel(ESF)

Crest

Storagegallery

EmplacementDrift

Drip shieldWaste package

South portal


Also the final purpose of the partitioning should be specified,that is the method of eliminating partitioned radionuclides.Which radioelements should be partitioned and which parti-tioning modalities should be retained: should radioelementsbe partitioned separately or as a group? Which purity andwhich chemical form must be given to the partitioned elementsin order to meet the constraints of the following stages leadingto their recycling and/or their permanent elimination? Whatconsequences can be expected on the design of the geolog-ical repository site, its cost and its long-term containment per-formances? The answers to these questions are of courselinked to the future of partitioned elements.The last stages ofdevelopment may include an industrial process pre-controlphase.

Apart from minor actinides, partitioning studies have con-cerned a selection of FPs (iodine, technetium and caesium).Some FPs, which are much less radiotoxic than MAs, showparticular mobility in the geosphere. Their lifetime, very long

for some, such as isotope 129 of iodine,may pose the threat of a return to thebiosphere in the very long term.However, the potential damage of theselow radioactive radionuclides is verylow, which currently authorizes the dis-charging of iodine into the sea.ALARA* type criteria should guidefuture decisions regarding the matter.

Enhanced partitioning must thereforemainly concern minor actinides in orderto reduce the radiotoxic source term.

Beyond aqueous method processes,studies of processes based on pyro-chemical techniques must be compre-

hensively pursued. The latter effectively present a potentialadvantage in terms of compactness. Partitioning is obtainedin one pass and may concern highly radioactive spent fuel.These characteristics make up a technique which, if theseadvantages were confirmed in regard to the disadvantages(corrosion, partitioning efficiency, etc.) and if it reached anindustrial development stage, could take its place in an inte-grated cycle on the reactor site, thus avoiding the transporta-tion of radioactive materials over long distances. However, itis advisable to pay close attention to the secondary waste,salts and technological waste, which may result.The combina-tion of pyrochemical and hydrometallurgical processes mayalso be envisaged.


Plutonium* contributes approximately 50% of the initialradiotoxicity and 90% one hundred years later.Thus, as soonas the spent fuel has been processed, that is, the plutonium(with uranium) that it contains has been extracted, the resid-ual radiotoxicity remains dominated by that of the fission prod-ucts (FPs) and of curium over approximately one hundredyears and, over a longer time frame, by that of other minoractinides (MAs) (americium and neptunium).

The FPs and MAs are currently all incorporated into vitrifiedwaste resulting from the reprocessing of spent fuel. A follow-ing stage would therefore consist of only including FPs infuture C waste.

The figure 65 shows the comparison of the decrease inradiotoxicity of the materials respectively contained in a spentfuel assembly, in a vitrified package produced today (MAs andFPs) and in a vitrified package from which the minor actinideswould have been eliminated (thus only containing FPs).

10,000

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100 1,000 10,000 100,000 1 000,000

Enhanced partitioning studies19 currently concern the minoractinides americium, curium and neptunium. For the hydromet-allurgical method, they are at the technical demonstrationstage and already deal with a significant quantity of spent fuel(approximately 15 kg placed in solution). The process stepsretained for the enhanced partitioning are largely based onindustrial knowledge regarding the Purex process used in LaHague. A first technical and economical evaluation of anenhanced partitioning workshop will provide clarification onthe technical modalities and economical conditions of use ofsuch a process.

This technical demonstration alone will, however, not be suffi-cient to enable the industrial application of the process.

Fig. 65. Decrease in the relative radiotoxicity as a function of time.(The radiotoxicity of the glass or spent fuel is estimated here in relation to that of the uranium which produced it.)

19. See infra, p. 67, the chapter entitled “The fuel cycle of future nuclearsystems”.



The transmutation of partitionedelements: future cyclesTransmutation is the operation by which highly radiotoxicradioelements are transformed into other elements withreduced or zero radiotoxicity.

The research carried out for more than 10 years providesnumerous clarifications and in effect confirms the possibility ofreducing the radiotoxic inventory present in spent fuel. But thiscan only take place at the cost of important technological andfinancial efforts, concerning all of the nuclear fuel cycle plantsand reactors, if a significant net gain in the radiotoxic inven-tory is to be recorded.

How useful would it be to transmute MAs if the disposal facil-ity reaches its currently calculated containment performances?Transmutation, in such a context, could appear as an addi-tional measure of safety in the eventuality of a premature lossof the disposal site’s containment.

Transmutation, implemented in this way, will lead to final wastewhich it will be necessary to dispose of. All elements are noteasy to transmute and the multiple recycling of plutonium andminor actinides, according to the scenario envisaged, couldlead to the production of increased quantities in minoractinides, of which in particular, curium. This highly radioac-tive and very hot element poses management problems whichremain yet to be solved.

The potential of various reactor systems for transmutation hasbeen studied. It emerges that only the fast spectrum reactors,or systems combining a sub-critical* core reactor with anaccelerator (ADS, Accelerator Driven System* 20) wouldenable transmutation efficiency to be obtained creating a realdifference in radiotoxic inventory. Nevertheless, transmutationremains a very complex and certainly expensive operation,which cannot be applied to all radionuclides.

Major technological questions are posed.Their resolution mayonly be envisaged in the context of the sustainable develop-ment of nuclear energy and the development of new nuclearenergy production systems of the fourth generation.

These questions concern all of the stages of future cycles:

• Which fuel and which waste reprocessing and recyclingprocesses to use?

• What types of reactors? To date, it is admitted that a fast neu-tron reactor is the most performant tool for obtaining thetransmutations of the elements envisaged.

• What is the economic impact for the entire cycle?

The Generation IV fast reactor route would enable the gener-ation of electric energy and a better use of the natural resource“uranium” in the future by converting uranium 238 into a fissileelement, via neutron capture.

An ADS, dedicated to transmutation and generating no elec-tricity, would be a more expensive and even more complexmachine because it involves the coupling and the stable andreliable operation of two sophisticated components: a highintensity accelerator and a sub-critical reactor core.

The time scale for implementing these new systems could bebetween approximately 30 and 40 years according to themeans that are attributed to them.

The continuation of transmutation studies will be carried outusing experimental irradiations of various materials in fastreactor cores (Phénix* reactor), and on progressively increas-ing quantities. It is on the international level that they mayprogress the best by sharing experimental means, in France,Japan and Russia.

The studies of scenarios will enable the best possible techno-logical combinations to be identified in view of optimizing mate-rial inventories.

Processes for the partitioning of radionuclides

Plutonium recycling is already an important stage for reducingthe radiotoxicity of spent fuel.

Beyond that, removing minor actinides from vitrified waste pro-duced today would enable their radiotoxicity and their thermalpower to be further reduced. The recovery of minor actinidesmay be a step toward their elimination by transmutation. Theconsequences on all of the steps of the fuel cycle must becarefully evaluated.

Hydrometallurgical processes may be preferred, becausethey are better known. However, the potential of pyrochemi-cal processes must continue to be examined.

Nevertheless the question remains of knowing at whichmoment to begin the enhanced partitioning method, in coordi-nation with the opening of reactor transmutation possibilities.Finally the net radiotoxic inventory which would result fromimplementing enhanced partitioning must be established.The economy of the process must also be specified in anALARA context.

20. See infra, p. 95, the chapter entitled: “Other avenues for the distantfuture: thorium cycle, hybrid systems, fusion”.



The conditioning of waste and the long-term behaviour of the packagesThe conditioning of B and C radioactive waste, originating fromthe reprocessing of spent fuel, has been carried out continu-ously according to the industrial standards approved by theSafety Authority, since the commissioning of the UP3 facilityin La Hague. It gives the waste a physical and chemical stabil-ity which prevents its dispersion into the environment. At theend of the chain, it leads to the production of packagesenabling the waste to be easily handled.

Three types of waste packages are currently standardized:

• Standard vitrified waste packages (SVWP) contain the quasi-totality of the initial radioactivity of spent fuel.They are char-

acterised by the emission of a thermalpower in the order of two kilowatts onthe date of their production;

• Standard compacted waste packages(SCWP) contain long lived intermedi-ate level waste. It mainly concernsmetallic elements of the structure ofspent fuel bundles (tubes, braces,grids);

• Long lived intermediate level techno-logical waste packages, cementedbecause not compactable, represent-ing only 0.1% of the initial activity.

The transmutation of minor actinides

The transmutation of minor actinides could enable the reduc-tion of the radiotoxicity of radioactive waste produced as of theadvent of 4th generation fast reactors, around 2030 to 2040.

Prior to their implementation, many technological deadlocksmust be removed regarding their design, their fuel (type andmanufacturing and reprocessing technologies), their nuclearmaterials inventory (recycling of radiotoxic materials), theirsafety and their economy.

Fast reactors would enable the use of large stocks of depletedand/or reprocessed uranium, thus conserving the naturalresource.

There are even more technological deadlocks to be removedfor the ADS.

Fig. 66. The Phénix fast reactor on the Marcoule site (Gard).

Fig. 67. Standard vitrified waste container (SVWC).

Fig. 68. Standard compactedwaste container (SCWC).

Fig. 69. Bitumined waste package.

Fig. 70. Technological wastepackage.



The oldest C waste, originating from the industrial cycle orfrom research, was, either stored whilst awaiting its vitrifica-tion, or already packaged in glass; B waste was transformedin forms different from current standards, in cement or bitumi-nous packaging matrices.

For most of this old waste, producers have already specifiedthe benchmark strategies that they intend to follow in order tocondition them. R&D actions are carried out on the benchmarkconditioning. This is for example the case of STE3 sludges inLa Hague, for which COGEMA plans to use a bituminouspackaging, suitable for the specificities of these sludges.

For existing packages industrially produced according to cur-rent standards, the research aims above all to evaluate theirdurability, or more generally their long-term behaviour, in stor-age and then disposal conditions.The results of these studiesthus contribute to the evaluation of the long-term containmentperformances of radioactive waste management modes, andtherefore the safety of the latter.

The quality of the conditioning carried out contributes to delay-ing the moment from which radionuclides start to migrate outof the package. Behaviour studies are thus interested in all ofthe packages and most particularly in vitrified waste packages.

The durability of vitrified waste packages has been studied forover twenty years. It will continue to retain attention becausethis package contains the highest radioactive inventory. Glassis currently the most durable material (matrix) used industri-ally in order to host and immobilize a large inventory of highlyradioactive radionuclides. Its behaviour over a few hundredsof years in storage conditions poses no problems. Over amuch longer term and in geological disposal conditions, stud-ies have already enabled the mechanisms and kinetics of

alteration in question to be identified. Studies still in progressaim to better determine the moment from which radionuclidesmay start to disperse outside of the package into the rock ofthe geological formation, then into the geosphere, to thenreach the biosphere.

While the French strategy consists of reprocessing spent fuel,studies on the long-term behaviour of spent fuel have never-theless been carried out in the hypothesis of long-term storageor even geological disposal. According to the decisions whichwill be taken at the end of the 15 year-period prescribed bythe French law, these studies could be stopped or redirectedto very specific aspects.

The research on the conditioning and long-term behaviour ofwaste packages must be continued in order to accompanytechnological developments, as for example the increase inthe burnup rate of spent fuel envisaged by EDF, which willresult in modifications of the type and quantity of radionuclideswhich are found in vitrified waste.

Finally, new conditioning matrices have been studied in orderto contain over long periods elements that are difficult to trans-mute and/or elements that are particularly mobile in geologi-cal disposal conditions. It will be advisable to evaluate the rel-evance of their implementation regarding the particular riskthat they may help to reduce and the overall cost that thisimplementation could represent. Nothing to date lets presumethat such an option must in principle be retained.

Fig. 71. Glass casting in the laboratory atMarcoule (Gard).

Fig. 72. Simplified diagram of the microstructure of spent fuel and thelocation of the various radionuclides.

Grain boundaries+ Mo, Tc, Ru, Rh, Pd

FracturesGapCladding-pellet gap

Inter-pellet gap

Closed porosity

Matrix

Zr cladding

ActinidesFission products (98 %)

14 C93 Zr36 Cl

14 C129 I135 Cs137 Cs79 Se99 Tc90 Sr36 Cl



Storage: a pending solutionThe most radiotoxic types of radioactive waste, B and C, areall stored to date in industrial installations operated by wasteproducers pending a final destination.

These installations operate without particular difficulties andtheir projected lifetime is approximately fifty years, with possi-ble extensions beyond this limit.

The studies on long-term storage, carried out within the frame-work of the 1991 act, have identified factors limiting the life-time of such installations, in particular the alteration of con-crete and the corrosion of metals. The risk of neglect by thesociety remains the intrinsic weakness of such an installationthe safety of which, medium and long-term, relies on continu-ous monitoring and maintenance, and on the possibility of

accessing information at any moment regarding the packageswhich are stored there.

In future, the studies will concern rather the way of best mas-tering the durability of the concrete and materials used in thestorage installations.

If in 2006 the decision was made to engage means in view ofthe creation of a geological repository site, it would then beadvisable to optimise the thermal management of the thermo-geneous packages, which put a strain on the cost of such aninstallation. It will be necessary to accurately evaluate conse-quences of a prolonged storage of these packages, enablingtheir cooling in economical conditions, prior to their permanentdisposal and to then determine the temperature acceptable bythe host rock, once the site is known.

Finally, according to the actinide partitioning modalities whichcould be envisaged, it would be advisable to continue the stud-ies on the storage of grouped or partitioned radioactive mate-rials, for example in the case of curium, in order to assess itsfeasibility and to evaluate its consequences on the fuel cycle.

Fig. 73. Upper part of the storage wells of the CASCAD installation inCadarache (Bouches-du-Rhône).

The containment of the radioactive materials

The conditioning of waste consists in the production of pack-ages which assure the containment of the radioactive materi-als and makes their handling possible.

The research on conditioning and the long-term behaviour ofwaste packages remains open, in order to accompany thetechnological developments in progress (increase in burnuprates, etc.) or the decisions expected by the Bataille act dead-line in 2006.

The relevance of using conditioning specific to a given elementmust be evaluated.

Studies on the long-term behaviour of packages, in particularof glass packages in disposal situation, must be continued inorder to confirm the demonstration of safety of geological dis-posal.

-40 m

31 m

Room 2Room 3

Model pit for spentfuel storage

8,3 m

6 m

8 m

Fig. 74. Galatée: a demonstration gallery of sub-surface storage suit-able for the long-term, recently constructed on the CEA’s Marcoulesite.This 40 metre long structure, with 8 m by 8 m cross-section,shows the components of such a warehouse and the logistics of con-tainer handling. It will be used for thermal experiments in view of thevalidation of the behaviour models and codes of a concrete structuresubjected to operating hazards, such as the loss of cooling.

Fig. 75. The Galatée facility viewed from outside.



Fig. 76. The Galatée facility viewed from inside.

The storage

Storage is the management mode which makes it possible toawait the arranging of an outlet for the final waste.

The durability of the concrete and materials used in the ware-houses, which limits their lifetime, may be the subject of com-plementary studies.

The heat released by some packages puts a strain on the costof the disposal site. The optimisation of the thermal manage-ment of these packages, is therefore to be undertaken as soonas the disposal site is known.

The issues and the feasibility of the storage of materials orig-inating from an enhanced reprocessing of spent fuel must beevaluated.



The fuel cycle of future nuclear systems

The design of the processes involved in the fuel cycle relieson two main determining elements: firstly the choice of a mat-ter management strategy (which must evidently be consis-tent with the capacity of the fleet of reactors to use this matterefficiently), and then the fuel object itself (its type, its compo-sition, its morphology): fuel is the backbone of the cycle and itschoice is closely linked to that of processes, involved in its fab-rication and processing.

Reflections carried out on 4th generation systems are currentlystill very plentiful, as much for reactors as for their fuels, forwhich highly diverse configurations may be envisaged: oxides,carbides, nitrides, in the form of pins, particles, filaments, oreven molten actinide salts. Such a profusion is at this stageabsolutely normal, and even fortunate, but does not enableexact orientations to be made for the processes to be imple-mented; it will actually be the cycle studies associated witheach of these concepts which may and must help decide onthe choices in terms of fuel.

On the other hand, concerning the matter management strat-egy, a few main orientation elements are already emergingfrom the reflections of the last few years on the internationallevel, in particular within the framework of the “Generation IV”Forum. The main expectations and conclusions which seemto come out at this stage regarding the research directions tobe privileged (also raising numerous questions, which cur-rently remain open) are summarized below.

Which material managementstrategy?The criteria which frame the reflection are those which areessential for nuclear systems of the future: sustainability, eco-nomic efficiency, safety, are the three main aspects by the yard-stick of which the forum community has chosen to evaluate thevarious concepts that can be envisaged. Even though the fuelcycle must consider these three issues, the most importantone is certainly the issue of “sustainability”, whether it con-cerns the preservation of natural resources, the minimisationof the environmental impact or the resistance regarding therisks of proliferation.

This becomes quite apparent when reading the graphs inFigure 77, presented during the forum’s work. These graphsindicate for various scenarios (open cycle and water reactors,

or closed cycles with deployment of fast neutron reactors), theevolution of the quantities of residual heavy nuclei on the onehand (which is an indicator of resources called into the dis-posal site), and the natural uranium requirements on the otherhand. It is established in an obvious way that the mostenhanced recycling options are the most effective regardingthe various components of the sustainability criterion:

• The upgrading of the energy potential of uranium 238 andthe multiple-recycling of plutonium in fast neutron reactors isof course the key factor for the preservation of resources21;

• The recycling of plutonium and minor actinides essentiallycontributes to minimizing the residual inventory in fissilenuclei, the potential noxiousness of waste and also its long-term thermogenous character.

The first and main central idea for the cycle thus emerges fromthese reports: sustainable nuclear-power seems to require arecurrent and enhanced recycling of actinides. However, the

21. For an explanation of the capacity of fast reactor for efficiently con-suming fertile materials such as uranium 238 and therefore for using theheavy metal resources, as well as possible, see infra p. 75, the chapterentitled: “On the origin of species (of reactors): systems and generations”.

2000 2020 2040

0

100

200

300

400

500

600

700

2060 2080 2100

Worldwide spent fuel

Hea

vy m

etal

mas

s (t

hous

and

tonn

es)

LWR + fast reactor

Year

LWR once through

Fig. 77a et 77 b. Prospective elements.Water reactors rapidly consume fissile resources and accumulateactinides. Fast reactors do not present these defects.


68 The fuel cycle of future nuclear systems

options remain open regarding recycling scenarios, regardingthe boundaries of all of the elements to be considered amongthe transplutonium elements (according to their inventory, theirproperties, their impact, the difficulties that their recycling mayentail); but the general outline seems clearly traced and leadsto the block diagram in Figure 78.

• The importance of retaining compact technologies, in orderto reduce investment costs; this aspect becomes importantif one choses decentralized processing options, with repro-cessing and recycling on the same sites as the reactors.These options avoid the transportation of large quantities ofspent fuel but lead to an increased number of plants withlower capacities;

• Finally, the necessity to favour implementation of “clean”technologies, that is minimising as much as is reasonablypossible the effluents discharged and the (secondary) tech-nological waste generated 22.

Which recycling processes? Again in this field, the reflection may seem plentiful; as indi-cated above, the choice of a cycle process depends on that ofa fuel, and it is obviously too soon to decide on precise options.But in order to orient or frame the reflections, a few generalideas mainly originating from industrial feedback or prospectsoffered by the advances in research may be brought up.

The selective recovery of actinides by use of their physicalproperties does not seem currently to be taking off as antici-pated in some respects. If indeed the objectives of a partition-ing of the actinides from all of the fission products is consid-ered, it in fact involves partitioning the heaviest nuclei from theothers: this evidence has however not given rise up to now tothe enhanced exploration of concepts based on “field effects”for spent fuel reprocessing processes.The aim of generalizedrecycling of all of the actinides may give fresh impetus to theresearch in this field, but the technological jump will most cer-tainly be significant.

Therfore, the current reflection is mainly centred around thepotential of “chemical” processes, usually distributed betweenhydrometallurgical (“aqueous” method) or pyrometallurgi-cal (“dry” method) processes.

The first have to their credit impressive industrial feedback:They make use of a mature technology. As shown by theresults obtained with the PUREX process implemented in the

2000

0

10

20

30

40

50

2020 2040 2060 2080 2100

LWR once through

Speculative resources

Knownresources

Worldwide uranium resource utilization

Fig. 77 b. Prospective elements. The worlwide utilization of uraniumresources depends on the type of reactors and fuel cycle, and onwhen they are put into use.

Fig. 78. Block diagram of the fast reactor cycle.

Fast reactorsintroduced2050

Fast reactors introduced 2030

Year

Cu

mu

lativ

e n

atu

ral U

(mill

ions

tonn

es)

This first point being defined, other orientations then emergefrom the reflections carried out. Perhaps less obvious or lessunanimous, they seem to say a lot about the questions posed:

• The importance of a grouped management of recycledactinides, which avoids the recovery of isolated fissile iso-topes.This seems to make the recycling process more resist-ant to proliferation (by reducing both the “strategic value” ofthe materials for the applications concerned, and their“accessibility” thanks to the presence of highly radioactivenuclei).This also goes in the direction of improved economicefficiency, by simplifying the matter management processes;

Uranium

Actinides

Reactor(s)

Processing

PF

22. Here we are mainly interested in the management of materials origi-nating from a uranium fuel cycle. The hypothesis of deploying systemsbringing thorium into play has been approached during expert meetingswithin the framework of the “Generation IV” forum: in spite of the poten-tial interests of such systems in some respects (abundance of naturalresources, lower generation of radiotoxic heavy nuclei), those do not seemto be put forward for the next generation of reactors (with the exception ofthe options studied of molten salt reactors, for which thermal spectrumbreeding with thorium 232 can be envisaged); this essentially relies onthe sustainability of the uranium resources in the hypothesis of an upgrad-ing of uranium 238, on the privileged options of recycling all of the heavynuclei, which reduce the question of the long-term radiotoxicity of theresidues, and also on the impact of the accumulated experience regard-ing the uranium system.



La Hague plant, hydrometallurgical processes procure veryhigh partitioning performances (recovery rate and purificationfactor of recycled materials) whilst resulting in a low flux of gen-erated technological waste.

In addition, they appear to offer a large potential to adapt (tofuel characteristics, but also to recycling specifications, asshown in the studies recently carried out on the complemen-tary partitioning of minor actinides).They also display undeni-able residual progress margins (in particular for increasingcompactness, thus reducing the cost of their implementation).They therefore seem to be the benchmark method for thedevelopment of “advanced” cycle concepts for the fourth gen-eration of reactors.

Pyrometallurgical processes are currently presented as themain alternative to “aqueous” processes, and are the subjectof a renewed development effort on the international level.Thegeneric principle of such processes consists of placing ele-ments to be partitioned in solution in a bath of molten salts(chlorides, fluorides, etc.) at high temperatures (in the order ofseveral hundreds of degrees Celsius), and then of operatingthe partitioning of the species of interest via diverse techniquessuch as extraction via molten metals, electrolysis, or selectiveprecipitation.The interest of this type of process mainly residesin the high solubilisation potential of ionic liquids (in order todissolve refractory compounds), in the low radiosensitivity ofthe inorganic salts used (which would enable the “on-line”reprocessing of fuels to be envisaged as of their unloading), intheir compactness (few successive transformation stages canlead to a recyclable product), as well as in the best aptitudespresumed for a joint management of the actinides. It is pre-sented moreover as the unavoidable, “natural” process, ofonline reprocessing of liquid fuels from molten salt reactors.

The Argonne 23 (see Figure 79) and Dimitrovgrad teams havecarried out important developments on such concepts, respec-tively for the reprocessing of metallic or oxide fuels, up to thecreation of pilot installations on which demonstration cam-paigns have been carried out. However at this stage stronguncertainties remain, the most noticeable concerning the levelof partitioning performances (in particular the actinide recov-ery rate) and the implementation on an industrial scale of thetechnology (secondary waste generated, particularly given theaggressiveness of the operating environments and condi-tions).

+ – –

Cadmium

Noble metals

Activemetals

Molten salt

Rare earths

Cadmiumliquid

cathode Solid

cathodeSpent fuel

U Pu

23. Argonne National Laboratory. This American research body is super-vized by the university of Chicago, for the department of the Energy of theUSA (DOE).

Fig. 79. The Argonne pyrochemical an process consists of electroly-sis in molten salt medium, with partitioning of the elements on thevarious components of the electrolyser.

Which lines of action for research?Apart from highly diverse exploratory research, which may becarried out on concepts radically removed from the existingones, a few large research avenues are taking shape relatingto the two main previously mentioned concepts.

Concerning the hydrometallurgical processes, efforts areorientated towards the following points:

• Firstly, adapting the current process to the characteris-tics of new fuels: this will mainly concern the dissolution ofthe fuel. The reagents and conventional dissolution condi-tions may prove to be unsuitable for certain “advanced” com-pounds. Earlier work carried out on uranium, carbide ornitride show however that for such compounds, a quantitativedissolution is accessible by using the conventional reagentof the Purex process (nitric acid), and that only minor adjust-ments are to be researched in order to optimize the operat-ing conditions;

• The second point resides in the adjustment of theprocesses in order to enable a grouped management ofthe actinides: it involves researching the means of extract-ing all of the actinides (major and minor) from the dissolutionsolution in order to then develop the compound to be recy-cled; this includes the development of molecular architec-tures and appropriate process diagrams, in the continuationof the work carried out during the last decade on “enhancedpartitioning” processes; the outline of such a concept, calledGANEX, has recently been proposed by CEA (see Figure80): in a preliminary stage, it is proposed to extract, the mainpart of the uranium contained in the spent fuel, then, in a sec-


70 The fuel cycle of future nuclear systems

ond stage, to partition jointly the plutonium and minoractinides (neptunium, americium, curium) by implementingan adapted version of the DIAMEX-SANEX process devel-oped within the framework of the studies carried out pursuantto line 1 of the December 1991 law; an effort to integrate therecovery and remanufacturing operations for this groupedmanagement of actinides to be recycled seems to be, in thesame order of ideas, an orientation to retain;

• An important objective also resides in the development ofthe formulation of extracting agents, in order to increasetheir resistance regarding radiolysis phenomena; thiswould offer the possibility of reprocessing barely “cooled” fuel;

• Finally, the technologies and their implementation con-stitute a determining research avenue to increase the com-pactness of the processes, whether they concern single tech-nologies (where remarkable progress margins have alreadybeen obtained with the development of liquid/low stay timeliquid contactors) or their integration (advances in the field ofonline control seem to be important factors for the simplifica-tion of industrial workshop architecture).

metals for the main part). Encouraged by the potential advan-tages of these concepts, exploratory studies, laboratory stud-ies and technological developments have currently been initi-ated or revived by various research teams. The results whichwill be produced in the next few years will be essential in orderto best identify their potential, best apprehend the difficultpoints and to orient the following phases of their development.There is still a long way to go before reaching the technicaland industrial maturity of such processes.

Independently from the process implemented, the strategicorientations retained for fuels of the future raise a certain num-ber of questions, the relevance and intensity of which willdepend finally on the options which will be fixed, but whichalready have to be considered at this stage. Below, non-exhaustively, a few examples:

• The concern for a “close” retention of fission products in reac-tor fuel, which leads to cladding or elaborated encapsulationdevices being envisaged (particle fuels for example) maymodify the accessibility of the materials to be recycled dur-ing reprocessing stages; new objects, new materials must beassociated with suitable destructuration concepts;

• These matrix materials must obviously be managed: accord-ing to their abundance and the nature of the destructurationprocesses, their presence may increase the complexity ofrecycling operations;

• The option of an “integral” recycling of actinides certainlyleads to final waste with reduced toxicity. In counterpart, itentails a “hotter” recycled fuel, which will require remote oper-ated remanufacturing processes;

• Particular attention is to be paid to the management of cycleeffluents for some fuel options (carbon-14 with nitride fuelsfor example) or installation options (liquid discharges obvi-ously entail more constraints for a recycling option on thereactor sites);

• According to some experts, one could also try to reduce thecosts of final waste disposal by removing particularly ther-mogenous fission products (Caesium 137, Strontium 90, seeFig. 81) from the waste.This option adds some complexity tothe processing operations, but could take advantage of theadditional freedom that intermediate storage may provide. Itdeserves at least some studies, in the general framework ofthe optimization of the back-end of the fuel cycle.

Irradiatedfuel

Dissolution

Preliminary Upartitioning

CoextractionAn + Ln

DisextractionAn

U

U + Pu + MA

FP Ln

Waste

DisextractionLn

Actinidesto be recycled

Fig. 80. A grouped actinide extraction concept: GANEX.

In the field of pyrochemical processes, the main objective ofthe research to be carried out resides in the confirmation ofthe potential of such concepts for industrial spent fuelrecycling operations. Although absolutely significant devel-opments and experiments have been carried out over a longperiod of time, few results currently concern the recovery ofplutonium and, all the more so, minor actinides, and also themanagement of spent salts. A great number of avenues cur-rently remain open, concerning both the choice of reactionalmedia (fluorides or chlorides, but also “room temperature” ionicliquids, which are currently experiencing important growth),and that of technologies (electrolysis or extraction by molten



The magnitude of the field of research to be carried out showsall the interest of an organized international cooperation, suchas is currently being established within the “Generation IV”Forum.

Finally, as was reported during the forum’s expert meetings, itis necessary to take into consideration the fact that the deploy-ment of 4th generation reactors may only intervene progres-sively, and that the 21st century fleet will present a large com-ponent of water reactors, the cycle installations of which willalso have to manage spent fuel, in order to produce final wastecompliant with the specifications and criteria which will prevail,and in order to supply new generation reactors: this “symbi-otic” character of the fleet will also constitute important inputdata for future choices.

10,000.0

1,000.0

100.0

10.0

1.0

0.110 100 1,000 10,000

Residual power (W/TWhe)

Pu (reproc. at 4 years)

Am (reproc. at 4 years)

Cm (reproc. at 4 years)

Fission product

Cs

Sr

Cooling time (years)

100,000

To summarize...The orientations outlined for the nuclear systems of the futuregive considerable importance to the fuel cycle operations (inparticular regarding the range of materials to be recycled).Weshall have to process new fuels, in a probably reinforced fieldof economical and environmental constraints. This multiplechallenge calls for innovations and must be dealt with as awhole: the entire chain of reactors, fuel and cycle, mustprogress coherently.

Two large avenues currently seem to be preferred: firstlyhydrometallurgical processes, strengthened by consistentindustrial feedback which attests their potential, and which stillappear to have important margins of adaptation and progress;and then the pyrometallurgical processes, promising in somerespects, but the potential of which are to be further explored.

Fig. 81. Contribution of the various radionuclides with the residualpower released by spent fuel (UOX, 55 GW.j/t).


235 713 millions 0.72

238 4.47 billions 99.275


Uranium resources

The element uranium Uranium is the heaviest of the natural elements remaining onEarth24. Natural uranium mainly consists of two isotopes: U 235and U 238.

the RAR reserves currently estimated. Of these 2 million, onlya part has been consumed in civilian reactors, leaving on theorder of 1.2 million tonnes of depleted uranium with approxi-mately 0.3% of U 235 which can be considered as a strategicreserve for the future. At the current rate of consumption(approximately 60,000 tonnes per year), “cheap” reservesshould last between 50 and 100 years. Beyond this horizon,the millions of tonnes of uranium contained in phosphates andthe billions of tonnes contained in the water of the oceans (thecontent is 3 parts per million) could be exploited.

In reality, the future of the “uranium” resources will depend agreat deal on the fuel cycle of the reactors which use them.Uranium is used quite unefficiently in water reactors: theextraction of approximately 200 g of natural uranium is neces-sary in order to obtain the fission of 1 gram of material in thistype of reactor. If one continues to use uranium in “open cycle”light water reactors, the uranium reserves may seem modestin relation to those of fossil fuels. However, a single recycling,notion without significance for fossil fuels, already significantlyincreases the scope of the resources. In parallel, the use offast neutron reactors would enable the energy potential of theuranium to be better used by efficiently consuming the fertileisotope U 238 in a closed fuel cycle26.With these nuclear sys-tems, the resources would no longer be a matter of concern.

Fig. 82. An open-cut uranium mine.

Isotope Period (years) Current relativeabundance on earth

(in % U total)

This isotopic composition of natural uranium is found every-where on Earth25, no physical or chemical process having ledto a significant separation of the two isotopes.

Uranium enters into the composition of at least two hundredminerals, and its average content in the earth’s crust is approx-imately 3 grams per tonne. It is present in practically all of therocks of the Earth’s crust, with particular concentrations inphosphates, certain igneous rocks or in the vicinity of oxida-tion-reduction boundaries in sedimentary rocks. Uranium isgenerally extracted from the subsurface by conventionalhydrometallurgical and mining techniques.

Uranium resourcesToday, most of the uranium produced in the world comes fromCanada, followed by Australia and Nigeria. Large deposits ofhigh-grade ore are yet to be to be exploited in Australia andCanada. Global reasonably assured resources (RAR), thatcan be recovered at a cost lower than $80/kg uranium, amountto approximately 2.5 million tonnes. Of course, resourcesdepend on the price that one agrees to pay in order to recoverthem: thus, RAR resources that can be recovered for less than$130 per kg of uranium are estimated at 3.3 million tonnes.

How vast are these reserves? By way of comparison, 2 mil-lion tonnes of uranium have been produced since the begin-ning of the nuclear power industry, that is a quantity close to

24. Tiny quantities of “natural” plutonium are found in uranium ore. Thisplutonium is formed by absorption of neutrons produced by the sponta-neous fission of uranium, 25. With the exception of the Oklo deposit, where natural nuclear reac-tions took place which consumed uranium 235 and disrupted the isotopiccomposition of the remaining uranium.

26. See supra and infra, pp. 67 and 75, the chapters entitled: “The fuelcycle of future nuclear systems” and “The origin of species (of reac-tors)…”.


74 Uranium resources

Fig. 83. Proven global reserves of uranium* (1.1.1999).* Reasonable resources assured recoverable for less than $ 80/kg U.

Canada326.4(13.0 %)

World total: 2,506.2 billion tonnes(excluding Chile et China)

Unit: Billion of toe

Other123.4(4.9 %)

Brazil162.0(6.5 %)

South Africa232.9(9.3 %)

Namibia149.3(6.0 %)

Gabon4.8(0.2 %)

Nigeria71.1(2.8 %)

Algeria26.0(1.8 %)

Spain3.1(0.3 %)

France12.5(0.5 %)

Ukraine42.6(1.7 %)

Russia140.9(5.6 %)

Australia607.0(24.2 %)

Mongolia61.6(2.5 %)

Kazakhstan436.6(17.4 %)

United States106.0(4.2 %)

Sou

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rvat

ory

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EA

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S a

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On the origin of species (of reactors):systems and generations

Nuclear reactor design begins by the layout in the reactorcore of fissile and fertile materials constituting the fuel, acoolant used to evacuate the heat produced by the fissionreactions, a moderator (possibly) which slows down neutrons,and a neutron absorber to control the chain reaction. Severaloptions are possible for each of these elements, and, while allof the combinations are not viable, many types of reactor canbe envisaged.

Fissile and fertile materialsThe most commonly used fissile nucleus in current reactors isU 235, a single “natural” fissile isotope. Other fissile nuclei thatcan be used are the odd plutonium isotopes Pu 239 andPu 241, produced by neutron irradiation of the fertile isotopeU 238. The mixture of fissile and fertile isotopes in the coreenables the operating time of the core to be increased, sincethe disappearance of fissile nuclei by fission is partially com-pensated (or totally if the reactor is a breeder reactor*) by theformation of new fertile nuclei via neutron capture on the fer-tile nuclei.

CoolantMany choices are possible for the coolant fluid: heavy water,ordinary water, gas (helium, CO2), liquid metals, etc. Thecoolant may circulate directly from the core to the turbine orexchange heat with a secondary circuit.The choice of coolanthas a great importance in the reactor’s technology, and largesystems are often classified according to it.

ModeratorAnother fundamental choice is that of the mean energy, ormean speed of the neutrons in the core. The choice betweenfast neutrons and slow neutrons thus determines two maingroups:

• In slow neutron or “thermal” reactors, the neutrons areslowed down by successive collisions on the light nuclei of amoderator material.The main moderator materials used areordinary water, heavy water (D2O) and graphite. As slow neu-trons have large interaction probabilities with the material,this type of reactor may operate with a fuel little enriched withfissile nuclei (natural uranium may even possibly be suffi-cient), but only a small part of the energy from the fuel’sheavy nuclei is exploited. A lot of these heavy nuclei aretransmuted by neutron capture in actinides that will be foundpresent in the waste;

• In fast neutron reactors (FR), the neutrons are not sloweddown in the reactor, and they more or less keep the energythat they had during their production by fission. Their inter-action probabilities with the material are low, this is why fastneutron reactors must have a high neutron flux, and containa lot of fissile material. On the other hand, in this field of neu-tron energy, fission reactions are favoured in relation to par-asite (capture) reactions: Fissile material is used much bet-ter than in a thermal neutron reactor. FRs are potentialburners of actinides, the latter being fissile with fast neutrons.

« If any species does not becomemodified and improved in a correspon-ding degree with its competitors, it willsoon be exterminated. »

Charles DARWIN, On the Origin of Species byMeans of Natural Selection, 1859.

Fig. 84. The fissile and capture cross-section* of uranium 235 as afunction of the energy of the neutron highlights two main fields: thatof slow neutrons, where the interaction probabilities of the neutronwith the uranium nuclei are high, and that of fast neutrons, where thecross-sections are much smaller.

1e61e51e4

1,000100101

0.10.01

0.0011e-41e-5

FissionCapture

Slow neutrons Fast neutrons

1e-5 1e-4 1e4 1e5 1e6 1e7

Neutron energy (eV)

0.001 0.01 0.1 1 10 100 1,000

Cro

ss s

ectio

n (b

arns

)


76 On the origin of species (of reactors):systems and generations

Current reactor familiesIn the 1950s and 1960s, practically all nuclear reactor typeswere envisaged, designed and even built! Following this bee-hive of creativity, “natural” selection ensured the survival of areduced number of families.

Gas reactors

Graphite-gas reactors enable the use of natural uranium.Theydeveloped in many countries (United Kingdom, France, Japan,Spain, Italy) until the United States, which up to the end of the1950s maintained the monopoly on enrichment, agreed toexport enriched uranium. From then on, all of these countriesprogressively abandoned this technology in order to switch tothe light water reactor type.The last was the United Kingdom,which started its first water reactor in 1995, and is the only oneto keep reactors of this type in operation today.

RBMK graphite - water reactors

It was this type of reactor which caused the Chernobyl acci-dent.The graphite moderator is penetrated by zirconium alloypressure tubes in which the boiling water circulates in order tocool the slightly enriched uranium fuel. This type of reactor isunstable in its design in certain operating domains, whichmakes it vulnerable to human error.The complete shutdown ofthis reactor family is programmed.

Fig.85. 1st to 2nd generation reactors: the large NUGG reactor (shutdown) and the small PWRs (in service) which succeeded it can beseen on the Bugey site.

Fig. 86. A RBMK reactor (unit no. 4 at Chernobyl).

Ordinary water reactors

With 86% of the fleet in operation and 79% of constructions inprogress throughout the world, ordinary (or “light”) water reac-tors represent the worldwide dominant species of nuclearreactors.

PWRs, and their Soviet version, the VVER, are the most com-mon.They are robust, reliable, and display continued progressin terms of availability, burnup rate, cycle time, ability to followfluctuations of the power grid and collective dose to operators.

Boiling water reactors (BWR), which represent approximatelya third of the capacity of PWRs, have also seen significantdevelopment, but have been slightly hindered by a few teethingdefects.Today, in Japan, the last orders have exclusively con-cerned boiling reactors.

CANDU heavy water reactors

In this type of reactor, the fuel is cooled by the circulation ofheavy water in the pressure tubes. The heavy water modera-tor absorbs very little of the neutrons, which enables this typeof reactor to use natural uranium. This specificity may attractcountries wishing to free themselves of uranium enrichment.The Canadians exported CANDUs to many countries (India,Pakistan, Romania, Korea, China).

The systems of tomorrowEven if water reactors are currently dominant, several types ofreactor have specific advantages that may one day competewith them:

High temperature reactors (HTR)

HTRs are thermal neutron reactors, moderated by a largemass of graphite and cooled by helium circulation.They use anoriginal fuel, the “coated particle” initially designed in England.This fuel, made from carbon and ceramic enables high refrac-



tory cores to be made, operating at high temperatures, whichoffers the possibility of high efficiency thermodynamic cycles.The great freedom offered to the designer via the particle fuelmakes this type of reactor suitable for accommodating a largevariety of fuel cycles.

Several HTR prototypes have been developed in the UnitedStates and in Germany. Made attractive by the recent progressin gas turbines, they are currently studied in the form of smallmodular reactors cooled by a helium circuit coupled directly toa turbine. With their large thermal inertia, HTRs are particu-larly safe, which may permit their safety systems to be simpli-fied; their excellent thermodynamic efficiency should make itpossible to amortize their investment cost rapidly, a cost whichis still high due to their low power density.

Fast neutron reactors (FR)

The great advantage of fast neutron reactors resides in theirability to produce as much or more fissile material than theyconsume. Fast neutron breeder reactors may therefore, viasuccessive recycling, use the quasi-totality of the energy con-tained in the uranium, one hundred times more than an ordi-nary water reactor.

In thermal spectrum reactors, actinides often capture neutronswithout fissioning, which leads to the formation of heavier andheavier nuclei, all radioactive, which put a strain on the neutroninventory of the reactor and is found in waste.

In fast spectrum reactors, capture and fission coexist for all ofthe actinides, which offers the possibility of balancing theirinventory.

Still by way of comparison, a typical UOX-PWR (1GWe) 16 kgof minor actinides. The recycling of Pu in the MOX formenables the Pu inventory to be stabilized, but the minoractinides are not burned and build up. A FNR replenisher ofthe same power can consume the minor actinides that it pro-duces 27 (see the block diagram of the FNR fuel cycle in chap-ter N). With this type of system, nuclear power may thereforegain in cleanliness.

The only FRs on which we have significant feedback are theones cooled by liquid sodium.This is an excellent coolant, notvery corrosive for stainless steels when it is pure, but whichspontaneously ignites with air and reacts quickly with water.

The Russians are studying FR models cooled with moltenlead, whereas the French are reopening, the helium-cooledFRs file after shutdown of the Superphénix 28.

The investment cost of FRs is much higher than that of PWRswith the same capacity. FRs therefore only have a chance toemerge if – or when – their specific quality, fissile materialeconomy, becomes a key factor of success.

In a more distant futureTo complete the list of possible future reactors, it is finally nec-essary to mention the molten salt reactors and the “ADS”(Accelerator Driven Systems), hybrid reactors coupled with aproton accelerator. Nuclear technology is young, and there isno lack of ideas to adapt it to new global requirements in termsof energy and environment. What is certain, is that sustain-able nuclear power will only exist within the framework of aresponsible radioactive waste management and fissile and fer-tile material recycling strategy.

Fig. 87. Formation of a plutonium 239 (fissile) nucleus via capture ofa neutron on uranium 238 (non-fissile).The fission of a nucleus produces several neutrons. Only one ofthese neutrons is necessary to maintain the chain reaction. Theother neutrons may form other fissile nuclei via capture on uranium238 in order to form plutonium 239. With a replenisher or breederreactor, as much or more fissile material can be produced than con-sumed.The fissile material therefore plays the role of a catalyser, constantlyregenerated during its consumption. With this type of reactor, it is thefertile material U 238, which is in fact finally consumed.

n

e°

e°

23.5 min 2.35 Tage

U238 U239 Np239 Pu239

27. See supra, p. 68, the block diagram of the fast reactor cycle.28. In Creys-Malville (Isère).

By way of comparison, a typical UOX-PWR (1GWe) needs110 t of natural uranium per year and produces 0.25 t of plu-tonium per year. A FNR replenisher of the same power wouldneed 15 to 20 t of Pu (constantly regenerated), and wouldconsume only approximately 1 to 2 tonnes of natural ura-nium per year. FNRs may even operate using the large stockof depleted uranium currently unused by the water reactorfleet. FNRs therefore solve the problem of resources.


78 On the origin of species (of reactors):systems and generations

WPu

WPu

WPu

Magnox(Graphite-gas

reactor)

AGR

VHTR FNRNa

FNRPb

MSR

MSR(Molten

salt)

The nuclear reactor phylum

GFR

Navalpropulsion

HTR RBMK (graphite

moderator andwater coolant)

U enriched reactors

Naval PWR + fuelreprocessing

BWR (Boiling water

reactor)

EPR

CivilianPWR

FR (Fast

neutronreactor)

ADS

SCWR

CANDUSGHWR(Steam

generating)

Heavy waterreactors

Graphitemoderatorreactors

FermiJoliot-Curie

2040Tomorrow

Gen

.IG

en.II

Gen

.III

Gen

.IV

2005Today

1986Chernobyl

19731st oil shock

1960Blossoming of the reactorconcept

1942The beginning

Fig. 88. The phylogenetic tree of nuclear reactors.Brief description of the main branches of the tree: reactors mayoperate with natural uranium or enriched uranium, but the use of nat-ural uranium restricts the choice of coolants to graphite and heavywater. The use of enriched U offers almost all possible choices ofcoolants and moderators. Some combinations are more fortunatethan others: the water coolant has had a lot of success, because it isalso a good moderator. Water reactors (PWR and BWR) constitutemost of the contingency of generations II (current) and III (nearfuture) reactors.The combination of a graphite moderator and a gas coolant pavesthe way to high temperature reactors.The branches of fast neutron reactors are still little developed.Only certain species of nuclear reactor have survived. Somebranches are extinct or in the process of becoming extinct: NUGGsfor economic competitiveness reasons, RBMKs for safety reasons.

But the selection criteria are changing, the world is evolving.Other species are emerging. The six concepts retained by the GenIV are at the top of the tree. Will they all be developed?

• WPu: Military plutonigenous reactor.• SGHWR: Heavy water reactors supplying industrial heat

(Steam Generating Heavy Water Reactor).• AGR: Graphite-gas reactors (Advanced Gas-cooled Reactor).• (V)HTR: (Very) High Temperature Reactor.• SCWR: Super Critical Water Reactor.• ADS: Hybrid spallation-fission system (Accelerator-Driven System).• FR: Fast Reactor.• MSR: (Molten Salt Reactor).



Fig. 89. The nuclear generations calendar.

First creations

Generation I

Generation IIUNGG

CHOOZ

PWR 900

PWR 1300

N4Generation IVEPR

Generation III

Current reactors

Advanced reactors

Systems of the future

• The first generation of reactors saw the daywhen the industrial technology of uranium enrich-ment was not yet developed. Reactors had to beable to operate with natural uranium (non-enriched), hence the use of moderators absorbingvery few neutrons, such as graphite or heavy water.This is why the field, called Natural UraniumGraphite Gas (NUGG), was developed in France.

• The second generation of reactors, deployed inthe 70s to 90s, constituted most of the global fleetcurrently in operation.This period was that of pres-surized water reactors PWRs and boiling waterreactors BWRs. The cumulated operation of morethan 10,000 years-reactors on the global levelproves the industrial maturity and the economiccompetitiveness of this technology. The fleet of 58pressurized water reactors that France has belongsto this second generation.

• The third generation represents the mostadvanced industrial state-of-the-art. It concerns so-called “evolutionary” reactors which benefit from the

feedback and industrial maturity of second genera-tion reactors, whilst integrating even moreadvanced specifications in terms of safety.

• Finally the development of the fourth generationhas as from now been engaged, within an interna-tional framework and with the objective of bringingthese new systems to technical maturity, with theprospect of industrial deployment by 2030.The pur-pose of these systems is to respond to the issuesof sustainable energy production, with a long-termvision, and in particular, to minimise radioactivewaste and to better use natural resources of fuel,as well as to meet new energy requirements: notonly the generation of electricity, but also hydrogenfor transportation and drinking water via the desali-nation of seawater.

These systems present significant evolutions andtechnological innovations (they can be called “rev-olutionary”) which require approximately twentyyears of development

Petite histoire des générations nucléaires



Nuclear systems of the future:an international framework for the development of a new generation of nuclear systems

The Generation IV InternationalForumThe objectives targeted for the systems of the future, as wellas the choice of key technologies to achieve them, are the sub-ject of a very active international cooperation, in particularwithin the framework of the Generation IV Forum.

Taking stock of the risks of shortages and medium-term energydependence, the American government has committed itselfto an effort to revive the means of generating electricity. In thefield of nuclear energy, this results in two complementaryactions:

• The first is purely American, and intends to facilitate the con-struction of new reactors in the United States in the shortterm (2010); it concerns the Nuclear power 2010 (NP 2010)programme. An ad hoc group, the Near Team DeploymentGroup (NTDG), has evaluated the reactors likely to be con-structed between now and 2010, has identified the possibleproblems to be solved on the technical, regulatory or admin-istrative level, and has proposed actions facilitating the short-term deployment of these third generation nuclear reactors;

• The second is the Generation IV International Forum. Itsfounding principle is the recognition of the advantages ofnuclear energy by the ten member countries. This energycould meet the growing energy needs throughout the world,in a procedure for sustainable development and prevention ofthe risks of climate change. This principle is recorded in theForum’s charter, and it is embodied by the commitment of aninternational R&D to define, develop and enable the deploy-ment of 4th generation nuclear systems by 2030. The mem-ber countries of the Generation IV International Forum areArgentina, Brazil, Canada, France, Japan, the KoreanRepublic 29, South Africa, Switzerland, the United Kingdom,Switzerland, the United States and the European Union.Other countries or international instances may also eventu-ally join this research effort.

Methodology of the choice of technological orientations

Three steps have already been taken:

• The evaluation of designs proposed by the participatingcountries, according to a highly codified methodology (thistask was carried out between April 2001 and April 2002);

• The selection of a small number of leading technological con-cepts judged as particularly promising during the evaluation(task carried out in May 2002);

• The elaboration of a development plan for these technologies,published in October 2002, preparing a later phase of interna-tional cooperation (main objective of the Forum from 2003).

Straightaway, a clear agreement was affirmed among the par-ticipants on the main objectives of the Generation IV pro-gramme and on the procedure. Four main objectives (“goalareas”) were defined in order to characterize the systems ofthe future. They must be:

• Sustainable: this means saving natural resources andrespecting the environment (by minimising the production ofwaste in terms of long-term radiotoxicity, and by optimallyusing natural fuel resources);29. South Korea.

France United Kingdom

Members of the

Generation IVinternational

Canada

USA

Brazil

Argentina

South Africa

South Korea

Japan

Switzerland

European Union

Fig. 90. Nuclear systems of the future: highly international R&D.


82 Nuclear systems of the future: an international framework for the development of a new generation of nuclear systems

• Economical: from the point of view of the investment costper kWe installed, the fuel cost, the operating cost of theinstallation and, consequently, the production cost of thekWh, which must be competitive in relation to that of otherenergy sources;

• Safe and reliable: with ongoing research in relation to cur-rent reactors, and by eliminating the need to evacuate the pop-ulation outside of the site as much as possible whatever thecause and the gravity of the accident inside the power plant;

• Resistant regarding the risks of proliferation, and easilyprotected against external aggressions.

Approximately one hundred engineers and scientists have par-ticipated in the first phase of the Forum’s work.For each systemconsidered (e.g. water, gas, liquid metal reactors) technicalgroups have been made responsible for the evaluation of thevarious concepts proposed in relation to the objectives and cri-teria retained, and these groups were also responsible for theelaboration of R&D plans for the concepts finally selected.Theevaluation methodology was developed and refined by a spe-cific workgroup which reduced the four main progress objec-tives mentioned above to approximately thirty basic criteria.

Transverse technical groups identified the necessary develop-ments in the field of fuel, the cycle procedures, the materials,and the safety of the energy products for the various systemsconsidered by the Forum. A coordination group led all of the

technical groups’ activity and assured the integration of theresults in the documents of the various stages and in the finalsummary.

The choices made within the Forum

Six nuclear systems were selected, which may enable notableadvances on the abovementioned criteria. These systemsenable applications other than electricity production, such asthe generation of hydrogen or seawater desalination.

The diversity of needs to be covered and the international con-texts explain that we do not end up with only a Generation IVsystem, but with a few of the most promising system designs,on which the Forum R&D member countries are now concen-trating.

Identity cards of the selectedsystemsThe selection operated in the Generation IV initiative showsseveral important lessons:

• In the choices retained the most discriminating criteria werethose of sustainable development. The range of evaluationson the economical or safety aspects turned out to be muchmore narrow. This results in a majority of fast spectrum andclosed cycle systems;

• The most innovative concepts find themselves penalised bygreat uncertainties regarding their definition and regardingthe possibility of removing technological difficulties for a pro-duction between now and 2040. In this class of nuclear sys-tems, the final choice falls on the molten salt reactor, interest-ing for the management of actinides and the deployment ofthe thorium cycle;

• The grouping into groups of reactors – homogenous from theperformances and R&D requirements point of view – provedto be important because it enabled the R&D knowledgebases to be taken into account and recommendationsaround important federal policies to be structured. By way ofexample, the gas-cooled group of reactors (RCG), comprizesan important research knowledge base regarding high tem-perature materials, helium circuits, and conversion by gasturbine. In addition, different variants are being studied forvarious market niches: very high temperature reactors for themass production of hydrogen, specialized reactors for burn-ing actinides, fast neutron spectrum version and integralrecycling for sustainable energy development;

• The various gas reactors (GFR, VHTR) translate the recog-nition of the interest for this coolant with, in particular, thepossibility that it offers for developing an upgradeable rangeof systems based on this technology.

EconomySavingnatural

resourcesExtracting the energyfrom fissile material

efficiently

Reducingthe risk

of proliferationBurning plutoniumwith an integrated

fuel cycle

Reductionof the production

of wasteRecycling

and transmutingminor actinides

Safety

Five basic criteria

Fig. 91. The criteria retained for the selection of nuclear systems of the future differ in their name and in their hierarchy from thoseretained for first and second generation reactors.Here, all of the criteria were placed on the table, and debated in the greatest transparency. They are all of purely civilian inspiration,and shared by the international community.The profitability and economy criteria of the resources (important forindustrialists) remain important. More innovative, the safety, wastereduction (important for the public) and reduction of proliferation risks(important for politicians) criteria are explicitly mentioned.



Fig. 92. SFR: “improved sodium”.This system includes a fast spectrumreactor associated with a closed cycleenabling the recycling of all of theactinides and the regeneration of pluto-nium. Due to the regeneration of fissile

Cold plenum

Hot plenumControl rods

Primarysodium (Hot)

Core

Pump

PumpPump

Hea

t exc

han

ger

Primary sodium (Cold)

Secondary sodium

Steam generator

Turbine Generator

Condenser

Heat sink

Electricalpower

SFR: “improved sodium”

LFR: “a lead concept”Fig. 93. LFR: “a lead concept”.This system comprizes a fast neu-tron reactor associated with aclosed fuel cycle, enabling optimaluse of the uranium.Several benchmark systems havebeen maintained in the selection.The unit powers go from 50-100MWe, for the so-called “battery” con-cepts, up to 1,200 MWe, includingthe modular concepts from 300-400MWe. The “battery” concepts have along-term fuel management (10 to30 years). The fuels may be eithermetal, or of the nitride type, andenable the recycling of all actinides.The main technological deadlock ofthe system concerns corrosion byliquid lead.

material in the core, this type of reactormay operate for a very long time withoutintervention on the reactor core.Two main options are envisaged:• the first, associated with a reprocessing

of metal fuel, leads to a reactor with an

intermediate unit power of 150-500 MWe • the second, characterized by a repro-

cessing of mixed oxide fuel (MOX), cor-responds to a reactor with high unitpower, between 500 and 1,200 MWe(reactor associated with PUREX repro-cessing).

The SFR presents very good naturalresources usage and actinide manage-ment properties. It was evaluated as hav-ing good safety characteristics.The oxide fuel system may be ready forindustrial deployment as of 2015.Several SFR prototypes exist throughoutthe world, in Japan (Joyo, Monju), Russia(BN600), and France (Phénix).The main research issues concern theintegral recycling of actinides (fuels com-prizing actinides are radioactive, thereforecomplicated to manufacture); the in serv-ice inspection (sodium is not transparent);safety (passive safety procedures arebeing studied); the reduction of the invest-ment cost (this type of reactor is stillexpensive). The changing of the water ofthe secondary fluid for supercritical CO2 isalso being studied, because it may enablethe safety to be improved, whilst allowingthe elimination of the intermediate sodiumcircuit, if the chemical sodium-CO2 inter-actions proves to be less violent thansodium-water interactions.

Header

U-tube heatexchangermodules

Reactormodule/fuelcartridge(removable)

Coolant module

Generator

Coolant

Rea

cto

rco

re

Reactor

Compressor

Turbine

Heat sink

Intercooler

Compressor

Pre

-co

ole

r

Recuperator

Electricalpower



SCWR: “water, but supercritical”Fig. 94. SCWR: “water, but supercritical”Two fuel cycles are envisaged for theSCWR, which correspond to two differentversions of the system: a thermal spec-trum reactor associated with an open fuelcycle and a fast spectrum reactor com-bined with a closed cycle for recycling allthe actinides. Both options have an identi-cal operating point in supercritical water:pressure of 25 MPa and core outlet tem-perature of 550° C enabling a thermody-namic efficiency of 44%. The unit power ofthe benchmark system is 1,700 MWe. TheSCWR was evaluated as having highpotential for economic competitiveness.The main research issue concerns corro-sion by water, in particular accelerated inrelation to current water reactors due to amuch higher operating temperature.

Fig. 95. VHTR: “making hydrogen withhelium?”The VHTR is a gas-cooled system associ-ated with a thermal spectrum core and anopen fuel cycle. The particularity of theVHTR is its operation at very high tempera-tures (>1,000° C) to supply the necessaryheat for water decomposition processes bythermal chemical cycle (iodine/sulphur) orhigh temperature electrolysis.The VHTR is dedicated specifically to theproduction of hydrogen, even if it mustalso enable the generation of electricity(alone or in co-generation).The benchmark system has a unit powerof 600 MWth and uses helium as acoolant. The core is made up of prismaticblocks or pebbles.Important research topics for the develop-ment of this system concern high temper-ature materials and the development ofhydrogen mass production technologies.

Controlrods

Supercritical water

Generator

Rea

cto

rco

re

Reactor

Pump

Condenser

Turbine

Heat sink

Electricalpower

VHTR: “making hydrogen with helium?”

Controlrods Graphite

reactorcore

Reactor

Pump

Hydrogen

Heat sink

Oxygen

Graphitereflector

Helium coolant

Blo

wer

Heatexchanger

Hydrogen productionplant

Water



GFR: “fast gas”Fig. 96. GFR: “fast gas”The GFR is a fast spectrum systemenabling the homogenous recycling ofactinides whilst maintaining a regenerationgain greater than 1. The benchmark con-cept is a helium-cooled once through reac-tor with high efficiency (48%). The evacua-tion of the residual power in the event ofdepressurisation implements natural con-vection. The power density in the core isdetermined in order to limit the transienttemperature of the fuel to 1,600° C. Theinnovative fuel is designed to retain fissionproducts (for a temperature lower than thelimit of 1,600° C), and to avoid their releasein accident situations. The recycling ofspent fuel is envisaged on the same site asthe reactor either via a pyrochemicalprocess or via a hydrometallurgicalprocess. The GFR is the most performantconcept in terms of natural resource usageand reduction of long-term waste. It islocated in the technological gas line, com-plementing thermal spectrum concepts, GT-MHR30 , PBMR31 and VHTR.The main research topics associated to thedevelopment of the GFR concern the reac-tor materials, which must be able to resistboth high temperatures and strong neutronirradiations. The most important issue is thedevelopment of a dense and refractory fuel.

Fig. 97. MSR: “a 2 in 1 system”The MSR is an epithermal spectrum sys-tem with the highly original implementa-tion of a molten salt solution used both asfuel (liquid) and coolant. The regenerationof the fissile material is possible with anoptional uranium-thorium cycle. The MSRintegrates in its design an online recyclingof fuel, and thus offers the opportunity ofgrouping on the same site electricity gen-erating reactor and its reprocessing plant.The salt retained for the benchmark con-cepts (unit power of 1,000 MWe) is asodium, zirconium and actinide fluoride.The spectrum moderation is obtained inthe core by the presence of graphiteblocks crossed by the fuel salt. The MSRcomprizes an intermediate fluoride saltcircuit and a tertiary water or helium cir-cuit for the generation of electricity. Thissystem was evaluated as having relativelygood safety and non-proliferation charac-teristics.The most important research issue con-cerns the development of the onlinemolten salt fuel recycling technology.

Control rods

Helium

Generator

Rea

cto

rco

re

Reactor

Turbine

Heat sink Heat sink

Electricalpower

Compressor

Inte

rco

ole

r

Recuperator

Pre

-co

ole

rMSR: “a 2 in 1 system”

Controlrods

GeneratorReactor

Turbine

Heat sink

Electricalpower

Compressor Intercooler

Recuperator

Pre

-co

ole

r

Chemical processing plant

Freezeplug

Purified salt

Coolant salt

Heatexchanger

Emergency dump tanks

30. GT-MHR : Gas-Turbine Modular High Temperature Reactor.31. PBMR : Pebble Bed Modular Reactor.

Pump

Pump



What research for the nuclearsystems of the future?Research on nuclear systems of the future must be based ona quality modelling. The basic physical phenomena aremostly well-known, which does not signify that their modellingis easy!

Fortunately, the progress of computer tools enables ambitiousmodelling to be envisaged. A new generation of calculationcodes is in the process of development in order to describethe behaviour of nuclear systems: these software platformsuse a “multiscale” (from microscopy to macroscopy) and multi-disciplinary (taking into account the interactions between neu-tronics and thermohydraulics, for example) approach.

In reactors of the future, the materials in general and the fuelin particular will be subjected to severe conditions, due to thehigh temperatures envisaged in certain reactor concepts, and

The second stage of work from the Forum is the internationalco-operation phase to consolidate systems feasibility byremoving technological deadlocks and validating their perform-ances. It is currently being established and France is playinga very active role.The systems, whose feasibility is to be con-firmed, will enter into a validation phase of their technical andeconomic performances.

According to the degree of innovation of the system, all thiswork should lead to sufficient technical maturity between 2015and 2025. It should enable important industrial deploymentsby 2040.

INPROIn 2000, the International Atomic Energy Agency (IAEA)launched the INPRO project (International Project onInnovative Nuclear Reactors and Fuel Cycles), which aims topromote the development of innovative nuclear systemsenabling future energy requirements to be met whilst respect-ing the objectives of economic competitiveness, safety, respectfor the environment, resistance to proliferation, and acceptanceby the public.

The importance of this project is to accompany and comple-ment technological developments, such as those carried outwithin the framework of the Generation IV Forum, there whereIAEA may have a specific contribution, for example by enablingthe participation of numerous countries, in particular develop-ing countries not yet using nuclear energy but interested inbenefiting from it, or thanks to its effectiveness in non-prolifer-ation and international controls.

Firstly (phase 1), the technical objectives of the project are:

• To determine, over a very large basis, the needs and objec-tives of countries, given the diversity of their situation, and tospecify how innovative nuclear systems may contribute tomeeting them;

• To define the criteria and methodologies for the analysis andcomparison of various innovative reactor concepts.

Secondly (phase 2), the Agency envisages that the project mayextend the definition of the criteria and the evaluation method-ology in order to help member countries of the Agency in theirown analysis of nuclear systems that best meet their needs.Different from the Generation IV Forum, the purpose of theproject is not to carry out technical R&D actions or to developinnovative reactors and systems.

The European MICANET and HTR-TN networksThe objective of the European MICANET network(MICHELANGELO Network) is to develop a European R&Dstrategy in the field of innovative systems and to contribute indefining projects from the 6th European R&D FrameworkProgramme in relation to the Generation IV Forum’s activity toenable exchanges best serving the interests of European play-ers.The HTR-TN network is more specifically dedicated to gas-cooled systems.

Bilateral cooperationsThe bilateral cooperation actions with the United States, Japanand Russia were redefined in 2001 with the aim of preservinga growing place for joint studies and developments regardingthe gas reactor technology, the extrapolation of this technol-ogy to fast neutrons, and the development of fuel reprocessingand remanufacturing processes, with integral recycling ofactinides.

The cooperation with the United States carried out since 2002to work with five common joint-financed projects on these top-ics (NERI-International actions within the framework of theCEA-DOE cooperation). Eventually, four of these projects mayintegrate Generation IV cooperation.

The cooperation with JNC (Japan Nuclear Cycle DevelopmentInstitute) enables the comparison between the gas-cooled andsodium-cooled fast neutron reactors to be extended, as wellas the sharing with JAERI of certain technological develop-ments (fuels, materials) and experimentation possibilities ontheir experimental helium-cooled HTTR reactor.

International initiatives complementing the Generation IV International Forum



caused by irradiation by the high flux offast neutrons. Corrosion is in generalaccelerated at high temperatures, andthis topic represents a research subjectin itself. Irradiation damages causedin the materials by fast neutrons arequalitatively different from those causedby slow neutrons, because of the pos-sibility that the former have of produc-ing nuclear reactions. Refractory alloysand ceramics, solid or composite, aregood candidates for nuclear applica-tions. These materials have recentlymade spectacular progress and areapplied in numerous industrial fields,but their adaptation to nuclear needswill require work.

One of the major barriers for the devel-opment of nuclear systems of the future is the fuel itself, whichmust combine mechanical and thermal resistance character-istics under irradiation, whilst complying with the constraintslinked to neutronics which severely restrict the geometry andthe materials that can be used. For example, one of the great-est challenges in the production of a gas-cooled fast reactorwill be to design a dense and refractory fuel.

Gen IV concepts are not only nuclear reactors: they aredesigned to operate with a well determined fuel cycle. Thereprocessing-recycling of fuel depends a great deal on thenature of the fuel, and on the reactor that can consume it.Thisis why we do not speak of an isolated “reactor”, but rather “sys-tem” to encompass the reactor and the reprocessing-recyclingof its fuel. Consequently, the partitioning, storage and trans-mutation of nuclear materials involved in these cycles willremain important research topics.

Sodium-cooled reactors: an expertise which remains on the agendaThe objective of maintaining and upgrading the expertise isapplicable in particular to sodium-cooled fast reactors, on

which France has acquired amajor technological advance interms of R&D, experimentationand industrial developments.Thanks to the knowledgeacquired during the developmentof the Phénix and Superphénixreactors and the EFR project,CEA masters all of the aspects ofthe sodium-cooled fast reactorsystem:

• The creation of installationssince the experimental Rap-sodie reactor (40 MWth) up tothe industrial Phénix (563MWth) and Superphénix (3,000MWth) prototypes;

2020 2030 2040 2050 2010 2000 2060 2070 2080

Fig. 98. Example of multiscale simulation, applied to materials.

Physical metallurgy

Mechanical metallurgy

Discrete DislocationDynamics

Digitalmesoscope

Local approachof the fracture

Structure mechanics

Atoms

Atomicclusters

Dislocations

Grain

Polycristallineaggregate

MaterialsR.E.V.

(representativeelementary

volume)

Recycling of the Pu in

the LWR (MOX)

Recycling of the Pu and MA of the LWRs

in Gen IV fast reactors

Global recycling of the actinidesin Gen IV fast reactor

U

U, Pu, AM

U, Pu, AM

Pu (U)

Gen. II

Gen.III

Gen.IV

UPu

Fig. 99. The succession of fuel cycles associated with the genera-tions of reactors.Currently, the plutonium from PWRs is recycled in MOX form.In 2020, generation IV PWRs will continue to exist, but the Pu thatthey produce will be burned (partially, but more efficiently) by thegeneration III reactors deployed at this time. The minor actinides pro-duced by this mixed Gen II - Gen III fleet may be partitioned andstored.In 2040, the first generation IV reactors will be deployed, and willburn the Pu which will have been placed in reserve for their start-up,in addition to the minor actinides accumulated earlier. The uraniumcomplement necessary for the operation of these reactors may besupplied by currently stored depleted uranium.Around 2050, these “Gen IV” reactors should be able to operate byrecycling the totality of their actinides.

Ganex on spentLWR fuel

(MOX et UOX)



• Industrial mastery of the main stages of the fuel cycle:- manufacturing of uranium and plutonium based fuels,- reprocessing of spent fuel with a 1981demonstration ofPhénix’s ability to use the plutonium that it produced itselfduring a previous cycle;

• Experience of the good in service behaviour of a large rangeof structure materials (mainly steels).

Such an experience is used within the framework of theresearch on waste management, because the Phénix reactoris currently used successfully for a series of experiments onactinide transmutation.

This expertise is also upgraded via international cooperation,mainly with Japan and the United States, within the GenerationIV Forum, as well as with Russia. One of the main challengesof this jointly carried out research is to provide sodium-cooledFRs with a good level of economic competitiveness, by mak-ing them more compact, and therefore cheaper on investment.CEA is also working on the SMFR, sodium-cooled modularfast reactor concept with the Argonne laboratory and theJapanese research institute JNC. This reactor has the partic-ularity of modest power and a very long stay time of the fuelin the reactor.

One of the developments that can be envisaged for sodium-cooled reactors consists of replacing the water of the second-ary circuit by another fluid less likely to react chemically withsodium. The case of a secondary circuit using supercriticalCO2 is currently being explored in detail at CEA. Would weknow how to make an FNR-Na with a secondary circuit usingsupercritical CO2? What would be its advantages and its dis-advantages in relation to a secondary circuit with water, interms of safety, and efficiency?

Gas-cooled reactors (GCR): a preferred development pointWithin the framework of the Generation IV InternationalForum, France has expressed a preferential interest foradvanced very high temperature gas-cooled (VHTR) systemsand for fast neutron systems with integral actinide recycling(GFR). It will also accompany developments regarding the fastneutron and sodium-cooled system (SFR). The very goodpositioning of gas reactors in the final evaluation, and thereforethe recognition of the interest for this concept by theGeneration IV Forum, backs up the decision made by CEA in2000 to extend its research on this topic.

Fig. 100. Reactor hall of the Phénix power plant. Established on theedge of the Rhône, an integral part of the Marcoule nuclear site,Phénix is a sodium fast neutron reactor. Its first divergence* tookplace in 1973 and the first kilowatt-hours delivered on the grid in July1974. The last few years have been marked by important renovationworks.The experimental programme mainly concerns actinide transmuta-tion, but the experience acquired also benefits the research onnuclear systems of the future.



Gas-cooled reactors

Gas-cooled reactors are currently experiencing renewedinterest due to their high operating temperature, which enablesa high efficiency energy conversion cycle, and nuclear energyuses other than the generation of electricity.In their thermal spectrum version, construction of industrial-scale reactors are possible in the medium-term. These reac-tors present recognized safety characteristics, as well as agreat deal of flexibility in the choice of fuel cycle.This is permit-ted via the association of three essential specificities: a partic-ularly confining particle fuel, a coolant, chemically inert helium(He), and finally, the exceptional physical properties of graphiteas a moderator and structure material.

In their fast spectrum version, which is still on the drawingboard, they offer the additional prospects of energy upgrade ofnatural uranium resources, within the framework of the fuelcycle reducing final waste and the risk of proliferation.

The relevance of this choice as a main avenue of research anddevelopment has been validated by the member countries ofthe Generation IV International Forum, who have retained twoof the systems proposed by CEA (the VHTR and the GFR),from the most promising progress concepts for the next fewdecades 32.

Thermal spectrum gas-cooledreactorsThe thermal spectrum High Temperature Reactor (HTR) con-cept differs notably from the other gas-cooled thermal neutronreactors which have been developed in the past: MAGNOXand AGR in Great Britain, and NUGG in France.

In relation to these concepts, HTRs differ by:

• The use of the He coolant enabling access to high tempera-tures (≈ 850° C), hence a much greater thermodynamic effi-ciency;

• The use of a finely divided fuel made up of coated particleswhich gives it much higher burnup rate capacities, and opensthe possibility of using different nuclear matter.

32. The DEN no. 1 monograph (to be published in 2006) will be entirelydedicated to gas-cooled reactors.

HTRs and other main systems

HTR BWR PWR FNR

Unit power 200-1,000 1,100 1,450 1,200type (MWe)

Efficiency (%) 48 33 33 41

Coolant He eau eau Na

Pressure (bar) 50-70 70 155 1-4

Inlet T (° C) 400 278 290 400

Outlet T (° C) 750-950 287 325 550

Moderator graphite water water without

Power density(MW/m3) 2-7 50 100 250

Burn-up rate(GWd/t) 100-800 30 60 100-200

The most recent ideas of modular design for HTRs furtherstrengthen their attractiveness from the point of view of safety,economy and the possibilities of deployment. The use of gasturbines finally enables a once through energy conversioncycle (Brayton cycle), to be envisaged, improving the efficiencyand the compactness of the installation. These are the rea-sons which contribute to the renewed interest in this system.

Particle fuel

The progress carried out in industry on gas turbines and hightemperature materials has paved the way for HTRs with oncethrough cycles, offering new prospects for increasing the ther-modynamic efficiency of the energy conversion system. Inaddition, significant advances in the technology of heatexchangers and magnetic bearings currently enable morecompact, cleaner and safer gas power plants to be designed.

All of these elements are originally modular HTR concepts,which illustrate the industrial projects, such as the GT-MHRdesigned by General Atomics, the PBMR developed by Eskomin South Africa or the Antares project from Framatome-ANP.


In addition, high temperatures pave the way for other nuclearenergy industrial applications, in particular the production ofhydrogen.

90 Gas-cooled reactors

Current trends for the HTR system are therefore to be consid-ered:

• Modular reactors with unit power in the 100 to 300 MWerange;

• Operating in once through cycle according to the Braytoncycle;

• Enabling the evacuation of the residual power to be assuredpassively and without using coolant fluid.

The very high temperature reactor(VHTR)Beyond the medium-term future, mentioned above regardingthe HTR, the gas-cooled reactor system has the ability todevelop towards even higher temperatures, with at stake aconsiderably improved energy conversion efficiency.Fig. 101. The use of particle fuel constitutes the main innovation of

HTRs.The kernel of fissile material (UO2, PuO2, UC, etc.) is surrounded byseveral successive layers (porous or dense pyrocarbon, SiC), usedto assure the protection of the fissile kernel, and the containment offission products. The whole thing is refractory (not metal) and highlyresistant, which enables this fuel to be forced to very high tempera-tures and very high burnup rates.This fuel has already been used successfully in the past. It is stillcapable of performance progress, by a judicious choice of coatingmaterials (all have not been explored, in particular, the replacementof the SiC layer by ZrC paves the way to very high temperatures, inthe order of 1,000° C). CEA is currently equipping itself with a pilot-installation for manufacturing this type of particle fuel (GAÏA installa-tion, in Cadarache).

Fig. 102. The ANTARES project from Framatome-ANP has a capac-ity of 600 MWth. It uses helium at 850/1,000° C with an intermediateheat exchanger, and has a wide range of applications.

Fig. 103. Thermal energy is converted a lot better, if it is produced athigh temperatures.With a PWR: 2 GWth are discharged to produce 1 GWe;With a VHTR: only 1 GWth would be discharged to produce thesame electric power. But this type of reactor also enables the cogen-eration of hydrogen and industrial heat to be carried out, which maybring the global conversion efficiency to approximately 70%.

Enhancement of nuclear heat utilization

Thermalefficiency 35 %

Thermalefficiency 70 %

Powergeneration

Powergeneration

Light water ractorSteam temperature: ≈ 300° CSteam cycle

Processheat

High temperature gas-cooled reactorGas temperature: ≈ 1,000° CCogeneration

Loss

Loss

Hydrogenproduction

300° C

30° C

950° C

600° C

30° C

250° C



(and price) that such a production would entail, the abovemen-tioned schema does not solve the problem of pollution. It isrecognized that the only hydrogen mass production methodsemitting no greenhouse gas are the high temperature electrol-ysis and the thermochemical partitioning of water from electric-ity and nuclear heat. The production of hydrogen by thermo-chemical method may be carried out in many ways. One of theways preferred by numerous research laboratories is the I-Sprocess, thus baptized because it makes the two reagents,iodine and sulphur intervene (without consuming them). Theprocess involves the decomposition of sulphuric acid, a stageat which the efficiency is highly dependent on the tempera-ture. A desired efficiency of 50% requires a temperature of900°C on the process level, that is approximately 1,000° C forthe coolant exiting the core. In practice, only a gas-cooledreactor has the possibility of meeting this requirement. It isfrom the latter that the main characteristics of the very hightemperature reactor follow.

To produce hydrogen from nuclearenergy ?The preoccupations linked to climate change, combined withimportant progress carried out recently on fuel cells, makesthe use of hydrogen as a clean energy vector more interestingthan ever.The American government has identified hydrogenas an essential element for the future economy, both for indus-trial needs such as the hydrogenation of heavy oils into lightfuels, or as transportation fuel.

However, hydrogen is not a primary energy and must be pro-duced, either by electrolysis or thermochemical dissociationof water. The high temperatures which may be reached innuclear reactors position gas-cooled reactors remarkably wellfor hydrogen mass production applications.

Currently, the very large majority of the global production ofhydrogen comes from reforming natural gas:Q + CH4 + 2 H2O → CO2 + 4 H2, which produces a lot of CO2,both in the chemical reaction and in the calorific contributionto the endothermic reaction.

The United States projects a quadrupling of its hydrogen con-sumption between now and 2017 to 10 million tonnes per year.Clearly, apart from the strong increase in gas consumption

Fig. 104. Future nuclear systems may produce both electricity andhydrogen.

Thermochemicalcycle, e.g.lodine/sulphur

Transmissionof electricity

CO2sequestration

CO2CO2

H2O

CO2

Electrolysis

Heat

Electricity

VHTR

Methanereforming

Industrialstorage

Energy,heat

Hydrogen vehicle

Hydrogen

Distribution



What research for the VHTR? The development of the VHTR will not be easy. Admittedly, theGerman AVR reactor has already reached core outlet temper-atures greater than 950° C. But above this temperature, tech-nological ruptures become necessary. The main avenues ofresearch are listed hereafter:

Calculation tools and methods:

HTR or VHTR cores present both a random geometry and het-erogeneities on very diverse size scales. These two charac-teristics require an adaptation of the neutron calculation tools:one of the channels pursued is the development of MonteCarlo type neutron calculation methods.

On the other hand, in gas reactors with once through cycle,the thermohydraulics of the core is strongly coupled with thatof the turbomachine: any change in the operation of one hasrepercussions on the operation of the other. These couplingsmust be taken into account and modelled in order to assurecontrol of the thermohydraulic behaviour of the system.

Fuel technology

The fuel is one of the deadlocks of gas reactors. For the VHTR,above all it involves finding a refractory fuel. Even if theyremain yet to be qualified, solutions already exist with UCO forthe fuel and ZrC for the cladding material.

Materials

It involves finding and developing mate-rials able to resist both high neutron flu-ence and high temperatures. Theresearch concerns refractory alloys,ceramics, and cermet and cercer com-posites.

Helium technology,components, equipment

First generation gas reactors use CO2

as a coolant fluid, and helium has beenlittle used in nuclear power. Current

research concerns tribology in helium, gas purification tech-niques, heat exchangers, pumps, turbines, as well as thermo-dynamic schemas enabling the best energy efficiency to beobtained from a helium-cooled reactor.

Fig. 105. Diagram of the thermochemical cycle of hydrogen produc-tion via the iodine-sulphur process.

Fig. 106. Example of research carried out for the development of theVHTR: CEA develops the test benches and loops for testing the maincomponents and equipment associated with helium technology.

••••

MaterialsHelium technologyComponent testsEquipment tests

Helium technological loop (Helite)

Test section 1,000° C

Recuperator

Test section 500° C

1,000° C

600° C500° C

100° C

200° C

1,000° CCooler

Cooler Compressor

HPC

Heating

(1 MW, Q ≈ 0,4 kg / s, T< 950° C, P > 7MPa)

H2 SO4Decomposition

H2 SO4DistillationHeat

T ~ 120° C

T ~ 850° C T ~ 450° C

Bunsen reaction

16H2O+9I2+SO2 → (H2SO4+4H2O)+(2HI+10H2O+8I2)

HIDecomposition

HIDistillation

H2O

H2O2



The gas-cooled fast reactor (GFR)In a long-term perspective aiming to meet the sustainabilityrequirement, the Gen IV forum has retained the gas-cooledfast reactor as a particularly interesting system.The latter mustsucceed in conciliating both the advantages of high tempera-ture gas reactors with those, known, of fast neutron reactors(optimal use of resources, reduction of waste production,transmutation of actinides). In addition, the specifications ofthe integrated cycle would reduce the risks of proliferation.

The reactors proposed will be based on the helium technol-ogy developed for the HTR and VHTR projects. Their speci-ficities are the fuel and its cycle, and the safety of the reactor.Their fuel cycle is at odds with the existing one because it isproposed to not partition U and Pu, and also to not partitionmajor actinides (U, Pu) from minor actinides (Np, Am, Cm).The core’s design (without blanket) will target the iso-genera-tion of plutonium and a non-proliferating cycle maintained onlyby the provision of depleted uranium.

The first studies have enabled the image of fuel for a gas fastreactor to be outlined.The latter must combine a high density

of fissile material with a good resistance to high temperaturesand to irradiation by fast neutrons. Several fuel concepts arecurrently being studied at CEA: a dispersed fuel, in which thefissile compound is presented in the form of grains or millimet-ric sticks dispersed within a “containing” matrix assuring thefunction of 1st barrier just like the PyC/SiC coatings of the HTRparticle; a fuel rod type concept with leaktight ceramic claddingis also being evaluated.

Towards a European demonstratorof 4th generation gas-cooled reactorWith the High Temperature Engineering Test Reactor (HTTR,30 MWth) which has been exploited since 1998 by JAERI,Japan currently has the most efficient test means on very hightemperature nuclear technologies, and on the nuclear produc-tion of hydrogen.The United States is preparing a first demon-stration of the production of hydrogen by thermochemicaldecomposition or electrochemical decomposition of water inthe Next Generation Nuclear Plant (NGNP, 600 MWth) projecton the national Laboratory site at Idaho. South Korea andChina are mentioning similar projects around 2020.

Fig. 107. High temperature gas reactors are already relativelymature, and may be deployed in “3+” Generation. These reactorsmay then develop towards even higher temperatures (VHTR), and/or towards a fast spectrum (GFR).

R&D• Particle fuel• Materials• He circuit technology• Calculation systems• Fuel cycle

HTRR&D• VHT resistant materials• Intermediate

heat exchanger• ZrC coated fuel• H2 production

VHTR

R&D• Fuel for fast neutron core• Cycle processes• Safety systems

GFR> Fast neutrons> Integral recycling

of the actinides



In this context, and given the industrial issues associated withthe very high temperature and nuclear production of hydrogentechnologies, CEA is studying a Study and TechnologicalDevelopment Reactor (REDT) at the Cadarache Centre, aim-ing to demonstrate the technological principles of the GFR.

The main development stages of the REDT may be:

• A first operating phase at 850-950°C with a thermal neutroncore aiming to demonstrate the European mastery ofupdated HTR technologies and of high temperature heatconversion processes for various applications: electricity, pro-duction of hydrogen by thermochemical cycle or high tem-perature electrolysis. Other applications may eventually com-plete the range of demonstrations possible: gasification ofthe biomass or desalination of seawater;

• A second operating phase, around 2020, with a fast neutroncore aiming to demonstrate the operating principles and spe-cific technologies of the GFR (the fuel in particular), thusrepeating the initial objectives of the REDT.

The REDT enables the upgrade of the wide experienceacquired in Europe on the high temperature reactor systems,and strengthens the position of European industrialists in theinternational competition to market reactors from this systemaround 2020.

The REDT could be considered as the main element of aEuropean test platform for key technologies for the VHTR andthe GFR, as well as for the various high temperature heatapplications. The purpose of this platform would be to supplythe necessary experimental conditions for the studies regard-ing the high thermodynamic efficiency cycles for the generationof electricity and the development of cogeneration processes.The platform would also enable the qualification of compo-nents for the conversion of energy (turbines, heat exchangers),and the study of processes for the production of hydrogen,gasification of the biomass and desalination of seawater.

The pre-project studies for this platform would come into theframework of the 7th European research and developmentframework programme as of 2007.



Other avenues for the distant future:thorium cycle, hybrid systems, fusion

The thorium cycle Thorium (Th 232) is a fertile material which is abundant innature. By absorbing a neutron and then by radioactive decay,it produces Pa 233 then U 233, a fissile isotope. The latter isinteresting, because its fission generates slightly more neu-trons than that of U 235 or Pu 239 in a thermal spectrum. Inthe 50s, these different reasons have led to interest in theU 233-thorium cycle; fuels were manufactured and used in var-ious reactors, of which the American Shippingport experimen-tal PWR, the Fort St. Vrain HTR and the German THTR.

Unfortunately, the emission of high energy (2.6 MeV) γ radia-tion by Tl 208 formed in recycled U 233-thorium fuels posesserious radiation protection problems in fuel manufacturinginstallations; this disadvantage is one of the reasons why theuranium-plutonium system is preferred 33 (the main reasonbeing that it would be necessary in any case to start a thoriumsystem with the only fissile material existing in nature, U 235;the thorium system, as opposed to the uranium system, maytherefore not be developed alone).

During the last few years, the thorium system has been thesubject of a new study, both because this system producesmuch fewer transuranium elements* and because roboticsand remote handling have made considerable progress, per-haps limiting the disadvantages linked with γ radiation. Theresults of these studies are summarized below:

• The best use of thorium is in molten salt thermal neutronreactors, which allow a reduced inventory in fissile materialand which are just as favourable on the resources level ason the waste level (reduction of the production of U 232source of Tl 208, of the reprocessing losses, of the conse-quences of accidental discharges, of the final waste); how-ever it does not enable doing without U 235 or Pu in order tostart the cycle and thus does not completely eliminate minoractinides;

• A Th-Pu cycle in a fast neutron reactor (critical or sub-critical)enables twice as much plutonium to be consumed as a U-Pu cycle (thanks to the absence of U 238), and large quan-tities of U 233 to be produced; once started, the U 233-tho-rium cycle may be self-sustained;

• A serious doubt remains on the possibility of using highlyenriched U 233; if an enrichment greater than 20% were pro-hibited for non-proliferation reasons, a significant quantity ofactinides would be found in the uranium-thorium cycle;

• The long-term radiotoxicity (1,000 years and beyond) ofwaste is dominated by residual U 233 and by severalradionuclides: Pa 231, U 232, U 234, Np 237. In most of thecases studied, beyond 104 to 105 years, uranium-thoriumcycles lead to a radiotoxic inventory which may be muchhigher than that of uranium-plutonium cycles. At that time,however, the radiotoxicity will have greatly decayed;

• A fast U 233-thorium reactor would be a good incinerator ofminor actinides, but the benefits from the point of view ofradiotoxic inventory of buried waste would not be significantbeyond 105 years;

• Conversely, the heat release from actinides produced in tho-rium-based cycles is much lower than in uranium-basedcycles; the result of this is that the “thermal” dimensioning ofthe disposal is only defined by the residual power of the fis-sion products. By contrast, the uranium-plutonium fuel cycleis handicapped by actinides with high thermal release(curium and, to a lesser extent, americium);

• Once the thorium is extracted from the mine, the daughterradionuclides which remain in the mine tailings decay veryquickly, at the rate of the period of 5.7 years from their topseries, Ra 228; it follows that, as opposed to uranium minetailings, the thorium mine tailings do not pose a real long-term problem.

The thorium based systems are therefore similar to uraniumsystems, as regards fission products and the quantities ofactinides in the very long-term; they are important for the “ther-mal” dimensioning of disposal, but present certain disadvan-tages for the remanufacturing of solid fuels after reprocessing(but the problem is the same for GEN IV cycles with integralrecycling of the actinides, because it will be necessary toremanufacture the fuel also by remote handling). Their maininterest resides in the increasing of resources; interest with avery distant timescale if fast spectrum uranium systemsdevelop normally, with closer timescales, in the opposite case.Under certain conditions, they would enable a reduction of thequantities of minor actinides produced. The thermal load ofglass could be diminished, with a subsequent reduction of theneeds in interim storage and disposal area.

33. This disadvantage only exists in the manufacturing of solid fuel; it is“drowned” in the highly radioactive background of a reprocessing instal-lation integrated near to a molten salt reactor.


96 Other avenues for the distant future:thorium cycle, hybrid systems, fusion

In such a scenario, where the failure of fast spectrum systemswould be postulated, thorium may only find its place in a ther-mal spectrum system capable of being self-sustained: themost attractive is the molten salt fuel system.The nuclear sys-tem would therefore be as follows:

• A fleet of water reactors producing plutonium;

• A fleet of thermal neutron molten salt reactors, started withplutonium produced in the former.

The thermal neutron molten salt reactors therefore seem tobe an alternative to fast spectrum reactors from the point ofview of a sustainable development of nuclear power.Consequently, this would require implementing two reprocess-ing processes, one by the aqueous method for water reactors,and the other one by the pyrochemical method for molten saltreactors.

The thorium based systems therefore present some clearadvantages and disadvantages. The result of this is that it isunlikely that they develop unless enormous amounts of fertilematerials are required in the future.

Accelerator-driven systems for the transmutation of wasteThe generation of electricity in a nuclear reactor is accompa-nied by the creation of heavy isotopes (“transuranium ele-ments”, heavier than uranium), some of which are radioactiveover long periods of time. Among them, plutonium has animportant energy potential, and France has chosen to extractit from spent fuels in order to recycle it in the fleet’s reactors(MOX fuel). Other transuranium elements, mainly neptunium(Np), americium (Am), and curium (Cm) isotopes constitute aproportion of the high level and long lived waste (HLLL).

As seen above, the isotopes of these minor actinides Np, Amand Cm are transmutable in a fast reactor. However, it is diffi-cult to introduce high proportions of minor actinides in the fuelof critical reactors, for neutronic reasons linked to the low pro-portion of delayed neutrons and to the low Doppler effect asso-ciated with these isotopes. For the transmutation of minoractinides, another approach consists of using, reactors oper-ating in subcritical mode driven by accelerators: the ADS(“Accelerator Driven Systems”), also known as “hybrid reac-tors”. In these systems, the neutron balance of the reactorrequires an external contribution of neutrons: the sub-critical-ity margin thus introduced (a few percent) would enable theuse of fuels loaded with a high actinide content under satis-factory conditions of safety. Therefore fleets of “double strata”reactors can be envisaged: for the French fleet, an assemblyof a few ADSs would assure the transmutation of minoractinides produced in the main fleet of electricity generatingreactors operating with U-Pu fuel.

Fig. 108. Principle of the ADS (Accelerator Driven System), or“hybrid reactors”.

Accelerator

Sub-critical reactor Fission

Neutrons

Transmutation

Protons 1 GeV10-100 mA

Spallation target

The principle of the ADS is simple: accelerated protons hit atarget located in the middle of the reactor’s core and producethe additional neutrons needed to complement the neutronbalance of a sub-critical reactor core. The production of neu-trons is carried out by the spallation process.The maintainingof neutron balance in the reactor is assured by controlling thebeam’s intensity.

Although the principle is conceptually simple, if they are con-structed, the ADS will be technologically and operationallycomplex installations.

In an industrial ADS system comprizing a ~1 GWth reactor,the associated proton accelerator must be of a very highpower (beam of protons with a power able to reach a few tensof megawatts: energy of ~1 GeV, optimal for the production ofneutrons, intensity of one to a few tens of mA, according to thechosen sub-criticality). Moreover, in order to avoid a too highnumber of power excursions, which would shorten the life ofthe reactor, the authorized number of undesired accelerationshutdowns is very low (a few breakdowns per year). The reli-ability requirement, unusual in the normal use of acceleratorsby physicists, is a major challenge for constructors. Only lin-ear accelerators should be able to supply proton beams withsuch performances, as the intensity of cyclotrons seems lim-ited to a few mA.

In order to produce a maximum number of neutrons, the spal-lation target will consist of a heavy element (rich in neutrons).The proton beam will be completely stopped in this target,which will therefore dissipate the totality of the beam power.The designing of these targets, probably liquid (lead or lead-bismuth), is an important technological challenge: the strengthof the entrance window crossed by the proton beam and sub-jected to high irradiation stresses, is essential, because it con-stitutes a barrier between the accelerator’s vacuum and thereactor; the evacuation of the heat produced by the beam andthe corrosion of the target’s shell by liquid metals are alsoimportant technological issues.



The reactor of an ADS will also be highly innovative.The trans-fer of the beam onto a reactor core target and the dissipationof the power produced require a very different design to thatof a conventional reactor, in particular as regards the safetybarriers (it seems difficult to encompass the entire acceleratorin a containment).

The designing of fuels incorporating large proportions ofactinides must call into play highly innovative concepts intoplay, both out of the reactor (strong γ activity and neutrons)and in the reactor (behaviour fairly unknown). Long stay timesin the reactor are necessary in order to destroy a significantproportion of minor actinides and, at the same time, actinideswith a higher atomic number are produced.The technologicalproblems linked to the behaviour in reactors of such fuels, totheir manufacturing, to the permanent disposal of spent fuelsor to their reprocessing and possible reconditioning for re-irra-diation, are highly complex and will require a great deal ofR&D.Finally, the ADS safety studies will be important because theymust validate an innovative design but also the new mode, ofdriving reactors with accelerators.

No ADS has been constructed yet since the first studies in the’50s concerning the use of accelerators in order to obtain anexterior supply of neutrons in a fission reactor.

However, linear proton accelerators and spallation neutronproduction targets have been constructed for other purposes 34

than that of the transmutation of nuclear waste (mainlyLANCSE at Los Alamos, in the United States, and ISIS, near

Oxford, in the United Kingdom).Although of lesser power and reliabilitythan those envisaged in the industrialADS, these installations have suppliedinteresting feedback. Other installationsare being prepared (the SNS neutronsource at Oak Ridge (United States),that of J-PARC at KEK, near Tokyo,Japan, where experiments on transmu-tation are planned).

ADS feasibility studies are now welladvanced. Work has been carried outon the national level, at CEA and in aCEA-CNRS collaboration, and on theEuropean level, under the aegis of theTechnical Working Group (TWG) andwithin the framework of the 5th and now,6th RDFP European projects.Industrialists have participed exten-sively in this work.

In the CEA-CNRS collaboration, zero power experiments havebeen carried out at Cadarache on the critical Masurca mock-up (CEA-Cadarache) and a high-intensity proton injector is inthe process of being constructed at CEA-Saclay.

Two significant steps could be taken within the framework ofthe 6th European Research Program: the completion of ademonstration experiment consisting of coupling a protonaccelerator to a reactor for the first time and the production bya group of European laboratories of a fairly detailed pre-proj-ect of a significant power demonstrator.

To date, no complete economic study of the ADS conceptexists, in particular because the fundamental choices regard-ing its elements (accelerator, spallation target, reactor type)are yet to be made. However, it is certain that the cost of anADS would be considerably higher than that of a critical reac-tor because, to the almost identical reactor cost, it is neces-sary to add those of the accelerator and the target.

The future of ADS is conditioned, firstly, by a decision regard-ing the continuation of the studies and establishment of thepartitioning-transmutation on an international level. Secondly,if the HLLL waste management mode by partitioning/transmu-tation is adopted, the two transmutation techniques, in criticalreactor or in sub-critical reactor (ADS) will have to be dealtwith, regarding the technological and economical aspects.

In any case, it will not be possible to deploy ADS on an indus-trial scale before a few decades, as they still require a veryimportant R&D and demonstration effort.

Intra-nuclear cascade Excited nucleus

Fission products Spallation residue

Evaporation

Fig. 109. Spallation mechanisms.

n

p (1 GeV)n

n

n

γ

γ

γ

α

α

α, β, γ decay

ππ∆

p

d

34. The ADS could also be a precious tool as a neutron source for tech-nological radiation tests of various materials and, in particular, fuels.



Thermonuclear fusionPotentially, fusion energy is one of the most interesting primaryenergy sources, because:

• There are no reserve problems (it consumes deuterium andlithium used to produce tritium; these elements are abundantin nature);

• The fusion reaction does not produce any high level andlong-lived radioactive waste;

• Fusion does not induce greenhouse gas effects (no produc-tion of CO2);

• A fusion reactor is intrinsically safe (immediate disappear-ance of plasma in the event of malfunction; no “nuclear mate-rial”).

But the industrial application of nuclear fusion* is still facedwith major technological challenges which will require inten-sive R&D prior to arriving at the electricity generation installa-tion construction stage.

Several fusion reactions of light nuclei may be used in princi-ple to produce energy. In practice, the only reaction to have asufficiently low energy to be considered is the nuclear fusionreaction between the nuclei of two hydrogen isotopes, deu-terium (D) and tritium (T):

D + T → 4He (the “α”; 3.5 MeV) + n (14.1 MeV)

This reaction can only be produced if the deuterium and tri-tium isotopes are completely ionised, otherwise atom-atom oratom-ion collisions, much more probable than nuclear fusion,prevent the nuclei from fusing. In the case of complete ionisa-tion and as of a few tens of keV of kinetic energy of D and T,this reaction is produced with a significant probability by “tun-nel effect”. It can therefore be used to produce energy, if it hasbeen possible to maintain the D and T nuclei in interaction,that is, if the plasma formed by the deuterium, tritium and elec-trons from the ionisation has been kept confined and suffi-ciently “hot”.

Two possible methods are offered to assure the confinement:

• Magnetic confinement, by which the plasma’s particles(charged) are maintained confined in a finite space by a suit-able magnetic field configuration;

• Inertial confinement, which in fact involves a compression-heating of a D-T mix by pulses from laser beams or conver-gent pulsed particle beams; fusion is produced and lasts aslong as the compression is sufficient, the process is repro-duced on each pulse.

In magnetic confinement systems, the most developed beingthe “tokamak” type, the heating of plasma (that is maintainingthe kinetic energy of the D and T nuclei at a value high enoughfor fusion to occur) takes place in many ways:

transfer of the energy from α particles from the fusion reactionto the D+T plasma; ohmic heating induced by the plasma’s

Fig. 110. Two possible magnetic configurations to confine theplasma: cylindrical and toroidal. In both cases, the D and T ionspropagate along the field lines. The toroidal configuration is the basisof most installations.

Fig. 111. Combinations of coils in a Tokamak to produce the mag-netic field confinement of plasma.



electric current; heating by high frequency electromagneticwaves or heating by neutral particle injection.

The state-of-the-art on fusion by magnetic con-finement

So that fusion can be used as an energy source, it is neces-sary that the energy produced by the fusion be greater thanthat injected to heat and maintain the plasma (Q = Pfus/Pext >1).This system, called “breakeven” is expressed by a constraintof the type:

n. τE > f (T)

where n is the density of plasma, τE the confinement time andT its temperature.

Considerable progress has been made in the last few decadeson the fulfillment of this criterion. By way of example, the Tore-Supra installation in Cadarache now produces plasmas con-fined over several minutes, and the European JET installation,in Culham, England, is close to meeting this Q>1 constraint.

Many technological problems, however, are yet to be solvedprior to envisaging the construction of an industrial installation,in which the α particles produced by the reaction would be suf-ficient to heat the plasma. These technological problems areof three orders:

• The toughness of the materials in contact with the plasma:

In an industrial system, the first lining must evacuate a veryhigh power density (it may locally exceed 20 MW/m2), supportthe very high neutron fluxes which will cross it in order to gointo the tritigenous blankets and enable the evacuation of alarge quantity of gaseous helium originating from the fusionreaction.The development, in the 80s, of the “divertor”, a spe-cial magnetic configuration making it possible to better man-age the fluxes to be evacuated from the plasma, has con-tributed a great deal to the progress accomplished during thelast two decades.

• The production of tritium in the lithium tritigenous blankets:

In such systems, the neutrons, originating from the fusionreaction continuously produce the tritium consumed in theplasma, by interaction with the lithium blankets (“tritigenousblankets”), thus avoiding the storage and handling of thisradioactive element. The overall quantity of tritium present inan industrial type installation is therefore only a few grams.However, tritium diffuses easily and the control of its diffusionis an important safety aspect.

• The minimisation of the activation of the blanket materials:

The neutrons interacting with the walls cause the appearanceof radioactive elements, via nuclear reactions. The choice ofthe composition of the blanket materials must be such that itminimises, in level and in time, the production of the reactivityinduced.

Inertial confinement-heating only seems possible with pho-ton beams (lasers) or heavy ions, but, even in this case, thescientific and technical problems to be solved do not enablean industrial-scale implementation in a foreseeable future.

The ITER project and nuclear fusionoutlookThe purpose of the global ITER nuclear fusion experimentalreactor project is to scientifically and technically demonstratethat it is possible to use fusion to produce energy. The part-ners are the European Union, Russia, Japan, the UnitedStates, China and South Korea.

The installation (Fig. 113) will be of the tokamak type.With sizeand performances similar to the industrial reactors envisaged(Q = 10, heating of the plasma to 66% by α particles), it will

Fig. 112. Performances reached by existing or project installations, inthe “Lawson vs. temperature parameter” diagram. It will be noted thatITER* is located at the limit of the ignition zone (a α particles fromthe fusion will assure 2/3 of the plasma’s heating).

Ignition

ITER

Central ion temperature (keV)

Law

son

para

met

er;n

.τE

(10

20m

-3s)



enable the research which is still necessary on materials andthe operation of a fusion reactor to be carried out in a realisticconfiguration.

The Cadarache site was retained to host this €4.5 bn installa-tion. The construction time is 12 years and ITER should beoperated during approximately twenty years.

If the results gathered and the studies of materials confirm thescientific and technological possibility of using nuclear fusionfor the production of energy, an industrial production reactorprototype, studied in parallel to the ITER operation, could thenbe constructed. Even then, the road leading to the industrialexploitation of nuclear fusion will be long, because the eco-nomic competitiveness of this mode of energy production stillremains to be demonstrated.

Fig. 113. Diagram of the ITER installation, global scientific and technical validation project for the use of fusion for the production of energy.

Central solenoid Blanket element

Vacuum chamberToroidal field

coils

Cryopump

CryostatPoloidal fieldcoils

Support columns

Heating of the plasma

Divertor

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Conclusion

The world of nuclear power is rapidly evolving and theprospects of increasing the global fleet are being confirmed.Nuclear energy is currently recognized by most organisationsissuing energy projections for future decades (InternationalEnergy Agency, World Energy Council) as an available, reli-able and environmentally friendly energy source because itdoes not emit polluting or greenhouse gases. Nuclear powerhas its place fully in the global energy mix.

France which has succeeded in one of the most ambitiousnuclear development programmes, can now promote thechoice of its energy policy to the exterior by showing its advan-tages.

However large obstacles must be mentioned: nuclear poweris not recognized by the Kyoto agreements as eligible forfinancing mechanisms aiming to limit greenhouse gas emis-sions. Although the future development of nuclear powerseems assured in Asia, in spite of that, it will largely depend ondemocratic debate in the West. Removing these obstaclesrequires a better acceptance of civilian nuclear power in theeyes of the public and its political representatives.This impliesthat industrialists and scientists must build confidence, in along and continuous process, where all mistakes, particularlyin the field of safety, must be avoided.

All in all, nuclear energy is a young energy: it is only 50 yearsold! It has come a long way since its birth, but the prospectsof progress are still very great.

In the short-term, continuous development progress can beexpected, and existing systems will benefit from it: this is theaim of the research supporting current industrial nuclearpower. This research concerns the reactor safety and theimprovement of competitiveness, particularly by extending thelifetime of power plants, but also by increasing the fuel burnuprate. A lot of incremental research is being carried out in part-nership with industry, in a not very spectacular way, becausein nuclear R&D, time constants are very long, and significantscientific results are not obtained every week. This R&D car-ried out in partnership with industrialists is an integral part ofthe quality of the French nuclear offer. In an internationalizedmarket such as that of nuclear power today, it constitutes oneof its main and recognized advantages.

In the long term, radical progress can be expected, even rup-tures associated with the development and the emergence ofnew types of nuclear reactors, that can be used for electricityproduction as well as for other applications, hence the impor-tance of the research on innovative reactors. These reac-tors cannot be studied in isolation.They are indissociable fromtheir fuel cycle. Moreover, nuclear power will only be sustain-able if nuclear materials are recycled: given its importance,research on reprocessing-recycling must be continued.CEA is commited to research programmes on future nuclearsystems, with international collaborations in which it plays aleading role: firstly the Generation IV International Forum,which has retained six concepts for the long-term R&D, fourof which are “closed cycle”. Other collaborations includeEuropean programmes and projects carried out bilaterally withthe United States, Japan, Russia and China.

The waste issue warrants close attention because it repre-sents a particularly sensitive point in the eyes of the publicopinion and political power. Research in progress has alreadyproduced technical solutions to partitioning, conditioning andstoring waste under good safety conditions. In view of a polit-ical decision on the implementation of these solutions, Frenchlaw prescribes carrying out research on all possible meth-ods of waste management.

More generally, development must not only be an escape intothe future, it must also properly finish up old operations: thisis the aim of research on dismantling, decontaminationand clean-up.

For all of this research, time and means are needed.

The CEA is backed by a solid nuclear industry, in particularAREVA and EDF, which have legitimate ambitions on theglobal energy market. This is an important advantage whichshould enable CEA to highlight the results from its research.

The world of research is evolving. Science in the 19th centuryand in the first half of the 20th century was dominated bygeniuses; then came the time of laboratories, but that time hasalso past. Now is the time for international networks and struc-tures. CEA must therefore adjust to these new conditions, byintegrating its R&D effort into international cooperation, on theEuropean level within the framework of research programme,and on the global level in the existing networks, as for exam-ple the Generation IV Forum. An international consensus on

MonoCEA GB 5/04/06 15:31 Page 101

102 Conclusion

the strategic and technical choices for the nuclear power of thefuture would present the interest of considerably increasingthe credibility of the solutions proposed in the eyes of the pub-lic opinion and decision makers.

In this stimulating overview, the CEA and its Nuclear EnergyDivision is monitoring developments in the world of nuclearpower. Every year it receives in its laboratories approximatelyfifty foreign employees, mainly from China, Russia and Japanand also transfers engineers to these countries. It participatesin the IAEA work on safety and non-proliferation, as well as inthat of OECD/NEA in technical, economical and social fields.

On the international scale, the Nuclear Energy Division isdevoted to the ambition of contributing to the peaceful and sus-tainable development of this energy.

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Glossary - index

Activity: number of disintegrations per unit of time within aradionuclide or a mixture of radionuclides. It is expressed in bec-querels (Bq), which corresponds to one decay per second. 19, 59,63, 97.

ADS: “Accelerator Driven System”, hybrid reactor coupling a sub-critical reactor core with a high energy proton accelerator.The lat-ter supplies the additional neutrons necessary to maintain thechain reaction thanks to spallation reactions. 62, 63, 77, 78, 96, 97,98.

ALARA: “As Low As Reasonably Achievable”. General manage-ment principle relating to radiation protection that consists in min-imising radioactive emissions or doses as much as is reasonablypossible, given economic and social constraints. 61, 62.

ANDRA: Agence nationale pour la gestion des déchets radioac-tifs.The French national agency for radioactive waste management.

ATALANTE: see chapters “The near future: research supportingthe existing nuclear power” and “Research regarding waste man-agement”. 49, 50.

Atom: the basic unit of matter. It is made up of a nucleus (itselfmade up of neutrons and protons) around which electrons gravi-tate. 12, 16, 43, 51, 87, 98.

Atomic number: a number assigned to each element accordingto Mendeleev’s classification. It is equal to the number of protonsin the nucleus of an atom of the element in question.

Barn: unit used to measure a nuclear cross section.(1 barn = 10-24 cm2). 75.

Barriers: in a nuclear reactor, all physical elements that isolatefuel radionuclides* from the environment. In a pressurized waterreactor*, it relates successively to the cladding of the fuel element,the shell of the primary circuit (including the vessel) and the reac-tor containment. 20, 29, 30, 32, 97.

Binding energy: the energy required to extract a particle from aphysical system, for instance a nucleus.

Boiling water reactor (BWR): reactors in which water is boileddirectly in the core. 11, 18, 53, 76, 78, 79, 89.

Breeder reactor/breeder: a reactor that produces more fissile*fuel than it consumes. New fissile nuclei are created by fissionneutron* capture by fertile* nuclei (non-fissile under the action ofthermal neutrons*) after several radioactive decays*. 12, 75, 77.

Burn-up: see Specific burn-up*.

Burn-up rate: in the literal sense, it corresponds to the percent-age of heavy atoms (uranium and plutonium) that underwent fis-sion* for a given duration. It is commonly used to evaluate thequantity of thermal energy per unit of fissile* matter massobtained in a reactor between fuel loading and unloading and isexpressed in megawatt days per tonne (MW·d/t).

Calculation software: the grouping of the simplified representa-tion (modelling) of a system or a process in software, in the formof coded mathematical expressions in order to simulate it.

Chain reaction: a string of nuclear fissions* during whichreleased neutrons* produce new fissions, in turn generating newneutrons producing new fissions and so on.

Cladding: envelope surrounding the fuel material, designed tomaintain its position in the reactor core, and to ensure its isolation.15, 16, 18, 19, 29, 47, 49, 51, 57, 64.

Climate change: see chapter “Energy in the world”. 33.

Conditioning (waste): operation by which nuclear waste is put ina stable and durable form. 8, 16, 17, 21, 23, 60, 63-65, 97.

Control cluster: see Control rod*.

Control rod: rod or collection of connected mobile shafts contain-ing matter that absorbs neutrons and that, according to its positionin the nuclear reactor core, influences its reactivity.

Coolant: fluid (gas or liquid) used for extracting the heat producedby fissions*. In a pressurized water reactor*, water plays therole of both a coolant and a moderator*. 9, 12, 49, 75, 77, 78, 82-93.

Contamination: undesirable presence of a radioactive substancein contact with a surface or inside an environment. 23, 24, 27, 29,31.

Core: region of a nuclear reactor in which a nuclear chain reactioncan occur. 9, 12, 13, 18, 23, 29, 30, 47-49, 53, 55, 56-58, 62, 75, 77,83-85, 91-94, 96.

Core melting: nuclear accident during which the nuclear fuel isheated to such extent that it melts.The resulting corrosive magma(the corium*) gathers at the bottom of the reactor vessel, whereit can cause further damage to the reactor. 30, 55.

Corium: mixture of molten materials resulting from the acciden-tal fusion of a nuclear reactor core. 55, 57, 58.

Critical: an assembly of material containing fissile matter can bequalified as critical when the number of neutrons* emitted by fis-sion* is equal to the number of neutrons disappearing by absorp-tion and leakage. In this case, the number of fissions observedduring successive intervals of time remains constant. Criticality*is the expression of an exact equilibrium between the productionof neutrons by fission and disappearances by absorption or leak-age. 29, 62, 96-98.

Cross section: measure of the probability of interaction of a par-ticle with a target-nucleus, expressed in barns (1 barn = 10-24 cm2).The cross section measures the probability that a given reactionwill occur between incident particles (neutrons for example) and atarget (uranium nuclei for example). In nuclear reactors, we mainlydistinguish reactions caused by neutrons: fission, capture, andelastic scattering. 75.

Daughter product: nuclide formed from the spontaneous decayof a radioactive nuclide.

Decommissioning: group of administrative and regulatory oper-ations to either file a nuclear installation in a lower category or todelete the initial filing. 23, 25.

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104 Glossary - index

Defence in-depth: see chapter “Nuclear safety and security”.27.

Desalination (of sea water). 9, 79, 82, 94.

Disintegration: transformation of an unstable nucleus into a sta-ble or unstable nucleus during which the number and the natureof the nucleons are modified.

Dismantling: group of technical operations that lead a nuclearinstallation to a chosen level of decommissioning*. 23-26, 30, 39,101.

Disposal facility (of nuclear waste): underground installation inwhich nuclear waste is disposed of, without prospect of retrieval.Retrieval would be possible in the case of a reversible storage*.

Divergence: start-up of the chain reaction* process in a reactor.88.

Dose (absorbed): quantity of energy absorbed locally per unit ofmaterial mass (inert or live). It is expressed in grays* (Gy): 1 graycorresponds to 1 joule of energy absorbed per kilogram of material.

Dose (effective): the sum of the weighted equivalent doses deliv-ered to the organs of a living body by internal or external irradia-tion.The unit of effective dose is the Sievert (Sv). For example, theaverage annual dose received yearly from natural origins (soil,cosmic rays…) is of the order of 2 milliSievert (mSv).

Dose (equivalent): in living organisms, the effects of a givenabsorbed dose* depend on the nature of the radiation (x, α, β, γ).In order to take these differences into account, one uses a multi-plicative factor to calculate an equivalent dose.

Dose (radioactive): see chapter “Nuclear safety and security”.27.

Economy of nuclear power. 39.

Electronvolt (eV): unit of energy used in nuclear physics, 1 eV =1.6·10-19 joule.

Enrichment: a process which, in the case of uranium, enablesisotope 235 concentration to be increased using various meth-ods (gaseous diffusion, ultracentrifugation, selective excitation bylaser) in relation to isotope 238 predominant in natural uranium. 17,18, 30, 31, 41, 53, 76, 79, 95.

Epithermal neutrons: neutrons located in the 10 eV* to 20 keVenergy range, approximately, and with a speed greater than thatof thermal neutrons*.

EPR: European Pressurized Reactor. See chapter “Preparing thereplacement of current reactors with more efficient and safer 3rd

generation reactors”. 53.

Fast neutrons: neutrons released during fission, moving at veryhigh speeds (20,000 km/s).Their energy is in the order of 2 millionelectronvolts*. 6, 9, 16, 40, 42, 52, 57, 62, 75, 76-78, 83, 86-88, 93-95.

Fast neutron reactors (FR): reactors without moderators* inwhich the majority of fissions are generated by the high energy neu-trons* produced by fission*, with as little slowdown as possible.16, 62, 68, 76, 78, 83, 88, 89, 95.

Fertile: a matter whose nuclei yield fissile* nuclei when theyabsorb neutrons, for example, uranium 238 which leads to pluto-nium 239. Matter is called sterile* if the contrary is true. 16, 17, 67,74, 75, 77, 93, 95, 96.

FIMA: (Fission per Initial Metallic Atom). The FIMA is a combus-tion rate unit for nuclear fuel, expressed in terms of the proportionof fissions made in a population of heavy metal atoms.

Fissile (nucleus): nucleus which can undergo fission* by neu-tron* absorption. However, the fissile nucleus does not undergofission, the composite nucleus formed after neutron capture does.13, 15, 16, 17, 18, 30, 62, 67, 75-77, 83, 85, 95.

Fission: the splitting of a heavy nucleus in two, accompanied byneutron emission, radiation, and high energy release. 12, 13, 16,19, 75, 77.

Fission products: nuclides* generated either directly by nuclearfission*, or indirectly by the decay of fission fragments. 12, 15, 16,19, 61, 64, 70, 71.

Fluence: dose unit used to quantify material irradiation.The num-ber of particles (neutrons) arriving per unit of surface area duringirradiation. 52, 56, 57, 92.

Fuel: matter containing the fissile nuclei which maintain the chainreaction* in the core of a nuclear reactor. 8, 15-18, 47-52, 56, 57, 67-71.

Fuel cycle: all steps followed by the fuel from extraction of the oreto waste disposal to the possible recycling of material in the reac-tor. 9, 17, 19, 43, 45, 47, 53, 62, 65, 67, 73, 74, 77, 84, 87-89, 93, 101.

Fuel rods: a small diameter tube closed at both ends, making upthe core of a nuclear reactor, containing fissile, fertile or absorbentmatter. When it contains fissile matter, the fuel rod is a fuel ele-ment*. 15, 17, 19, 48, 51, 56, 57, 93.

Generation (of nuclear reactors). 7, 11, 53, 68, 69, 79.

GIF or Gen IV: international collaboration for the development ofnuclear systems of the 4th generation. 78, 93, 96.

Glove box: containment in which material can be manipulatedwhile isolated from the operator. Handling takes place using glovesfixed in a leaktight way to openings provided in the wall of the con-tainment. Generally, it is set to partial vacuum to contain radioac-tive substances.

Gray: unit of absorbed radioactive dose, corresponding to theabsorption of 1 joule of energy per kilogram of matter.

GWe: electric power provided by a power plant.

GWth: thermal power provided by the same power plant.

Heavy nuclei: denomination given to isotopes* of elements withproton numbers (atomic number) greater than or equal to 80. Allof the actinides and their daughter products are in this group. 17,67, 68, 75.

Heavy water: deuterium oxide (D2O). 11, 12, 53, 54, 75, 76, 78, 79.

Hot Cell: highly shielded cell of a hot laboratory in which high levelsubstances are handled using remote manipulator arms.

Hybrid system: system that combines a spallation neutron*source with a subcritical* reactor for the transmutation* ofnuclear waste or for energy production. 78.

Hydrogen. 9, 33, 36, 55, 57, 79, 82, 84, 90-92, 94, 98.

Incineration (of Nuclear waste*): destruction of actinides, espe-cially minor actinides*, in nuclear reactors through fission* andneutron* capture. 27

INES scale: scale of gravity of nuclear incidents and accidents.30.

Ionising radiation: radiation capable of producing ions when itpasses through matter.

Irradiation: a living organism’s or a material substance’s expo-sure to radiation.

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Isotopes: forms of the same chemical element whose nuclei havean identical number of protons and a different number of neutrons.16, 18, 27, 73, 75, 96, 98.

ITER: prototype reactor for the study of nuclear fusion, developedin the frame of an international collaboration. See chapter “Otheravenues for the distant future: thorium cycle, hybrid systems,fusion”. 99, 100.

LECI: Laboratoire d’Études des Combustibles Irradiés (IrradiatedFuel Studies Laboratory) at CEA Saclay. 23.

Light water: ordinary water as opposed to heavy water. 43, 53,57, 67, 68, 73, 76, 87, 90.

Light water reactors (LWR): a family of reactors in which ordi-nary water is used both as a coolant and as a moderator.The fam-ily of LWRs includes pressurized water reactors* and boilingwater reactors*. 87, 90.

MeV: mega electron-volt. This unit of energy is generally used toexpress the energy released through nuclear reactions. 1 MeVcorresponds to 1.6 10-13 Joules.

Minor actinides: heavy nuclei formed in a reactor by successivecapture of neutrons* from the fuel’s nuclei. These isotopes* aremainly neptunium (237), americium (241, 243) and curium (243,244, 245). 8, 16, 19, 31, 59, 61-63, 67, 69, 70, 77, 87, 93, 95-97.

Moderator: material formed of light nuclei which slow down theneutrons by elastic scattering. It must capture as few as possibleso as not to “waste” the neutrons and be sufficiently dense toensure an effective slowing down of the neutrons. 12, 53, 75, 76, 78,79, 89.

MOX (Mixed OXides): mixture of uranium (natural or depleted)and plutonium oxides. 17, 18, 31, 41, 48, 53, 55, 56, 77, 83, 87, 96.

Neutron: a fundamental electrically neutral particle, whose massis 1.675·10-27 kg.This nucleon* was discovered in 1932 by Britishphysicist James Chadwick. Neutrons and protons constitute theatom’s nucleus. Neutrons can provoke fission* reactions in fis-sile* nuclei. This energy is used in nuclear reactors.

Neutron balance: the result of neutron productions and losses ina reactor.

Neutron flux: the number of neutrons crossing a unit surface areaper unit of time. 56, 57, 75, 87, 99.

Neutronics: the study of neutrons*’ path in fissile* and non-fis-sile environments and the reactions they provoke in matter, in par-ticular in nuclear reactors in terms of multiplication, establishmentand control of the chain reaction*. 51, 52, 56, 57, 86, 87, 92, 96.

Neutron spectrum: energy distribution of the neutron* populationpresent in the reactor core.

Nuclear fusion: a nuclear reaction in which two light nuclei bindtogether to form a heavier nucleus. 98, 100.

Nuclear system: possible means of constructing nuclear reac-tors capable of functioning under satisfactory safety and economicconditions, defined mainly through (1) the fuel type, (2) neutronenergy involved in the chain reaction, (3) moderator and coolanttype.

Nucleons: particles that make up an atom’s nucleus, i.e. protonsand neutrons*, which are linked together by the strong interac-tion that causes nucleus cohesion.

Nuclide: a nuclear type characterized by its number of protons Z,its number of neutrons* N and its mass number A, equal to thesum of the number of protons and neutrons (A = Z + N);Radionuclide*: a radioactive isotope*, sometimes also called aradioisotope.

Package: a kit made up of packing for transport, storage and/ordisposal and of specified radioactive* material contents. 20, 31,60, 61, 63-66.

Partitioning: chemical process used to separate the elementscontained in spent fuel.The PUREX process isolates uranium andplutonium ; other more advanced processes (DIAMEX, SANEX,GANEX) are under study, in order to separate actinides from lan-thanides, or actinides from each other. 8, 21, 59-62, 68-70, 87.

Phénix: prototype of sodium-cooled, fast neutron reactor. Seechapter “Nuclear systems of the future: an international frameworkfor the development of a new generation of nuclear systems”. 62,63, 83, 88.

Plutonium: element formed by neutron capture on uranium nucleiin the core of nuclear reactors. Plutonium can be recycled innuclear reactors, for example in the form of MOX* fuel, becauseits odd isotopes are fissile*. 8, 12, 15-18, 30, 31, 40, 48, 59-62, 67,70, 75, 77, 83, 87.

Poisons (Neutronic*): elements with a high neutron* capturecapacity, used to fully or partially compensate for excess reactiv-ity* in fissile* environments. Four natural elements have notableneutron-absorbing properties: boron (thanks to its isotope* B 10),cadmium, hafnium and gadolinium (thanks to its isotopes Gd 155and Gd 157). Some are called “consumable” because they disap-pear progressively during reactor combustion. Some fission prod-ucts* are neutron poisons because they absorb neutrons.

Poisoning (nuclear fuel): the phenomenon of neutron captureby certain fission products that build up during irradiation (xenon135, samarium 149, etc.), which deteriorate the neutron bal-ance*.

Potential radiotoxicity (of a certain amount of radionuclides, inwaste for example). Potential radiotoxicity, defined as the productof the radionuclide inventory through the dose “ingestion” factor ofthose radionuclides, is an indicator of the power to harm of thisquantity of radionuclides in an accident situation. 31, 59.

Pressurized water reactor (PWR): reactors in which heat istransferred from the core to the heat exchanger via the water keptunder high pressure in the primary circuit to keep it from boiling.79, 87, 89, 90, 95.

Primary energy: see chapter “Energy in the world”. 33.

Processing (of spent fuel): chemical process used to separaterecyclable nuclides in the spent fuel. The rest is then consideredas a waste and receives an appropriate conditioning. (SeeVitrification*.) 8, 16, 17, 59, 68, 78.

Proliferation: uncontrolled dissemination of the military nucleartechnologies, or of the nuclear matter used by those technologies.7, 9, 30, 31, 40, 41, 67, 68, 82, 85, 86, 89, 93, 95, 102.

Radioactive half-life: period after which half the radioactive*atoms initially present have disintegrated. 19.

Radioactivity: property of certain natural and artificial elementsto spontaneously emit alpha and beta particles or gamma radia-tion.This term more generally designates the emission of radiationaccompanying the decay* of an unstable element or fission*. 7,9, 20, 23, 25, 27-29, 31, 32, 51, 59-61, 63, 70, 100.

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106 Glossary - index

Radioecology: study of the transfer of radionuclides into the bios-phere. 28.

Radionuclide: radioactive isotope (see Nuclide*).

Radionuclide inventory: quantity of fission products andactinides contained in irradiated fuel, generally expressed inBq/gMLi or in g/tMLi (Becquerels or grams per tonne of initialheavy metals). These quantities depend on the type of fuel andthe irradiation conditions (combustion rate, etc.).

Radon: a radioactive gas resulting from decaying uranium andthorium present in the Earth’s crust. 27, 28.

Reactivity: deviation from unity of the ratio of the number of neu-trons produced by fission and the number of neutrons lost in areactor core. In a reactor, reactivity is zero when it is critical*, pos-itive if it is supercritical* and negative if it is sub-critical*.

Reactor CANDU: reactor cooled and moderated by heavy water.CANDU reactors can use fuel made of natural uranium. 43, 54,76, 78.

Reactor Jules Horowitz (JHR): see chapter “The near future:research supporting the existing nuclear power”. 49.

Reactor RBMK: reactor with a water coolant and a graphite mod-erator.This type of reactor was involved in the Chernobyl accident.76.

Recycling: Re-use in reactor of nuclear matter produced by theprocessing* of spent fuel. 8, 9, 17, 18, 40, 53, 59, 61, 62, 63, 67-71,77, 83-88, 93, 96, 101.

Resources (in uranium): see chapter “Uranium resources”. 73.

Rheology: branch of mechanics which studies the behaviour ofmaterials under stress situation. 58.

Risk: see chapter “Nuclear safety and security”. 27.

Safety (nuclear): measures taken to mitigate the danger associ-ated to nuclear activities or installations, by measuring and control-ling the associated risk. 19, 32, 57.

Simulation: see chapter “The near future: research supportingthe existing nuclear power”. 47.

Sintering: operation which consists in soldering the grains of ametal or ceramic compacted powder, by heating this powder belowits melting temperature. 17, 48.

Spallation: a nuclear reaction involving a target heavy nucleusand a particle, most often a high energy proton.Through succes-sive reactions, a beam of these particles can produce a large num-ber of neutrons*, among others. A one-billion electronvolt protonprojected on a lead target can generate 25-30 neutrons. 78, 96-98.

Specific burn-up (or burn-up or combustion rate): total energyreleased per unit of mass in a nuclear fuel. Generally expressedin megawatt x day per tonne.

Stability valley: line of the stable isotopes in a diagram represent-ing nuclides according to their number of protons and neutrons.

Storage (of nuclear waste): installation in which nuclear wastepackages are stored, with the prospect of an ulterior retrieval. 21,23, 31, 32, 64-66, 71, 87, 96.

Sub-critical: a system is qualified as sub-critical when the num-ber of neutrons* emitted by fission is lower than the number ofneutrons disappearing by absorption and by leakage. In this case,the number of fissions observed during successive time intervalsdecreases. 62, 95, 96, 98.

Thermal-hydraulics: a branch of physics dedicated to heat trans-fers and fluid mechanics. 51, 56, 57, 86, 92.

Thermal neutrons: also known as slow (or thermalized) neu-trons*, neutrons in thermal equilibrium with the material in whichthey move at a speed in the order of 2 to 3 km/s. Their energy islower than 1 electronvolt*. 9, 12, 16, 76, 77, 89, 94-96.

Thorium: this heavy element, abundant in nature, could be usedfor nuclear energy production. Its isotope Th 232 is fertile and hasa fuel cycle analogue to the U 238 fuel cycle. 95.

TOE: unit of energy corresponding to a Tonne of Oil Equivalent.

Transmutation: transformation of an isotope* into another, morespecifically that of a long-lived radioactive isotope into a short-livedor a stable isotope* through a nuclear reaction (neutron* cap-ture, fission*). 8, 21, 59, 62, 63, 87, 88, 96-98.

Transport (of nuclear matter): see chapter “Nuclear safety andsecurity”. 27.

Transuranium elements: all of the elements whose atomic num-ber is greater than that of uranium.These heavy nuclei result fromuranium through neutron* capture or radioactive decay* and notfrom fission*, and can be divided into seven isotope* families:uranium, neptunium, plutonium, americium, curium, berkelium andcalifornium. 95, 96.

UOX: standard fuel for light water reactors* made from uraniumoxide enriched* in uranium 235. 16, 55-57, 60, 71, 77, 87.

Vessel: receptacle containing the core of the reactor and itscoolant fluid*. 13, 23, 29, 51, 52, 56, 57, 58.

Vitrification: operation which consists in incorporating waste in aglass melt to give them a stable conditioning under the form ofstorable waste packages. 16, 17, 64.

Waste (nuclear): unusable residue, result of the utilization ofnuclear energy. 7, 9, 16, 17, 19-21, 25, 31, 46, 59-66, 82, 101.

Zircaloy: an alloy of zirconium and one or several other metals(tin, iron, chromium, nickel, niobium) that is particularly resistantfrom a mechanical and chemical point of view. It is used for fuelcladding in light water reactors. 15.

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