nuclear waste.docx

8/2/2019 NUCLEAR WASTE.docx

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NUCLEAR WASTEMANAGEMENT

Nuclear power is characterised by the very large amount of energy available

from a very small amount of fuel. The amount of waste is also relatively small.

However, much of the waste is radioactive and therefore must be carefullymanaged as hazardous waste.Since the radioactive wastes are essentially created in a nuclear power reactor,it is accepted that they are the responsibility of the country which uses

uranium to generate power. There is no moral or legal basis for the

responsibility to be elsewhere.

Radioactive wastes comprise a variety of materials requiring different types ofmanagement to protect people and the environment. They are normally

classified as low-level, medium-level or high-level wastes, according to theamount and types of radioactivity in them.

Another factor in managing wastes is the time that they are likely to remain

hazardous. This depends on the kinds of radioactive isotopes in them, and

particularly the half-lives characteristic of each of those isotopes. (The half-

life is the time it takes for a given radioactive isotope to lose half of its

radioactivity. After four half lives the level of radioactivity is 1/16th of the

original and after eight half lives 1/256th, and so on.)

The various radioactive isotopes have half-lives ranging from fractions of a

second to minutes, hours or days, through to billions of years. Radioactivity

decreases with time as these isotopes decay into stable, non-radioactive ones.

The rate of decay of an isotope is inversely proportional to its half-life; a short

half life means that it decays rapidly. Hence, for each kind of radiation, thehigher the intensity of radioactivity in a given amount of material, the shorter


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the half lives involved.Three general principles are employed in the

management of radioactive wastes:

concentrate-and-contain dilute-and-disperse delay-and-decay.

The first two are also used in the management of non-radioactive wastes. The

waste is either concentrated and then isolated, or it is diluted to acceptable

levels and then discharged to the environment. Delay-and-decay however is

unique to radioactive waste management; it means that the waste is stored andits radioactivity is allowed to decrease naturally through decay of the

radioisotopes in it.

Types of radioactive waste (radwaste)Low-level Waste is generated from hospitals, laboratories and industry, as wellas the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters etc.

which contain small amounts of mostly short-lived radioactivity. It is not

dangerous to handle, but must be disposed of more carefully than normal

garbage. Usually it is buried in shallow landfill sites. To reduce its volume, it is

often compacted or incinerated (in a closed container) before disposal.

Worldwide it comprises 90% of the volume but only 1% of the radioactivity of

all radwaste.

Intermediate-level Waste contains higher amounts of radioactivity and mayrequire special shielding. It typically comprises resins, chemical sludges and

reactor components, as well as contaminated materials from reactor

decommissioning. Worldwide it makes up 7% of the volume and has 4% of the

radioactivity of all radwaste. It may be solidified in concrete or bitumen for

disposal. Generally short-lived waste (mainly from reactors) is buried, but

long-lived waste (from reprocessing nuclear fuel) is disposed of deep

underground.


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High-level Waste may be the used fuel itself, or the principal waste separatedfrom reprocessing this. While only 3% of the volume of all radwaste, it holds

95% of the radioactivity. It contains the highly-radioactive fission products

and some heavy elements with long-lived radioactivity. It generates aconsiderable amount of heat and requires cooling, as well as special shielding

during handling and transport. If the used fuel is reprocessed, the separated

waste is vitrified by incorporating it into borosilicate (Pyrex) glass which is

sealed inside stainless steel canisters for eventual disposal deep underground.

On the other hand, ifused reactor fuel is not reprocessed, all the highly-radioactive isotopes remain in it, and so the whole fuel assemblies are treatedas high-level waste. This used fuel takes up about nine times the volume of

equivalent vitrified high-level waste which is separated in reprocessing. Used

fuel treated as waste must be encapsulated ready for disposal.

Both high-level waste and used fuel are very radioactive and people handling

them must be shielded from their radiation. Such materials are shipped in

special containers which prevent the radiation leaking out and which will not

rupture in an accident.

Whether used fuel is reprocessed or not, the volume of high-level waste is

modest, - about 3 cubic metres per year of vitrified waste, or 25-30 tonnes of

used fuel for a typical large nuclear reactor. The relatively small amount

involved allows it to be effectively and economically isolated.

Radioactive materials in the naturalenvironment

Naturally-occurring radioactive materials are widespread throughout the

environment, although concentrations are very low and they are not normally

harmful. However, human activity may concentrate these so that they need

careful handling- eg in coal ash and gas well residues.


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Soil naturally contains a variety of radioactive materials - uranium, thorium,

radium and the radioactive gas radon which is continually escaping to the

atmosphere. Many parts of the Earth's crust are more radioactive than the

low-level waste described above. Radiation is not something which arises justfrom using uranium to produce electricity, although the mining and milling of

uranium and some other ores brings these radioactive materials into closer

contact with people, and in the case of radon and its daughter products, speeds

up their release to the atmosphere.

Wastes from the nuclear fuel cycle

Radioactive wastes occur at all stages of the nuclear fuel cycle - the process of

producing electricity from nuclear materials. The fuel cycle comprises the

mining and milling of the uranium ore, its processing and fabrication into

nuclear fuel, its use in the reactor, the treatment of the used fuel taken from

the reactor after use and finally, disposal of the wastes.

The fuel cycle is often considered as two parts - the "front end" which stretches

from mining through to the use of uranium in the reactor - and the "back end"which covers the removal of used fuel from the reactor and its subsequent

treatment and disposal. This is where radioactive wastes are a major issue.

Low-Level and Intermediate-LevelRadioactive WasteIn Canada, low-level radioactive waste (LLRW) contains material with

radionuclide content that is above established clearance levels and exemption

quantities but generally has limited amounts of long-lived activity. LLRW

generally does not require significant shielding during handling and interim

storage. Shielding refers to a barrier between stored waste and nuclear

workers, such as a concrete wall or protective clothing.Intermediate-level


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radioactive waste (ILRW) typically shows levels of penetrating radiation

sufficient enough to require shielding during handling and interim storage.

Canada does not have, at present, a long-term management facility to accept

all low and intermediate-level waste. The owners of low- and intermediate-

level waste (L&ILRW) are responsible for managing the waste they produce.

This usually takes place on site within its own facility.

How is low-level and intermediate-levelradioactive waste managed?The owners of low- and intermediate-level radioactive waste (L&ILRW) are

responsible for managing the waste they produce. This usually takes place on

site within its own facility. Currently, Canada does not have a long-term

management facility for low- and intermediate-level waste to accept all low-

and intermediate-level radioactive waste. All L&ILRW in Canada is currently

held on site in interim storage facilities, which are safe, secure and

environmentally sound.

Certain types of radioactive waste, such as that from hospitals, universities and

industry, contain only small amounts of radioactive materials with short half-

lives. This means that radioactivity decays away in hours or days. After safely

holding the waste until the radioactivity has decayed to levels authorized by

the CNSC, it can then be disposed of by conventional means (in local landfill or

sewer systems).

With the notable exception L&ILRW originating from nuclear power plants,

low- and intermediate-level radioactive waste that requires long-term

management may be returned to the manufacturer or may be transferred to an

authorized waste management operator such as the waste management facilityoperated by AECL at itsChalk River Laboratorieson a fee-for-service basis.
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3) High-level radioactive wasteHigh-level radioactive waste is used (irradiated) nuclear fuel and/or waste that

generates significant heat. Canadas nuclear power program has produced

over two million used fuel bundles over the past half century. If these bundles

were stacked end-to-end, they would fit into a space the size of six hockey

rinks stacked to the top of the boards. At present, there are currently no long-

term management facilities for high-level nuclear fuel waste anywhere in the

world. All used nuclear fuel in Canada is currently held on site in interim

storage facilities, which are safe, secure and environmentally sound. Finding

solutions for the long-term management of used nuclear fuel is the

responsibility of theNWMO.

How is high-level radioactive waste

managed?All used nuclear fuel in Canada is currently held on site in interim storage

facilities, which are safe, secure and environmentally sound. Interim storage of

used nuclear fuel at a nuclear facility typically consists of two phases known

as wet storage and dry storage.

Initially, used nuclear fuel bundles are stored under water in bays or poolsafter they have been removed from the reactors. These reinforced, leak-proof

facilities enable the fuel to cool off in a shielded and secure facility.

After 6 to 10 years in wet storage, the used nuclear fuel can be safely

transferred to dry storage in concrete canisters, containers or silos.

At present, there are currently no operating long-term management facilities

for used nuclear fuel anywhere in the world, although some are under
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development. Finding solutions for the long-term management of used nuclear

fuel is the responsibility of theNWMO.

4) Uranium mine and mill wasteUranium mine waste rock and mill tailings are specific types of radioactive

waste generated during the mining and milling of uranium ore and

production of uranium concentrate. In addition to tailings, mining activities

produce large quantities of mineralized and unmineralized waste rock,

excavated in order to access the uranium ore body. The tailings andmineralized waste rock contain significant concentrations of long-lived

radioactive elements, primarily thorium-230 and radium-226, which will not

significantly decrease over a long period of time.

How are uranium mines and mills managed?In general, long-term management in near-surface facilities adjacent to the

mines and mills is the only practical option for these wastes, given the large

volumes of waste generated in mining and milling operations. The tailings are

monitored and managed in facilities, such as engineered tailing ponds or

placed back in mined-out open pits.Cameco CorporationandAreva Resources

Inc.manage the only operating uranium mines and mills in Canada.

Image: Engineered tailing pond (Source: AREVA)

Regarding inactive facilities, such as the mining and tailings facilities around

Elliot Lake, in Ontario, the facilities have been decommissioned and the former
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operators continue to carry out monitoring and maintenance activities. There

are also former uranium mining and milling sites located in Saskatchewan,

Ontario and the Northwest Territories. These inactive sites are being managed

for the long-term by their former owners or the federal or provincialgovernment.

There is an initiative to remediate inactive legacy uranium mine and mill sites

in Northern Saskatchewan that were decommissioned during the end of the

Cold War era and do not meet todays environmental standards.

Through regular facility visits and inspections, harmonized with

theSaskatchewan departments of Environment and Resource

Management,andLabour,CNSC staff monitor these waste management

facilities to protect workers, the public and the environment.

Commission Blasts Outdated Nuclear Waste Management Policy

Vanessa Kurzweil | 02/28/12

Current U.S. policy for the management of used nuclear reactor fuel andradioactive waste is damaging and costly, according to a

recentreportissued by theBlue Ribbon Commission on Americas Nuclear

Future(BRC) to theDepartment of Energy(DOE).

The BRC report attributes the dearth of waste management options to decades

of ineffective nuclear policy. As a result, the U.S. currently lacks a long-term

disposal site for radioactive waste. The majority of used fuel in the U.S. is

instead stored at local reactor sites.

The failure to establish a long-term disposal site actually wastes taxpayer

money, according to the report. Since 1998, DOE has been contractual

obligated to transport nuclear waste from over 100 reactors to a long-term

disposal site. In the absence of such a facility, lawsuits against the DOE for its

breach of these obligations have already cost taxpayers nearly $2.2 billion in
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litigation costs, settlements, and legal judgments. The agency estimates such

payments will total $20 billion by 2020.

To address these problems, the Blue Ribbon Commission recommends

amending theNuclear Waste Policy Act(NWPA) to permit short-term sites to

be used for disposal. Passed in 1987, an amendment to the NWPA effectively

designated Nevadas Yucca Mountain region the countrys only long-term

nuclear waste disposal site and banned the use of other sites until the project is

operational.

However, after years of legal challenges from local Nevadans, funding

shortfalls, and political pressure, the DOEwithdrewits application to begin

construction on the Yucca Mountain site in 2010. As a result, the countrys

waste management options are now severely limited.

The Commissions report posits that both the congressional mandate and the

DOEs failure to meet its waste disposal obligations have further eroded the

trust of a public that is already deeply suspicious of nuclear power.

The Commission recommends that Congress overhaul the process of selecting

waste disposal sites to make it more transparent and consensual in order to

avoid the complications that surrounded the Yucca Mountain project.

The Commission also recommends the creation of a new organization to take

over nuclear waste management from the DOE. According the Commission,

the DOEs multiple regulatory priorities, variable annual budget, and poorpublic image demand such a change.

Safety of Radioactive Waste and Spent Fuel Management

The objective of the IAEA programme on Radioactive Waste and Spent Fuel

Management is to provide support to the IAEA Member States in establishing a
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proper safety framework for the management of radioactive waste and spent

fuel. Activities under this programme include the development ofIAEA safety

standards for predisposal management and disposal of radioactive waste and

spent fuel, the assistance to the Member States on the use and application ofthese Safety Standards, the coordination of the Waste Safety Standards

Committee, and providing the Secretariat for the meetings of the Contracting

Parties of the Joint Convention on the Safety of Spent Fuel Management and on

the Safety of Radioactive Waste Management.

Both the development of the Safety Standards, as well as the activities related to

their use and application, are aimed towards securing the best possible benefit

to the IAEA Member States. As such the needs of the Members States areidentified, inter alia, from:

The outcomes of international conferences, meetings and workshops During meetings of the Safety Standards committees Direct interactions with the Member StatesInternational Projects

International projects and working groups are organized to work towards

harmonization of approaches to the safety of predisposal management and

disposal of radioactive waste, and to provide a forum of exchanges for the

Member States.

Examples of such international projects include the CRAFT project which deals

with the demonstration of safety of predisposal facilities, and thePRISMproject, which deals with the demonstration of safety of near surface disposal

facilities. In addition, an international Joint Working Group has been

established to address the safety of dual purpose transport and storage casks

for spent nuclear fuel in a holistic manner.

The development and implementation by the Member States of a

comprehensive radioactive waste management strategyfor high level waste

and spent fuel, including disposal, is an important priority. In this regard,the GEOSAF project focuses on the demonstration of operational and long term
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safety of geological disposal facilities and the development of a specific

programme on the disposal of high level waste and spent fuel.

Services to Member States

Assistance is provided to the Member States, upon their request, through

national, regional and interregional technical cooperation projects, as well as

through peer reviews of radioactive waste management programmes.

When the natural uranium is mined from underground and open pit mines, it

consists of 99.3 % U-238 and only 0.7% of U-235. The extracted ore goes

through the ordinary mineral dressing processes (crushing, grinding,

screening, flotation, and gravity separation) to increase the U-235

concentration. It is then chemically processed to form "yellowcake" (U3O8).

Then, uranium hexafluoride gas (UF6) is produced by fluorination of U3O8. As

a gas, it undergoes enrichment to increase the U-235 content from 0.7% to

about 3.5%. It is then turned into a hard ceramic oxide (UO2) for assembly as

reactor fuel elements.

The nuclear fuel consists of cylindrical pellets of compacted UO2 in 3 to 4

meter long and about 0.1 m in diameter zircaloy tubes. Approximately, one

pellet of UO2 will generate energy equivalent to one ton of coal. About 30 to

60 fuel rods are bundled to form a fuel assembly.

The fuel rods in the nuclear reactor generated heat

through nuclear fission. When a neutron is absorbed into

a U-235 atom, it becomes an unstable U-236. By electric

repulsion, U-236 splits into fission products (ex. Barium,

Krypton, and etc.). The binding forces are converted into

energy in the form of heat and Gamma radiation. When


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this reaction occurs under controlled environment, two free neutrons will be

available for continued fission processes.

A 1-MW nuclear power plant typically contains

about 100 tons of uranium fuel. Once a year,

about one-third of the fuel rods are removed and

replaced with fresh fuel. The spent fuel rods are

composed of about 94% of U-238, U-235,

radioactive fission products, and other radioisotopes. Although they represent

a small proportion of the spent fuel, only 3.5%, they are highly radioactive and

continue to generate heat and release radiation long after the fuel is removedfrom the reactor. Most spent fuel from nuclear power plants is stored in pools

of water at the reactor site, temporarily. The water works as a coolant and

radiation shield.

United States policies governing the permanent

disposal of high-level radioactive waste are defined by

the Nuclear Waste Policy Act of 1982 as amended.

This act specifies that high-level radioactive waste will

be disposed of underground, in a deep geologic

repository and that Yucca Mountain, Nevada, will be

the single candidate site for characterization as a

potential geologic repository. This act provides for a

procedure and timetable for the site selection,

construction, and operation of HLW mined geologic repositories.

Uranium Fuel Cycle Nuclear Organizations

o The American Nuclear Society (ANS) is a not-for-profit,international, scientific and educational organization established

by a group of individuals who recognized the need to unify the

professional activities within the diverse fields of nuclear scienceand technology.
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o The International Atomic Energy Agency (IAEA) serves as theworld's central intergovernmental forum for scientific and

technical cooperation in the nuclear field, and as the international

inspectorate for the application of nuclear safeguards andverification measures covering civilian nuclear programs.

o The Nuclear Energy Institute (NEI) is the policy organization ofthe nuclear energy and technologies industry and participates in

both the national and global policy-making process.

o The World Nuclear Association is the global industrialorganization that seeks to promote the peaceful worldwide use of

nuclear power as a sustainable energy resource for the comingcenturies.
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