r. testoni , s. segantin , m. zucchetti -...
TRANSCRIPT
R. Testonia, S. Segantina,b, M. Zucchettia,b
a DENERG, Politecnico di Torino, Italyb Plasma Science and Fusion Center, MIT, Cambridge (MA), US
Overview
Progress in nuclear energy
Radiation induced degradation of Polychlorinated Biphenyls (PCBs)
Conclusion
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Overview
Progress in nuclear energy
Radiation induced degradation of Polychlorinated Biphenyls (PCBs)
Conclusion
3/21
Technical Aspects
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Energy studies
=
Interdisciplinary
studies
Environmental Aspects
Politic and Social AspectsEconomic Aspects
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From the purely technological point of view, two directions can be followed:
• Simple solutions that make it possible to reduce the growth of energy
needs in developing countries, focusing on efficiency, savings and
conversion, and that will lead to the reduction of social and geographical
disparities in its availability and its use.
• Most advanced technological innovation, that aim to seek new
energy sources and high-tech energy-intensive approach, in developed
countries.
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Four main actions can be pursued to face the energy issue:
• rationalize the use of energy;
• abandoning a development model based on endless growth;
• equalize the per capita consumption in the world;
• innovate and develop new energy sources.
The current energy economy based on fossil fuels is not sustainable at long
term. Alternatives must be concrete, and able to withstand the economic,
environmental and social issues that provide the current boundary
conditions. One solution to the energy problem does not exist.
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Two case studies
Nuclear energy in the framework of
energy issue and the development of a
new technology in the fusion nuclear
field.
The environmental impact of PCBs
and the use of irradiation techniques to
degrade them as possible solution to
reduce their environmental impact.
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Overview
Progress in nuclear energy
Radiation induced degradation of Polychlorinated Biphenyls (PCBs)
Conclusion
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The role of nuclear energy in the field of development of new energy source
is recognized by the world scientific community. However, an open debate
on nuclear energy concerns the solution of the problem of radioactive
waste, reinforcing nuclear safety and developing research into reactors of
the future.
Fission energy Fusion energy
Acceptance by the public is doubtful
and depends on:
• the safe continuing operation of
existing plants,
• the trends in energy demand, in
particular electricity,
• the ability to meet a share of demand
in a competitive way.
It is seen as a candidate long-term
solution for the following reasons:
• a clean energy,
• no core melting risks,
• no proliferation,
• very low amount of radioactive
waste.
The scientific community is devoting many efforts in fusion development.
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Most of the studies and experiments on nuclear fusion
are currently devoted to the Deuterium-Tritium (DT) fuel
cycle.
Roadmap to fusion power
Fusion energy is one of
the most challenging and
complicated fields for
Engineering and Physics.
The next milestone is ITER, but some of the engineering challenges still have
to be solved.
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Tokamak Main Component
First Wall
It is the inner layer of the vacuum vessel,
it faces the plasma column therefore it is
subjected to high thermal loads and high
energetic particles, such as neutrons.
Magnets
They are surely the most
expansive and conceiving part of a
machine based on magnetic
confinement of plasma.
Vacuum vessel
Its main objective is to maintain the
vacuum inside its volume where
plasma is supposed to run and
fusion reactions are supposed to
take place.
Cooling system
It is a key component also for the energy
supply: it removes thermal energy from
plasma and transfer it to the turbine letting
us get electricity.
Biggest challenge: keep the cryogenic temp. for cooper super-conduction.
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• It is the flagship of a new generation of
fusion devices
• It is a tokamak conceptual design
proposed by Massachusetts Institute of
Technology (MIT)
• It represents a cheaper, smaller but
even more powerful, faster way to
achieve fusion energy
• Its design is always changing and every
new idea is applied and integrated to the
design
ARC development is based on forefront technologies
Technological development such as High Temperature Superconductors,additive manufacturing, new diagnostics allowed to think to a new concept:Affordable Robust Compact (ARC) fusion reactor
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Affordable Robust Compact (ARC) fusion reactor –
Main innovations
1. The idea of ARC’s concept began when a
new generation of superconducting materials
became available on industrial scale. The most
important innovation are its magnets, that are
made of Rare Earth Barium Copper Oxide
(REBCO). This material shows a quite high
critical temperature ~ 80K, which is almost
twenty times higher than copper’s critical
temperature, and is able in a very thin tape to
generate a magnetic field of tens of Teslas.
2. A second innovation integrated in this device is the approach to blanket, cooling
system and tritium breeder all of them: a single material (FLiBe) satisfies all
functions done by those components.
(Sorbom et.al, 2015)
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Affordable Robust Compact (ARC) fusion reactor –
Main innovations
3. Thanks to new manufacturing systems such as 3D printing,
this tokamak is also designed to be quickly demounted and
reassembled since the number of components is allowed to be
very low.
4. The most innovative characteristics of ARC, in
our opinion, is the load-following capability.
Since plasma can quickly change its power
output, a load following power plant can be
connected to a grid characterized by several
other intermittent energy input, such as solar and
wind based power plants. In this case, the ARC
reactor could be not only the base-load energy
producer, but also a load-following one, capable
to cover peak requests and other plant
shutdowns.
Example of electric energy stratification divided by type of plants and their role
(Sorbom et.al, 2015)
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Overview
Progress in nuclear energy
Radiation induced degradation of Polychlorinated Biphenyls (PCBs)
Conclusion
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Chemical properties Chlorinated aromatic hydrocarbons
209 isomers
tech. PCBs containing up to 80 isomers
Physical properties High chemical and thermal stability (>1000°C)
Low flammability
High heat conductivity
Electrical insulator
High solubility in rubber
High solubility in fat
No solubility in water
PCBs characteristics
• dielectric fluids,
• heat transformer fluid,
• lubricants,
• vacuum pump fluids,
• etc.
PCBs use in energy field
The widespread use of PCBs in
such applications presents a major
environmental issue because of
the toxicity and long lifetime of
these compounds in ambient
conditions.
Banned in developed countries, but still widely used in developing countries.
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Incineration
PCBs can be effectively destroyed by Incineration at more than 1000 degC.
Drawback: process that converts some of the PCBs into more toxic materials
(dioxins) wherever the flame temperature is lower than 1000 degC.
Radiolytic degradation
Radiolytic degradation of PCBs is expected to overcome the disposal problems.
PCBs in the organic solvents, such as transformer oils, may be reduced into benign
inorganic chloride and practically non-toxic biphenyl, without formation of any
dioxins. Such treatment leaves the solvents practically unchanged so that they can
be recycled instead of incinerated.
This approach may be adapted to remove PCBs in sediments and soils by
combining it with extraction or other treatment methods.
Methods for PCBs disposal
Radiolytic degradation is the most sustainable PCBs disposal technique.
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Gamma-ray degradation of PCBs in oil
In general, it is known that gamma irradiation of chlorinated hydrocarbons in alkaline
polar solvents results in the production of free radicals via chain dechlorination to
the next less chlorinated species.
It is not expected to lead to dechlorination by direct reaction of the solvated
electrons with the PCBs, because the oil contains substantial quantities of other
aromatic compounds, which also react with solvated electrons very rapidly.
PCB transformation occurs primarily through reductive dechlorination, forming lower
chlorinated PCBs and biphenyl. The highest degradation rates of PCBs can be
achieved by solubilizing PCBs in water using a surfactant prior to irradiation.
Radiolytic degradation techniques
Gamma degradation effectiveness is dependent on PCBs solvent.
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Beta-irradiation
Beta-emitting radioactive sources may be used, while industrial application
processes mainly use electron beams (EB) accelerators. In general, an industrial
pollutant is irradiated with beta particles in order to induce in it chemical
transformations (or biological sterilisation) in such a way that the pollutant itself
could be more easily treated with conventional techniques for its environmental
processing, or it could be easily recycled.
The technique that is being investigated uses an EB linear accelerator (Linac) with a
3 MeV electron energy. The main safety and radioprotection problems that deal with
the use of EBs are the following: particle-man interaction (accidental irradiation),
shielding of gamma and beta diffuse radiation, device maintenance operations,
decommissioning of the apparatuses.
The activity is focusing on the safety and environmental aspects, and also on the
studies of interaction between beta particles and matter, applied to the proposed
case.
Radiolytic degradation techniques
A complete chemical destruction of PCB occurs with electrons of this energy.
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Overview
Progress in nuclear energy
Radiation induced degradation of Polychlorinated Biphenyls (PCBs)
Conclusion
Energy studies involve not just technical aspects, but also environment,
material science, and politics (interdisciplinary studies).
In this work, two case studies on advanced technological innovation as a
part of simple solutions for the energy problem were reported.
The first case study involves the progress of nuclear energy in the framework
of energy issue and a new generation of fusion reactors: Affordable Robust
Compact fusion reactor.
The second case study concerns the environmental impact of
polychlorinated biphenyls (PCBs). The use of beta-irradiation technique to
degrade PCBs is presented as one feasibility solution in order, both from the
technological point of view and from the economical convenience to reduce the
environmental impact of these compounds.
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Thank you for your
attention!