Un nucléaire durable pour une énergie d'avenir. Claude Guet CEA

Transcription

1 Un nucléaire durable pour une énergie d'avenir Claude Guet CEA

2 Energy Needs 2 Energy is essential for development: Raising productivity, both industrial and agricultural Reducing poverty Improving health care Need of reliable and secure access to sources of energy: 1.6 billion people have no access to electricity, 2.4 billion people have no access to modern fuels and rely on traditional biomass for cooking and heating 2 factors: demography and economical development 2050 : World population increased by 3 billions it will be necessary to double the energy production 70% of growth is likely to come from developing countries World challenge remains to satisfy basic needs: water, energy, food

3 Energy Needs and Sustainable Development 3 Fossil energy will be depleted over the next decades for oil and gas, the next century for coal, while they presently provide 85% of the world energy Man-made GHG emission into the atmosphere has lead to global climate change and this may have dramatic consequences ( see IPCC reports) Reconciling growth in energy consumption with fossil depletion and environment protection with a view towards sustainable development. The factor 4 paradox: Twice more energy and twice less CO2. Save energy, diversify energy sources and intensify R&D on innovative technologies (today, R&D ~ 0.3% of the 3.7 G world energy market).

4 Renewable Energies 4 In principle wind and direct solar energy can produce enough electricity or heat But intermittency and difficulties of storage still prevent these energies to share a significant part of the mix So far, the only easy massive storage for renewable energies is hydraulic storage Today there is no solution for even a mid term massive storage (> a week). And, unfortunately, no realistic solution is foreseen for the next future. «There is no choice between nuclear or renewables, nuclear and renewables have to go together»

5 5 Reach the highest possible level of electricity production without GGE by optimizing nuclear facilities operating as a baseload. Develop decentralized complementary resources such as solar (photovoltaic or thermal) which naturally produce electricity in a non-continuous and nonpredictable way Improve the ability to instantaneously and cost-effectively adapt electricity production to the needs of consumers on the grid, through various storage techniques and smart grid technology Develop electricity for transportation through hybrid or electric vehicles (batteries, fuel cells, secend-generation biofuels)

6 Public debates and a new legislation Act on sustainable management of radioactive materials and waste (June ) Main orientations: Reduction of quantity and toxicity of radioactive wastes by processing spent fuels Storage of radioactive materials before future reprocessing Deep geological depository of ultimate radioactive wastes 6 Associated research: Deep geological storage (reversible > 100 y) and selection of a site 2015 document for autorisation; 2025 starting the exploitation Separation and transmutation of High-Level-Long-Lived waste studies and research in relation with those on the new generation of nuclear reactors so that an assessment can be made in 2012 of the industrial prospects and a prototype installation set in operation by 2020

7 attractive features of nuclear energy 7 An almost domestic energy Uranium is distributed over the World. Uranium supply is not an issue of energy security as oil or gas can be As cheap as fossil and an economical cost which is predictable. When a power plant is built : a predictability of cost for the next 60 years. The cost of uranium is only about 5% of the KWh cost Even if prices increase it won t change dramatically the price of a KWh Nuclear produces no CO 2

8 Impediments to nuclear 8 Social sustainibility is hindered by: Risks of weapon proliferation : access to fissile nuclear material ( 235 U or 239 Pu) Storage of radioactive waste over years or more :Wastes have the potential to leak, threaten water supplies anf human health Safety of nuclear plants: Chernobyl disaster Need to address these issues in a rigorous manner Reduce the risks to such a low level so that advantages of nuclear largely balance these risks

9 Can nuclear power counter global warming? 9 Presently: 436 nuclear power reactors (in 31 countries) yield 372 GWe 16% of total world electricity (31% in Europe, only a few % in developing countries) Mostly LWR s Maximal hypothesis: 1kWe/capita in 2075 with the half by nuclear Need 4000 GWe to be produced by nuclear power. 10 times more nuclear reactors Is there enough uranium to reach this goal with LWRs? LWRs ( 1GWe) need 180 tons Unat per year => tons/year needed presently known recoverable U reserves are 4.7 million tonnes (< 100 /kg) For < 200 /kg, go up to 15 million tons. At higher prices: phospates, sea water, coal At current consumption rate ( t/y) reserves exhausted in about 200 years Assume in 2050: 1300 GWe and 150 t/gwe/y => reserves exhausted by end lifetime LWRs alone can t cope with climate change Sustainability of nuclear only if fast breeders (FBR) are used

10 Odd-N nuclei fission with thermal neutrons Even-N nuclei capture thermal neutrons 10

11 Thermal/Fast neutron reactors 11 Slow neutron reactors (thermal reactors) Uranium is dispersed in a slowing down medium (graphite, water, heavy water). Removal of heat done with coolants such as carbon dioxide gas or water 238 U gets converted to artificially fissile 239 Pu, after irradiation in a reactor. 2 basic types: U has two isotopes : 235 U (0.7%) fissile with thermal neutrons with high probability whereas 238 U not fissile but fertile Thermal neutrons optimise the fission/capture ratio those that can use natural uranium as fuel: GGNR or Magnox Graphite moderator and CO2 coolant CANDU or PHWR : heavy water as moderator and coolant natu reactors, both GGNR and CANDU require to be fed with fresh fuel regularly those that require enriched uranium as fuel. Needs an enrichment plant LWR (VVER) use uranium enriched to between 3 and 5 per cent LWRs can run 15-18months without a fuel change LWRs have two variants: BWR and PWRs.

12 Fast neutron reactors: Fission and Breeding Take advantage of the 238 U energy potential 12 # neutrons from fission of 239 Pu large enough: to yield a new fission of 239 Pu to yield a capture by 238 U and β decay of 239 U and 239 Np to yield 239 Pu. Breeding it requires high-energy neutrons => no moderator a coolant must be used to extract the heat. Sodium most convenient. Need of an initial supply of about 5 tons of Pu for a 1.2 GWe FBR About 0.25 tons Pu produced annually => doubling time of 20 years Deployment depends on the initial availability of plutonium to be produced by LWRs (and also the cooling time before reprocessing) Need for reprocessing But the availability of natural uranium is no more a problem Thorium which is even more abundant could also be used

13 Nuclear Power Plants in France PWR units on 19 sites MW : 34 units MW : 20 units MW : 4 units Net installed capacity : 63 GWe (second electronuclear park at worldwide level) Energy independence increase 26 % in 1973, 50 % in nuclear TWh in 2007, 78% of total Hydro 12% Fossil 10% Environment preservation In comparison to gas-fired power plant, the French electronuclear park allows to avoid the discharge of 130 millions tons of CO 2 per year, i.e the equivalent of CO 2 emissions of the transport sector in France.

14 Generation III: European Pressurized Reactor (EPR) 14 Designed and developed by AREVA Main design features: increased safety enhanced economic competitiveness scaled up to an electrical power output of 1600 MWe Bring burn up to 65 GWd/t using 5% enriched uranium oxide or MOX fuel. The Olkiluoto island with two existing nuclear power plants. Flamanville with already two operating reactors

15 15 Enhanced reliability to reduce the number of significant incidents Improvement of the reliability of the systems Ability to tackle with possible human errors In case of incident: the facility is robust enough to prevent evolution to severe accident The probability of core melting reduced to less than 10-5 per year and per reactor (to be compared to 10-4 for the existing reactors) If an accident occurs: the facility is designed to limit the consequences of the accident by: no emergency evacuation beyond the proximity of the plant no permanent rehousing of people no long-term restriction in the food consumption Satisfactory protection against external hazards (airplane crash, explosion, earthquake )

16 16 Rapsodie (Cadarache) ( ) EXPERIMENTAL REACTOR Phénix (Marcoule) ( ) PROTOTYPE REACTOR INDUSTRIAL PLANT Superphénix (Creys-Malville) ( )

17 17 Sodium fast reactor Gas fast reactor Mature Requires substantial improvements to ensure high safety standards and economical competitiveness More promising technological gaps requiring innovative developments Technologically risky

18 Closing the fuel cycle a 25 years old industrial experience t HM spent fuel reprocessed 1200 t HM MOX fuel recycled 1100 t HM /yr of spent fuel discharged from PWRs Up to t HM /yr of spent fuel reprocessed (domestic + foreign)

19 Future processes for Nuclear Fuel Cycle 19 Waste minimization Proliferation resistance Several options under investigation U and Pu recycling PUREX type Heterogeneous recycling 2 different rods One with Pu+U Other with MA Homogeneous recycling (GANEX) A single fuel R T FP, MA R T FP R T FP MA U Pu U Pu U Pu MA

20 20 PUREX (U and Pu separately) 99,8% efficiency Reprocessing plant Valuable materials U Uranium Pu PF AM Structure wastes Technological wastes Plutonium Spent fuel Ultimate wastes Fabrication of MOX Vitrified wastes Compacted wastes Wastes In cement

21 COEX coextraction and coprecipitation of U and Pu Spent fuel No pure plutonium separation R U Pu T Ude FP MA Pools Conversion LWR U Shearing & dissolution Residues Rinsing Hulls & end fittings Compaction Separation by COEX F.P. Concentration Vitrification Universal canister U, Pu Conversion (U,Pu)O 2 Reprocessing and MOX fabrication on the same site Mox fabrication MOX Assemblies FRs or LWRs

22 The spent nuclear fuel 22 Uranium (95%) Fission Products (4%) Plutonium (1%). Minor Actinides (0.1%) UOX average Content

23 Final waste toxicity 23 SPENT FUEL U ore GLASSES FPsONLY GLASSES FPs+MAs

24 24 Hall d entreposage des déchets HA à La Hague Hall d entreposage des déchets MAVL à La Hague

25 Proliferation and Nuclear Weapons 25 Main proliferators identified worldwide did not develop a civil nuclear program. North Korea does not produce a single nuclear KWh. production of fissile material for nuclear weapons: 235 U (highly enriched 93%) 239 Pu ( weapon grade; reactor grade?) Possibility of production of HEU undetected production of HEU in a declared enrichment facility or in an unsafeguarded facility that has been secretly duplicated Clandestine diversion of Pu from spent fuel With reprocessing in a small, undeclared facilty (see N. Korea) NPT withdrawal by states for the purpose of developing nuclear weapons Risks of proliferation through theft by terrorists

26 How to counter proliferation? 26 Put major efforts on safeguards at all levels Reinforce NPT and its additional protocole Reinforce IAEA Reliable remote monitoring technologies Discourage the spread of fuel cycle technologies while supporting the expansion of nuclear power to meet the needs of individual nations Support establishment of reliable nuclear fuel supply at a cost that precludes the need of enrichment and reprocessing capabilities Advanced fast reactors coupled with advanced closed fuel cycles meet these requirements

27 Nuclear Future: A need for substantial R&D 27 Extending the lifetime of reactors Better (new) materials to sustain higher irradiation, chemical corrosion, mechanical stress, higher temperature.. Fast Breeder Reactors: core studies for a better void coefficient for a better breeding factor without blankets from oxides to carbides (higher density, higher thermal conductivity) or metals Recycling of Minor actinides Homogeneous incorporation of MA in fuel Heterogeneous recycling Waste management Ageing of glasses Transport of radioelements in clay

28 Strong demand for new materials Materials for cladding and structural materials Fuel materials materials able to sustain intense irradiation (fast neutrons) materials able to sustain high temperature, thermal creep materials able to sustain high mechanical stress and corrosion. Materials able to sustain high burn-up Ageing issues. New grades of steel : Oxide dispersion strengthened steel (ODS) for cladding resisting swelling and High T Ceramics and composites (SiC-SiC ) resisting very high temperature Liquid metal technologies.

29 Damage of materials under irradiation a massively multiscale problem 29 Defects created by irradiation Interstitials vacancies Migration Clusters Extended structures Effects on mechanical properties Performance degration Failures Neither experiment nor theory has yet captured the complexity in a single framework Go beyond observation and modelling to control the evolution of defect structures and interrupting their development before performance degradation Wigner effect: formation of metastable defect structures Energy stored by defects can lead to a catastrophic release of energy remember the Windscale fire ( graphite moderator at C)

30 Experimental needs 30 In-situ measurements of neutron irradiation with atomic or nano-scale resolution => initial damage processes Coarser grained experiments to capture migration, formation of clusters, degradation of main using properties: ductility, toughness.. Synthesis of nanostructured materials for trapping defects at interfaces before they cluster => defect-tolerant materials, self-healing 18%Cr 1%W 0.3%Ti 0.3%Y2O3 ODS steel extruded at 1100 C Bright Field TEM images (transverse) Bright Field TEM images (longitudinal) Bright field TEM images

31 Joint Accelerator for Nano-science and Nuclear Simulation 31 JANNuS is a multi-ion beam irradiation platform that combines several ion accelerators with modern in situ and ex situ diagnostics At Saclay, a triple ion beam facility allows the simultaneous production by ion beams of nuclear recoil damage and implantation of a large array of ions for well-controlled modelling-oriented experiments. At CSNSM Orsay, a 200 kv Transmission Electron Microscope is coupled with two ion accelerators => in-situ observation of the material microstructure modifications induced by ion irradiation/implantation.

32 three ion beam irradiation facility at CEA-Saclay 32 Tandetron 2,25 MV Casemate 65 Casemate 66 Irradiation triple beam Irradiation double beam Irradiation single beam Analysis by ion beam Y7 Y8 T4 Yvette 2,5 MV Y6 Casemate 61 Y4 Y00 E4 E5 Y5 Y0 E3 E2 E0 E1 Casemate 64 Casemate 63 É pim é th é e 3 MV Source ECR Casemate 62 Hydrogen for triple beam Gas implantation H and He Ballistic damage < 100 dpa/ 6h H, D, He beams Y. Serruys et P. Trocellier (2007) DEN/DMN/SRMP

33 Multiscale modeling of materials 33 1 c Time Structure Microstructure 1 y Dislocations defects clusters 1 s Atoms Plasticity Finite elements (EF) 1 ps Electrons MD AkMC Dislocations dynamics (DD) OkMC Electronic structure Ab initio (DFT) Length 1 nm 1µm 1mm

34 Nuclear Fuel Chemistry Innovative nuclear fuels for future reactors ( Na FNR and Gas FNR) Recycling of U and Pu => Saving of resources Co-processing of actinides => increased proliferation resistance Mixed actinide fuels

35 Basic research in chemistry 35 Chemistry and physics of actinides and actinide-bearing materials and the 5f-challenge Requires advances in our understanding of strongly correlated electron systems More accurate understanding of complexes of actinide and fissions products at all stages of fuel reprocessing, dissolution of waste forms designing new molecular systems for controling chemical selectivity in advandes separation technologies Synthesize, characterize, simulate Exploiting the complexity of organisation at the mesoscale in solutions or at interfaces New separation systems with increased selectivity of target species Fundamental effects of radiation and radiolysis in chemical processes

36 Long term behaviour of nuclear glasses Theoretical and modelling issues Glassy transition and slow dynamics Stress corrosion : from subcritical fracture propagation to rupture Ageing of glasses Need for high performance algorithms Need for better inter-atomic potentials Need to couple MD with hydrolysis reactions Diffusion of water in fractures (mesoscopic scale) coupling with MD Multiscale modeling of melted nuclear glasses for process engineering

37 Long term diffusion of radionucleides in porous material Theoretical and modelling issues Applications to: clay and deep depository Concrete damaged glasses Homogenization mathematical techniques Account of charge effects

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