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Proliferation Safe Nuclear Power Does that exist ?

Proliferation Safe Nuclear Power Does that exist ?. Y. KADI CERN, AB Depart. 19 June 2008, JAI, Oxford. A new primary energy source.

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Proliferation Safe Nuclear Power Does that exist ?

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  1. Proliferation Safe Nuclear Power Does that exist ? Y. KADI CERN, AB Depart. 19 June 2008, JAI, Oxford Y. KADI, CERN

  2. A new primary energy source • By 2050, the world’s consumption (+ 2%/y) should reach 34 TW, of which 20 TW should come from new energy sources:A major innovation is needed in order to replace the expected “decay” of the traditional energy sources! • This implies a strong R&D effort, which is the only hope to solve the energy problem on the long term. This R&D should not exclude any direction a priori! • Renewables • Nuclear (fission and fusion) • Use of hydrogen • Can nuclear energy play a major role? • Nuclear energy has the potential to satisfy the demand for a long time (at least 15 centuries for fission, essentially infinite for fusion), and is obviously appealing from the point of view of atmospheric emissions. Y. KADI, CERN

  3. Y. KADI, CERN

  4. World nuclear electricity production by scenarios (INPRO Phase-IA Report) Schematic illustration of the four SRES storyline families (Source:IPCC) Potential global market for nuclear electricity, hydrogen, heat and desalination for the A1T Scenario assuming aggressive nuclear cost improvements Y. KADI, CERN

  5. Which type of nuclear energy? • Nuclear fusion energy: not yet proven to be practical. Conceptual level not reached (magnetic or inertial confinement?). ITER a step, hopefully in the right direction. • Nuclear fission energy: well understood, and the technology exists, with a long (≥ 50 years) experience, however, present scheme has its own problems: • Military proliferation (production and extraction of plutonium); • Possibility of accidents (Chernobyl [1986]; Three Mile island [1979]); • Waste management. • However, it is not given by Nature, that the way we use nuclear fission energy today is the only and best way to do it. One should rather ask the question: Could nuclear fission be exploited in a way that is acceptable to Society? Y. KADI, CERN

  6. Uranium demand only slightly improved by MOX • typical new LWR (EPR): • 10 years to build • 60 years operation China’s planned reactors :≈ 2.5 Million tons of U Y. KADI, CERN

  7. Yellow cake or yellow coal ? Mining effort needed to produce 1 GWe x 30 years = 6.1 TWh Y. KADI, CERN

  8. The problem of nuclear waste at very long lifetime Warning: long-lived radio-toxicity of MOX waste 10 x larger Y. KADI, CERN

  9. How many “Sellafield” for MOX ? Y. KADI, CERN

  10. Radioactive Waste from LWRs at end of present nuclear deployment: 1.8 Million ton How radio-active? ≈ 108 Sv/ton ≈105 times the initial Uranium used. It decays back to radio toxicity of initial Uranium only after ≥ 106 years (geologic times) at end of present nuclear deployment: 1.8 106 x 108 = 1.8 1014 Sv[recommended ICRP max. dose to radiation workers 2.0 mSv/year] Main concerns Leaks in the environment (biosphere) Proliferation (Pu239): world’s waste stockpile about 5 ÷ 10 times the military Pu stockpile at end of present nuclear deployment: 600’000 critical Pu masses Y. KADI, CERN

  11. Evolution of radiotoxicity of nuclear waste • TRU constitute by far the main waste problem [long lifetime – reactivity]. The system should be optimized to destroy TRU. Same as optimizing for a system that minimises TRU production. Interesting for energy production! Typically 250kg of TRU and 830 kg of FF per GWe Y. KADI, CERN

  12. CAPRA Core (CEA) Plutonium incineration in fast neutron reactors Y. KADI, CERN

  13. Consequence on Core Safety Parameters • Successive recycles in reactors with a thermal neutron spectrum continuously lower the isotopic grade of the Pu, leading to the necessity to increase the total Pu/(U+Pu) ratio. Consequently, the void coefficient in a PWR may no longer be negative in all circumstances. • The recycling of Pu + MA in conventional Fast Reactors (FRs) brings about several adverse effects: • on cycle operations (heat and dose rate at fabrication, reprocessing, transportation) • on global core performance and safety (Sodium void, Doppler effect, etc.) • This limits the Pu + MA content and consequently the transmutation capacity of the core, resulting in a higher proportion of FRs in the park. • If MAs are directly mixed with the fuel (homogeneous recycling), the worsening of safety parameters such as coolant void or Doppler effect sets stringent limitation on MA content: typically ≈ 2.5 wt% in large FRs. The variation is almost linear with MA concentration. Heterogeneous recycling (subassemblies at core periphery) brings about lesser penalties on core parameters allowing higher contents of MAs, but still limited to ≈ 30 to 40% in mass due to high He release Y. KADI, CERN

  14. Consequence on Core Safety Parameters Y. KADI, CERN

  15. Proliferation Resistant Nuclear Fuel Cycle • Recommended topics of R&D for methods to accelerate reduction of current stockpile of separated plutonium: • LWR fuel cycle with extended fuel burnup; • Ultra-long lived fuel for high conversion reactors with ten years or longer lifetime; • Thorium-uranium oxide fuel; • HTGR with Th fuel design; • Fast spectrum reactors which would breed and burn material without reprocessing Y. KADI, CERN

  16. Proliferation Resistant Nuclear Fuel Cycle • Pu burning with Th is more proliferation resistant than with uranium • No production of additional Pu from U • The proliferation risk of Pu burning with Th in Fast Neutron Reactor (FNR) or Accelerated Driven System (ADS) is mainly due to 233U. The amount produced of 233U is about one third that of the Pu incinerated in Pu/Th MOX fuel. An intrinsic barrier to proliferation with 233U is provided by the gamma emission from 232U. • PWR with Th and medium enriched U (20% enriched) is proliferation resistant. This is because U amount in a fresh fuel assembly (130kg) is remarkably smaller than the bare critical mass (750kg of 20% enriched U). At the end of the fuel irradiation, however, plutonium is produced, which could be used for weapon purposes. Y. KADI, CERN

  17. Thorium as fuel in a system breeding 233U It is the presence of the accelerator which makes it possible to choose the optimum fuel. Low equilibrium concentration of TRU makes the system favourable for their elimination: Pu 10–4 in Th vs 12% in U. Y. KADI, CERN

  18. Thorium as fuel in a system breeding 233U • Equilibrium concentrations are orders of magnitude lower than in a Uranium-plutonium based fuel Y. KADI, CERN

  19. Thorium as fuel in a system breeding 233U • Pure Thorium does not fission, in practice, seeds are needed to start energy production: ==> Any fissionable material can be used (233U, 235U, 239Pu or TRU) • TRU's are destroyed by fission, a process which produces energy and makes the method economically attractive (TRU's still represent 40% of the energy delivered by the reactor which produced them) Y. KADI, CERN

  20. Neutronic Properties Y. KADI, CERN

  21. Neutronic Properties Th-232 capture probability Th-232 fission probability Y. KADI, CERN

  22. Thorium use in Reactors ThC and ThO2 have been used with great success in high temperature reactors operated until now in different countries: • AVR and THTR in Germany • Peach Bottom and Fort St. Vrain in USA • Dragon-reactor in Great Britain as a European project. In heavy water reactors the use of Thorium partly is common practice, too: • PHWR (Pressurised heavy water reactors) in India • Fast breeder system with Th to breed U 233 in India Light water reactors have been tested with Thorium containing fuel elements in the past • insertion of some Th-elements in the reactor Shippingport (USA) • insertion of Th-containing fuel elements in Lingen and Obrigheim (D). Y. KADI, CERN

  23. Thorium use in Reactors For the future application there is much work preparing the use of Thorium in different types of reactors: • use of Thorium to convert weapon grade Plutonium in a HTR-gasturbine-project (common activity of USA and Russia) • potential future application of Thorium in the pebble bed HTR (South Africa, China) • use of the potential for a application of MOX-fuel in LWR-plants in operating commercial reactors in different countries (PuO2/ThO2-mixtures) • use of Thorium in molten salt reactor-concepts • insertion of Thorium containing fuel elements in AHWR (Advanced Heavy Water Reactors) • CANDU-reactors in Canada are planned to use Plutonium and Thorium • in ADS-concepts (Accelerator Driven Systems) Thorium can be applied in a subcritical blanket. New fuel U 233 can be bred and actinides can be destroyed. Y. KADI, CERN

  24. Thorium use in Reactors Concept of the HTR-Module (200 MWth) for Plutonium conversion a) Vertical section through the reactor b) Data of the core Y. KADI, CERN

  25. Thorium use in Reactors MSRE (MOLTEN SALT REACTOR EXPERIMENT) EXPERIMENTAL REACTOR 8 MWth (ORNL) 3 FUEL TYPES: URANIUM ENRICHED 30% WITH 235UPURE 233U239Pu FUEL SALT66%LiF-29%BeF2-5%ZrF4-0,2%UF4 OPERATED 5 YEARS(LOAD FACTOR 85%)WITHOUT ANY INCIDENT MSRE OPERATED 1965-1969, SHUTDOWN IN 1969 Y. KADI, CERN

  26. Thorium use in Reactors The use of thorium-based fuels in nuclear reactors has attractive features • Higher melting point of Th metal (1750°C) compared to U metal (1130°C) and of ThO2 (3300°C) compared to UO2 (2800°C) • Thermal conductivity of Th is better than U • Both of these thermal properties allows higher margins for the design and for the operation of reactor cores • Less long-lived minor actinide production • 233U is a good fissile material both in fast and thermal neutron spectra • There is a potential for breeding with 233U/Th cycle But: • Neutron balance is very tight for breeding in thermal spectrum ( strict FP and Pa management) • Thorium cycle has a penalty for long term waste radiotoxicity (231Pa) • Some aspects of thorium cycle require specific design and operation features for the reactor and fuel cycle facilities (reactor operation, fuel processing, fuel refabrication) Y. KADI, CERN

  27. Basic Principle of Energy Amplifier Systems • One way to obtain intense neutron sources is to use a hybrid sub-critical reactor-accelerator system called Accelerator-Driven System:  The accelerator bombards a target with high-energy protons which produces a very intense neutron source through the spallation process.  These neutrons can consequently be multiplied (fission and n,xn) in the sub-critical core which surrounds the spallation target. Y. KADI, CERN

  28. General Features of Energy Amplifier Systems Subcritical system driven by a proton accelerator: • Fast neutrons (to fission all transuranic elements) • Fuel cycle based on thorium (minimisation of nuclear waste) • Lead as target to produce neutrons through spallation, as neutron moderator and as heat carrier • Deterministic safety with passive safety elements (protection against core melt down and beam window failure) Y. KADI, CERN

  29. Safety margin from prompt criticality • For a critical system, it is measured by the fraction of delayed neutrons. For the Energy Amplifier, it is an intrinsic property, and can be chosen. • Subcriticality implies strong damping of reaction to reactivity insertion, making the system very stable (presence of higher modes in neutron flux). Keff < ksource The parameters of the system can be chosen so that k < 1 at all times. Y. KADI, CERN

  30. Reactivity Insertions • Figure extracted from C. Rubbia et al., CERN/AT/95-53 9 (ET) showing the effect of a rapid reactivity insertion in the Energy Amplifier for two values of subcriticality (0.98 and 0.96), compared with a Fast Breeder Critical Reactor. • 2.5 $ (Dk/k ~ 6.510–3) of reactivity change corresponds to the sudden extraction of all control rods from the reactor. There is a spectacular difference between a critical reactor and an EA (reactivity in $ = r/b; r = (k–1)/k) : Y. KADI, CERN

  31. A Th/Pu fueled ADS Y. KADI, CERN

  32. Reprocessing • In the case of the ADS (Energy Amplifier project), pyroprocessing is regarded as a key technology in many aspects. In comparison the acqueous reprocessing, it promises • Compactness and simplicity; • Less secondary wastes; • Proliferation resistance (no separation of the TRUs); • And fuel fabrication and reprocessing at the reactor site Y. KADI, CERN

  33. Evolution of the reactivity for ThPu fuel Y. KADI, CERN

  34. Evolution of the reactivity for UPu fuel Y. KADI, CERN

  35. A Th/Pu fuelled ADS • Application au cas de l’Espagne [C. Rubbia et al. CERN/LHC/97-01 (EET)], dans un AE spécialisé pour l’incinération de TRU. • Le taux d’élimination des TRU de 402 kg/an correspond à 30,6 kg/TW.hth à comparer au taux de production de TRU par un REP de 14 kg/TW.hth • Dans le cas de l’Espagne, avec 5 EA il faudrait 37 ans pour éliminer les TRU tout en produisant 8% de la consommation d’énergie (100 Mtep/an) Y. KADI, CERN

  36. Radiotoxicity • The radiotoxicity of spent fuel reaches the level of coal ashes after only 500 years, and is similar to what is predicted for future hypothetical fusion systems Y. KADI, CERN

  37. 2+ UO 2 UO +PuO 2 2 2+ PuO 2 ROAD MAP FOR A DEMO Technology of pyrochemical reprocessing of fuel High power accelerators technology Technologies of fast reactors with lead-bismuth coolant Liquid metal targets technology Accelerator-driven nuclear waste burner Y. KADI, CERN

  38. Y. KADI, CERN

  39. Global Parameters Y. KADI, CERN

  40. Transmutation Rates Plutonium incineration in ThPu based fuel is more efficient and settles to approximately 43 kg/TWh, namely 4 times what is produced by a standard PWR (per unit energy). The minor actinide production is very limited in this case. Long-Lived Fission products incineration is made possible in a very efficient way through the use of the Adiabatic Resonance Crossing Method. Such a machine could in principle incinerate up to 4 times what is produced by a standard PWR (per unit energy). Y. KADI, CERN

  41. Conclusions • Can atomic power be green ? Physics suggests it can !! • Accelerator-driven systems have additional safety margins, which give operational flexibility to future systems for safe and clean energy production and/or waste transmutation (including nuclear weapons) • Present accelerator technology offers the possibility for applying a closed thorium cycle, but also for an open once-through ‘cycle’ using thorium oxide with some topping fuel and a very high fuel burnup. The Energy Amplifier is one of the examples with high potential • Next step: DEMO ? when ? where ? Y. KADI, CERN

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