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Fast Reactor Physics Konstantin Mikityuk , FAST reactors group @ PSI fast.web.psi.ch

Fast Reactor Physics Konstantin Mikityuk , FAST reactors group @ PSI http://fast.web.psi.ch Thorium Energy Conference 2013 CERN Globe of Science and Innovation Geneva, Switzerland, October 27-31, 2013. Outline. Fast reactors: breeding. Fast reactors: past and future.

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Fast Reactor Physics Konstantin Mikityuk , FAST reactors group @ PSI fast.web.psi.ch

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  1. Fast Reactor Physics Konstantin Mikityuk, FAST reactors group @ PSI http://fast.web.psi.ch Thorium Energy Conference 2013 CERN Globe of Science and Innovation Geneva, Switzerland, October 27-31, 2013

  2. Outline. • Fast reactors: breeding. • Fast reactors: past and future. • Fast reactors: few R&D projects in Europe. • Fast reactors: could Th become a fuel? • Sustainability • Safety • Proliferation resistance • Radiotoxicity and decay heat • Summary: advantages and disadvantages of Th for FR

  3. Fast reactors: breeding.

  4. Fast critical reactor A fast neutron critical reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons. Such a reactor needs no neutron moderator, but must use fuel that is relatively rich in fissile material when compared to that required for a thermal reactor. PWR SFR

  5. 239 233 239 233 232 238 239 233 Breeding fissile 94Pu β– 27 d Uranium fuel cycle 93Np β– 22 m fissile fertile 92U (n,γ) β– 2.35 d 91Pa A production of new fissile isotopes in the nuclear reactor is a kind of transmutation called a breeding and non-fissile isotopes (U-238 and Th-232), which give birth to the new fissile isotopes, are called fertile. Thorium fuel cycle β– 23.5 m fertile 90Th (n,γ)

  6. Neutron balance in a critical reactor keff = Production rate / (Absorption rate + Leakage Rate) = 1 P = A + LR P = A_fissile + A_fertile + A_parasitic + LR A_fissile A_fissile A_fissile A_fissile h = 1 + BR + L h – Number of n’s emitted per neutron absorbed in fissile fuel BR – Breeding Ratio: Number of fissile nuclei created per fissile nucleon destroyed L – Number of neutrons lost per neutron absorbed in fissile fuel

  7. Breeding: h for main fissiles • Average number of fission neutrons emitted per neutron absorbed as a function of absorbed neutron’s energy for three fissile isotopes Best for breeding

  8. Breeding • Burning of Pu-239 and U-233 in a fast neutron spectrum (>105 eV) provides the highest number of fission neutrons per neutron absorbed in fuel. • The extra neutrons can be absorbed by fertile isotopes with a rate which is equal or even higher than the fissile burning rate. • The fast neutron spectrum reactor with BR>1 is called a breeder and with BR=1—an iso-breeder. • Fast neutron spectrum allows to efficiently “burn” fertile U-238 or Th-232—via transmutation to fissile Pu-239 or U-233.

  9. Fast reactors: past and future.

  10. First "nuclear" electricity – fast reactor. • In 1949 EBR-I – Experimental Breeder Reactor I – was designed at Argonne National Laboratory. In 1951 the world’s first electricity was generated from nuclear fission in the fast-spectrum breeder reactor with plutonium fuel cooled by a liquid sodium. First “nuclear” electricity : four 200-watt light bulbs. Courtesy of ANL.

  11. Fast reactors: 1946 – 2013 Na Hg NaK LBE Hg MWth

  12. The Generation IV International Forum (GIF) is a cooperative international endeavor organized to carry out the R&D needed to establish the feasibility and performance capabilities of the next generation nuclear energy systems. • Argentina, Brazil, Canada, France, Japan, Korea, South Africa, the UK and the US signed the GIF Charter in July 2001, Switzerland in 2002, Euratom in 2003, China and Russia both in 2006. • Six nuclear energy systems were selected for further development: • Gas-cooled fast reactor (GFR) • Sodium-cooled fast reactor (SFR) • Lead-cooled fast reactor (LFR) • Very-high-temperature reactor (VHTR) • Supercritical-water-cooled reactor (SWCR) • Molten salt reactor (MSR)

  13. Generation-IV systems: keywords • Sustainability • Safety • Economics • Reliability • Proliferation-resistance

  14. Fast reactors: few R&D projects in Europe.

  15. European sodium-cooled fast reactor. ESFR Power: 3600 MWth Coolant: sodium@1 bar Fuel: (U-Pu)O2 Clad: stainless steel EURATOM FP7 project

  16. Lead-cooled fast reactor demonstrator. ALFRED Power: 300 MWth Coolant: lead@1 bar Fuel: (U-Pu)O2 Clad: Stainless steel Consortium: Italy, Romania, Poland, …

  17. Gas-cooled fast reactor demonstrator. ALLEGRO Power: 75 MWth Coolant: helium@70 bar Fuel: (U-Pu)O2 Clad: Stainless steel Consortium: Czech Republic, Hungary, Slovakia, …

  18. Fast reactors: could Th be a fuel?

  19. Sustainability. Spent fuel cooling Fast reactors Separation of elements Fuel fabrication Geologic repository Depleted U stock (According to calculations) fast reactors can operate in an equilibrium closed U-Pu fuel cycle with BR=1 (amount of fissile produced = amount of fissile consumed) fed by only depleted (or natural) uranium AcO2 + FP AcO2 + FP FP + losses AcO2 Ac U-dep “Ac” = “actinides”, i.e. U + Np + Pu + Am + Cm + ... “FP” = fission products

  20. 242 244 245 242 241 242 243 244 m 238 239 240 241 242 243 237 239 240 238 234 235 238 239 237 EQL-U: mass balance in SFR (simplified model) –2 –3 3 0 96Cm mass number β+ β– 18.1 y 163 d 17 17 9 4 26 min 16 h M (n,2n) (n,γ) –3 –4 –1 21 9 3 95Am fission α 16 h 17 4 28 4 10 4.98 h 14.3 y –14 –678 –84 6 12 10 181 102 94Pu –62 –6 87.7 y 2 7 min 2.35 d 2.1 d 5 853 1 –1 –5 –8 –844 –1 –142 –1000 (Cm) (Am) (Pu) (Np) (U) 93Np 5 1 6 6.75 d 23.5 m 2 854 –1 –1 –140 1 6 854 92U FP +1000 feed fuel

  21. Sustainability. Could the same reactors operate in an equilibrium closed Th-U fuel cycle? (According to calculations) the answer is yes, but since no U-233 (main fissile isotope for this cycle) is available, we face a problem Th disadvantage: How to start thorium fast reactor? What fissile material to use? Plutonium? Uranium-235? Uranium-233 generated somewhere else?

  22. 237 238 233 239 234 235 236 231 232 238 237 233 232 232 231 234 233 228 EQL-Th: mass balance in SFR (simplified model) –1 –4 1 Th advantage: very low amount of minor actinides Th disadvantage: production of U-232—precursor of gamma emitters 94Pu 87.7 y 1 2.1 d 6 –2 6 93Np 6.75 d 8 1 –39 –2 –35 –4 –877 49 10 8 1 79 92U 68.9 y 1 955 6 4 27 d 1.3 d 6.7 h –5 –2 –957 –0 –35 –999 (Pu) (Np) (U) (Pa) (Th) 6 4 91Pa 1 22 m 959 26 h 6 –35 959 6 90Th FP 1.9 y 1 +1000 feed fuel

  23. EQL-U and EQL-Th fuel compositions in SFR (%wt)

  24. EQL-U and EQL-Th neutron balance • Blue bars are isotope-wise contributions to absorption (sum up to 1) • Red bars are isotope-wise contributions to production (sum up to k-inf) Th disadvantage:lower k-infinity k-inf = 1.30533 k-inf = 1.17023

  25. Safety. • We look at just two reactivity effects: Doppler effect and (sodium) void effect having in mind other reactivity effects (less fuel type dependent) Thermal expansion effects (not considered) Void reactivity effect

  26. EQL-U and EQL-Th fuel reactivity effects in SFR Infinite medium (no leakage component) Doppler (Nominal → 3100 K) Void (Nominal → 0 g/cm3) Isotope-wise decomposition: Th advantage: stronger Doppler and weaker void effects

  27. EQL-U and EQL-Th fuel reactivity effects in SFR Why void effect is weaker in case of EQL-Th? Sodium removal leads to spectral hardening—shift to the right Pu-239: grows quicker U-233: grows slower

  28. Proliferation resistance. 233 239 231 232 233 232 239 238 232 233 231 239 fissile Th advantage: misuse of U-233 is protected by presence of U-232 94Pu 2.35 d β– Uranium fuel cycle 93Np 23.5 m β– fissile fertile 92U (n,γ) 27 d β– β– 91Pa Thorium fuel cycle Th disadvantage: fissile precursor has higher half life, potential to be separated β– 22 m fertile 90Th (n,γ)

  29. EQL-U and EQL-Th fuel RT and DH (no FP) Th advantage: Radiotoxicity and decay heat of EQL fuel are lower for ~10000y

  30. Summary.

  31. Summary... Th disadvantages • Past and current fast reactors were/are based on U-Pu cycle. Operational experience with thorium-uranium fuel is low. • Experience in fuel manufacturing and reprocessing is lower for Th-U fuel compared to U-Pu. • Fissile fuel for Th-U cycle (U-233) is not available. • U-232—precursor of hard gamma emitters—is produced in Th-U cycle (n2n reaction is higher in fast spectrum). • k-infinity of equilibrium fuel is lower for Th-U cycle compared to U-Pu one. This means that to reach iso-breeding the blankets of fertile material can be required. • Fissile precursor of U-233 (Pa-233) has higher half life (compared to Np-239)—potential to be separated and decayed to pure U-233.

  32. Summary... Th advantages • Calculational analysis with state-of-the-art codes shows that fast reactor can operate as an iso-breeder in Th-U cycle closed on all actinides. • There is very low amount of minor actinides in EQL-Th fuel cycle. • Doppler effect is stronger and void effect is weaker in EQL-Th fuel compared to EQL-U. • Misuse of U-233 is protected by presence of U-232 (predecessor of hard gamma emitters). • Radiotoxicity and decay heat of EQL-Th fuel are lower during the first 10000 years of cooling compared to the EQL-U fuel.

  33. Thank you. Questions?

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