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Wir schaffen Wissen – heute für morgen Fast Reactor Physics Konstantin Mikityuk, FAST reactors PSI Thorium Energy Conference.

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Presentation on theme: "Wir schaffen Wissen – heute für morgen Fast Reactor Physics Konstantin Mikityuk, FAST reactors PSI Thorium Energy Conference."— Presentation transcript:

1 Wir schaffen Wissen – heute für morgen Fast Reactor Physics Konstantin Mikityuk, FAST reactors PSI Thorium Energy Conference 2013 CERN Globe of Science and Innovation Geneva, Switzerland, October 27-31, 2013

2 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 3 Fast reactors: breeding.

4 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. SFR PWR

5 5 Breeding U 93 Np 94 Pu 91 Pa 90 Th β–β– β–β– β–β– β–β– Thorium fuel cycle Uranium fuel cycle (n, γ ) fertile fissile 23.5 m 2.35 d 22 m 27 d 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.

6 6 Neutron balance in a critical reactor A_fissile P=A_fissile + A_fertile + A_parasitic + LR P=A + LR k eff = Production rate / (Absorption rate + Leakage Rate) = 1 A_fissile  =1+BR+L  – 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 7 Breeding:  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 8 Breeding  Burning of Pu-239 and U-233 in a fast neutron spectrum (>10 5 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 9 Fast reactors: past and future.

10 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 11 Fast reactors: 1946 – 2013 MWth Hg NaK Na LBE

12 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  Six nuclear energy systems were selected for further development: 4.Very-high-temperature reactor (VHTR) 5.Supercritical-water-cooled reactor (SWCR) 6.Molten salt reactor (MSR) 1.Gas-cooled fast reactor (GFR) 2.Sodium-cooled fast reactor (SFR) 3.Lead-cooled fast reactor (LFR)

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

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

15 15 European sodium-cooled fast reactor. Power: 3600 MWth Coolant: bar Fuel: (U-Pu)O 2 Clad: stainless steel ESFR EURATOM FP7 project

16 16 Lead-cooled fast reactor demonstrator. Power: 300 MWth Coolant: bar Fuel: (U-Pu)O 2 Clad: Stainless steel ALFRED Consortium: Italy, Romania, Poland, …

17 17 Gas-cooled fast reactor demonstrator. Power: 75 MWth Coolant: bar Fuel: (U-Pu)O 2 Clad: Stainless steel ALLEGRO Consortium: Czech Republic, Hungary, Slovakia, …

18 18 Fast reactors: could Th be a fuel?

19 19 Sustainability. Depleted U stock Spent fuel cooling Fuel fabrication Fast reactors Geologic repository Separation of elements U-dep Ac AcO 2 + FP FP + losses “Ac” = “actinides”, i.e. U + Np + Pu + Am + Cm +... “FP” = fission products AcO 2 (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

20 U 93 Np 94 Pu 95 Am 96 Cm FP – – –14 6 – –84 12 –62 10 –6 410 – –2 3 – –4 21 – –5 –8 –844 –1 –142 –1000 (Cm) (Am) (Pu) (Np) (U) 242 m feed fuel 6.75 d 2.1 d 87.7 y 23.5 m 2.35 d 7 min 14.3 y 4.98 h 26 min 18.1 y 16 h 163 d –1 (n,2n) β–β– (n, γ ) β+β+ fission M mass number α EQL-U: mass balance in SFR (simplified model)

21 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 22 EQL-Th: mass balance in SFR (simplified model) U 93 Np 94 Pu 91 Pa 90 Th –35 feed fuel m h d h 4 27 d 955 – – y 234 – – – d – d 238 –4 1 1 – y y FP –5 –2 –957 –0 –35 –999 (Pu) (Np) (U) (Pa) (Th) Th advantage : very low amount of minor actinides Th disadvantage : production of U-232—precursor of gamma emitters

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

24 24 EQL-U and EQL-Th neutron balance k-inf = k-inf =  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

25 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 26 EQL-U and EQL-Th fuel reactivity effects in SFR Th advantage : stronger Doppler and weaker void effects Infinite medium (no leakage component) Doppler (Nominal → 3100 K) Void (Nominal → 0 g/cm 3 ) Isotope-wise decomposition:

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

29 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 30 Summary.

31 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 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 years of cooling compared to the EQL-U fuel.

33  Thank you. Questions?


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