Comparative Study of ADS-burners with Thermal, Intermediate and Fast Neutron Spectrum for Transmutation of Minor Actinides

Transcription

1 Comparative Study of ADS-burners with Thermal, Intermediate and Fast Neutron Spectrum for Transmutation of Mor Actides L.I. Ponomarev RRC Kurchatov Institute and MUCATEX, Moscow ~ 90% of radiotoxicity of the spent nuclear fuel is contributed by the transuranium (TRU) elements, i.e. isotopes of plutonium, neptunium, americium and curium

2 Two schema of atomic power: Two component scheme: thermal reactors, fast reactors. Three component scheme: thermal reactors, fast reactors, reactor-burners. How to select the most effective reactor-burner?

3 Pu U Th Fuel manufacturg Neutron source Fast reactors Thermal reactors Burner s Interim storage Fuel reprocessg MA, LLFP Utilization Buryg Three - component nuclear power system with a closed nuclear fuel cycle

4 List of the hazard TRU isotopes 238 Pu, 239 Pu, 240 Pu, 241 Pu, 242 Pu 237 Np 241 Am, 242m Am, 243 Am 243 Cm, 244 Cm, 245 Cm, 246 Cm

5 Transuranium elements content spent fuel (Nuclear reactor with power 1 GWel produces ~ 1 tonn of RW per year) Atomic concentration, % Mass RW after 30 Nuclide years storage, VVER PWR [10] kg/tonn Np Pu Pu Pu Pu Pu Am Am-242m < 0.01 < Am Cm-243 < Cm Cm Cm-246 < TOTAL

6 Present nuclear wastes Medium Half-Life (<100 años) Short Half-Life (< 30 dias) High A actides Thermal and Fast Fission Fast Fissión Low Fission Cross Section TRU Transmut Fast Sp Av. Flux Intensity (n/cm2/s) 3,00E+15 Cm242 Cm243 Cm244 Cm245 Second 1 Time Unit α / SF α / EC/ SF α / SF α / SF Hour / 6.2E /0.29/ 5.3E / 1.35E / 6.1E-7 Day ,446 29,068 18, ,695 Year 3E+07 18,130 2,798 6,257 2,922 64,7% 8,0% 65,2% 11,4% Am241 Am242 Am242m Am243 Am244 α / SF β / EC IT / α / SF α / SF β / EC 100 / 3.77E / /0.46/1E / 3.7E / 4E-2 432,225 0, , ,922 0,001 3,652 17,792 1,844 4,892 #ЗНАЧ! 13,1% 8,4% 87,0% Pu238 Pu239 Pu240 Pu241 Pu242 Pu243 α / SF α / SF α / SF β / α α / SF β 100 / 1.9E / 3.1E / 5.7E / 2.45E / 5.5E , , ,805 14, ,707 0,001 4,220 3,477 9,033 2,688 11,354 6,775 37,5% 19,4% 54,8% 14,2% 61,1% 30,6% Np237 Np238 Np239 α / SF β β 100 / 2E ,095 0,006 0,006

7 Usual criterion of transmutation efficiency: the transmutation rate q MA [kg/year] or number of neutrons per one MA fissioned nucleus. It depends on the MA fission cross-sections σ f and the neutron flux Φ of the reactor-burners.

8 Proposed transmutation efficiency criteria transmutation rate q MA [kg/year]; transmutation time τ [year]; feedg ratiou ε = Pu/MA.

9 In the equilibrium regime the MA transmutation rate q MA is equal to MA feedg rate. Feedg ratiou ε = Pu/MA is the relative amount of plutonium (or other fissile nuclides) necessary to mata the given subcriticaly k.

10 Transmutation rate τ = τ + τ out τ - is the time of MA irradiation reactor necessary for the total transmutation of the loaded MA together with all TRU produced by MA and Pu the transmutation chas. τ out - is the duration of the outer nuclear fuel cycle (NFC). Today: τ out / τ 3.

11 τ = 0 t ω f ( t ) dt where ω f (t) is the probability density of TRU fission. In the equilibrium regime TRU G = q [ 1 MA 0 t 0 ω ( t f, )]dt, q t MA τ τ = G TRU / q MA

12 ω f (t), years E E E E E E E-02 Pu NpMA 0.0E t, years τ Pu = 46 years τ MA = 67 years

13 ADS chosen for comparison Heavy water reactor (thermal spectrum); Molten salt reactor (termediate spectrum); Lead-bismuth reactor (fast spectrum). Proton accelerator-driver: power 10 MW; energy 1 GeV; current 10 ma.

14 Fast Intermediate Thermal λ f, 1/year A

15 Characteristics of chosen ADS-burners at Keff=0.95 (accelerator power W a = 10 MW, E a = 1 GeV, I a = 10 ma) Reactor characteristics Neutron spectrum Fast Intermediate Thermal Subcriticality k ADS power, MW Neutron flux Φ, n/cm 2 s Pu/MA loadg the equilibrium cycle, tonn 1.1/ / /0.5 Pu/MA feedg content ε MA transmutation rate qma, kg/year Transmutation time τ, years ~20 ~205 ~ 55 Transmutation time of 1 tonn of TRU τ/ G TRU, years/tonn ~15 ~75 ~110

16 Characteristics of chosen ADS-burners at Keff=0.97 Reactor characteristics Neutron spectrum Fast Intermediate Thermal Subcriticality k Accelerator power, MW ADS power, MW Neutron flux Φ, n/cm 2 s Pu/MA loadg the equilibrium cycle, tonn 1,5/1,9 12.0/ /0.9 Pu/MA feedg content ε 0, Ttransmutation MA rate qma, kg/year Transmutation time τ, years ~30 ~220 ~60 Transmutation time of 1 tonn of TRU τ/ G TRU, years/tonn ~15 ~70 ~70

17 TRU Loses The duration τ c of the sgle transmutation cycle c τ = τ + τ c Because τ c << τ it is necessary several reprocessg cycles to transmute the TRU mass G TRU out c Reprocessg losses: n rep = τ / τ c Q = χ loss n rep, χ loss is the loss of MA durg one reprocessg cycle. At n rep ~ 10 and Q < 10-3 it is necessary to have χ loss < Such a level of losses is discussed now MSR-technology only.

18 CONCLUSION Our consideration shows that ADS with LBE blanket is evidently more effective from the pot of view τ and ε : τ ~ 15 years, ε ~ Molten salt ADS has preferences the reprocessg: τ~ τ. For the fal conclusion it is necessary to compare the efficiency of the critical reactor-burners (thermal and fast), takg to account their outer NFC.