Activation Calculation for a Fusion-driven Sub-critical Experimental Breeder, FDEB

Transcription

1 Activation Calculation for a Fusion-driven Sub-critical Experimental Breeder, FDEB K. M. Feng (Southwestern Institute of Physics, China) Presented at 8th IAEA Technical Meeting on Fusion Power Plant Safety July 2006, Vienna, Austria 1

2 I. Background Chinese economy has grown up and will continue to grow up fast. The GDP growth rates has been higher than 7% in last decades. Forecast, the 2020 s GDP will be near four times of 2000 s. China has biggest population in the world, more than 1.3 Billions, and will continue to increase to 1.6 to 2.0 Billions, near the middle of this century. China has limited energy resources. Coal, oil, hydro-power, including Uranium resources are very limited. The air-pollution problem, green-hose effect in China has been already very serious, mainly by coal burning. 2

3 China Oil Supply Outlook mb/d % 80% 60% 40% 20% 0% % Production Demand Imports as % of demand (right axis) 3

4 Background (Con t). If large-scale use the nuclear fission energy, several hundreds nuclear power stations should be built in China. Therefore, we need some new technologies for to build more safe, breeder type reactor. Fusion Breeder So that we should also consider how to dispose so large amount of high-level wastes(hlw) from the nuclear power plants. Fusion-transmutation Reactor A fusion breeder requires a lower level of fusion technology, so under the fuel demand in China, could probably come into the market much earlier than a pure fusion reactor. 4

5 Fusion reactor design activities at SWIP Conceptual Design of Fusion Breeder TETB, TETB-II, TETB-III TCB FEB, FEB-E, FDEB Hi-tech. Development Program (Supported by China MOST) ADS Design Study (national 973 project) Fusion-transmutation Reactors (CNNC project,national Nature Fund) FDTR, CFER-ST design ITER TBM Program ( CH PT) DEMO design?

6 Based on FDEB design, a 1:10 model has been built, showing the details of the reactor structure including the cooling tubes, manifolds, etc. Fig.1 Structure model (1:10) Fig.2 3-D Schematic view of FDEB design6

7 Main objectives of the FDEB To To demonstrate the the engineering feasibility of of fusion fusion breeder FDEB To To demonstrate its its capability of of fissile fissile fuel fuel production (( 100kg 100kg Pu-/yr Pu-/yr )) As As a component test test tool tool for for the the next next step, step, DEMO DEMO To To demonstrate the the feasibility of of transmutation long-lived nuclear wastes 7

8 Main parameters of FDEB design Parameters Units Values Fusion power [MW] 143 Plasma major radius [m] 4.0 Plasma minor radius [m] 1.0 Neutron wall loading [MW/m 2 ] 0.8 Tritium breeding ratio [TBR] 1.1 Pu-239 production [kg/y] ~100 Availability factor [%] 50 Assumption of activation analyses: Assumption of activation analyses: FDEB will be continuously operated under full power, rather than pulsed operation. 8

9 II. Calculation Procedure Activation Codes and Data Library FDKR/(CCC-541) --- a activation calculations code which special development for the fusion breeder; AF-DCDLIB --- a decay chain library to match the FDKR code; decay data are from ENDF/B-6 Nuclides in the AF-DCDLIB: Actinides 85 Activation products 319 Fission products 157 Total 581 9

10 Neutron Transport Calculation BISON Based on the BISON 1.5, a modified 1-D Neutron transport and burn-up calculation code was developed. BISON58---To match the BISON3.0, a new data library was compiled. Total nuclides 58 in the library; energy group structure: 46 groups for neutron 21 groups for gamma - Main data from the evaluated nuclear data file ENDF/B-6; - The neutron cross-section are processed by NJOY. 10

11 Th-U cycle transmutation/decay chains 11

12 U-Th cycle transmutation/decay chains 12

13 Data Data library library BISON BISON Transport Transport calculation calculation BISON3.0 BISON3.0 (N) (N) Data Data library library REAC44 REAC44 Data Data library library AF-DCDLIB AF-DCDLIB Activation Activation calculation calculation FDKR FDKR Input Data Input Data COVERT COVERT Transport Transport calculation calculation BISON3.0 BISON3.0 (G) (G) Dose Dose Rate Rate DOSE DOSE Fig.3 The codes and flow for activation calculation 13

14 Coolant (He) Inlet/outlet He cooling channel Shield Section Be 33% LLi 37% U 30% Liquid Lithium Be 43% LLi 37% U 20% Be 61% LLi 37% U 2% Fig.4 The cross section of outboard blanket Be/U Pebble bed with LLi 14

15 1-D model for Activation calculation Breeding Zone 400 plasma 170.o % % He 90% U % 2%, 20% 30% LLi 37% % He 20% SS316 5% Be 33-61% % 2. B 4 C 75% 316SS 5% He 20% FW Blanket Vacuum Cell Shield Insulator

16 III. Results and Discussion Major activation sources in the FDEB can be classified into four kinds: Actinides transmutation products of neutron captures by fission materials; Fission products due to fission reactions of fuel; Activation products activation of the FW, blanket and other components; Tritium tritium breeding reaction. 16

17 Neutron Flux (n/s.cm -2 ) Averged neutron wall-loading:0.8mw/m Energy (MeV) Fig.4 Distribution of neutron spectrum in the FW 17

18 Activation Products Major contributors of activation products in FW Nuclides Activity,(e+10Bq) Afterheat,(MW) BHP,(km3) Half-life Cr e e e d Mn e e e d Mn e e e h Fe e e e y Ni e e e+06 36h Co e e e d Co e e e d Co e e e y Mo e e e+05 66y W e e e d W e e e d Total 5.48e e e+07 18

19 Calculation results shows that: The maximum specific activity (8.84e+5 MBq /cm 3 ) occurs in the first wall; Main decay afterheat due to the beta-decay of Mn-56(68.3%), W-187(13.9%) and Co-58(9.1%), respectively; Total BHP at shutdown is 3.36e+07 km3 of water based on the NRC regulations specified in 10CFR20. 19

20 Fission Products In general, the inventory of fission products depends upon the fission rate occurring in blanket; Most of the fission products exhibit activity characteristics of short half-lives; In this calculation, about 200 kinds of fission products are calculated using the activation calculation code, FDKR. 20

21 Major contributors of Fission products Nuclides Activity,e+10Bq Afterheat, MW BHP,km3(air) Half-life Sr e e e d Sr e e e y Y e e e d Zr e e e d Ru e e e d Xe e e e d I e e e d I e e e d Cs e e e d Ce e e e d Pm e e e y Total 2.23e e e+08 21

22 Actinides Main contributors of actinides results from the reaction chains: β- (n, γ) β- 238 U + n 239 U 239 Np 239 Pu 23.5m 2.35d Fission Actinides are characterized by: -- long half-lives; -- heavy alpha activity; -- high toxicity; -- long-lived biological hazard. 22

23 Major contributors of actinides Nuclides Activity, e+10bq Afterheat, MW BHP,km3(air) Half-life U e e e e+08y U e e e d U e e e e+09y U e e e m Np e e e e+06y Np e e e d Pu e e e y Total 4.63e e+08 23

24 Decay behavior of Radioactivity after shutdown Fig.5 Radioactivity as a function after shutdown Radioactivity of actinides decays rapidly within a few days because of dominant nuclides U-239 and Np-239 have very short half-lives. 24

25 Afterheat Fig.6 Afterheat as a function after shutdown 25

26 Decay behavior of BHP after shutdown BHP of actinides drops down very slowly because of the long-lives of the major contributor. Fig.7 BHP as a function of after shutdown 26

27 U-232 U-232 is one of high toxicity and long-lived γ decay emitter ; U-232 can generate several toxic products through α decay; It is characterized by: (1) High decay power generation (~4W/g); (2) γ rays emitter with high energy of (~1-2MeV/decay); (3) High neutron generation with the reaction of light elements; (4) A generation of toxic gaseous decay products (such as Ra-220). From the viewpoint of reprocessing, U-232 is one of important nuclides in a fusion breeder design. 27

28 Fig.8 Transmutation and decay chain of U

29 Np-237 Np-237 is main contributor of actinides in the discharged fuel of FDEB design; Np-237 can be generated by the (n, γ) reaction of U-235 and the (n,2n) reaction of U-238; It will produces several toxic decay products through decay path (such as Pa-233, Th-229, Ra-225); It is one of the most important nuclide when considering the disposal of HLW. 29

30 Average concentration in U versus irradiation time, (%) Irradiation time, (yr.) U e e e e-07 Np e e e e-02 Pu e e e e-01 The calculation results shown that: The concentration of U-232 is acceptable in reprocessing technology of spent fuel at present time 30

31 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Radioactivity,Ci Actinides F.P. Act. P. Tritium Contribution of radioactivity sources in FDEB 31

32 Summarization of all sources in FDEB * Sources Activity, [Bq] Afterheat, [MW] BHP, [km3(air)] Actinides 2.72e e+08 Fission products 2.13e e+08 Activation products* 7.50e e+07 Tritium 1.41e e e+05 Total 5.74e e+08 * 316SS is as structure material. Radioactivity Afterheat BHP 2.44E+05 MBq/W(t) 3.6% of operating power 1.70E+03 km 3 /kw(t) 32

33 Comparison of radioactivity with PWR and FBR Sources Reactor types PWR FBR FDEB Actinides 1.16e e e+14 Fission products 4.63e e e+14 Activation products 9.03e e e+13 Total, MBq 6.70e e e+14 Afterheat, MW BHP, km3/kw(t) 4.80e e e+03 * Normalized to 1000 MW(e) power. 33

34 Source Geometry 3d model Nuclear Data MCNP Decay γ-source distribution Decay γ-fluxes & responses Loop over cells MCTAL MCTAL MCFISP MCFDKR FISPACT FDKR Material data Irradiation conditions Activation & decay data Decay γ-sources FISPMC FDKRMC 3-D activation calculation is under way. 34

35 IV. CONCLUSIONS Development of the sub-critical fusion breeder might be one of options as middle-application of fusion energy in the future. Although the fusion breeder exhibit activity characteristics similar to the fission reactor, but its inventory and hazards are lower than that of similar fission reactor, such as a PWR; The calculation results show that the concentration of actinides, U-232 and Np-237 in discharged fuel will be acceptable for the reprocessing of spent fuel. 35

36 Thank you for your attention! 36

37 Welcome to 21th IAEA FEC, Chengdu, China Information Center of SWIP,Chengdu 37