International Thorium Energy Conference 2015 (ThEC15) BARC, Mumbai, India, October 12-15, 2015

Transcription

1 International Thorium Energy Conference 2015 (ThEC15) BARC, Mumbai, India, October 12-15, 2015 Feasibility and Deployment Strategy of Water Cooled Thorium Breeder Reactors Naoyuki Takaki Department of Nuclear Safety Engineering 1

2 Contents Background and Motivations Core design of water cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 2

3 Thorium Resource Map World wide 1500 thousand tons

4 Energy Potential of Thorium It is often said that thorium is more abundant in nature than uranium. It is true but the current identified quantity is comparable with that of uranium. Assuming thorium use in breeder type reactors, energy of ~10 6 GWy could be potentially added. equivalent to 1,000 LWRs operation for several 1,000 years To achieve this, enough fissile material needed to ingnite wet (fertile) thorium. 4

5 Objective / Motivations Develop water-cooled, oxide-fueled thorium breeder reactor Why water/oxide? well-established established plant/fuel technology Why breeder? make full use of resource for world sustainability Why thorium? Diversify fission energy resource Smaller MA production Breeding potential with negative void effect No severe energetics during CDA 5

6 Breeder type thorium reactors Shippingport PWR (USA) Past studies AHWR (India) RBWR (Hitachi, UCB) Our study PHBR (PWR with tight pitch fuel & D 2 O) (TCU) Moderator Light water Heavy water Light water Heavy water Breeding Ratio >1.05 Total Burnup 15 GWd/t 24 GWd/t 45 GWd/t 70GWd/t Core Heterogeneous Design Pressure tube Axial hetero Homogeneous Movable fuel with blanket No blanket Pin gap - - Very tight 1mm > 2.5 mm Void Coeff. Negative Negative Negative Negative Shutdown Margin Enough Enough Not enough Enough 6

7 Contents Background and Motivations Core design of water cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 7

8 Design window of H2O cooled thorium breeder 60 Limit line for negative VRC Geometrical gap limit (>1mm) for triangular Limit line for breeding Shippingport, LWBR Moderator to Fuel Volume Ratio (MFR) [-] 2 8

9 Design window of D2O cooled thorium breeder Limit of negative void reactivity Limit of breeding MFR 1.0 Feasiblewindow area of of breeding Design breeding and negative void reactivity And negative void reactivity Moderator to Fuel Ratio [-]

10 Reactor / fuel type comparison 10 Reactor type Coolant Fuel type BLBR (BWR with tight pitch) PHBR (PWR with tight pitch) H 2 O D 2 O U-Pu oxide Th-Pu oxide Th-U233 oxide BLBR : Boiling Light water Breeder Reactor PHBR : Pressurized Heavy water Breeder Reactor

11 Fissile Inventory Ratio with Burnup for PHBR 1.4 U-Pu_11.5w% U-Pu_12.5w% MFR U-Pu_13.5w% Th-Pu_15w% Th-Pu_15.6w% Th-Pu_17w% MFR= Achievable Burnup [GWd/t]

12 Fissile Inventory Ratio with Burnup for PHBR U-Pu_11.5w% U-Pu_12.5w% 1.3 U-Pu_13.5w% Th-Pu_15w% Th-Pu_15.6w% 1.2 Th-Pu_17w% Th-U233_6.6w% Th-U233_7.2w% Th-U233_7.7w% Achievable burnup [GWd/t]

13 Detailed enrichment survey (PHBR, ThTh-233U fuel) w% 7.6w% 7.7w% MFR= w% MFR=0.5 MFR= w% MFR=0.8 1 MFR=1.0 Achievable burnup [MWD/t] , , , , ,00, ,20, ,40,000 13

14 Reactor / fuel type comparison 14 Reactor type Coolant Fuel type BLBR (BWR with tight pitch) PHBR (PWR with tight pitch) H 2 O D 2 O U-Pu oxide Th-Pu oxide Th-U233 oxide BLBR : Boiling Light water Breeder Reactor PHBR : Pressurized Heavy water Breeder Reactor

15 Fissile Inventory Ratio & Burnup for BLBR MFR= MFR=1.0 Th- 233 U MFR=1.0 Th-Pu U-Pu_10.4w% U-Pu_11.5w% U-Pu_12.5w% Th-Pu_13.7w% Th-Pu_15w% Th-Pu_15.6w% Th-U233_5.5w% Th-U233_6.7w% Th-U233_7.7w% , ,00,000 1,50,000 2,00, ,50,000 3,00,000 Achievable burnup [GWd/t]

16 Doppler coefficients E E E-20 Reference BWR -1.0E E-05 U-Pu -3.0E-05 Th-Pu -4.0E E-05 Th-U E E MFR BLBR -1.0E E E E E E E-05 Th-U233 Reference BWR U-Pu Th-Pu MFR PHBR Reference BWR Kashiwazaki-Kariwa Unit2, TEPCO

17 Void coefficients E E E E+00 U-Pu 5.0E E+00 U-Pu -5.0E E-03 Th-Pu Reference BWR -5.0E E-03 Th-Pu Reference BWR -1.5E E-03 Th-U E E-03 Th-U E E E MFR BLBR Reference BWR Unit2, TEPCO -3.0E-03 Kashiwazaki-Kariwa MFR PHBR

18 Core specifications of PHBR U-Th fuel (282) D2O reflector (96) B4C control rod (19) 18

19 Fuel specifications of PHBR U-Th fuel (282) D2O reflector (96) B4C control rod (19) 19

20 Control rods U-Th fuel (282) D2O reflector (96) B4C control rod (19) 20

21 Cladding material integrity Evaluated fast neutron fluence : n/cm2 because of long cycle length (1,300 3 days) with hard spectrum Limitation for Zircaloy-4 : n/cm2 U-Pu FBR Th-Pu D2O PWR Th-U233 D2O PWR UOX LWR Other cladding material that can withstand higher fluence with small σa has to be employed. SiC 21

22 Impacts of SiC clad. on keff and CR SiC Zircaloy SiC Zircaloy 22

23 Impacts on core performances Zircaloy-4 SiC Burnup reactivity loss %dk/kk Control rod worth %dk/kk Av. discharged bunup GWd/ton Fissile Inventory Ratio By changing cladding material to SiC, neutronic performances were improved. 23

24 Void reactivity coefficient (cm) Zone wised local void coefficients at EOEC Zircaloy case (%dk/kk /%void) SiC case (%dk/kk /%void) Coefficients are negative all over the core. 24

25 Neutron fluence and spectrum 1.6E+01 Zircaloy SiC 1.4E E+01 Fast fluence 1.0E+01 Limitation Zircaloy < SiC < E E E E E+00 1.E-04 1.E-02 1.E+00 1.E+02 Neutron Energy [ev] 1.E+04 1.E+06 25

26 Contents Background and Motivations Core design of water cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 26

27 Deployment scenario Current phase Natural uranium UOX Fuel Fabrication LWR Reprocessing Disposal Thorium Pu (Th,Pu)O 2 Fuel Fabrication Th/Pu (Th,Pu)O 2 Fueled PHBR? Reprocessing Disposal Transition phase U-233 Th/U-233 Breeder phase Thorium (Th,U-233)O 2 Fuel Fabrication (Th,U-233)O 2 Fueled PHBR Reprocessing Disposal 27

28 Replacement of UU -LWR by Th Th--HPWR U-LWR 30 Th-233U PHBR Th-Pu PHBR Years 60GWe U-LWRs can be replaced within a century. 28

29 Reprocessing capacity and SF amount , , ,000 Stored SF of U-LWR , , Reprocessing capacity for U-LWR Pu supply 20,000 from LWR exhausted within15,000 a century. SF generated from U-LWR SF from Th-U3 PHBR ,000 5,000 SF from Th-Pu PHBR Years Deployable capacity of PHBR depends on Pu stockpile Installed UU -LWR capacity Reprocessing capacity

30 Contents Background and Motivations Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 30

31 Synergetic system with UU -Pu reactors Sustainable energy system with matured plant technology Diversified fission resources Efficient MA transmutation & easier fuel handling (less heat) Better energy balance than ADS 31

32 Contents Background and Motivations Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 32

33 Indice for difficulties in diversion Critical Mass Enrichment technology Implosion technology Heat production U kg Required Not required None Pu (Weapon grade) 10kg Not required Required Small U-233 (Weapon grade) ( 1ppm U-232) 16kg Not required Not required Small 33

34 Contents Background and Motivations Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 34

35 Cost impact Cost reduction factors No need for enrichment (vs. LWR) Proven PWR plant technology (vs. FBR) Cheaper resource (vs. UO 2 fuel) Cost increase factors Heavy water coolant (vs. LWR) Tritium production (vs. LWR) Challenging reprocessing technology (vs. UO 2 fuel) High gamma fuel handling (vs. UO 2 fuel) 35

36 Cost evaluation of PHBR Power output Burnup Cycle length Cycle interval Batch number Capacity factor 3450MWt 1340MWe 61.2GWd/t 1,000days 30days 3 97% Parameters assumed Low Nominal High Unit Construction yen/kwe Th Fuel yen/ton Fabrication yen/tonhm Reprocessing yen/tonhm 36

37 Generation cost O&M cost Capital cost Fuel cost LWR (5.3 yen/kwe) Evaluated by FEPC in Plant : 1300MWe PWR 3 2 FBR (2.6 yen/kwe) Evaluated by JAEA in Plant : 1500MWe MOX-FBR 1 0 Low Nominal High 37

38 Contents Background and Motivations Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Proliferation resistance of Th cycle Generation cost Concluding remarks 38

39 Remarks (1/2) Thorium resource is abundant but available fissile mass determines how many thorium reactors can be deployed. Th reserves Energy derived from thorium. Pressurized heavy water breeder reactor (PHBR) with Th-U233 fuel shows breeding capability with high burnup (>60GWd/t) and negative void effect. Tritium and ThO 2 reprocessing are tough challenges. 39

40 Reamarks (2/2) All LWRs can be replaced by PHBR by using Pu recovered from the LWR s SF within a century. PHBR works both in transition and sustainable phase. Careful examination should be made for proliferation resistance of Th-cycle. Strong gamma High proliferation resistance. Generation cost of thorium fueled PHBR could be competitive with LWR owing to high BU and CF. Further study required to reduce uncertainty. 40

41 What I want to share Th shows some preferable characteristics but is not magic fuel. It is basically the same as Uranium. Th reactor produces similar nuclear wastes if the cycle is not closed. Closed cycle just minimizes the waste. Scientists must be humble, objective, mustn t exaggerate. 41

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