Strategy for large scale introduction of Th reactors harmonizing with current and future U-Pu reactors

Transcription

1 Strategy for large scale introduction of Th reactors harmonizing with current and future U-Pu reactors Naoyuki Takaki Department of Nuclear Safety Engineering 1

2 Tokyo City University In 2009, the name was changed from Musashi Institute of Technology to TCU. Focused on research topics to serve the sustainable development of society: these key areas are energy, information, environment, urban renewal and welfare. Main campus in Setagaya, Tokyo Yokohama campus, Kanagawa Atomic Energy Research Laboratory TRIGA-Ⅱ(100kW) Cooperative Major in Nuclear Energy (Graduate school) 2

3 Keen on thorium study TEPCO Advanced Reactor Gr., R&D center JSFR Tokyo Institute of Technology Research Laboratory for Nuclear Reactors Tokai University Dept. of Nuclear Engineering Reflector Fission products Residual uranium Trace MA Reflector Tokyo City University Dept. of Nuclear Safety Engineering Natural Uranium 1. Water-cooled thorium breeder reactor 2. Travelling Wave Reactor (CANDLE) with Th for power flattening 3. U-Th fueled PWR & BWR 4. U-Th fueled HTTR 3

4 Contents Background and Motivations Findings from our past studies Objectives Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Conclusions 4

5 Motivations Water cooled, oxide fueled thorium breeder reactor Why breeder reactor? Make full use of nuclear fuel resource Minimize fossil fuel utilization and the impact to the environment Inevitable energy source for sustainable development of the world 5

6 Water cooled, oxide fueled thorium breeder reactor Why water and oxide? Well-established plant/fuel technology Reliable and acceptable for utilities and public Transparent coolant for better maintenance Continuity of matured operation and maintenance technologies/experiences. 6

7 Water cooled, oxide fueled thorium breeder reactor Why Thorium? Diversify fission energy resource Smaller MA production Breeding potential with negative void effect No severe energetics during CDA 7

8 Differences with past studies Shippingport PWR (USA) Past studies AHWR (India) RBWR (Hitachi, UCB) Our study HPWR (TCU) Moderator Light water Heavy water Light water Heavy water Breeding Ratio >1.02 Total Burnup ~15 GWd/t ~24 GWd/t ~45 GWd/t ~75GWd/t Core Heterogeneous Design Pressure tube Axial hetero Homogeneous Movable fuel with blanket No blanket Pin gap - - Very tight ~1mm ~4 mm Void Coeff. Negative Negative Negative Negative Shutdown Margin Enough Enough Not enough Enough 8

9 Contents Background and Motivations Findings from our past studies Objectives Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Conclusions 9

10 Burnup [GWd/ton] Design window of H 2 O cooled thorium breeder Limit line for negative VRC Geometrical gap limit (>1mm) for triangular Limit line for breeding Shippingport, LWBR Moderator to Fuel Volume Ratio (MFR) [-] 10

11 Design window of D 2 O cooled thorium breeder Burnup[GWd/t] Limit of negative void reactivity Limit of breeding Feasible area of breeding and negative void reactivity Moderator to Fuel Ratio [-] MFR

12 Relative Neutron Spectra perlethargy[#/cm 2 s] Neutron Spectrum MFR= MFR= Energy [ev] 12

13 Findings from our previous studies Design window of thorium breeder is wider for D2O than H2O. Thermal spectrum is not necessarily optimal to achieve breeding capability with high burn-up even in case of Th. The lower power density shows better breeding / burnup. D2O thorium reactor (3.5GWt, MFR<1) is feasible to achieve; Breeding (>1.05) with negative void reactivity coefficient Higher burnup than LWR (>75GWd/t) Homogeneous, simple core with large pin gap ( 4mm) Acceptably small fissile/hm inventory (15ton/200ton) Similar core size (<4m) with current PWR. Fast neutron fluence exceeds the limit of Zircaloy-4! Generation costs of D2O PWR is less than that of LWR (but more than JSFR). 13

14 Core configration of HPWR U-Th fuel (282) D 2 O reflector (96) B 4 C control rod (19) 19 Control rods are arranged over the core. Control rods design is based on Monju. The total rod worth at fully inserted position is evaluated as -6.5 %dk/k that is enough at cold zero power. 14

15 Specifications TABLE III Design parameters Core Thermal power [MWt] 3500 Cycle length [days] 1300 Batch number 3 Fuel type 232 Th- 233 U mixed oxide 233 U enrichment [wt%] 8 Core height [mm] 3700 Core Diameter [mm] 4050 Coolant Fuel assembly D 2 O Assembly Type Hexagonal Number of fuel assemblies 282 Fuel Assembly Pitch [mm] 230 Number of fuel pins in an assembly 169 Pellet diameter of fuel pin [mm] 13.1 Outer diameter of fuel pin[mm] 14.5 Fuel pin gap [mm] 4.5 Fuel Pin Pitch [mm] 17.6 Cladding material Zircaloy-4 The core is designed for power of 3.5GWt with cycle length of 1,300 days by 3 batch refueling. It is simple homogenous core without any blankets. The enrichment of U-233 is 8wt%. Fuel pin gap of 4.5 mm which facilitates heat removal. This core achieves averaged discharge burn up of about 80GWd/t and breeding ratio of

16 Flux per Lethargy Cladding material integrity Evaluated fast neutron fluence : n/cm 2 Limitation for Zircaloy-4 : n/cm 2 because of long cycle length (1,300 3 days) with hard spectrum 2.50E+01 U-Pu FBR 2.00E E E+01 Th-U233(D2O) Th-Pu15%(D2O) LWR (UO2) FBR Th-U233 D2O PWR UOX LWR Th-Pu D2O PWR 5.00E E+00 1E-03 1E-02 1E-01 1E+00 1E+01 1E+02 1E+03 1E+04 1E+05 1E+06 1E+07 Energy (ev) Other cladding material that can withstand higher fluence with small σ a has to be employed. SiC 16

17 Objectives Evaluate core performance of D 2 O cooled thorium breeder (HPWR) with SiC cladding. Picture a strategy to introduce Th-HPWR harmonizing with current LWR and future FBR with U-Pu cycle. 17

18 Contents Background and Motivations Findings from our past studies Objectives Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Conclusions 18

19 Method 燃料交換 Refueling 計算開始 Start Parameter パラメータ入力 input Cell セル計算 calculation(srac-pij) Lattice burnup calc. (SRAC-CELLBURNUP) reached to 規定燃焼ステップ数に到達 burnup step end? No Yes 炉心拡散計算 Diffusion calc. (SRAC (COREBN) - CITATION ) 炉心燃焼計算 Core bunup calc. (SRAC (COREBN) - サイクル期間燃焼 Reached to one cycle? No Yes Reached to 規定サイクル数に到達 Prescribed cycle? No Yes 計算終了 End Nuclear data liblary: JENDL-3.3 Core calculation: SRAC (3 dimensional, HEX-Z model) Design parameters used in optimization Units Total power output MWt 3,500 Coolant material D 2 O Cladding material Pellet diameter of fuel Outer diameter of fuel pin Pellet power density (average) Core diameter Core height Cycle length Batch number Moderator to fuel ratio mm mm W/cc mm mm Days - - SiC ,054 3,700 1,

20 Impacts on keff and CR SiC Zircaloy SiC Zircaloy 20

21 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. 21

22 130cm 120cm Heavy water reflector Void reactivity coefficient Zone wised local void coefficients at EOEC Zircaloy case (%dk/kk /%void) (cm) Core tank Upper nozzle Gas plenum Upper zone (360~370cm) Middle zone (180~190cm) Lower zone (0~10cm) Inner core Zone (1 st layer) Middle core Zone (5 th layer) -2.58E E E E E E-07 Outer core Zone (10 th layer) -8.32E E E 燃料 A 燃料 B 燃料 C Lower nozzle Core tank Upper zone (360~370cm) Middle zone (180~190cm) Lower zone (0~10cm) SiC case (%dk/kk /%void) Inner core Zone (1 st layer) Middle core Zone (5 th layer) Outer core Zone (10 th layer) -3.74E E E E E E E E E-08 :Locally voided area Coefficients are negative all over the core. 22

23 Neutron Spectrum per lethergy Neutron fluence and spectrum 1.6E E E E E+00 Fast fluence Limitation Zircaloy < SiC < Zircaloy SiC 6.0E E E E+00 1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06 Neutron Energy [ev] 23

24 Contents Background and Motivations Findings from our past studies Objectives Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Conclusions 24

25 Deployment scenario Current phase Natural uranium UOX Fuel Fabrication LWR Reprocessing Disposal Thorium Pu (Th,Pu)O 2 Fuel Fabrication? (Th,Pu)O 2 Fueled HPWR Th/Pu 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 HPWR Reprocessing Disposal 25

26 Installed capacity [GWe] Replacement of U-LWR by Th-HPWR U-LWR 2+3 3Th- 233 U HPWR Th-Pu HPWR Years 60GWe U-LWRs can be replaced within a century. 26

27 SF generation & Rep cap. [ton/y] Stored SF of LWR [ton] Assumed reprocessing capacity and SF amount 1800 Reprocessing capacity for U-LWR 45, , SF from U-LWR SF from Th-U3 HPWR Stored SF from U-LWR 35,000 30,000 25,000 Pu supply from 20,000 LWR exhausted within 15,000 a century. 10, SF from 5,000 Th-Pu HPWR Years Deployable capacity of Th reactor depends on Pu stockpile at the beginning U-LWR capacity Reprocessing capacity 27

28 Contents Background and Motivations Findings from our past studies Objectives Core design of D 2 O cooled thorium breeder Deployment strategy Synergetic system with U-Pu reactors Conclusions 28

29 Synergetic system with U-Pu reactors U nat U dep LWR U, Pu, MA MA HLW (FPs Only) U nat FBR U, Pu, MA MA HLW (FPs Only) MA Storage Th MA (after cooling) Th-BR HLW (FPs Only) All actinides (mainly Th and U-233) 29

30 Prominent features of synergistics U U Th LWR U, Pu MA FBR U, Pu HPWR MA MA (after cooling) HLW (FPs Only) MA Storage HLW (FPs Only) HLW (FPs Only) A) Efficient MA transmutation B) Better fuel handling due to less heat from MA C) Better energy balance than ADS D) Matured plant technology E) Enhanced energy production All actinides (mainly Th and U-233) 30

31 Conclusions Heavy water cooled thorium reactor (HPWR) is feasible to be introduced by using Pu recovered from spent fuel of U-LWR while keeping continuity with current LWR infrastructure. HPWR can also be operated as sustainable energy supplier and MA transmuter to realize future society with less waste and abundant energy. HPWR generates 3.5GW thermal power with long cycle length (1,300days 3batches) with high burnup (75GWd/t) and negative VRC all over the core and all through the cycle. 31

32 Published papers 1. Sidik, P.; Takaki, N.; Sekimoto, H. Impact of different moderator to fuel ratios with light and heavy water cooled reactors in equilibrium states. Ann. Nucl. Energy 2006, 33, Takaki, N.; Sidik, P.; Sekimoto, H. Feasibility of Water Cooled Thorium Breeder Reactor Based on LWR Technology; American Nuclear Society: La Grange Park, IL, USA, 2007; pp Sidik, P.; Takaki, N.; Sekimoto, H. Feasible region of design parameters for water cooled thorium breeder reactor. J. Nucl. Sci. Technol. 2007, 44, Sidik, P.; Takaki, N.; Sekimoto, H. Breeding capability and void reactivity analysis of heavy-water-cooled thorium reactor. J. Nucl. Sci. Technol. 2008, 45, Sidik, P.; Takaki, N.; Sekimoto, H. Breeding and void reactivity analysis on heavy metal closed-cycle water cooled thorium reactor. Ann. Nucl. Energy 2011, 38, Takaki, N.; Srivastava, A.; Takeda, A. Core Design of Heavy Water Cooled Thorium Breeder Reactor with Negative Void Reactivity and Improved Breeding Performance. In Proceedings of ICAPP 2011; Curran Associates, Inc.: Nice, France,

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