Readiness of Current and New U.S. Reactors for MOX Fuel

Transcription

1 Readiness of Current and New U.S. Reactors for MOX Fuel North Carolina and Virginia Health Physics Societies Joint 2009 Spring Meeting New Bern, North Carolina 13 March 2009 Andrew Sowder, Ph.D., CHP Project Manager HLW & Spent Fuel Management Program

2 Motivation for this Review Use of mixed uranium-plutonium oxide (MOX) fuel in light water reactors is a mature technology Timing nuclear renaissance U.S. policy shifts mature technology state of knowledge Pu-recycle as a bridge to other fuel cycle options Question: Are there knowledge gaps and technology barriers that could inhibit use of MOX in U.S. reactor fleet (current and GEN III/III+)? 2

3 Substantial Existing Knowledge Base U.S. Government and National Labs Regulatory and licensing documents Reactor vendors Utilities Academia International organizations (IAEA, NEA) EPRI 3

4 Drivers, Constraints, and Concerns Regulatory environment Energy security Nonproliferation Public opinion Resource utilization Waste management Economics Technology This review 4

5 Current Context for Considering MOX 2000 U.S. Russia Plutonium Disposition Agreement 2001 National Energy Policy Development Group 2003 Advanced Fuel Cycle Initiative MOX lead-test assemblies irradiated in Catawba Unit launch of Global Nuclear Energy Partnership Utilities pursuing extended reactor lifetimes Seventeen companies/consortia pursuing licensing for > 30 new units 2008 DOE -TVA MOU for technical exchange on advanced fuel cycles 2008 DOE Yucca Mountain License Application, Second Repository Report and Draft GNEP PEIS 2009 New U.S. administration and waste policy MOX as bridge between once-through and advanced fuel cycles 5

6 Open Fuel Cycle 10 20% U nat Savings Once-through cycle in U.S. Suitable for: secure U supply nonproliferation credentials simplicity Poor U resource utilization Less than 1% of potential energy recovered 6

7 LWR Fuel: Waste or Resource? 7

8 Closed Fuel Cycles 15 25% U nat savings 35 95% U nat savings Fast reactor fleet required Complex technical challenges yet to be addressed Much higher utilization of U resources Manifold increase in energy recovery Nonproliferation concerns Potential for reducing long-lived wastes for disposal Repository still required 8

9 What is MOX Fuel? Standard LWR fuel employs low enrichment 235 U as primary fissile isotope in bulk 238 U matrix (as sintered/ceramic UO 2 ) = UOX Mixed oxide (MOX) fuel incorporates 239 Pu as primary fissile isotope in bulk 238 UO 2 matrix All LWRs operating on UO 2 based fuel eventually derive a substantial fraction of energy from 239 Pu fission 9

10 Plutonium Grades Isotope Weapons Grade (wt%) Reactor Grade (wt%) 238 Pu Pu Pu Pu Pu Weapons grade (WG) derived from low burnup uranium fuel to optimize 239 Pu content Reactor grade (RG) recycled Pu from spent UOX fuel irradiated in an LWR at high burnup 10

11 MOX vs. UOX Fuel Physically very similar predominately UO 2 Neutronics are different; Pu has: harder neutron spectrum shorter neutron lifetimes and fewer delayed neutrons greater σ f and σ tot for 239 Pu greater capture to fission ratio Differences greater for RG Pu than WG Pu Use of MOX fuel results in: reduced effectiveness of thermal neutron absorbers (control/shutdown rods, soluble boron, poisons) faster core response to reactivity transients large thermal neutron flux gradient at MOX UOX interfaces slower reactivity decrease with increasing burnup potentially enhanced pressure vessel embrittlement localized power peaking (esp. in fresh MOX) 11

12 MOX vs. UOX Fuel (cont d) Radiation protection: fresh fuel will contain significant Pu content irradiated fuel will have a much higher neutron dose ( 238 Pu, 242 Cm, 244 Cm) but comparable gamma Higher heat loads in irradiated MOX require longer cooling times (2 6 x) greater cooling capacity in spent fuel pool Greater fission gas/helium release in irradiated MOX Higher fissile content in irradiated MOX Transportation of fresh MOX fuel Cat I special nuclear material Additional security per recently revised 10 CFR 73 12

13 MOX Impacts on Reactivity Control Effect control/shutdown rods and soluble boron exhibit less worth (as do gadolinium and xenon) decreased reactivity safety margins (notably shutdown margin) with respect to transients, ΔT Remedy increase soluble boron concentration or use enriched boron (PWR) use higher worth control/shutdown rods use burnable absorbers isolate MOX fuel relative to control rod locations add control/shutdown rods (PWR) use higher worth control/shutdown rods increase soluble boron concentration or use enriched boron (PWR) increase soluble boron injection rate and/or boron enrichment for standby liquid control systems 13

14 Global MOX experience MOX use in thermal reactors considered a mature technology Early programs (ca. 50 s and 60 s) in the U.S., Italy, Germany, and Belgium Routine loading of MOX in reactors in France, Germany, Switzerland, Belgium, and India (with Japan to follow) MOX fuel loaded in 20 of 28 French 900 MWe PWRs MOX fuel performance comparable to that of UOX Partial MOX cores feasible in wide range of LWR designs both PWR and BWR designs as suitable hosts to date, MOX experience limited to partial cores MOX issues can be overcome while also satisfying safety and design margins 14

15 MOX in French 900 MW PWR Fleet Number of MOX Fuel Assemblies Loaded IAEA Current Trends in Nuclear Fuel for Power Reactors. IAEA General Conference 51. Nuclear Technology Review Supplement GC(51)inf-3-att5 15

16 MOX Irradiation in U.S. Reactors Reactor PWR/ BWR MOX LTA Start Total Number of Assemblies Total Number of Fuel Rods Vallecitos BWR 1960s Big Rock Point BWR Dresden-1 BWR San Onofre-1 PWR Quad Cities-1 BWR Ginna PWR Catawba-1 PWR full 17 x 17 assemblies 16

17 U.S. DOE Surplus Pu Disposition Program U.S. and Russia to meet obligations for disposition of 34 MT weapons grade Pu via irradiation in reactors : Duke Energy irradiates 4 lead test assemblies (LTAs) in Catawba Unit 1 LTAs manufactured in France from U.S.-origin Pu irradiation for two 18-month cycles assembly growth issues NOT related to MOX MOX fuel performance testing considered successful MOX Fuel Fabrication Facility under construction at Savannah River Site, Aiken, SC Total estimated 1700 PWR MOX fuel assemblies over 15-years 17

18 U.S. Fleet by Vendor/Model, Size, and Lifetime Reactor Vendor Type Units in operation Units >750 MWe Units in operation beyond 2039* Units >750 MWe in operation beyond 2039* Westinghouse PWR Combustion PWR Engineering Babcock and Wilcox PWR Total PWRs GE BWR2 BWR GE BWR3 BWR GE BWR4 BWR GE BWR5 BWR GE BWR6 BWR Total BWRs Total *Assumes 60 year operating lifetime. 18

19 Existing U.S. Reactors as Candidates for MOX Assumptions: commercial MOX use in U.S. no earlier than year minimum remaining lifetime greater flexibility in late GEN II reactors (ca. 1980) Result: ~ 50% of current fleet as potential candidates Number of Operational Reac tors yr reactor lifespan Year NOTE: Similar estimate from DOE: 3 Palo Verde CE System 80 PWRs + 48 other late model (ca. 1980) designs (34 PWRs + 14 BWRs) = 51 total [M. Todosow (BNL) to P. Fink (INL), 15 October 2007] 19

20 Global MOX Supply Existing French and UK production capacity of ~235 MTHM/yr 100 MTHM/yr of French capacity dedicated to MWe PWRs using 30% cores U.S. DOE MOX facility under construction ~ 70 MTHM/yr max to support MWe PWRs with 40% MOX cores Planned Japanese Rokkasho facility ~130 MTHM/yr to support reactors, most with partial cores MOX use in the U.S. is supply limited, NOT reactor limited, for the next years 20

21 GEN III/III+ Reactor Designs for U.S. Market Generation Design Vendor Output (MWe) Under NRC Review NRC Design Cert. GEN III ABWR GEH 1300 US APWR MHI 1700 AP1000 Westinghouse 1100 GEN III+ US EPR Areva 1600 ESBWR GEH 1520 Full MOX core capability reported in open literature for ABWR, AP1000, US-EPR, and US-APWR Construction of an ABWR at Ohma, Japan, for 100% MOX European Utility Requirements (EUR) explicitly call for reactor designs capable of 50% MOX cores 21

22 Preliminary Findings Existing Reactors Most if not all reactors capable of accommodating partial MOX loadings with either no or only minor modifications and operational changes No technical barriers identified thus far to partial MOX loading (30% or less) in at least half of existing U.S. fleet, based on review of: DOE sponsored reviews and analysis International MOX experience LTA irradiation history in PWRs and BWRs 22

23 Preliminary Findings Existing Reactors Amendment of reactor license (substantial but manageable undertaking) demonstration of fuel performance, safety margins re-evaluation of plant design basis NRC staff has expressed favorable views on MOX licensing based on European experience Additional reactivity control required for MOX due to reduced control rod worth and shutdown margins addressed through use of higher soluble boron concentrations and/or enriched 10 B, burnable absorbers, or higher worth control rods Plant wide changes to address: security radiation protection and shielding increased minimum cooling periods, increased cooling capacity for spent fuel pool, spent fuel criticality No negative impact on return to 100% UOX cores 23

24 Preliminary Findings GEN III/III+ Reactors All GEN III/III+ designs should accommodate high MOX core loading (50% to full cores) 50% MOX core loading target per European Utility Requirements Core loadings of 50% or greater generally require MOX-specific design Full MOX core capacity reported for ABWR, AP1000, US-EPR, US- APWR Limited information on specific design capabilities with respect to MOX loading Limited information on differences between designs for U.S. and international markets MOX use in new reactors may be restricted due to plant specific design aspects (e.g., spent fuel pool capacity) 24

25 Together Shaping the Future of Electricity 25

26 Backup Slides 26

27 Waste Management Perspective Actinides are primary long-term risk drivers for disposal of HLW and SNF Transmutation of actinides would simplify disposal Pu Minor actinides: Np, Am, Cm 1.00E E-01 Mean Dose mrem/y 1.00E E E E E-06 DoseTc-99 DoseI-129 DoseNp-237 DoseU-233 DoseTh-229 DosePu-239 DoseU-235 DoseU-238 DoseU-234 DoseTh-230 DosePu-240 DoseU-236 Total 1.00E E E E E E+06 Time

28 Costs: Fuel Cycle Costs a Function of Uranium and PUREX Reprocessing Unit Costs* Fuel Cycle Cost (mills/kwhe) $104 $208 $312 $416 $520 Uranium Unit Cost ($/kgu) FC1: Once-Through FC2: Purex $500/kgHM FC2: Purex $750/kgHM FC2: Purex $1000/kgHM FC2: Purex $1250/kgHM FC2: Purex $1500/kgHM *EPRI, Nuclear Fuel Cycle Cost Comparison Between Once-Through and Plutonium Single- Recycling in Pressurized Water Reactors. [Report , February 2009]. 28