1. EPRI Extended Storage Collaboration Project December 7-8, 2010 Charlotte, North Carolina Preliminary DOE Gap Analyses and R&D Needs Team Members Pacific Northwest National Laboratory: Brady Hanson Sandia National Laboratories: Christine Stockman Oak Ridge National Laboratory: John Wagner Idaho National Laboratories: Sandra Birk, Abdelhalim Alsaed Savannah River National Laboratory: Natraj Iyer Lawrence Livermore National Laboratory: Bill Halsey

2. 12/07/2010 2 Policy Issues Consequences Policy The Administration’s decision to cancel Yucca Mountain means that the nation will need to store used fuel for the foreseeable future (>120 yrs). Issues Licenses for long term dry storage of used fuel are issued for 20 years, with possible renewals up to 60 yrs. A new rule-making will allow the initial license for 40 years with one possible 40-year extension. Questions regarding – retrieval and transport of used fuel after long term storage – storage and transportation of high burnup fuel (>45 GWD/MTU) Consequences Technical bases need to be developed to justify licensing; – used fuel storage beyond 60 to 80 years – retrievability and transportation of used fuel after long-term storage – transportation of high burnup fuel

3. 12/07/2010 3 UFD Storage Work Packages How do we address these consequences? R&D Opportunities –Data gap analysis –Plan to address gaps –Development of technical basis Security –Regulatory assessment –Identify areas peculiar to long-term storage –Evaluate vulnerability analysis methodology improvements Conceptual Evaluations –Develop process for development of technical basis –Evaluate several scenarios for decision makers Transportation UFD Storage Implementation Plan Goals 1 yr: Project Implementation Plan Framework 5 yr: Project Implementation Plan & Development of Technical Basis 10 yr: Field operating project

4. 12/07/2010 4 Assumptions At some point, DOE will be responsible for very long term storage (VLTS) of used fuel Active monitoring and aging management plans to mitigate issues if they arise Followed by ultimate disposition- awaiting Blue Ribbon Commission recommendations –Geologic repository 8 generic scenarios being investigated by the Used Fuel Disposition Campaign –Reprocessing facility Retrievability (integrity) of used fuel after VLTS must be maintained –Defense in depth suggests desire to maintain clad integrity and fuel source term Especially important for repository scenarios with advective flow –Maintain ability to tailor fuel content under reprocessing scenarios Potential for multiple movements of used fuel –From orphaned sites? –Centralized storage? –Ultimate disposition

5. 12/07/2010 5 If Geologic Disposal is Recommended The DOE needs may be more “conservative” than current practice –Meet fuel retrievability as defined in ISG-2, Rev. 1 –May desire minimization of cladding breaches (including pinhole leaks and hairline cracks) and not just “protected…against degradation that leads to gross rupture” (ISG-1, Rev. 2)

6. 12/07/2010 66 Develop the technical bases to demonstrate VLTS for a period of up to 300 years. Low and high burnup fuel Develop technical bases for fuel retrievability and transport after long term storage. Develop the technical basis for transport of high burnup fuel. Compare DOE gap analyses with those of NRC and NWTRB Obtain industry input Solicit data and information Reevaluate and prioritize gaps and needs R&D Opportunities Objectives

7. 12/07/2010 7 Tasks Identify major storage system components Define functional requirements Identify mechanisms affecting VLTS Identify gaps Prioritize testing needs Conduct tests/analyses Initiate modeling and simulation work Develop monitoring capability INL Dry Cask Storage Characterization (DCSC) Project

8. 12/07/2010 88 Storage System Components I.Fuel I.Pellet II.Fuel/Clad III.Assembly II.Cask I.Basket II.Internals III.Canister IV.Overpack III.ISFSI I.Pad II.Rebar III.Physical Protection IV.Monitoring Systems I.Remote inspection II.In-package sensors III.Security

9. 12/07/2010 9 Storage Functional Requirements Regulatory Requirements: –10CFR72 Allows for storage up to 120 years (60 yrs in-pool and 60 yrs dry storage) Used fuel cladding must be protected against degradation that leads to gross failure Must maintain confinement of intact and damaged used fuel Must be retrievable –NUREG-1536 requires maintenance of; Protection against environmental conditions Thermal performance Radiological performance Confinement Sub-criticality Retrievability Minimize cladding breaches 9

10. 12/07/2010 10 Identify mechanisms effecting VLTS A Features, Events, and Processes (FEPS) methodology combined with an extensive literature review is used to identify degradation mechanisms Systems analyzed: Fuel/clad system Fuel assembly Hardware Baskets Neutron Poisons/Shields Container Over pack Pad Monitoring, security, institutional control Topics investigated for each system: Goes back to Functional Requirements: Thermal Radiation Confinement Criticality Retrievability/Transportation FY10 focus on commercial LWR used fuels under normal operating conditions

11. 12/07/2010 11 Current Technical Bases Industry Experience: Technical issues addressed from past R&D program; [EPRI/DOE/NRC Dry Cask Storage Characterization (DCSC) Project at INL] –No cask functional degradation observed after 15 years –Assemblies look the same No sticking; no significant bowing upon removal No visual signs of degradation –No leaks during storage –No significant additional fission gas release to rod internals –No significant hydride reorientation –No creep during storage –“Creep life” remains –Most severe conditions during first 20 years??? Challenge: Demonstrate similar behavior for up to 300 years

12. 12/07/2010 12 Technical Bases Required Industry Experience: What hasn’t been addressed? –Effect of marine environment Cannot rule out corrosion and stress corrosion cracking –Advanced cladding materials and assembly designs Bulk of publicly available data is on Zry-2 and Zry-4 –MOX fuel –Long-term concrete degradation –High burnup fuel (>45GWD/MTU) Hydride reorientation Hydride embrittlement Creep Plenum gas pressure Corrosion Challenge: Demonstrate material degradation behavior for high burnup used fuel over a long storage period.

13. 12/07/2010 13 Criteria for Ranking Are there multiple Systems, Structures, and Components (SSCs) Important to Safety (ITS) to fulfill the function? Is it a primary SSC ITS? What is the likelihood of occurrence? What are the potential consequences? –Would it occur under geologic disposal conditions anyway? Can it be readily mitigated? –Assume repackaging or repairs are possible

14. 12/07/2010 14 General Needs- Temperature Profiles (High) Since most mechanisms are temperature dependent, accurate (i.e., not conservative or peak) temperature profiles (axial and radial) of fuel and cask materials must be modeled and validated –Need detailed temperature history During wet storage for X years During drying Over very-long-term storage periods (i.e., up to 300 years) Industry input –Temperature profiles and associated assumptions –Typical loading patterns to date –Future loading (how long will oldest fuel be in pool?)

15. 12/07/2010 15 General Needs- Drying Issues (High) Since many degradation mechanisms are dependent on or accelerated by the presence of water, need to model and measure how much water remains in a cask after drying. –Develop dryness criteria and methods for achieving and verifying compliance –Determine how much water remains in a cask after drying Chemisorbed, physisorbed, free, trapped –Understand the influence of fuel condition on drying and verifying dryness –Determine need for mitigation Industry input –Experience, Lessons Learned –Participation in ASTM Standard update

16. 12/07/2010 16 General Needs- Fuel Retrieval (High) Investigation of retrieval methods and potential impacts on ITS SSCs –Wet (back in pool) Lower temperature “Quench” Breached fuel –Dry Transfer System Examine fuels from one or more ISFSIs Near-term need to address orphan fuel problem Industry input –Experience, Lessons Learned –Details on dry transfer systems

17. 12/07/2010 17 General Needs- Monitoring Systems (High/Medium) Monitoring and Sensor systems (to minimize need to open package frequently) –Internal Temperature Pressure H 2 O Xe, Kr O 2 Dimensions (creep, bowing, etc.) –External Dose Welds (or develop welding techniques that are less susceptible to SCC) –Security Industry input –Package designs/how instrumentation could be accommodated

18. 12/07/2010 18 Reexamine INL DCSC (Medium/High) Additional 10+ years Obtain data on low burnup fuels and cask components –Don’t have baseline data Instrument casks Obtain information for development of the Test & Evaluation Facility for high burnup fuels INL Dry Cask Storage Characterization (DCSC) Project

19. 12/07/2010 19 General Needs- Subcriticality (Medium) Demonstrate subcriticality for transportation and retrieval operations – Burnup Credit Radiochemical assay data for isotopic concentration validation Critical benchmark experiments for credited isotopes Fuel depletion characteristics –Moderator Exclusion Industry input –Code validation data –Needs?

20. 12/07/2010 20 FY10 Initial Findings: Fuel 20 Stressor Degradation Mechanism Influenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal and Mechanical Fuel FragmentationYes Low Restructuring/ SwellingYes Low RadiationNone Chemical Attack of fission products on cladding Yes Low Fuel oxidationYes Low Example of Pellet Cracking and Flow Path for ATM-106 rod NBD-107 (taken from Guenther et al. 1988, Figure E.1.g)

21. 12/07/2010 21 FY10 Initial Findings: Cladding 21 Stressor Degradation Mechanism Influenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal Annealing of Radiation Effects NoYesMedium Metal Fatigue caused by temperature Fluctuations Yes Low Phase change TBD Radiation Embrittlement Yes TBD Chemical Emissivity changes from Zn or oxidation TBD H 2 effects: Embrittlement, Delayed Hydride Cracking Yes High OxidationYes Medium Wet Corrosion: Waterlogged Rods, Radiolysis, General, Pitting, SCC, Crevice, Galvanic, Fission Products NoYesTBD MechanicalCreepYes Medium Inner clad oxidation from CSNF Abstraction Model Radial hydrides from Kubo et al., 2010 LWR Fuel Performance Mtg.

22. 22 FY10 Initial Findings: Grid Spacers, Fuel Baskets 22 StressorDegradation Mechanism Influenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal and MechanicalCreepYesNoN/A Metal fatigue caused by temperature fluctuations Yes Low ChemicalWet corrosionNoYesLow StressorDegradation Mechanism Influenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal and MechanicalCreepYes Low Metal fatigue caused by temperature fluctuations Yes Low ChemicalWet corrosionNoYesLow Grid Spacers Fuel Baskets Top weld crack in fuel basket from 15-yr demo at INL Upper grid spacer and differing fuel rod growth from INL test

23. 23 FY10 Initial Findings: Neutron Poisons and Shields 23 StressorDegradation Mechanism Influenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal and MechanicalEmbrittlement and cracking Yes Low Metal fatigue caused by temperature fluctuations YesNoN/A CreepYesNoN/A RadiationPoison burnupYes Low Embrittlement and Cracking Yes Low ChemicalWet corrosion (Blistering) NoYesLow StressorDegradation MechanismInfluenced by VLTS or /Higher Burnup Additional Data Needed Importance of R&D Thermal and MechanicalEmbrittlement, cracking, shrinkage, and decomposition Yes Low RadiationPoison burnupYes Low Embrittlement and Cracking Yes Low ChemicalWet corrosionNoYesLow Neutron Shields Neutron Poisons Example of BORAL blistering from EPRI

24. 12/07/2010 24 FY10 Initial Findings: Container 24 StressorDegradation MechanismInfluenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal and Mechanical Embrittlement of elastomer O-rings Yes Low Temperature Fluctuations Relax Seals and Bolts Yes Medium Radiation Embrittlement of Elastomer O-rings Yes Low Chemical Humid Oxidation Yes High Marine Environment Yes High Wet Corrosion: General, Pitting, SCC, Crevice, Galvanic Yes High Cask bottom cover plate bolt corrosion observed in 15-yr demo at INL White coloring on metal gasket from remaining water after 5 yr storage. Aida et al., IAEA 2010

25. 12/07/2010 FY10 Initial Findings: Overpack 25 StressorDegradation MechanismInfluenced by VLTS or Higher Burnup Additional Data Needed Importance of R&D Thermal Dry OutYes Low FatigueYes Low Freeze ThawYes Low Radiation Aggregate GrowthYes Low Decomposition of WaterYes Low Chemical Aggregate ReactionYes Low Calcium leachingYes Low Chemical AttackYes Low Corrosion of Embedded Steel Yes Low Mechanical Blocked Air FlowYesNoN/A CreepYesNoN/A ShrinkageNo N/A Examples of concrete degradation at INL ISFSI

26. 12/07/2010 26 Preliminary List of High and Medium Priority R&D Needs (Normal Conditions) SystemIssue Importance of R&D Cladding Annealing of Radiation Effects Medium OxidationMedium H 2 effects: Embrittlement, Delayed Hydride Cracking High CreepMedium Container (Welds, Bolts, Metal Seals) Humid Oxidation High Marine Environment High Wet Corrosion: General, Pitting, SCC, Crevice, Galvanic High Temperature Fluctuations Relax Metal Seals and Bolts Medium Monitoring Systems Develop New Performance Confirmation Monitoring Systems Medium

27. 12/07/2010 27 Accident Conditions & Data Needs Which SSCs are important to analyze? Which mechanisms? If systems are monitored, then corrective actions can be taken to mitigate any accidents –Have to assure that dose and release criteria are met

28. 12/07/2010 28 ESCP Input & Assistance Provide better quality pictures of DCSS and ISFSIs Provide release of pictures Participate in the fuel survey led by SRNL –Availability of fuel, provide history, wet or dry, cask handling, schedule, cost Provide data on newer cladding (M5, ZIRLO, etc.) and assembly designs (e.g., partial length rods) “Waste” –Is any utility willing to take sectioned pieces of fuel rods, remaining fuel rods, etc. after testing back?

29. 12/07/2010 29 FY11 Work Plan & Pathforward  Objectives:  Complete gap analyses (by February 2011)  Accident conditions  Transportation  Develop Experimental and Modeling Plan  DOE workshop February 2011  Prioritize data needs (by end of March 2011)  Input from EPRI ESCP committee  Compare with NRC and NWTRB gap analyses  Input from international collaborators  Develop testing and modeling needs for TEF  Issue M1 Milestone Report (June 2011)  Initiate testing and modeling to fill gaps