Team Members Pacific Northwest National Laboratory: Brady Hanson

1. EPRI Extended Storage Collaboration ProjectDecember 7-8, 2010Charlotte, North CarolinaPreliminary 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. 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. UFD Storage Work PackagesHow 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. 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. 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. R&D Opportunities Objectives • 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 6

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. Storage System Components • Fuel • Pellet • Fuel/Clad • Assembly • III. ISFSI • Pad • Rebar • Physical Protection • Cask • Basket • Internals • Canister • Overpack • Monitoring Systems • Remote inspection • In-package sensors • Security 8

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. 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 10

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 • Nocreep during storage • “Creep life” remains • Most severe conditions during first 20 years??? Challenge: Demonstrate similar behavior for up to 300 years 11

12. Technical Bases Required • Industry Experience: What hasn’t been addressed? • Effect of marine environment • Cannot rule out corrosion andstress 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. 12

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. 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. 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. 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. General Needs- Monitoring Systems (High/Medium) • Monitoring and Sensor systems (to minimize need to open package frequently) • Internal • Temperature • Pressure • H2O • Xe, Kr • O2 • 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. 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. 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. FY10 Initial Findings: Fuel Example of Pellet Cracking and Flow Path for ATM-106 rod NBD-107 (taken from Guenther et al. 1988, Figure E.1.g) 20

21. FY10 Initial Findings: Cladding Radial hydrides from Kubo et al., 2010 LWR Fuel Performance Mtg. 21 Inner clad oxidation from CSNF Abstraction Model

22. FY10 Initial Findings: Grid Spacers, Fuel Baskets Grid Spacers Upper grid spacer and differing fuel rod growth from INL test Fuel Baskets Top weld crack in fuel basket from 15-yr demo at INL 22

23. FY10 Initial Findings: Neutron Poisons and Shields Neutron Poisons Neutron Shields Example of BORAL blisteringfrom EPRI 23

24. FY10 Initial Findings: Container Cask bottom cover plate bolt corrosion observed in 15-yr demo at INL White coloring on metal gasket from remainingwater after 5 yr storage. Aida et al., IAEA 2010 24

25. FY10 Initial Findings: Overpack Examples of concrete degradation at INL ISFSI

26. Preliminary List of High and Medium Priority R&D Needs (Normal Conditions) 26

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. 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. 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 29