EPRI Extended Storage Collaboration Project December 7-8, 2010 Charlotte, North Carolina Preliminary DOE Gap Analyses and R&D Needs Team Members Pacific.

EPRI Extended Storage Collaboration ProjectDecember 7-8, 2010Charlotte, 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

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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

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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

TransportationUFD Storage Implementation Plan Goals• 1 yr: Project Implementation Plan Framework• 5 yr: Project Implementation Plan & Development of Technical Basis• 10 yr: Field operating project

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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

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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)

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• 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

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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

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Storage System Components

I. FuelI. PelletII. Fuel/CladIII. Assembly

II. CaskI. BasketII. InternalsIII. CanisterIV. Overpack

III. ISFSII. PadII. RebarIII. Physical Protection

IV. Monitoring SystemsI. Remote inspectionII. In-package sensorsIII. Security

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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

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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 assemblyHardware Baskets Neutron Poisons/Shields Container Over pack Pad Monitoring, security, institutional control

Topics investigated for each system:

Goes back to Functional Requirements:ThermalRadiationConfinementCriticalityRetrievability/Transportation

FY10 focus on commercial LWR used fuels under normal operating conditions

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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 to300 years

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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.

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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

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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?)

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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

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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

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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

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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

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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?

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FY10 Initial Findings: Fuel

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StressorDegradation Mechanism

Influenced by VLTS or Higher

Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical

Fuel Fragmentation Yes Yes Low

Restructuring/ Swelling Yes Yes Low

Radiation None

Chemical

Attack of fission products on cladding

Yes Yes Low

Fuel oxidation Yes Yes Low Example of Pellet Cracking and Flow Path for ATM-106 rod NBD-107 (taken from Guenther et al. 1988, Figure E.1.g)

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FY10 Initial Findings: Cladding

21

StressorDegradation Mechanism

Influenced by VLTS or Higher

Burnup

Additional Data Needed

Importance of R&D

Thermal

Annealing of Radiation Effects

No Yes Medium

Metal Fatigue caused by temperature Fluctuations

Yes Yes Low

Phase change TBD TBD TBD

Radiation Embrittlement Yes Yes TBD

Chemical

Emissivity changes from Zn or oxidation

TBD TBD TBD

H2 effects: Embrittlement, Delayed Hydride Cracking

Yes Yes High

Oxidation Yes Yes Medium

Wet Corrosion: Waterlogged Rods, Radiolysis, General, Pitting, SCC, Crevice, Galvanic, Fission Products

No Yes TBD

Mechanical Creep Yes Yes Medium

Inner clad oxidation from CSNF Abstraction Model

Radial hydrides from Kubo et al., 2010 LWR Fuel Performance Mtg.

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FY10 Initial Findings: Grid Spacers, Fuel Baskets

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Stressor Degradation Mechanism

Influenced by VLTS or Higher Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical Creep Yes No N/A

Metal fatigue caused by temperature fluctuations

Yes Yes Low

Chemical Wet corrosion No Yes Low

Stressor Degradation Mechanism

Influenced by VLTS or Higher Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical Creep Yes Yes Low

Metal fatigue caused by temperature fluctuations

Yes Yes Low

Chemical Wet corrosion No Yes Low

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

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FY10 Initial Findings: Neutron Poisons and Shields

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Stressor Degradation Mechanism

Influenced by VLTS or Higher Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical Embrittlement and cracking

Yes Yes Low

Metal fatigue caused by temperature fluctuations

Yes No N/A

Creep Yes No N/A

Radiation Poison burnup Yes Yes Low

Embrittlement and Cracking

Yes Yes Low

Chemical Wet corrosion(Blistering)

No Yes Low

Stressor Degradation Mechanism Influenced by VLTS or /Higher Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical Embrittlement, cracking, shrinkage, and decomposition

Yes Yes Low

Radiation Poison burnup Yes Yes Low

Embrittlement and Cracking

Yes Yes Low

Chemical Wet corrosion No Yes Low

Neutron Shields

Neutron Poisons

Example of BORAL blisteringfrom EPRI

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FY10 Initial Findings: Container

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Stressor Degradation Mechanism Influenced by VLTS or Higher

Burnup

Additional Data Needed

Importance of R&D

Thermal and Mechanical

Embrittlement of elastomer O-rings

Yes Yes Low

Temperature Fluctuations Relax Seals and Bolts

Yes Yes Medium

Radiation Embrittlement of Elastomer O-rings

Yes Yes Low

Chemical Humid Oxidation Yes Yes High

Marine Environment Yes Yes High

Wet Corrosion: General, Pitting, SCC, Crevice, Galvanic

Yes Yes High

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

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FY10 Initial Findings: Overpack

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Stressor Degradation Mechanism Influenced by VLTS or Higher Burnup

Additional Data Needed

Importance of R&D

Thermal

Dry Out Yes Yes Low

Fatigue Yes Yes Low

Freeze Thaw Yes Yes Low

Radiation

Aggregate Growth Yes Yes Low

Decomposition of Water Yes Yes Low

Chemical

Aggregate Reaction Yes Yes Low

Calcium leaching Yes Yes Low

Chemical Attack Yes Yes Low

Corrosion of Embedded Steel

Yes Yes Low

Mechanical

Blocked Air Flow Yes No N/A

Creep Yes No N/A

Shrinkage No No N/A

Examples of concrete degradation at INL ISFSI

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

System Issue Importance of R&D

Cladding

Annealing of Radiation Effects Medium

Oxidation MediumH2 effects: Embrittlement, Delayed Hydride Cracking

High

Creep Medium

Container (Welds, Bolts, Metal Seals)

Humid Oxidation HighMarine Environment High

Wet Corrosion: General, Pitting, SCC, Crevice,

GalvanicHigh

Temperature Fluctuations Relax Metal Seals and Bolts Medium

Monitoring SystemsDevelop New Performance

Confirmation Monitoring Systems

Medium

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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

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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?

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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