ML20171A409
| ML20171A409 | |
| Person / Time | |
|---|---|
| Issue date: | 06/19/2020 |
| From: | Joseph Borowsky, Donald Chung, Paul Kallan, Zhian Li, Timothy Mccartin, David Tang, John Wise Office of Nuclear Material Safety and Safeguards, NRC/NRR/DNRL/NRLB |
| To: | |
| Kallan P | |
| References | |
| ML20160A145 | |
| Download: ML20171A409 (14) | |
Text
Risk Tool for Spent Fuel Dry Storage Spent Fuel Margins Workshop June 23, 2020 Donald Chung, Joseph Borowsky, Zhian Li, Timothy McCartin, David Tang, John Wise Division of Fuel Management US Nuclear Regulatory Commission
Risk Tool for Spent Fuel Dry Storage Intent and Purpose Expand the use of risk information in our regulatory activities Suggest level of review, based on risk insight Allow for a more consistent review process and improve efficiency and safety Provide a means to document and incorporate new risk information from future reviews
Risk Tool for Spent Fuel Dry Storage Additional Purpose RIRP N-20-0X Recommendation II-1: NRC should develop an Acceptance Review Grading process that would assign varying levels of review to an application, from the time it is initially received, based on risk insights. This is a Category 2 recommendation which would require NRC to revise its internal review guidance and practices. This would not be a formal guidance but more of a suggestion for level of review.
Risk Tool for Spent Fuel Dry Storage Expectations (Defining Spent Fuel Performance Margins)
Develop a grading process that:
Requires no rulemaking No development of formal guidance Achievable in a relatively short period of time
Risk Tool for Spent Fuel Dry Storage What is the INL Dry Cask Risk Tool?
Provides a basic risk-informed framework that can be used to support recommendations of the depth and breadth of LAR reviews Provides the user with a rationale behind the risk estimation of each specific change A methodology that incorporates available risk insights and supports the identification and prioritization of safety significance in licensing changes
Risk Tool for Spent Fuel Dry Storage How will it be used Informal guidance for staff reviewer Provide a preliminary risk-informed estimation for each specific change in a LAR Supplement insights from staff subject matter experts Support review decisions along with other considerations: complexity, regulatory requirements, quality of applications, etc.
Risk Tool for Spent Fuel Dry Storage Three Components in the Risk Tool Grades (green, yellow, red, blue)
Flow chart and gates for identifying licensing action and associated risk significance Rationale document provide the bases behind risk estimation
Risk Tool for Spent Fuel Dry Storage Grades Risk LAR Review Significance Process Risk Significance Determination Criteria Redundancy of preven ve measures or mul ple condi ons necessary for accident ini a on.
Failure of redundant systems, or independent concurrent conditions required for accident initiation.
If quan ta ve data is available: Insigni"cant increase (by a factor of less than one order of magnitude) of release of radioactive isotopes theoretically possible.
Low Efficient Standard reevalua on process of the system that requires only an adap on of new parameters.
Low chance of making a signi"cant evalua on error during safety evalua ons by the licensee and high chance of catching such an error by the reviewer.
No direct eect of LAR item on current opera on procedures.
Detec on of evalua on error or "aw likely (e.g., due to surveillance).
No immediate danger to public or personnel due to signi"cant safety margins.
Medium In Detail If quan ta ve data is available: Medium increase (by a factor of less than two orders of magnitude) of release of radioactive isotopes theoretically possible.
Error in LAR safety evalua ons could directly lead to an accident that includes a release of radioac ve material, Extensive, criticality, or undetected issue, and significantly increased radiation exposure of the public or operating personnel.
High Thorough, Very No reliable redundancy in the system.
If quan ta ve data is available: Signi"cant increase (by a factor larger than two orders of magnitude) of release of Detailed radioactive isotopes theoretically possible.
Based on Extensive See Rationale Risk Significance No risk signi"cance es ma on possible without considera on of addi onal factors.
Determination
Risk Tool for Spent Fuel Dry Storage Flow Chart & Gates LAR Design Approved Contents Increase Burnup Burnup Credit Burnup 2.1.1. 2.1.2.
Enrichment 2.2.
Uranium Mass 2.3.
Different Geometry Assembly Weigth Configuration La ce Type 2.4.1.
2.4.2. 2.4.3.
Damaged Fuel Cooling Time Condition Heat Load 2.5.3.
2.5.1. 2.5.2.
Burnable Poisons 2.6.
Canister Loading Pa ern 2.7.
Cladding Type 2.8.
Reactor Type of SNF 2.9.
Non-Fuel Hardware 2.10.
Risk Tool for Spent Fuel Dry Storage Rational Document Rational Example:
1.2.3.5. Cask Hardware Cask hardware includes keepers, lanyards, small bolts and nuts, cotter pins, etc. Further, the cask hardware is classified as a Category C item in NUREG/CR-6407 (J. W. McConnell 1996). It is part of the structure of a dry storage system, and a hardware modification does not significantly affect the confinement, shielding, heat removal, or criticality control capabilities of the dry storage system.
Thus, the risk significance associated with a LAR item that includes a modification of the cask hardware is determined as low.
Risk Tool for Spent Fuel Dry Storage Other Considerations Complexity of change Regulatory requirements Possible cumulative effect for combination of multiple changes
Implementation Risk tool is expected to be completed in July WG will brief staff reviewers on the methodology for grading reviews A preliminary procedure will be developed to pilot the risk tool; pilot effort is targeted to begin in the fall WG will evaluate the effectiveness of the risk tool and results will be made public at future public meetings The risk tool will be updated periodically to incorporate new risk insights
Risk Tool for Spent Fuel Dry Storage Questions?
Risk Tool for Spent Fuel Dry Storage What has changed since NUREG-1864?
Modern cask designs Increased capacity Hotter spent fuel (2 years vs 10 years)
Absorber plates More complicated loading patterns Licensing duration 20 to 40 years Uncertain path forward Interim Storage Sites Storage in-place