ML19064B075
| ML19064B075 | |
| Person / Time | |
|---|---|
| Issue date: | 01/30/2019 |
| From: | Jonathan Evans, Hartle B NRC/NRR/DRA |
| To: | |
| References | |
| Download: ML19064B075 (22) | |
Text
Risk-Informed Technical Specification Initiative 4b: Risk
-Informed Completion TimesBrandon Hartle, Reliability and Risk Analyst Jonathan Evans, Reliability and Risk Analyst PRA Licensing Branch A, Division of Risk Assessment, NRRNEI Lessons
-Learned Workshop, January 30
-31, 2019 Executive Summary
- TSTF-505 and 4b LARs require the highest quality submittals
-505 Rev. 2 issued November 2018-Revision resolves issues, except Loss of Function Conditions
-505 Rev. 2 2
Initiative 4b Overview
- Risk-Informed process to extend TS CTs based on plant configuration
- Risk evaluation using current configuration to calculate a specific CT called Risk
-informed Completion Time (RICT)
- Frontstop= existing TS CT
- Backstop = 30 day maximum
- Applies to planned and emergent conditions 3
Initiative 4b Overview
- NEI 06-09 Rev. 0
-Introduced term "PRA Functional" as an alternative to Operable and allowed a RICT for all PRA Functional configurations
-This replaces design basis analysis requirements with PRA success criteria in the TSs*NRC SE on NEI 06 Restricted definition of "PRA Functional" as capable of meeting "design basis analysis requirements" or "appropriate disposition or programmatic restriction will be provided"-"A RICT can only apply to (restorative) TS Required Actions that are not Mode changes or unit shutdown" 4
Attributes of a RICT Program*Integrates Plant Risk
-Manage multiple SSC outages
-Manage broader scope of SSCs (TS and non
-TS)*Flexible Configuration Management
-Decisions include real
-time risk insights
-Focus on repair, not necessarily shutdown
-Emergent problems
- Ongoing/continuous risk awareness 5
Description of TSTF
-505 Rev. 1
- Defined Conditions, Required Actions, and CTs within scope*Added new Conditions, Required Actions, and CTs to replace TS 3.0.3 and mode change conditions
- Added a new program in TS Chapter 5, "Administrative Controls," entitled the "Risk
-Informed Completion Time Program." *Provided additional clarity for RICT entry using PRA Functional to extend CT for loss of function (LOF) mode change conditions (e.g., 3.0.3 conditions) 6 Early Challenges for TSTF-505 Rev. 1*Vogtlepilot 4b review on
-going in 2016
- 5 other TSTF
-505 reviews submitted before pilot completed*Discrepancies between NEI 06
-09 and TSTF
-505 Rev. 1 were discovered during these integrated reviews
- Implementation of the TSTF in these LARs would have resulted in indeterminate and potentially substantive reduction in safety margin 7 Issues With TSTF
-505 Rev. 1
- Included changes to the Technical Specifications beyond scope of NRC SE on NEI 06-09-Included PRA Functional to extend CT for configurations with loss of capability to achieve design basis success criteria-Added new TS 3.0.3 Conditions and Required Actions to replace default TS 3.0.3 entry and included PRA Functional to extend CTs in the new TS-Included (in model TSTF
-505 SE) justification for adequate defense
-in-depth and safety margin which relied on assuming NRC's restricted definition of "PRA Functional," without additional disposition or programmatic restrictions for TS 3.0.3 and mode change CTs 8 TSTF-505 Rev. 1 Suspension
- NRC staff suspended approval of TSTF
-505, Rev.1, explaining concerns identified during review of plant
-specific LARs:-Definition of PRA Functional
- SE on NEI 06
-09 limited use of PRA Functionality by requiring remaining performance capability to meet design basis analysis requirements (e.g., maintain functional capability to perform at level of one operation train)
-TS Conditions Involving Mode Changes or Unit Shutdowns
- SE on NEI 06
-09 "a RICT can only apply to (restorative) TS Required Actions that are not Mode changes or unit shutdown-"
9 TSTF-505 Rev. 1Condition B does not meet design basis analysis requirements, therefore, would not meet intent of SE for NEI 06
-09 1 0 TSTF-505 Rev. 2 1 1 TSTF-505 Rev. 2 Changes*Removed Loss of Function Conditions
-Staff concerned with maintaining adequate defense in depth and safety margins
-The conditions in Table 1 require additional justification that those are not Loss of Function*Newly Developed PRA Method Administrative Control Constraint
- Conditions not modeled in the PRA are in scope
-Can be plant specific, PRA model dependent
-Table 1 in Model application requires additional justification 1 2 TSTF-505 Rev. 2 Changes*Common Cause Failures (CCF)
-Included in the TS Admin Section to address emergent failures-CCF PRA Modeling to be handled on a plant specific basis
- All hazards require technically adequate dispositions
-External hazards need to be systematically considered
-Addressing only the impact on baseline risk is insufficient
-Impact on configuration specific change in risk should be addressed 1 3 Initiative 4b Loss of Function Considerations
- 4b allows the use of PRA Functional and calculation of RICT when all trains are Inoperable
-But available equipment can provide design basis success parameters upon demand OR-Define and justify adequate defense in depth and safety margins when available equipment can only provide PRA success parameters
- Change in Backstop for CT upon Inoperability of all trains from 30 days to 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s-Consistent with approved and used TSTF
-426 which allows a maximum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when all trains are Inoperable 1 4
- Using design basis success criteria for PRA Functional for loss of all trains alleviates need for justifying PRA success criteria, i.e.,-Use only SSCs relied on in the original TS specified safety function-Ensure design basis success criteria for parameters are met for all design basis initiators
- May deviate by requesting TS changes for Inoperability of all trains using PRA Functional with supporting information
-This review may be complex and resource intensive
-Suggest only using on a limited basis 1 5 Initiative 4b Loss of Function Considerations TSTF-505 and 4b LAR Content 1 6Risk-InformedInserviceInspection50.6 9SSC Categorization 5b, Risk-InformedSurveillanceFrequenciesNFPA-805,Risk-Informed FireProtection 4b, Risk-InformedCompletionTimesRequ ired scope , l e v el of de t a i l , techn ical robustness, an d p lant representa t i o n*Greate r re l iance on PRA*M ore f l e x i b i l i ty fo r l icensee*M ore com p l exstaf f re v i ew TSTF-505 and 4b LAR Content
- Scope, level of detail, and technical adequacy of PRA are to be commensurate with application
-Requires confidence in plant specific PRA models
- Up-to-date full-scope PRA peer reviews-Supporting Requirements assessed to Capability Category II for all PRA hazards
- Facts and Observations (F&Os) resolved or dispositioned prior to LAR submittal*Deviations from NRC accepted guidance and pilot applications add to review time and resources 1 7 4b Application Review Best Practices*Pre-submittal meetings
-Familiarizes staff with licensee's strategy and goals
-Allows for clarifications to reduce acceptance review pitfalls*Reviewing recent submittals
-Helps licensee anticipate and address common RAIs
-Minimizes deviations from acceptable approaches/templates
- F&O Closure Observations
- Audits-Assists with NRC review of complex 4b applications
-Clarifies information in the LAR to reduce RAIs 1 8 Conclusions
-505 Rev. 2 issued November 21, 2018
-Revision resolves issues, except for loss of function conditions
-3 Initiative 4b LARS in house; 3 SEs issued
-505 Rev. 2
- TSTF-505 and 4b LARs require the highest quality submittals
-Complex reviews that rely on the technical adequacy of the PRA
-High quality submittals needed to support efficient review by the NRC*Progress/Path forward
-With issuance of the SE for TSTF
-505 Rev. 2, we expect a large number of submittals in 2019
-Reviewing previous submittals and using best practices will facilitate efficient NRC review 1 9 List of Acronyms
- CC -Capability Category
- CCF -Common Cause Failure
- CDF -Core Damage Frequency
- CT -Completion Time
- F&O -Facts and Observations
- LAR -License Amendment Request
- LERF -Large Early Release Frequency
- NRC -Nuclear Regulatory Commission
- PRA -Probabilistic Risk Assessment
- RAI -Request for Additional Information
- RICT -Risk Informed Completion Time
- SE -Safety Evaluation
- SR -Supporting Requirement
- SSC -Systems, Structures, and Components
- TS -Technical Specification
- TSTF -Technical Specifications Task Force 2 0 References
- TSTF-505, Revision 1, "Provide Risk
-Informed Extended Completion Times
-RITSTF Initiative 4b," June 14, 2011, and Model Application dated January 31, 2012 (ADAMS Accession No. ML120330410
).*Draft Revised Model Safety Evaluation of TSTF
-505, Revision 2, "Provide Risk-Informed Extended Completion Times
-RITSTF Initiative 4b," May 1, 2018 (ADAMS Accession No. ML17290A005).
- Letter from Timothy J. McGinty, U.S. Nuclear Regulatory Commission, to Technical Specifications Task Force, "Issues With Technical Specifications Task Force Traveler TSTF
-505, Revision 1, "Provide Risk
-Informed Extended Completion Times
-RITSTF Initiative 4B," dated November 15, 2016 (ADAMS Accession No. ML16281A021
).*Final Safety Evaluation For Nuclear Energy Institute (NEI) Topical Report (TR) NEI 06 09, "Risk
-Informed Technical Specifications Initiative 4b, Risk
-Managed Technical Specifications (RMTS) Guidelines," May 17, 2007 (ADAMS Accession No. ML071200238
).2 1 References
- Topical Report NEI 06
-09, Revision 0
-A, "Risk-Informed Technical Specifications Initiative 4B, Risk
-Managed Technical Specifications (RMTS) Guidelines," October 2012 (ADAMS Package Accession No. ML122860402
).*Regulatory Guide 1.174, Revision 3, "An Approach for Using Probabilistic Risk Assessment in Risk
-Informed Decisions on Plant
-Specific Changes to the Licensing Basis," January 2018 (ADAMS Accession No. ML17317A256).
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