Risk-Informed Technical Specification Initiative 4b: Risk-Informed Completion Times

Brandon 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

• TSTF-505 Rev. 1 suspended November 2016

• 3 plant-specific 4b LARs in house; 3 SEs issued

• NRC SE for TSTF-505 Rev. 2 issued November 2018– Revision resolves issues, except Loss of Function Conditions

• 3 LARs in house for TSTF-505 Rev. 2

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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 conditions3

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 06-09– 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”

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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

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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)

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Early Challenges for TSTF-505 Rev. 1

• Vogtle pilot 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

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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

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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…”

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TSTF-505 Rev. 1

Condition B does not meet design basis analysis requirements, therefore, would not meet intent of SE for NEI 06-09

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TSTF-505 Rev. 2

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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

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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

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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 demandOR– 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 hours– Consistent with approved and used TSTF-426 which allows a

maximum of 24 hours when all trains are Inoperable

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• 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

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Initiative 4b Loss of Function Considerations

TSTF-505 and 4b LAR Content

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Risk-Informed InserviceInspection

50.69 SSC Categorization

5b, Risk-InformedSurveillance Frequencies

NFPA-805, Risk-Informed Fire Protection

4b, Risk-InformedCompletion Times

Required scope, level of detail, technical robustness, and plant representation

• Greater relianceon PRA

• More flexibility for licensee

• More complex staffreview

TSTF-505 and 4b LAR Content• Scope, level of detail, and technical adequacy of PRA are to

be commensurate with application

• Compare total CDF and LERF against RG 1.174 acceptance guidelines– 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

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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

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Conclusions

• NRC SE for TSTF-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– 3 LARs in house for TSTF-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

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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

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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

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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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