ML24110A003

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NRC Staff Slides for PWROG Rmc Meeting April 2024
ML24110A003
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Issue date: 04/24/2024
From: Mike Franovich
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RISK MANAGEMENT COMMITTEE - PWROG/BWROG MEETING APRIL 24, 2024 MICHAEL X. FRANOVICH, DIRECTOR DIVISION OF RISK ASSESSMENT OFFICE OF NUCLEAR REACTOR REGULATION

AGENDA

Introduction:

Mike Franovich

NRR Leadership Perspectives on RIDM: Mike Franovich

Risk Informing Fuel Enrichment Activities: Mike Franovich

GREATR Working Group Initiative: John Hanna

Efforts on RASP Handbook Update: John Hanna

Fire Protection Significance Determination Process Updates: Michelle Kichline

Update on IDHEAS: Michelle Kichline

  • Increased Enrichment (IE) Rulemaking On September 8, 2023, the FRN (88 FR 61986) was published requesting comments (due November 22, 2023) on the Increased Enrichment Rulemaking Regulatory Basis.

On November 6, 2023, the FRN (88 FR 76143) was published, extending the public comment period from the originally November 22, 2023, due date to January 22, 2024.

Three alternatives for control room design criterion of 10 CFR 50.67 and GDC-19 are under consideration.

Within the Regulatory Basis document, FRN (88 FR 61986), staff recommended pursuing rulemaking to amend the control room design criteria and update the current regulatory guidance accordingly with revised assumptions and models and continue to maintain appropriate and prudent safety margins.

3 RISK-INFORMING FUEL ENRICHMENT ACTIVITIES

RISK-INFORMING FUEL ENRICHMENT ACTIVITIES, CONT'D.

  • IE Rulemaking, Contd
  • Leveraging Commission-directed PRA policies Severe Reactor Accident policy statement (50 FR 32138; August 8, 1985)

Safety Goals for the Operations of Nuclear Power Plants; Policy Statement (51 FR 30028; August 21, 1986 PRA Policy Statement (60 FR 42622, August 16, 1995)

Commission SRM-SECY-98-144, Staff RequirementsSECY-98-144White Paper on Risk-Informed and Performance-Based Regulations, (ML003753601)

  • Assessing advancements in radiation protection recommendations and standards, as well as PRA methodologies and technology, has propelled the field of nuclear risk assessment to a higher level of maturity.

4

RISK INFORMING FUEL ENRICHMENT ACTIVITIES, CONT'D.

  • IE RM - Implementing Guidance (Revision to RG 1.183, Rev. 1)

Purpose:

Enable the use of higher burnup/increased enrichment fuels and improving design basis accident evaluations by incorporating risk insights into radiological consequence analyses.

  • IE rulemaking schedule will bound the scope of changes the staff can pursue.
  • Outreach Activities:
  • Conducted three workshops to foster a participative process.
  • Public meetings are being planned for May to provide status on the effort.

5

NRR LEADERSHIP PERSPECTIVES ON RIDM WHILE ENSURING A POSITIVE CULTURE

  • Conducting early alignment meetings
  • Focusing on safety questions first, then exploring how to accomplish this in our regulatory framework
  • Fully integrating risk experts early in the process
  • Being more deliberate in discussing all aspects of risk
  • Communicating the why behind decisions
  • Routinely making timely decisions even when differing views exist
  • Abiding by our values (ISOCCER and NRCs Leadership Model) 6

7 RIPE SUBMITTAL BEST PRACTICES ANTONIOS ZOULIS

BEST PRACTICES (FOR LICENSEE CONSIDERATION)

  • Consider requesting a pre-submittal meeting before submitting a request using RIPE. Staff recommends licensees address the following during the pre-submittal meeting:
  • A description of the issue and whether compliance with any regulations will be impacted
  • How the screening questions will be answered
  • How risk was calculated, including a description of any surrogates used, and the risk results
  • Ensure application is consistent with 50.90 (or if exemption, 50.12)
  • Ensure application is consistent with RG 1.174
  • Consider providing NRC staff access to the integrated decisionmaking panel (IDP) report on a secure portal when the RIPE request is submitted to support efficient staff review.

PRINCIPLES OF RISK-INFORMED DECISION MAKING (RIDM) 9 Licensees can request license amendments or exemptions to any current regulations using 10 CFR 50.90 and 50.12.

The burden is on the licensee to make an adequate justification.

Must submit risk-informed application consistent with RG 1.174 integrated RIDM principles

10 RIDM for RIPE Acceptable PRA Model IDP Issue contributes

<5E-7/yr to CDF Issue contributes

<5E-8/yr to LERF Minimal increase in the frequency of a risk-significant accident initiator Minimal decrease in availability, reliability, or capability of an SSC Minimal increase in consequences (dose)

Minimal decrease in the capability of a fission product barrier Minimal decrease in DID or SM Acceptable Cumulative Risk Performance Monitoring Strategies Meets current regulations unless it is an exemption

RIPE AND RIDM

  • RIPE was developed to leverage the principles of risk-informed decision-making (RIDM) discussed in RG 1.174 to streamline the NRC review process for very low risk-significant license amendment and exemption requests.
  • Ensuring the increase in risk due to the proposed change is small, is only ONE of the five principles of RIDM. Likewise, it is only ONE of the requirements for RIPE.
  • To justify that a proposed change is acceptable, the NRC staff must ensure all five of the principles of RIDM are met. As such, justification for how each of the principles of RIDM will be met needs to be included in the submittal.
  • The impact of the proposed change on defense-in-depth (DID) and safety margins (SM) is specifically included as a RIPE screening question. Only citing the very low risk significance of the proposed change is not an adequate justification for ensuring that DID and SM are maintained. The DID considerations from RG 1.174 provide additional guidance that should be used to answer that screening question. Inadequate/vague assessment of adverse impact on DID and SM is typically the weakest link in most RIPE submittals that have a challenge being accepted or approved.

11

EXAMPLE - RIPE LICENSE AMENDMENT REQUEST -

GIZMATIC

  • Gizmatic* needed as part of room cooling for LLOCA concurrent with LOOP.
  • Normal room cooling is not powered by emergency power.
  • License amendment request to retire system in place and remove system from design bases and final safety analysis report.
  • "Gizmatic" not modeled in PRA.
  • Surrogate used that assumes core damage will occur if a LLOCA and LOOP occur together (5.6E-7/yr*.0261/yr) of 1.54E-7
  • Approved TSTF-505 and 50.69 license amendments
  • (Note: this is a simplistic example to illustrate the basic elements in a RIPE submittal.

Experience has shown that most RIPE submittals involve complicated technical/regulatory issues that require detailed assessments of the adverse impacts.)

12

  • Fictitious system for illustration purposes only.

RIPE LAR CONTENT 13 Acceptable PRA Model IDP Issue contributes

<5E-7/yr to CDF Issue contributes

<5E-8/yr to LERF Surrogate demonstrates risk below RIPE thresholds.

IDP acceptability demonstrated from previous approved risk-informed initiative.

PRA technical acceptability demonstrated from previously approved risk-informed initiatives Configuration control condition required by TSTF-505 provides reasonable assurance PRA model remains technically acceptable.

14 Minimal increase in the frequency of a risk-significant accident initiator Minimal decrease in availability, reliability, or capability of an SSC Minimal increase in consequences (dose)

Minimal decrease in the capability of a fission product barrier RIPE LAR CONTENT (CONT.)

Changes do not impact frequency of LLOCA or LOOP, other risk significant initiators would not be impacted by change.

Slight decrease in reliability of equipment; however, given duration of accident and environmental conditions in room, impact of room cooling would be minimal.

Change is not material to the filtration, ventilation, and pathways that would impact consequences from dose.

Change would not impact ability of containment to mitigate releases due to accident.

15 Minimal decrease in DID or SM Acceptable Cumulative Risk Performance Monitoring Strategies RIPE LAR CONTENT (CONT.)

LLOCA concurrent with LOOP is not a credible accident. However, in the unlikely event that it would occur, operators can prop doors open to prevent excess heat rise and avoid equipment failure (Time, Training, Procedures)

Cumulative risk is low and is tracked to ensure plant remains below threshold.

Performance monitoring is in place to ensure key assumptions and conditions remain in place such that performance would not challenge overall conclusion of the risk-informed evaluation.

16 Minimal decrease in DID or SM (additional considerations)

RIPE LAR CONTENT (CONT.)

Ensure all adverse impacts are identified.

Clearly describe the extent and implications of each adverse impact.

Avoid vague or generic justifications for minimal adverse impact. Ensure the rational is detailed enough to stand alone without unstated inferences or assumptions.

Ensure the justification for minimal adverse impact describes the supporting plant documentation with adequate detail.

Ensure any reliance on manual actions includes specific descriptions of procedure steps, adequate recognition of need for action, adequate time to implement, configuration control, and training.

ENHANCING OVERSIGHT OF PRA CONFIGURATION CONTROL ANTONIOS ZOULIS 17

Conduct public meeting Workshop with Tabletop sites/Industry Stakeholders Mar 2023 Developed Working Group recommendations for near-term path forward Feb/Jun 2023 Obtained Alignment with NRC Mgt. on PCC Proposal Mar 2023 PCC Project Milestones Issue near-term oversight guidance (OpESS)

Jan 2024 Issue SDP and Regional Panel Guidance Spring 2024 Issue Public and Recommendations Reports on Tabletops Jun 2023 Begin OpESS June 2024 Develop long-term oversight process 2026 / 2027 Conduct SDP Workshop and Gather feedback from Industry Mar 2024 and Apr 2024 Conduct Training KM Session for OpESS Jan 2024

KEY MESSAGES Operating Experience Smart Sample (OpESS) is a balanced and performance-based approach that provides maximum flexibility for regional implementation The OpESS was issued (ML23255A006)

"Just-in-Time" training sessions on OpESS for PRA CC were provided to regional inspectors Cross-regional review panel process will ensure consistent application across the Regional Offices. Guidance for cross-regional panels is currently in DRAFT.

Staff are reviewing industry feedback from public meetings on PRA CC SDP that occurred on Mar 21 and Apr 18, 2024.

OpESS will inform the long-term recommendations for PCC, targeted for implementation in the 2027 ROP inspection cycle.

19

ANTICIPATED OpESS TIMELINE

  • Slow roll-out in 2024 with limited initial use (Teams inspections initially, kickoff in June 2024).
  • Additional "Just-in-Time" training will be conducted for inspectors, as needed.
  • Expand use after initial inspections (2025).
  • Limited Resident sites as opportunities arise w/SRA oversight.

20

SDP KEY POINTS

  • Utilize Be riskSMART framework.
  • Maintain regulatory predictability.
  • Utilize existing known processes.
  • Reliable consistent SDP outcomes.
  • Review and incorporate Industry feedback.

21

PCC SDP DRAFT PATHWAY More than Minor

  • IMC 0612, App. E, Section 8, Maintenance Rule GREEN
  • IMC 0609, App. K, Maintenance Risk Assessment
  • PCC specific screening guidance DRE
  • SRA/Licensee Coordination 22

AREAS OF FURTHER DISCUSSION AND PATH FORWARD

  • Finalize current PRA CC Minor / More than Minor guidelines.
  • Begin OpESS inspections (2024-2025)
  • Continue collaboration with Industry.
  • Evaluate and refine SDP approaches as necessary given any issues that are identified through inspections.
  • Evaluate and refine OpESS, as necessary (2025).
  • Develop final recommendations for oversight (2026).

23

Q&A 24

RISK ASSESSMENT METHODOLOGY UPDATES JOHN HANNA AND MICHELLE KICHLINE 25

GREATR WORKING GROUP INITIATIVE JOHN HANNA 26

GREATR WORKING GROUP INITIATIVE GREATR Group (previously known as RASP Users Group) re-launched in 2023 Team is comprised of Risk Analysts from Office of Research, INL and SRAs from all four regions First three tasks, which are complete, were associated with FLEX in the SPAR models, specifically:

Updating the unavailability/unreliability values of Phase 2 equipment with the latest/greatest values from the PWROG Nominally turning "off" the N+1 equipment (with analyst discretion to turn "on" if deemed appropriate Nominally setting the mission time for SBO/ELAP scenarios at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> vs. 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> previously (once again, with analyst discretion to turn "on" if deemed appropriate)

Next three tasks, which are in-process are:

Improving the Offsite Power/EDG recovery modeling in the SPAR model to reflect as-built/as-operated plant Clarifying guidance on Initiating Event assessments under different processes (e.g., SDP vs. MD8.3 or ASP)

Rewrite of RASP Manual, Volume 1 - see next slide for greater (pun intended) detail.

27

EFFORTS ON RASP HANDBOOK UPDATE JOHN HANNA 28

EFFORTS ON RASP HANDBOOK UPDATE

  • Scope of Update - Internal Events, i.e., Volume 1 only... for now!
  • Schedule for Update Public Meeting will be held to discuss the three tasks being worked on - targeting May/June 2024, however initial indications are there will be scheduling challenges Work to be completed in CY 2024
  • Specific sections of the RASP Manual we anticipate revisions will be necessary:

Recovery and Repair - Section 6.0 Initiating Event Analysis - Section 8.0 - see work of GREATR sub-group Human Reliability - Section 9.0 Loss of Offsite Power Initiating Events - Section 10.0 - see work of GREATR sub-group 29

FIRE PROTECTION SIGNIFICANCE DETERMINATION PROCESS (SDP)

UPDATES MICHELLE KICHLINE 30

INSPECTION MANUAL CHAPTER 0609 APPENDIX F REVISIONS

  • Adopt revised HRRs and ignition source categories for electrical cabinets, dry transformers, and electric motors from NUREG-2178 Vol. 2, Fire Modeling Guidance for Electrical Cabinets, Electric motors, Indoor Dry Transformers, and the Main Control Board.

Includes revised counting rules for electrical cabinets and revised fire base heights.

Loose and contained transients will be replaced with generic and transient combustible control location (TCCL) transients, each with distinct HRR profiles.

31

ADDITIONAL INSPECTION MANUAL CHAPTER 0609 APPENDIX F REVISIONS

  • Adopt new guidance for high energy arching fault HEAF ZOIs, HRRs, non-suppression probability, counting rules, and ignition frequencies from NUREG-2262, High Energy Arcing Fault Frequency and Consequence Modeling.
  • Update ZOI and time to damage tables and plots to apply the heat soak method instead of the point source method. The heat soak method is described in NUREG/CR-6850, Vol 2, EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, Volume 2: Detailed Methodology and NUREG-2232, "Heat Release Rate and Fire Characteristics of Fuels Representative of Typical Transient Fire Events in Nuclear Power Plants."

In the heat soak method, ZOI and time to damage are no longer just a function of peak HRR.

They now also depend on HRR profile (heat flux exposure).

The point source method will be retained for FDS 2 and 3 scenarios - no changes to hot gas layer (HGL) calculations.

32

IDHEAS UPDATE MICHELLE KICHLINE 33

COMPLETED WORK

  • Published NUREG-2256, Integrated Human Event Analysis System for Event and Condition Assessment (IDHEAS-ECA) in July 2022.
  • Published Research Information Letter (RIL) 2021-14, Integrated Human Event Analysis System Dependency Analysis Guidance (IDHEAS-DEP) in November 2021. It will be replaced by NUREG-2258 in 2025.
  • Developed and presented the following papers at the July 2023 PSA/HMIT/NPIC Conference Base SPAR Model Human Failure Event Application of IDHEAS-ECA (ML23066A086)

Estimating the Contributions to Human Error Probability from the Convolution of the Distribution of Time Available and Time Required (ML23067A017)

Application of Human Reliability Analysis to DI&C Control Room Modernization (ML23067A201)

  • Issued IDHEAS-ECA software update (version 1.2) to incorporate additional time distributions (log normal) in March 2024.

34

WORK IN PROGRESS

  • Document use of IDHEAS-ECA to reassess selected risk-significant human error probabilities (HEPs) used in the SPAR models.
  • Use IDHEAS-ECA to reassess selected FLEX HEPs used in the SPAR models.
  • Document data sources, data verification, and calculational methods used to develop IDHEAS-ECA in a series of RILs.
  • Document time uncertainty analysis for IDHEAS (IDHEAS-TIME).
  • Develop an IDHEAS-ECA desktop guide.
  • Update IDHEAS-ECA software to incorporate dependency analysis per IDHEAS-DEP.

35

PLANNED FUTURE WORK

  • Complete error recovery module for IDHEAS-ECA.
  • Document HEP uncertainty analysis.
  • Demonstrate use of IDHEAS-ECA for small modular reactors (SMRs).

36

SUBSEQUENT LICENSE RENEWAL UPDATES SLR TIERED APPROACH JOHN WISE 37

STATUS OF U.S. PLANTS 38 Status of Applications:

https://www.nrc.gov/reactors/operating

/licensing/renewal/subsequent-license-renewal.html 10 SLR applications have been received (as of 03/24) 7 safety reviews complete Monticello, Summer, and Browns Ferry in progress 0

10 20 30 40 0-10 10-20 20-30 30-40 40-50 50-60 Operating Reactors Years in Service 40 y 60 y 80 y licenses subject to 80y environmental impact reassessment

RENEWAL APPLICATION REVIEW EFFICIENCIES 39 High degree of stakeholder interest Commission direction (SRM M231102, ML23345A214) risk inform renewal reviews leverage operating programs leverage previous reviews leverage the agency and industrys operating experience in aging management Tiered Approach"

LEVEL (TIER) OF APPLICATION REVIEW 40 The degree to which the NRC staff examine plant documentation to:

verify statements in the application

gain a better understanding of the proposed aging management programs (AMPs)

Standard (High)

Modified (Medium)

Confirmation (Low)

Application Operating experience AMP and TLAA basis documents Engineering analyses Implementing procedures Inspection and test results Corrective actions Application Operating experience AMP and TLAA basis documents Application Operating experience

TIERING PROCESS 41 Is it a standardized, proven program?

Is the AMP typically associated with SSCs of lower risk?

To what degree can later oversight provide assurance of effectiveness?

Insights from recent reviews & operating experience?

Generic Tier Do plant-specific considerations change the generic answers?

Does the plant reference prior reviews?

Approach consistent with NRC guidance?

Plant-Specific Tier

USE OF PRA INSIGHTS IN THE TIERING PROCESS 42

  • PRAs typically have not explicitly addressed passive component aging
  • Maintenance and inspection programs have been largely successful in preventing significant passive component failures Rigorous code requirements for design and inspection (e.g., ASME, ACI)

Very low initiating event frequencies

  • Uncertainties in long-term aging phenomena Challenge to predict future behavior from past performance Burn-in Maturity Wear-out Chance of Failure

RENEWAL REVIEWER RISK MINDSET 43 What can go wrong?

Degradation can impact component integrity How likely is it?

Degradation initiation frequency estimated from data or models (though often qualitative)

Consequence?

Passive component failure (leakage, blockage of fluid flow, loss of support in seismic event)

Acceptance criteria Unacceptable potential for component failure (no prescriptive guidance) 10 CFR Part 54: demonstrate that the intended functions of each SSC will be maintained NUREG-2192, Standard Review Plan Detection of aging effects should occur, and corrective actions taken, prior to a loss of intended function of the structure or component

PRA INPUTS INTO THE TIERING PROCESS 44 Despite challenges in applying PRA, a broader concept of risk can provide practical insights to the appropriate rigor of review

  • NRC standardized plant analysis risk (SPAR) model results, such as:

Initiating event percent contribution to CDF for internal events Risk important systems (risk achievement worth)

Component importance grouped by system

  • Prior to each of the first SLR reviews, NRC has invited applicants to share similar information from their PRAs
  • Additional perspectives are welcomed Does this program apply to a risk significant system?

RISK-INFORMED MATERIAL ASSESSMENTS DAVID RUDLAND 45

RISK-INFORMED MATERIALS ASSESSMENT

  • Reach alignment among NRC and industry PRA and material engineer communities on the interpretation of safety margins as it applies to materials issues related licensing actions.
  • Reach alignment on the interpretation of defense-in-depth as it applies to materials issues related licensing actions.
  • Reach a common understanding on the potential impact of changes to inspection frequencies on other key attributes, such as reactor coolant pressure boundary integrity.
  • Reach a common understanding on how plant operators maintain adequate performance monitoring to ensure SSC functionality.
  • Address concerns relating to the capability of PRA models to model passive system reliabilities and capture impact of operating experience in the event those reliabilities develop adverse trends.
  • Explain how the cumulative impacts of various relaxations are monitored and managed to prevent adverse impacts on safety.

46

RISK-INFORMED DIGITAL I&C SHILP VASAVADA 47

RISK-INFORMED DIGITAL I&C

  • Ensure that the guidance used to identify surrogate events are effective.
  • Ensure that the standards used to model I&C systems in PRA have the capability to capture and model inter-and intra-I&C system dependencies accurately.
  • Availability of quantitative values for software CCFs will enhance the acceptability of PRA in future risk-informed initiatives.
  • Remain engaged with industrys DI&C community during the development of implementing guidance.

POANHI SEISMIC EVALUATION STATUS SHILP VASAVADA 49

POANHI SEISMIC EVALUATION STATUS

  • Evaluations completed for seven sites
  • Plants at these sites have screened out
  • POANHI seismic hazard reports for each plant site have been made publicly available in ADAMS
  • Evaluations ongoing for remaining Near-Term Task Force (NTTF) Recommendation 2.1 Group 1 plants 50

POANHI SEISMIC EVALUATION STATUS Complete Upcoming Vogtle (ML23006A091)

Summer Sequoyah (ML23192A447)

Beaver Valley Watts Bar (ML23192A447)

DC Cook Browns Ferry (ML23192A447)

Dresden North Anna (ML23214A177)

Oconee Robinson (ML23244A231)

Callaway Peach Bottom (ML23346A238) 51

DISCUSSION AND Q&A 52

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