ML24051A156

Final NRC Staff Slides for PWROG Rmc Meeting December 2023 Revised Slide Format - Wo Notes

ML24051A156
Person / Time
Issue date:	12/06/2023
From:	Christine Briggs, Antonios Zoulis NRC/NRR/DRA, NRC/NRR/DRA/APOB
To:
References
Download: ML24051A156 (53)

Text

RISK MANAGEMENT COMMITTEE -

PWROG/BWROG MEETING DECEMBER 6, 2023 MICHAEL X. FRANOVICH, DIRECTOR DIVISION OF RISK ASSESSMENT OFFICE OF NUCLEAR REACTOR REGULATION

AGENDA Introduction - Mike Franovich

• Promoting Integrated Decision Making

• SPAR Model Updates Risk-Informed Approaches to Control Room Dose Design Criteria/Increased Enrichment Rulemaking - Elijah Dickson Digital I&C Update - Sunil Weerakkody POANHI Status - Shilp Vasavada Risk Informed Ultimate Heat Sink - NRC Perspective - Antonios Zoulis PRA Configuration Control Process - Status Update from August - Antonios Zoulis NRC Perspective on NRC and Industry Catalogue of PRA Methods - Mehdi Reisi Fard 2

PROMOTING INTEGRATED DECISION MAKING

• NRCs 2023 Risk Forum (ADAMS Accession No. ML23275A129) was held on September 12.

• Objective was to share practices across the operating, new, and advanced reactor communities

• Over 400 stakeholders participated in the meeting, experts from NASA, FAA, and multiple industry groups and utilities.

• Key discussions regarding the incorporation of risk-informed decisionmaking (RIDM) into an organizations culture highlighted that the NASA, FAA, and the NRC share similar challenges in incorporating RIDM.

• The forum offered an opportunity to highlight successes of leveraging RIDM and graded approaches to make safety improvements and support decisionmaking

• The feedback received at this meeting will inform and further the development and use of RIDM at the NRC.

3

INTEGRATED DECISION MAKING (2)

• NuScale SDAA Review Updates

• Collected design-specific risk information and insights during the pre-application engagement

• Shared insights with reviewers and senior management

• Insights supported acceptance review decisions

• Risk insights supported grading the level of review effort for different FSAR chapters

• Actively using and communicating risk insights to resolve challenging technical issues using RIDM principles

• Integrated teams spanning multiple technical disciplines 4

INTEGRATED DECISION MAKING (3)

• RIDM Principles Communication Tool - a space for all views - NRC pilot on an SMR review Principle 1: Meets current regulations or exemption requested Basis

Principle 2: Consistent with the defense-in-depth philosophy Basis Basis

Principle 3: Maintains sufficient safety margins Basis

Principle 4: Increases in risk is small and consistent with the intent of the Commissions Safety Goal Policy Statement Basis

Principle 5: Performance measurement strategies available for monitoring Basis

Not Met Partially Met Met 5

INTEGRATED DECISIONMAKING (4)

RIPE UPDATE

• The NRC received NEI 21-01 Revision 2, Industry Guidance to Support Implementation of NRCs Risk-Informed Process for Evaluations, in October 2023 (ML23306A074), which incorporates NEIs recommendations to enhance the use of RIPE.

• The NRC identified no major issues with NEIs guidance.

• The NRC will revise its guidance documents to incorporate NEIs recommendations, consistent with the staffs preliminary assessment of the recommendations, as documented in letter dated October 25, 2023 (ML23285A270).

• Ultimately, after the staff completes several additional RIPE reviews, the final agency position on RIPE will be provided using the Regulatory Guide process.

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SPAR MODEL UPDATE

• Benchmarking against the licensee's models allows the SPAR models to reflect the as-built, as operated plants.

• Increased use of risk insights highlights the need to maintain the plant-specific PRA tools to support licensing and inspection activities.

• Differences due to outdated models could lead to additional time/resources needed during oversight or licensing.

• Voluntarily provide PRA information to support INL and NRC updating of the SPAR models.

• In FY2023, six SPAR models updates for five sites have been completed and an update is ongoing for four sites.

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INCREASED ENRICHMENT RULEMAKING -

CONTROL ROOM (CR) DOSE ASPECTS 8

RISK INFORMED APPROACHES TO CR DOSE DESIGN CRITERIA/INCREASED ENRICHMENT 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.

• 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.

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RISK-INFORMED APPROACHES TO CR DOSE DESIGN CRITERIA/INCREASED ENRICHMENT RULEMAKING (CONT'D)

Example:

NUREG 0800, Standard Review Plan (SRP),

Chapter 15.0.1, Radiological Consequence Analyses Using Alternative Source Terms., Table 1, Accident Dose Criteria.

Presents well-established dose-based criteria for the EAB and LPZ for a series of design basis accident which represent varying degrees of plant damage states.

Each design basis accident acceptance criteria are based on an assumed frequency of occurrence over the facilities operating license.

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RISK INFORMED APPROACHES TO CR DOSE DESIGN CRITERIA/INCREASED ENRICHMENT RULEMAKING (CONT'D)

• A question below related to the control room design criterion of 10 CFR 50.67 was listed in the FRN to solicit input and feedback from the public.

"Would a graded, risk-informed method, to demonstrate compliance with a range of acceptable control room design criterion values instead of a single selected value provide the necessary flexibilities for current and future nuclear technologies up to but less than 20.0 weight percent U-235 enrichment?"

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RISK INFORMED APPROACHES TO CR DOSE DESIGN CRITERIA/INCREASED ENRICHMENT RULEMAKING (CONT'D)

Example:

SRP acceptance criteria for the EAB and LPZ is consistent with rationale and stated criteria found in ANSI ANS 51.1-1983, Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants.

ANSI ANS 51.1-1983 establishes dose-based acceptance criteria based on a spectrum of normal operations and events identified in accordance with their best-estimate frequency of occurrence and divided into five categories representing plant conditions.

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DIGITAL I&C COMMON-CAUSE FAILURE 13

PROGRESS AND NEXT STEPS

• Issued draft BTP 7-19 for public comment on October 24, 2023

• Held public meeting on November 14, 2023

• Received NEI comments on November 21, 2023

• Participated in NRC/RES-EPRI meeting on November 27, 2023

• Status: NRC working group is in the process of addressing public comments.

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RISK-INFORMED D3 ASSESSMENT PROCESS Identify each postulated CCF Address the CCF using a risk-informed approach Model the CCF in the PRA (Section B.3.4.2)

Determine the risk significance of the CCF (Section B.3.4.3)

Determine appropriate means to address the CCF (Section B.3.4.4)

Determine consistency with NRC policy and guidance on RIDM (Section B.3.4.1)

Address the CCF deterministically Justify alternative approaches 15

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.1)

Determine Consistency with NRC Policy and Guidance on RIDM

• Review applications that use risk-informed approaches for consistency with established NRC policy and guidance on RIDM

• RG 1.174

• RG 1.200

• Current staff review guidance for new reactors includes:

• SRP Chapter 19

• DC/COL-ISG-028

• SRP Chapter 19 provides review guidance for addressing the principles of risk-informed decision-making, including defense in depth 16

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.2)

Model the CCF in the PRA

• Determine if the base PRA meets PRA acceptability guidance

• Evaluate how the CCF is modeled in the PRA and the justification that the modeling adequately captures the impact of the CCF on the plant

• Options for modeling the CCF in the PRA include:

• Detailed modeling of the DI&C system

• Use of surrogate events 17

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.3)

Determine the Risk Significance of the CCF

• The risk significance of a CCF can be determined using a bounding sensitivity analysis or a conservative sensitivity analysis

• A bounding sensitivity analysis:

• Assumes the CCF occurs

• Provides a description of the baseline risk

• A conservative sensitivity analysis:

• Provides a technical basis for a conservative probability (less than 1) of the CCF demonstrating that defense in depth is addressed

• Addresses the impact of this assumption on PRA uncertainty 18

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.3)

Determine the Risk Significance of the CCF

• The quantification accounts for any dependencies introduced by the CCF, including the ability for operators to perform manual actions

• A CCF is not risk significant if the following criteria are met for the sensitivity analysis:

• The increase in CDF is less than 1 x 10-6 per year

• The increase in LERF is less than 1 x 10-7 per year 19

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.4) 20

RISK-INFORMED D3 ASSESSMENT (SECTION B.3.4.4)

• If a CCF is not risk significant, standard design and verification and validation processes are sufficient to address the CCF

• If a CCF is risk significant, the following apply, with a level of technical justification commensurate with the risk significance of the CCF:

• The application identifies the CCF vulnerabilities or causes

• The application provides a description of how it addresses the CCF vulnerabilities or causes (including any conditions or limitations)

• The application provides a technical basis explaining how it addresses the identified CCF vulnerabilities or causes and prevents or mitigates their effects 21

PROBABILITY OF DI&C CCFS Licensing Post-Licensing Purpose Implementation of SECY-22-0076 PRA update to reflect the as-built, as-operated plant Value Bounding value for the probability of DI&C CCFs for a risk-informed D3 assessment Representative or realistic values for the probability of DI&C CCFs 22

PROBABILITY OF DI&C CCFS (2)

Timeframe Licensing Post-Licensing After SECY approval D3 evaluation using bounding assessment DI&C CCF probabilities considered sources of uncertainty Sensitivities to determine impact (key uncertainty or not)

Risk management actions if identified as key uncertainty Near Term D3 evaluation using bounding assessment Use failure data (and expert elicitation) to identify and align on order of magnitude Consensus approach Not a key uncertainty Long Term D3 evaluation using conservative assessment Use failure data to determine and align on realistic failure probabilities Consensus approach Not a key uncertainty 23

POANHI SEISMIC ASSESSMENT STATUS 24

POANHI SEISMIC EVALUATION STATUS

• Evaluations completed for six 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 25

POANHI SEISMIC EVALUATION STATUS Complete Upcoming Vogtle (ML23006A091)

Summer Sequoyah (ML23192A447)

Peach Bottom Watts Bar (ML23192A447)

DC Cook Browns Ferry (ML23192A447)

Dresden North Anna (ML23214A177)

Oconee Robinson (ML23244A231)

Callaway Beaver Valley 26

RISK-INFORMED ULTIMATE HEAT SINK

- NRC PERSPECTIVE 27

Climatic changes have resulted in units being challenged with potential TS power reductions/shutdowns based on UHS temperature.

Most plants have already implemented Technical Specifications Task Force (TSTF) Traveler 330, "Allowed Outage Time -Ultimate Heat Sink, which allows monitoring UHS temperature hourly on a rolling 24-hour clock to verify that average UHS temperature does not exceed TS limits.

Some plants have been granted License Amendment Requests (LARs) to increase their TS temp limit via analyses which credits available margin.

BACKGROUND 28

STAFF EVALUATED SEVERAL OPTIONS USING THE BE RiskSMART FRAMEWORK Add risk element on deterministic approach (Risk informed Process for Evaluations (RIPE). or Generic RIPE for Topical Reports (RAPTR)) - This option would investigate using RIPE to streamline the processing of plant-specific license amendment requests to modify UHS TS.

Move UHS into RICT - Use Risk Management Actions (RMAs) as part of the Risk Informed Completion Time (RICT) - This option would require development of approved criteria for using risk information to modify the UHS limits/durations that could be adopted by licensees when applying for a RICT amendment.

Change TS from UHS to Component Cooling Water (CCW) temperature (or similar)

Delete TS and create a TS program that addresses the function Examine related issues to (UHS) temperature limits.

Extend duration for UHS temperature averaging (e.g., 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />) 29

Option 1 Add risk element on deterministic approach (RIPE or RAPTR) - This option would investigate using RIPE to streamline the processing of plant-specific license amendment requests to modify the UHS TS.

Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdown required by TS as a result of short term UHS temperatures greater than the Surveillance Requirement (SR) but below the design limit.

Results of plant specific risk informed assessment which meets the requirements of Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis", and RIPE screening criteria.

TS violation.

Erosion of safety margin to UHS design temperature.

UHS temp is not modeled in the Probabilistic Risk Analysis (PRA) and use of surrogates are unlikely to meet very low safety significance threshold.

May not be able to meet the 5 principles of risk-informed regulation required by RG 1.174.

Pre-stage Diverse and Flexible Coping Strategies ( FLEX) Diesel Generator(s)(DGs), and/or other equipment dependent on plant specific components challenged by elevated UHS temperatures.

Additional assessment required.

Low potential for successfully meeting RIPE criteria.

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Option 2 Move UHS into RICT - Use RMAs as part of the RICT - This option would require development of approved criteria for using risk information to modify the UHS limits/durations that could be adopted by licensees when applying for a RICT amendment.

Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdowns required by TS as a result of short term UHS temperatures greater than the SR but below the design limit.

Same as Option 1, except for RIPE specific criteria Pre-stage FLEX DGs and/or other equipment dependent on plant specific components challenged by elevated UHS temperatures.

Additional assessment required.

Low potential for successfully meeting RG, 1.174 criteria.

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Option 3 Change TS from UHS to CCW temperature (or similar)

Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdowns required by TS as a result of short term UHS temperatures greater than the SR but below the design limit.

Multiple safety related loads served by Service Water may NOT be served by CCW, such that CCW temp may not be the limiting temp (i.e., EDGs).

As a result, multiple new TS may need to be created.

N/A Not viable as a generic option.

Potential success path as a plant specific LAR.

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Option 4 Delete TS and Create a TS program that addresses the function Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdowns required by TS as a result of short term UHS temperatures greater than the SR but below the design limit.

Deletion of TS is not consistent with the 10 CFR 50.36, Technical specifications requirement to be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto Creation of a TS program would require significant resources to investigate different UHS configurations and attempt to define an acceptable program.

N/A Not Recommended.

Per TSTF-330 Traveler:

The staff clearly indicated that the AOT approach was not an option because NRC management concern that it was not appropriate to allow an AOT in which there was no specific operator/licensee action that could reasonably be taken to restore from the conditions (i.e.,

relying on environmental conditions to restore the TS limits).

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Option 5 Examine generic/plant-specific related issues to UHS temperature limits.

Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdowns required by TS as a result of short term UHS temperatures greater than the SR but below the design limit.

Due to the plant specific design of UHS, this evaluation would need to be a living document to account for most temperature limiting component based on multiple factors. including heat exchanger tube plugging, UHS slit build-up/debris entrainment, minimum UHS level, instrument inaccuracy, Net Positive Suction Head (NPSH), uncertainties, etc.

N/A Not viable as a generic option.

Potential success path as a plant specific LAR.

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Option 6 Revise TSTF-330 to extend duration for UHS temperature averaging (ex. 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />)

Pros Cons Potential Risk Mitigation Actions Recommendation Avoid plant shutdowns required by TS as a result of short term UHS temperatures greater than the SR but below the design limit.

Erosion of safety margin Significant resources required.

Use existing RMAs credited for TSTF-330 Additional assessment required.

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Comments/Other Options for Consideration?

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ENHANCING OVERSIGHT OF PRA CONFIGURATION CONTROL 37

Conduct public meeting Workshop with Tabletop sites/Industry Stakeholders Mar 2023 Developed Working Group recommendations for near-term path forward Feb/Jun 2023 PCC Project Milestones Develop near-term oversight guidance (OpESS)

Fall 2023 Develop Enf./SDP strategy and Regional Panel Guidance Dec 2023 Issue Public and Recommendations Reports on Tabletops Jun 2023 Begin OpESS 2nd/3rd Quarter CY 2024 Develop long-term oversight process 2026 for 2027 Gather feedback on proposal from NRC and Industry Winter 2023-2024 Conduct Training for OpESS and SDP 1st Half 2024 Conduct Public Meeting with Industry on PRA CC SDP 2024 38

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

Cross-regional review panel process will ensure consistent application across the Regional Offices.

The OpESS is still DRAFT (ML23312A335) and nearing completion.

OpESS is intended to be resource neutral and is part of the overall performance-based and balanced approach that will eventually determine the long-term recommendations for PRA Configuration Control (PCC), which is targeted for implementation in the 2027 ROP inspection cycle.

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WHAT IS OpESS?

OpE - Operating Experience and SS - Smart Sample = OpESS The OpESS is designed as an additional tool to be used by agency staff in ROP baseline inspection preparation.

The information and trends identified from OpESS inspections may provide further indication that a specific issue warrants additional agency action.

Each OpESS has a unique and sequential identifier.

https://www.nrc.gov/reactors/operating/ops-experience/operating-experience-smart-sample.html 40

WHAT WILL THE OpESS LOOK LIKE?

Balanced approach will ensure that inspectors only review aspects from approved and implemented risk-informed initiatives.

Performance-based in that sampling will be reviewed and adjusted annually until issuance of final recommendations.

x

• Not all sites would get sampled each year with the OpESS, intent is to use as warranted.

• WG will provide inspectors with guidance (insights/specifics) on appropriate use/utilization of the OpESS.

OpESS SFCP NFPA 805 RICT 50.69 41

OpESS INSPECTIONS Inspections which would focus on completed changes (i.e., backward-looking):

1.

71111.21M, Comprehensive Engineering Team Inspection, (CETI),

2.

71111.21N.05, Fire Protection Team Inspection (FTPI),

3.

37060, 10 CFR 50.69 Risk-Informed Categorization Inspections which would focus on current in-progress changes (i.e., forward-looking):

Resident Baseline: 71111, (with latitude for possible interactions) 1.

71111.06, Flood Protection Measures, 2.

71111.13, Maintenance Risk Assessments and Emergent Work Control, 3.

71111.18, Plant Modifications (Primary),

4.

71111.24, Testing and Maintenance of Equipment Important to Risk, 5.

71151, Performance Indicator Verification, 6.

71152, Problem Identification and Resolution (PI&R) 42

OpESS PROPOSED DETAILS

1. Verify processes are in place to ensure the PRA is maintained with the as-built as operated plant.

2. Verify significant modifications to the plant screened for review and any needed updates to the PRA and the Model of Record (MOR).

Guidance applied in 2-stages:

1.

Forward looking (future plant changes that are being considered for inclusion into the PRA) and, 2.

Backward looking (past completed plant changes, already implemented into the MOR).

Intent is to revise the OpESS for the subsequent annual ROP Cycles based upon observed performance and refocus, as necessary.

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CRITERIA TO SELECT THE OpESS

1.

Implementation of RIP 2.

MOR updates since LA/SE 3.

Timing of last MOR update 4.

SRA Coordination 44

ANTICIPATED OpESS TIMELINE

• Effective date anticipated for January 1, 2024; Not expected to be utilized until 2nd quarter of 2024 at the earliest.

• KM Session in January 2024.

• Additional Just-in-Time training will be conducted for inspectors, as needed.

• Slow roll-out in 2024 with limited initial use (Teams inspections initially, likely 2nd / 3rd Quarters).

• Expand use after initial inspections, (2024-2025).

• Likely maximum opportunities of ~20 (10 CETI and 10 FPTI),

Realistically, anticipate <50% of these for 10 total at most.

• Limited Resident sites as opportunities arise w/SRA oversight.

• Minimum sampling in 2024.

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SDP KEY POINTS

• Utilize Be riskSMART framework.

• Keep it simple.

• Utilize existing processes.

• Preliminary Meeting 2nd Qtr. CY2024. Recent example in Inspection Report 05000400/2023003 (ML23310A314) 46

PCC SDP PROPOSED DRAFT PATHWAY More than Minor

• IMC 0612, App. E, Section 8, Maintenance Rule GREEN

• IMC 0609, App. K, Maintenance Risk Assessment DRE

• SRA/Licensee Coordination 47

DRAFT SDP PATHWAY FOR PCC - DETAILS Cross Regional Review Panel proposed screening path:

Pathway utilized for General Guidance

• IMC 0612, App. B, Issue Screening More than Minor IMC 0612, App. E., Section 8, Maintenance Rule x

• IMC 0609, Att. 04, Initial Characterization of Findings Go to IMC 0609 App K (Maintenance Risk Assessment) x

• IMC 0609, App. K, Maintenance Risk Assessment and Risk Management SDP 48

DRAFT SCREENING CRITERIA FOR PCC IMC 0609, App. K, Maintenance Risk Assessment SDP Utilized for General Guidance.

Step 4.2 Determinaon of Risk De"cit ICDP metric vs. Delta CDF ICDPD = ICDP Actual - ICDP Flawed Deficit (ICDPD) < 1E-6 = GREEN Otherwise perform Detailed Risk Evaluation (DRE)

Proposed exposure duration limited to:

1 year or last model change (most limiting).

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NRC PERSPECTIVE ON NRC AND INDUSTRY CATALOGUE OF PRA METHODS 50

KEY MESSAGES

• The NRC PRA methods database is being developed as A knowledge management tool.

• The database will not be used as a regulatory decisionmaking tool.

• The NRC staff if closed collaborating with EPRI to significantly reduce the duplication of effort between the NRC and industry activities.

• Different goals and potential uses necessitate the creation and maintenance of two separate databases.

• A public meeting was held on October 25th.

• The NRC and NEI made presentations on both the NRC and industry PRA method database development efforts.

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STATUS OF NRC DATABASE DEVELOPMENT Completed the identification and documentation of PRA methods for internal fires, seismic hazards, and internal floods.

• Finalized entries incorporated feedback from EPRIs review.

• Shared with EPRI to serve as a starting point for industry activities.

Draft internal events methods are undergoing internal review.

• Used industry PRA methods database work as starting point.

Some difficulties in identifying methods associated with high winds, external flooding, and other hazards.

• The initial database will likely have limited method information for these hazards.

• May be a potential area for collaboration between the NRC and industry.

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DISCUSSION AND Q&A 53