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NEI Perspective on Performance Monitoring in Use of Probabilistic Fracture Mechanics for Optimizing Inspections of Non-RPV Pressure Vessels, April 27, 2023
	ML23115A030
Person / Time
Site:	Nuclear Energy Institute
Issue date:	04/27/2023
From:	; Nuclear Energy Institute
To:	Ali Rezai; NRC/NRR/DNRL/NPHP
References
	Download: ML23115A030 (1)
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NEI Perspective on Performance Monitoring in Use of Probabilistic Fracture Mechanics for Optimizing Inspections of Non-RPV Pressure Vessels April 27, 2023

Content Problem Statement Licensee Relief Requests Risk-informed vs PFM Methodologies Purpose of PM Programs for Identifying New Degradation Phenomena Industry Perspective on PM

Inherent Cadence of PM across the US PWR Fleet Existing Supplemental PM Programs Summary and Conclusion

Problem Statement Optimizing inspections has been justified using various analytical methods, including Probabilistic Fracture Mechanics (PFM), with significant margins of safety and no adverse impact on performance.

NRC granted relief with no conditions on four (4) pilot plants alternatives to defer non-RPV pressure vessel component inspections for up to 30 years based on PFM methodologies.

Subsequently, the NRC has not granted that same relief to defer these inspections beyond 20 years unless licensees commit to some type of performance monitoring (PM).

There are no regulatory or technical bases for requiring PM and the type of PM that would be acceptable for PFM applications

Licensee Relief Requests to Extend non-RPV Pressure Vessel Component Inspections EPRI Technical Basis Documents:

3002014590 - PWR SG MS and FW Nozzles 3002015906 - PWR SG Other Class 1 and 2 Welds/Components 3002015905 - PWR Pressurizer Welds/Components 3002018473 - BWR Heat Exchanger Welds/Components Probabilistic Fracture Mechanics (PFM) and Deterministic Fracture Mechanics (DFM) substantiate high flaw tolerance of these components and supports increased examination intervals Plant specific applicability is demonstrated with actual operating transient cycles using plant geometry bounded by the analysis in the applicable EPRI Report and in some cases with substantial margin Submittals do not make use of the stations probabilistic risk assessment (PRA) and therefore are not risk-informed changes to licensing basis

Risk-informed vs PFM Methodologies Risk-informed Methodologies (Failure Potential and Consequences)

(What can go wrong? How likely is it? What are the consequences?)

RG 1.200, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities

RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis

Require evaluation of consequence of failure (PRA)

PM Required PFM Methodologies (Failure Potential, Consequences not Considered)

RG 1.245, Preparing Probabilistic Fracture Mechanics Submittals The purpose of PFM is to model the behavior and degradation of systems more accurately and consequentially draw more precise and accurate conclusions about situations relative to performance criteria or design assumptions.

May be used in conjunction with or in support of risk-informed decision-making for licensing basis changes

Consequences of failure are not considered unless applied with PRA

No mention of Risk-informed or PM

Guidance for PFM Submittals RG 1.245 Preparing Probabilistic Fracture Mechanics Submittals No mention of Consequences or PM U.S. NRC Technical Letter Report TLR-RES/DE/CIB-2018-01, Important Aspects of Probabilistic Fracture Mechanics Analyses No mention of PM Consequences referenced in terms of PRA EPRI Letter to NRC 2019-016, White Paper on Suggested Content for PFM Submittals to the NRC PM included only when PFM submittal makes use of PRA

Purpose of PM RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis

Monitoring and trending performance characteristics to verify aspects of the underlying analyses, research, or bases for a requirement (e.g., measuring battery voltage and specific gravity, inservice inspection of piping)

Other PM Measures

Leak before Break (LBB)

Industry tracking of OE (including international)

BACC program and other walkdowns

PWR RCS leakage monitoring programs PM employs examination techniques to monitor Known Failure and/or Known Degradation Mechanisms

Programs for Identifying New Degradation Phenomena (Unknown Unknowns)

EPRI Materials Degradation Matrix (MDM) and Issues Management Table (IMT)

The objective of the EPRI MDM is to identify knowledge gaps associated with degradation phenomena that may detrimentally affectpower reactor operations, reactor safety, or regulatory climate

NEI 03-08 materials initiative was developed to ensure proactive management of materials degradation issues. The MDM and IMT are primary tools applied by EPRI to address the intent of the materials initiative NRC Research into Proactive Management of Material Degradation (PMMD)

Goal is to proactively address potential future degradation in operating plants to avoid failures and to maintain integrity, operability and safety Research through these programs, not PM, is the effective approach for discovering new (unknown unknowns) degradation mechanisms

Industry Perspective on PM Inherent Cadence of PM across the US PWR Fleet Matrix for postulated timing of alternative request applications and current operating license

Considers each component individually (SG, Pressurizer)

Combines components, considering all are low allow steel The following matrices illustrate the inherent PM for future submittals

International units would provide additional data

US PWR Fleet Performance Monitoring Plant Name End of Current Year US PWR Fleet - SG & PZR Performance Monitoring License 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 Diablo Canyon 1 2024 Diablo Canyon 2 2025 Key Ginna Comanche Peak 1 2029 2030 X Have not applied Point Beach 1 2030 SER Issued (7)

Robinson 2 Comanche Peak 2 2030 2033 X Relief Request in Progress (19)

Oconee 1 Oconee 2 2033 2033 X - End of the current deferral period Point Beach 2 2033 % of US fleet applied for relief = ~42%

Prairie Island 1 2033 Calvert Cliffs 1 Arkansas Nuclear 1 2034 2034 X

D.C. Cook 1 2034 Oconee 3 2034 Prairie Island 2 2034 Watts Bar 1 2035 Millstone 2 2035 X Calvert Cliffs 2 Beaver Valley 1 2036 X 2036 Saint Lucie 1 2036 Salem 1 D.C. Cook 2 2036 X 2037 Davis-Besse 2037 Farley 1 2037 Arkansas Nuclear 2 2038 North Anna 1 2038 North Anna 2 2040 Salem 2 Sequoyah 1 2040 X 2040 Farley 2 2041 McGuire 1 Sequoyah 2 2041 2041 X

Summer 2042 X Catawba 1 2043 X Catawba 2 2043 X McGuire 2 Saint Lucie 2 2043 2043 X X Byron 1 2044 Callaway 2044 Waterford 3 2044 Millstone 3 2045 Palo Verde 1 2045 Wolf Creek 1 2045 Byron 2 2046 Palo Verde 2 2046 Shearon Harris 1 2046 Braidwood 1 2046 Beaver Valley 2 2047 Palo Verde 3 2047 South Texas 1 2047 Braidwood 2 2047 Vogtle 1 South Texas 2 2047 X 2048 Vogtle 2 Seabrook 1 2049 X 2050 Surry 1 2052 Turkey Point 3 2052 Surry 2 2053 Turkey Point 4 2053 Watts Bar 2 2055

US PWR Fleet Performance Monitoring Plant Name End of Current Year US PWR Fleet - SG & PZR Performance Monitoring License 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 Diablo Canyon 1 2024 Diablo Canyon 2 2025 Key Ginna 2029 X Comanche Peak 1 2030 ASME Section XI Exams Have not applied Point Beach 1 2030 ASME Section XI Exams SER Issued (7)

Robinson 2 Comanche Peak 2 2030 2033 ASME Section XI Exams X Relief Request in Progress (19)

Oconee 1 2033 Oconee 2 2033 X - End of the current deferral period Point Beach 2 2033 ASME Section XI Exams % of US fleet applied for relief = ~42%

Prairie Island 1 2033 ASME Section XI Exams Calvert Cliffs 1 Arkansas Nuclear 1 2034 2034 ASME Section XI Exams X

D.C. Cook 1 2034 ASME Section XI Exams Oconee 3 2034 Prairie Island 2 2034 ASME Section XI Exams Watts Bar 1 2035 ASME Section XI Exams Millstone 2 2035 X Calvert Cliffs 2 Beaver Valley 1 2036 X 2036 ASME Section XI Exams Saint Lucie 1 2036 ASME Section XI Exams Salem 1 D.C. Cook 2 2036 X 2037 ASME Section XI Exams Davis-Besse 2037 ASME Section XI Exams Farley 1 2037 Arkansas Nuclear 2 2038 ASME Section XI Exams North Anna 1 2038 ASME Section XI Exams North Anna 2 2040 ASME Section XI Exams Salem 2 Sequoyah 1 2040 X 2040 ASME Section XI Exams Farley 2 2041 McGuire 1 Sequoyah 2 2041 2041 ASME Section XI Exams X

Summer 2042 X ASME Section XI Exams Catawba 1 2043 X ASME Section XI Exams Catawba 2 2043 X ASME Section XI Exams McGuire 2 Saint Lucie 2 2043 2043 X ASME Section XI Exams ASME Section XI Exams X

Byron 1 2044 Callaway 2044 ASME Section XI Exams Waterford 3 2044 ASME Section XI Exams Millstone 3 2045 ASME Section XI Exams Palo Verde 1 2045 ASME Section XI Exams Wolf Creek 1 2045 ASME Section XI Exams Byron 2 2046 Palo Verde 2 2046 ASME Section XI Exams Shearon Harris 1 2046 Braidwood 1 2046 Beaver Valley 2 2047 ASME Section XI Exams Palo Verde 3 2047 ASME Section XI Exams South Texas 1 2047 ASME Section XI Exams Braidwood 2 2047 Vogtle 1 South Texas 2 2047 X 2048 ASME Section XI Exams Vogtle 2 Seabrook 1 2049 X 2050 ASME Section XI Exams Surry 1 2052 Turkey Point 3 2052 ASME Section XI Exams Surry 2 2053 Turkey Point 4 2053 ASME Section XI Exams Watts Bar 2 2055 ASME Section XI Exams

US PWR Fleet Performance Monitoring Start of Next Plant Name Inspection Year US PWR Fleet - SG & PZR Performance Monitoring Interval 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 Diablo Canyon 1 2025 Diablo Canyon 2 2026 Ginna 2030 Comanche Peak 1 2031 = Next Inspection Period Point Beach 1 2031 Robinson 2 2031 SER Issued (7)

Comanche Peak 2 2034 Relief Request in Progress (19)

Oconee 1 2034 Oconee 2 2034 Point Beach 2 2034 Prairie Island 1 2034 Calvert Cliffs 1 2035 Arkansas Nuclear 1 2035 D.C. Cook 1 2035 Oconee 3 2035 Prairie Island 2 2035 Watts Bar 1 2036 Millstone 2 2036 Calvert Cliffs 2 2037 Beaver Valley 1 2037 Saint Lucie 1 2037 Salem 1 2037 D.C. Cook 2 2038 Davis-Besse 2038 Farley 1 2038 Arkansas Nuclear 2 2039 North Anna 1 2039 North Anna 2 2041 Salem 2 2041 Sequoyah 1 2041 Farley 2 2042 McGuire 1 2042 Sequoyah 2 2042 Summer 2043 Catawba 1 2044 Catawba 2 2044 McGuire 2 2044 Saint Lucie 2 2044 Byron 1 2045 Callaway 2045 Waterford 3 2045 Millstone 3 2046 Palo Verde 1 2046 Wolf Creek 1 2046 Byron 2 2047 Palo Verde 2 2047 Shearon Harris 1 2047 Braidwood 1 2047 Beaver Valley 2 2048 Palo Verde 3 2048 South Texas 1 2048 Braidwood 2 2048 Vogtle 1 2048 South Texas 2 2049 Vogtle 2 2050 Seabrook 1 2051 Surry 1 2053 Turkey Point 3 2053 Surry 2 2054 Turkey Point 4 2054 Watts Bar 2 2056

Existing Supplemental PM Programs Boric Acid Corrosion Control (BACC) Programs Routine Engineering and Operations Walkdowns Fatigue Monitoring Programs PWR RCS Leakage Monitoring Systems

WCAP-16465, Standard RCS Leakage Action Levels and Response Guidelines for Pressurized Water Reactors (ML070310082) NEI 03-08 Needed Requirement Action Level 1: One seven (7) day rolling average of daily Unidentified RCS leak rates >

0.1 gpm Action Level 2: Two consecutive daily Unidentified RCS leak rates > 0.15 gpm Action Level 3: One daily Unidentified RCS leak rate > 0.3 gpm

Plant Tech Spec Limits

RG 1.45, RCPB Leakage Detection Systems

Summary and Conclusion Probabilistic Fracture Mechanics (PFM) Methods are not risk-informed (magnitude of consequences are not considered)

Existing regulatory and industry guidance for PFM submittals does not require consideration of performance monitoring unless also applying PRA PM is effective for known failure mechanisms while EPRI (MDM and IMT) and NRC (PMMD) research programs were developed to proactively address potential future degradation Existing PM programs, including international operating experience, provide supplemental indications of any potential issues The postulated timing of applications for extension of these specific component inspections results in inherent PM across the US PWR Fleet Therefore, PM on a plant specific basis is not required for deferrals greater than 20 years justified by PFM methodologies

QUESTIONS?

ML23115A030

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