ML24311A157

Slides for Pre-submittal Public Teleconference Meeting for License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors

ML24311A157
Person / Time
Site:	Wolf Creek
Issue date:	11/06/2024
From:	Evergy, Wolf Creek
To:	Samson Lee NRC/NRR/DORL/LPL4
Lee S, 301-415-3168
References
Download: ML24311A157 (1)

Text

Internal Use Only Pre-Submittal Meeting License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors Wolf Creek Generating Station DATE: November 2024

Internal Use Only AGENDA

• Scope of License Amendment Request (LAR)

• 10 CFR 50.69 LAR Overview

• Probabilistic Risk Assessment (PRA) Model Technical Adequacy

• Other Hazard Assessments

• LAR Schedule

• Summary, Questions, Comments, & Discussion 2

Internal Use Only 3

Scope of LAR The proposed amendment would add a condition to the WCGS license, which documents the NRCs approval for use of 10 CFR 50.69 The license condition identifies the processes to be used for categorization of structures, systems and components (SSCs):

Internal events, internal flooding, internal fire - PRA model Shutdown risk - Shutdown safety assessment process Passive component risk - Arkansas Nuclear One, U2 (ANO-2) method External hazards - IPEEE screening updated using the screening process in the ASME/ANS PRA Standard, except for seismic and high winds Seismic risks - Alternative EPRI approach as described in the LAR High winds risks - Alternative bounding approach as described in the LAR

Internal Use Only 10 CFR 50.69 LAR Overview Follows NEI 00-04 (except for seismic and high winds):

PRA evaluations utilizing internal events, internal flooding, and fire PRA models Non-PRA evaluations such as external events screening and shutdown safety assessment Seven qualitative criteria in Section 9.2 of NEI 00-04 Defense-in-depth assessments Passive categorization using ANO-2 methodology (in lieu of ASME Code case N-660)

External Hazards Initially screened in accordance with General Letter 88-20 Subsequently screened per a plant-specific evaluation using the external hazard screening significance process identified in ASME/ANS PRA Standard RA-Sa-2009 External hazards screening assessment was independently peer reviewed All external hazards screened from applicability except for seismic and high winds 4

Internal Use Only PRA Model Technical Adequacy Internal Events and Internal Flooding PRA

Full scope peer review against ASME/ANS RA-Sa-2009 performed in June 2019

F&O closure reviews performed in accordance with Appendix X to NEI 05-04 and NEI 17-07

No open F&Os Internal Fire PRA

The Fire PRA was prepared using the methodology defined in NUREG/CR-6850, Fire PRA Methodology for Nuclear Power Facilities

Peer reviewed against ASME/ANS RA-Sa-2009 performed in November 2021

Independent assessment of F&O closures performed in October 2022

No open F&Os High Winds

High winds PRA has been peer-reviewed and all F&Os are closed

Model has a pending review for a PRA upgrade (discussed later). Thus, the LAR proposes an alternative approach that is conservative and bounding.

5

Internal Use Only Other Hazard Assessments - Seismic and High Winds Proposes use of the alternative approach for seismic risk categorization using the same process licensed for LaSalle, as described in the LAR and EPRI 3002017583 The LAR provides site-specific information related to the WCGS seismic hazard, which is summarized on the next slide Proposes use of an alternative approach that is conservative and bounding; the approach identifies components susceptible to failures due to high winds 6

Internal Use Only Approach for Addressing Seismic Risks

• The approach for assessing seismic risk follows the same approach licensed for LaSalle

• Approach based on EPRI 3002017583, information provided in the LAR, and information that the LAR incorporates by reference (e.g., RAI responses)

• The WCGS GMRS exceeds the SSE in a portion of the response spectrum between 1.0 and 10 Hz (> Tier 1)

• WCGS was not required to develop an SPRA in response to the Fukushima accident (< Tier 3)

• WCGS meets the criteria for Tier 2 per EPRI 3002017583 (moderate hazard) 7 Comparison of the WCGS GMRS to the SSE

Internal Use Only Approach for Addressing High Winds Risks The High Winds (HW) PRA model is still pending review for an upgrade following completion of a newly developed industry method; however, the HW PRA is a highly developed model that meets the PRA Standard requirements, has been independently peer reviewed, and all F&Os are closed.

In lieu of using the existing HW PRA, WCGS proposes an alternative bounding approach for assessing HW risk during 10 CFR 50.69 categorization A HW fragility analysis has been performed, which evaluated plant equipment and provided a component level screening for identifying components susceptible to HW hazards The HW PRA is sufficiently developed to identify components that will be included in its scope (e.g., components in the HW PRA scope will be considered HSS)

The approach is summarized on the next slide 8

Internal Use Only Approach for Addressing High Winds Risks Per the HW Fragility Analysis, if a component is high wind impact screened with justification that the component is within a Seismic Category 1 structure, then it is not susceptible to a HW failure, and thus, is assigned HW LSS Components within Seismic Category 1 structures generally do not have failures due to HW exposure If a component is not screened high wind impact screened with justification that the component is within a Seismic Category 1 structure per the HW Fragility Analysis and is not included in the HW Plant Response Model and Quantification, then the component is assigned HW LSS This accounts for components that are mostly balance of plant equipment or are items not generally modeled in the PRA.

If a component is not screened high wind impact screened with justification that the component is within a Seismic Category 1 structure per the HW Fragility Analysis and is included in the HW Plant Response Model and Quantification, then the component is assigned HW HSS 9

Internal Use Only Shutdown Risks and Integral Assessment

• Shutdown risk follows the process described in NEI 00-04, Section 5.5

• Will use the shutdown safety management plan described in NUMARC 91-06

• Integrated assessment performed using NEI 00-04, Section 5.6 10

Internal Use Only LAR Schedule Projected submittal in December 2024 with requested approval within one year following acceptance A 60-day implementation period is proposed 11

Internal Use Only Summary

• The 10 CFR 50.69 LAR is scheduled to be submitted in December 2024 with approval requested within one year after acceptance

• The PRA models are technically acceptable for 50.69 categorization

• The categorization approaches follow NRC-endorsed NEI 00-04, with the exception of:

Seismic - uses the same alternative approach approved for LaSalle (EPRI Tier 2 methodology)

High Winds - uses an alternative approach that is conservative and bounding Questions, Comments, and Discussion 12