ML23255A099

Slides for September 15, 2023 Public Meeting on Poanhi Seismic Evaluations

ML23255A099
Person / Time
Site:	North Anna
Issue date:	09/15/2023
From:	Clifford Munson, Shilp Vasavada NRC/NRR/DRA/APLC, NRC/NRR/DEX
To:
Miller G
References
Download: ML23255A099 (1)

Text

Evaluation of Seismic Hazard and Risk Under the Process for Ongoing Assessment of Natural Hazard Information (POANHI)

SEPTEMBER 15, 2023 SHILP VASAVADA AND CLIFFORD MUNSON

POANHI Process for Seismic Evaluations To date, five POANHI seismic hazard and risk evaluations have been completed Implemented hazard and risk screening process for each plant Plants have screened out POANHI seismic hazard reports for each plant site have been made publicly available in ADAMS Reports provide:

Description of seismic hazard reevaluation Multiple tables of site geologic profile, GMRS, and hazard curves POANHI seismic evaluations are ongoing for remaining NTTF Recommendation 2.1 Group 1 plants Previous public meetings have provided a forum for discussion of seismic hazard reevaluations and screening process Todays meeting will revisit screening process in response to questions sent to POANHI Seismic email account.

2

POANHI Decision-Making Flowchart 3

Seismic Risk Evaluation Using POANHI Hazard -

General Approach

• Use latest available information to obtain a key input (termed plant-level fragility) for risk evaluation.

• SPRA results, if licensee submitted a SPRA report in response to post-Fukushima actions

• Risk-informed LARs or GI-191 information, if licensee did not submit a SPRA report in response to post-Fukushima actions

• This is consistent with approach discussed in previous public meetings.

• Use convolution approach as discussed in previous public meetings.

• Use average of 1, 5, 10, and 100 Hz results consistent with approach in flowchart and discussions in previous public meetings.

4

Additional Risk Evaluation

• Utilize available plant-specific seismic risk insights; examples:

• Dominant risk contributors

• Frequencies of interest based on differences between NTTF 2.1 and POANHI GMRS

• Safety enhancements performed by licensee via permanent plant modifications

• If issues resolved, staff will issue final letter and hazard report

• If issues remain, staff will:

• Engage Senior Management Review Panel (SMRP)

• Enter formal regulatory process, if approved by SMRP 5

Approach

• DORL PM will issue final letter with the hazard report to licensee, documenting results of NRC staff evaluation

• Any outcome other than no further regulatory action will have licensee engagement before letter is issued

• NRC is internally considering methods of licensee engagement

• As with normal ListServ process, letter and hazard report will be made publicly available in ADAMS about 5 days following issuance

• Licensees can engage through their assigned PM if they have any technical questions about the letter or report 6

POANHI Seismic Email Account

• Members of the public and external stakeholders can submit any comments or feedback to the staff by emailing POANHI.Seismic@nrc.gov

• A total of 7 comments received to date

• First comment addressed during the November 2022 public meeting

• Delayed responses to remaining comments were provided in July 2023 (due to technical issues with email inbox)

• Most recent comment received in August (response in progress)

• Summary of comments and responses will be provided in the POANHI periodic report (expected publication date is CY23 Q4)

• Future comments should continue to be sent to email address above 7

POANHI Seismic Email Account (Contd)

• Summary of Select Comments:

• NRCs reference rock definition; incorporation of epistemic uncertainty in depth to reference rock and weighting of shear wave velocity profiles

• Explanation of control point elevation used in the site response analysis to ensure consistency between the prior and new seismic hazard calculation

• Clarification of NRCs screening process and computation of the average delta SCDF for two screened out plants (response in progress) 8

Schedule

• Complete

• Vogtle (ML23006A091)

• Sequoyah (ML23192A447)

• Watts Bar (ML23192A447)

• Browns Ferry (ML23192A447)

• North Anna (ML23214A177) 9

• Upcoming (Estimated dates)

• Summer (Q4 2023)

• Peach Bottom (Q4 2023)

• DC Cook (Q4 2023)

• Robinson (Q1 2024)

• Dresden (Q1 2024)

• Oconee (Q1 2024)

• Callaway (Q2 2024)

• Beaver Valley (Q2 2024)