ML23187A574

Summary of June 29, 2023, Meeting with Southern Nuclear Operating Company

ML23187A574
Person / Time
Site:	Vogtle
Issue date:	08/22/2023
From:	Gleaves W NRC/NRR/VPOB
To:	Southern Nuclear Operating Co
References
EPID: L-2023-LLA-0002
Download: ML23187A574 (1)

Text

August 22, 2023 LICENSEE: Southern Nuclear Operating Company FACILITY: Vogtle Electric Generating Plant, Units 3 and 4

SUMMARY

OF JUNE 29, 2023, MEETING WITH SOUTHERN NUCLEAR OPERATING COMPANY On June 29, 2023, at 4:00 p.m. Eastern Daylight Time (EDT), the U.S. Nuclear Regulatory Commission (NRC) held a virtual public meeting with representatives of Southern Nuclear Operating Company (SNC or the licensee). The purpose of the meeting was to discuss the SNC-proposed changes to the license including technical specifications (TS) for Vogtle Electric Generating Plant (VEGP) Units 3 and 4. This discussion centered on VEGP Units 3 and 4 License Amendment Request (LAR)22-002, Technical Specification 3.8.3, Inverters - Operating, Completion Time Extension, dated January 3, 2023 (Agencywide Documents Access and Management (ADAMS) Accession No. ML23003A797) and supplement dated June 13, 2023 which provided responses to NRCs requests for additional information (RAI) (ML23164A270).

Discussion was on SNCs response to RAI #2 and RAI #4.

With regard to RAI #2 that requested SNC to explain, from a probabilistic perspective at a high level, both the relevance of the precedents cited in the LAR and the basis for the proposed 14-day extension and the allowed completion times that maintain acceptable thresholds for Conditional Core Damage Frequency (CDF) and Conditional Large Early Release Frequency (LERF) for VEGP Units 3 and 4.

The NRC staff explained that the submittals explain that the CDF and LERF numbers are below the thresholds in Regulatory Guide (RG) 1.177 set for operating plants. Since VEGP Units 3 and 4 have not operated commercially the NRC staff asked how SNC evaluated the uncertainties in the analysis to justify the numbers presented in the LAR. SNC explained that each hazard had a comprehensive uncertainty analysis. SNC did review the sources of uncertainty and the assumptions on an application specific basis. Of the hazards where they were uncertain of the impact, only loss of offsite power did not screen out in the base case so a sensitivity analysis of the uncertainty revealed that its impact to CDF was negligible, in fact it improved the CDF.

NRC staff also asked about the unresolved list in the response to RAI #1 and whether those were considered when doing the uncertainty analysis. SNC stated that they reviewed the list of open findings with a similar perspective as to impact on the application. SNC did not identify anything that would be specifically applicable to this application and was discussed in the original LAR request.

With regard to RAI #4, the staff requested SNC provide a list of the maintenance activities to restore an inoperable inverter to OPERABLE status including the time to finish each activity and all of them with worst case margin(s) to address reasonable uncertainties in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.36, TS 1.3, and guidance in RG 1.177.

The NRC staff discussed having sent precedents to SNC of similar RAIs for other licensees as RAI #4. The staff indicated that SNC in their RAI #4 response would have typical maintenance activities and timeline durations for an inoperable inverter as in LAR Table 1 of approximately 7 days and possibly greater than 7 days by up to a half of a day. The staff further stated that SNC would need additional time as stated in their response due to unforeseen difficulties. The NRC staff offered to discuss these maintenance activities as bins in regard to activities supporting 7-day and 14-day completion times (CTs). The staff requested further clarity on what is included in the inverter maintenance activities as to what is captured in a 7-day and 14-day bin, whether those activities supported a 7-day or 14-day CT and further definition of what is meant by unforeseen circumstances in terms of a time period in hours or days. The discussion with SNC elicited the examples of the unforeseen difficulties that relate to the maintenance activities for the 7-day and 14-day bins that the NRC staff might consider if the information was submitted on the docket. SNC mentioned that in addition to the uncertainty of the maintenance activities included in the restoration time for an inoperable inverter, that the regulatory burden for requesting licensing changes and enforcement related discretion, plant mode changes including shutdown, as well as preparation time for those requests can be minimized should this proposed request for CT change be approved. The staff further discussed generic troubleshooting inherent with VEGP inverters and their maintenance and repair activities based on vendor data that could support the need for 14-day restoration of an inoperable inverter rather than a 7-day one. SNC expressed difficulties with the vendor in determining the actual inverter maintenance activities, obtaining replacements (e.g., inverter parts and components),

training of SNC personnel to perform the inverter maintenance activities rather than relying on vendor staff, and other real-life circumstances.

SNC requested NRC issue these clarifications as a second round RAI. The NRC staff will evaluate the information provided by SNC during this meeting and will assess the changes needed for a second round RAI. The NRC staff estimated that the 2nd round RAI may be sent on or before July 28, 2023, and if that estimate changes SNC will be kept up to date.

The meeting notice and agenda are available in ADAMS (ML23121A085). A list of attendees is enclosed.

There were approximately 22 participants on the call, including NRC staff, SNC staff, and public.

No questions or comments for the staff from the public were proffered. The meeting ended at 4:51 p.m. EDT. The staff did not receive any Public Meeting Feedback forms.

Please direct any inquiries to me at 301-415-5848 or Bill.Gleaves@nrc.gov.

Sincerely,

/RA/

William C. Gleaves, Senior Project Manager Vogtle Project Office Office of Nuclear Reactor Regulation Docket Nos.52-025, 52-026

Enclosure:

List of Attendees cc: Listserv

LIST OF ATTENDEES June 29, 2023 NRC Meeting with Southern Nuclear Operating Company Name Organization Billy Gleaves Brian Wittick Tanny Santos Garry Armstrong Lauren Nist Shivani Mehta NRC Wendell Morton Sheila Ray Charles Moulton Thinh Dinh Ed Kleeh Chris Welch Keith Dorsey Dan Williamson Eddie Grant Tony DeSalvatore Southern Nuclear Operating Company and Ken Lowrey Contractors William Garrett Alex Gilbreath Larry Dempker Jana Bergman Members of the Public Enclosure