ML25190A545
| ML25190A545 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/11/2025 |
| From: | Minzer J Plant Licensing Branch II |
| To: | Coleman J Southern Nuclear Operating Co |
| References | |
| EPID L-2025-LLA-0080, RG 1.183 | |
| Download: ML25190A545 (1) | |
Text
July 11, 2025 Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 - REGULATORY AUDIT IN SUPPORT OF REVIEW OF THE LICENSE AMENDMENT REQUEST REGARDING ALTERNATE SOURCE TERM USING REGULATORY GUIDE 1.183 REVISION 1 (EPID L-2025-LLA-0080)
Dear Jamie Coleman:
By letter dated May 12, 2025 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML25132A313), Southern Nuclear Operating Company (SNC, the licensee) submitted a license amendment request (LAR) for the Vogtle Electric Generating Plant (Vogtle), Units 1 and 2, respectively. The proposed LAR would revise the Vogtle, Unit 1 and 2, licensing basis to support a full scope application of an Alternate Source Term methodology following the guidance of Regulatory Guide 1.183 Revision 1.
The Nuclear Regulatory Commission (NRC) staff has identified the need for a regulatory audit to examine the SNCs non-docketed information with the intent to gain understanding, to verify information, or to identify information that will require docketing to support the basis of the licensing or regulatory decision.
The NRC staff will conduct the audit virtually via Microsoft Teams using a licensee-established electronic portal available to NRC staff from approximately July 17, 2025, through March 16, 2026, with formal audit meetings to be scheduled during this period as needed. The NRC staff reserves the right to extend the audit, if necessary. The detailed audit plan is enclosed with this letter.
If you have any questions, please contact me at (301) 415-0610 or by email at jack.minzerbryant@nrc.gov Sincerely,
/RA/
Jack H. Minzer Bryant, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425
Enclosure:
Audit Plan cc: Listserv
Enclosure REGULATORY AUDIT PLAN BY THE OFFICE OF NUCLEAR REACTOR REGULATION TO SUPPORT THE REVIEW OF THE LICENSE AMENDMENT REQUEST REGARDING ALTERNATE SOURCE TERM USING RG 1.183 REVISION 1 SOUTHERN NUCLEAR OPERATING COMPANY VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 DOCKET NOS. 50-424, AND 50-425
1.0 BACKGROUND
By letter dated May 12, 2025 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML25132A313), Southern Nuclear Operating Company (SNC, the licensee) submitted a license amendment request (LAR) for the Vogtle Electric Generating Plant (Vogtle), Units 1 and 2, respectively. The proposed LAR would revise the Vogtle, Unit 1 and 2, licensing basis to support a full scope application of an Alternate Source Term methodology following the guidance of Regulatory Guide (RG) 1.183 Revision 1.
The Nuclear Regulatory Commission (NRC) staff from the Office of Nuclear Reactor Regulation (NRR) has initiated its review of the LAR in accordance with NRR Office Instruction LIC-101, License Amendment Review Procedures (ML19248C539).
2.0 REGULATORY AUDIT BASIS A regulatory audit is a planned license-or regulation-related activity that includes the examination and evaluation of primarily non-docketed information associated with the LAR. An audit is conducted to gain understanding, to verify information, and to identify information that will require docketing to support the basis of a licensing or regulatory decision. An audit will assist the NRC staff in efficiently conducting its review and gaining insights to the licensees processes and procedures. Information that the NRC staff relies upon to make the safety determination must be submitted on the docket. This audit will be conducted in accordance with NRR Office Instruction LIC-111, Regulatory Audits, Revision 2, dated December 2024 (ML24309A281), with exceptions noted within this audit plan.
The NRC staff will perform the audit to support its evaluation of whether SNCs LAR can be approved per Title 10 of the Code of Federal Regulations, Section 50.90, Application for amendment of license, construction permit, or early site permit. The NRC staffs review will be informed by NUREG-0800, Standard Review Plan. The audit will assist the NRC staff with understanding the licensees proposed LAR.
3.0 REGULATORY AUDIT SCOPE AND METHODOLOGY NRCs objectives of the audit are the following:
Gain a better understanding of the detailed calculations, analyses, and bases underlying the LAR and confirm the NRC staffs understanding of the LAR.
Gain a better understanding of plant design features and their implications for the LAR.
Identify any information needed to enable the NRC staffs evaluation of the technical basis used for this application.
Identify any information needed to enable the NRC staffs evaluation of whether the proposed changes challenge design-basis functions or adversely affect the capability or capacity of plant equipment to perform design-basis functions.
Identify questions and requests that may become formal requests for additional information (RAI) per NRR Office Instruction LIC-115, Processing Requests for Additional Information (ML21141A238).
The NRC staff will audit the technical information and methods that the licensee used to determine the impact on the plant, and the licensees evaluation of defense-in-depth.
4.0 INFORMATION AND OTHER MATERIAL NECESSARY FOR THE AUDIT The NRC staff will request information and an audit meeting(s) throughout the audit period. The NRC staff will use an audit items list to identify the information (e.g., methodology, process information, and calculations) to be audited. The NRC staff will provide the final audit items list as an enclosure to the audit summary report, which will be publicly available. The attachment to this audit plan includes the initial audit items list. Throughout the audit period, the NRC staff will provide SNC with audit questions and audit-related requests so that the licensee can better prepare for audit discussions with NRC staff. Any information accessed through the licensees portal will not be held or retained in any way by NRC staff. The NRC staff requests the licensee to have the requested audit information listed in the audit items list to be readily available and accessible for the NRC staffs review via a Web-based portal.
5.0 TEAM ASSIGNMENTS The audit team will consist of the following NRC staff from NRR.
John G. Lamb, Division of Operating Reactor Licensing (DORL)/Plant Licensing Branch 2-1 (LPL2-1)
Jack Minzer Bryant, DORL/LPL2-1.
Sean Meighan, Division of Risk Assessment - Accident Dose Analysis Joseph Messina, Division of Safety Systems (DSS)/Nuclear Methods and Fuel Analysis Branch (SFNB)
Jack Vande Polder, DSS/SFNB Anthony Torres, Division of Engineering and External Hazards (DEX)/External Hazards Branch (EXHB)
Mike Mazaika, DEX/EXHB 6.0 LOGISTICS To support the review schedule communicated to SNC when the NRC staff accepted the LAR for technical review, audit activities will be performed remotely and virtually using Microsoft Teams, teleconference, and a Web-based portal or other virtual meeting space created by the licensee. The NRC staff information requests and communications with licensee staff will be coordinated through the NRCs licensing project manager.
A desktop audit will take place between July 17, 2025, through March 16, 2026. The NRCs licensing project manager will inform the licensee of the entrance and exit meeting dates when they are established. The NRC staff may change and/or add audit dates and times, or extend the audit, if necessary. An audit meeting agenda and questions, if needed, will be sent in advance of the audit meeting.
The NRC staff requests the licensee to have the information referenced in Section 9.0 of this audit plan available and accessible for the NRC staffs review via an internet-based portal within five days of this audit plan. The NRC staff requests that any supplemental information requested be available and accessible for the NRC staffs review within 5 days of the date of the NRCs notification to the licensee of the new requests. The NRCs licensing project manager will inform the licensee via routine communications when the NRC staff no longer needs access to the portal. The NRC staff requests the licensee to notify the NRCs licensing project manager when an audit item is added to its portal by sending an e-mail to the NRC licensing project manager.
7.0 SPECIAL REQUESTS The NRC requests access to requested documents and information through a Web-based portal that allows the NRC staff and contractors to access documents over the Internet. The following conditions associated with the online portal must be maintained while the NRC staff and contractors have access to the online portal:
The online portal will be password-protected. A separate password will be assigned to each member of the NRC staff and NRC contractors participating in the audit.
The online portal will prevent the NRC participants from printing, saving, downloading, or collecting any information directly from the online portal.
Conditions of use of the online portal will be displayed on the login screen and will require acknowledgment by each user.
Username and password and/or other Web-based portal access information should be provided directly to members of the NRC staff and contractors as needed. The NRC licensing project manager will provide the licensee with names and contact information of the NRC staff and contractors participating in the audit. All other communications should be coordinated through the NRC project manager.
8.0 DELIVERABLES The NRC staff will develop any RAI, as needed, via NRR Office Instruction LIC-115 and issue such RAI separately from audit-related correspondence. The NRC staff will issue an audit summary report prior to completing its review of the LAR.
9.0 AUDIT QUESTIONS/DISCUSSIONS Item #
Audit Question/Discussion 1
(ARCB)
Provide information on the initial conditions, inputs, assumptions, and modeling associated with the RADTRAD runs for each design basis accident.
2 (SFNB)
Section 3.4 of the LAR states the following regarding the treatment of transient fission gas release (TFGR) during a locked rotor accident (LRA):
low power assemblies would be far less susceptible to reaching DNB
[departure from nucleate boiling] conditions than high powered assemblies and would have a much lower RPF [radial peaking factor]. It is not expected that fuel at these high burn ups would be part of the 5% of fuel that is estimated to reach DNB conditions following an LRA. If they were, a significantly lower RPF could be applied in calculating the fission product gap release. Therefore, the current licensing basis radiological consequence analysis assumptions for an LRA, particularly the use of a 1.7 RPF, results in a fission product release that would bound the release from high burnup assemblies operating at much lower powers even if using the maximum observed TFGR of 20% from RIL 2021-13 (Reference 4). Further, as can be seen from the analysis described in this LAR, the locked rotor consequences are very low even with the conservative assumptions described. As such, no additional TFGR is applied in the determination of the LRA radiological consequences described in this LAR.
Departure from nucleate boiling (DNB) may not be the only fuel failure mechanism that occurs during an LRA. Please explain if other failure mechanisms, such ballooning and burst or pellet-cladding mechanical interaction, would occur during a LRA at Vogtle, Units 1 and 2. If other failure mechanisms would be expected to occur, please explain if the assumption of 5% of the rods failing during an LRA remains bounding if the other failure mechanisms are considered and if neglecting the TFGR during the event remains bounding.
3 (SFNB) to the LAR states that the RG 1.183 Revision 1 Table 4 non-loss-of-coolant-accident (non-LOCA) fuel-cladding gap release fractions are employed for non-LOCA accidents that result in fuel failures. The gap release fractions in RG 1.183 Revision 1 Table 4 are applicable as long as the RG 1.183 Revision 1 Figure 1 pressurized water reactor rod-average power envelope is met. Please explain if this envelope will be met and if it is included in the SNCs cycle reload checklist.
Item #
Audit Item 1
SGTR RADTRAD modeling 2
MHA-LOCA RADTRAD modeling (mini-purge flow rates, Source Terms) 3 Control Rod Ejection Accident RADTRAD modeling 4
Locked Rotor Accident RADTRAD modeling 5
Fuel Handling Accident RADTRAD modeling 6
Main Steam Line Break RADTRAD modeling 7
Microshield Files
ML25190A545 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DRA/ARCB/BC NRR/DSS/SFNB/BC NAME JMinzerBryant KZeleznock KHsueh SKrepel DATE 07/09/2025 07/10/2025 07/11/2025 07/11/2025 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/BC NAME JMinzerBryant MMarkley (EMiller for)
DATE 07/11/2025 07/11/2025