ML25097A342
| ML25097A342 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/09/2025 |
| From: | Samson Lee Plant Licensing Branch IV |
| To: | Gerfen P Pacific Gas & Electric Co |
| Lee S, 301-415-3158 | |
| References | |
| EPID L-2024-LLA-0177 | |
| Download: ML25097A342 (1) | |
Text
April 9, 2025 Ms. Paula Gerfen Senior Vice President, Generation and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant P.O. Box 56, Mail Code 104/6 Avila Beach, CA 93424
SUBJECT:
DIABLO CANYON NUCLEAR POWER PLANT, UNITS 1 AND 2 REGULATORY AUDIT PLAN IN SUPPORT OF LICENSE AMENDMENT REQUEST TO ADOPT RISK-INFORMED COMPLETION TIMES FOR TECHNICAL SPECIFICATIONS 3.3.1 AND 3.3.2 (EPID L-2024-LLA-0177)
Dear Ms. Gerfen:
By letter dated December 24, 2024, Pacific Gas and Electric Company submitted a request to amend the license for Diablo Canyon Nuclear Power Plant, Units 1 and 2.1 The proposed amendments would permit the use of risk-informed Technical Specification (TS) completion times for certain actions required by TS 3.3.1 and TS 3.3.2 when limiting conditions for operation are not met.
The U.S. Nuclear Regulatory Commission (NRC) staff will conduct a virtual regulatory audit to support its review of the license amendment request. A regulatory audit is a planned activity that includes the examination and evaluation of information that is not docketed. The audit will be conducted to enhance the NRC staffs understanding of the request and to identify information that may be needed on the docket to support our regulatory findings.
In accordance with the enclosed audit plan and requests, the audit team will review documentation and calculations that support the proposed amendments. For efficiency, the team requests that you establish a secure online portal for remote access to this material. The team will also interview the licensees subject matter experts using video-and teleconferencing.
1 Accession No. ML24359A002 in the Agencywide Documents Access and Management System (ADAMS).
If you have any questions, please contact me by telephone at 301-415-3168 or by email to Samson.Lee@nrc.gov.
Sincerely,
/RA/
Samson S. Lee, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323
Enclosure:
Audit Plan cc: Listserv
ML25097A342 NRR-106 OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DRA/APLA/BC NAME SLee PBlechman RPascarelli DATE 4/7/2025 4/8/2025 4/4/2025 OFFICE NRR/DORL/LPL4/BC NRR/DORL/LPL4/PM NAME TNakanishi SLee DATE 4/9/2025 4/9/2025
Enclosure REGULATORY AUDIT PLAN IN SUPPORT OF LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATIONS BY ADOPTING RISK-INFORMED COMPLETION TIMES FOR TECHNICAL SPECIFICATIONS 3.3.1 AND 3.3.2 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-275 AND 50-323 1.0
Background
By letter dated December 24, 2024,1 Pacific Gas and Electric Company requested amendments to the facility operating licenses for Diablo Canyon Nuclear Power Plant, Units 1 and 2 (Diablo Canyon). The licensees proposed amendments would modify the Diablo Canyon technical specifications (TSs) to permit the use of risk-informed completion times (RICTs) in TS 3.3.1, Reactor Trip System (RTS) Instrumentation, and TS 3.3.2, Engineered Safety Feature Actuation System (ESFAS) Instrumentation. For certain other TSs, the licensee has already been authorized to implement Technical Specifications Task Force (TSTF) traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF [Risk-Informed TSTF] Initiative 4b.2 To do so, the licensee is applying industry guidance prepared by the Nuclear Energy Institute (NEI); specifically, NEI 06-09, Revision 0-A, Risk-Informed Technical Specifications Initiative 4b, Risk-Managed Technical Specifications (RMTS) Guidelines.3 The U.S. Nuclear Regulatory Commission (NRC) staff in the Office of Nuclear Reactor Regulation(NRR) has initiated its review of the license amendment request (LAR) in accordance with office instruction LIC-101, Revision 6, License Amendment Review Procedures.4 2.0 Regulatory Audit Basis A regulatory audit is a planned activity to examine and evaluate information that provides the technical basis for actions related to a license or regulation. An audit allows the NRC staff to gain insights to the licensees processes and procedures. In the case of a LAR, the NRC staff can clarify its understanding of the request, verify the information submitted, and identify additional information that the staff needs to make a licensing or regulatory decision. Information that the NRC staff relies upon to make a safety determination or decision must be submitted on the docket.
1 Accession No. ML24359A002 in the Agencywide Documents Access and Management System (ADAMS).
2 ML18183A493.
3 ML12286A322.
4 ML19248C539.
The NRC staff will perform this audit to support its evaluation of whether the licensees requests 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. It will be conducted in accordance with NRR LIC-111, Regulatory Audits, Revision 2, dated December 30, 2024.5 Exceptions, if any, are described in this audit plan. The NRC staffs review will be informed by NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light-Water Reactor] Edition, Section 19.2, Review of Risk Information Used to Support Permanent Plant-Specific Changes to the Licensing Basis: General Guidance, dated June 2007.6 The audit will help the NRC staff to understand the licensees proposed programs for implementing RICTs and applying them to certain TSs.
3.0 Regulatory Audit Scope The audit team will view the documentation and calculations that provide the technical support for the LAR. The scope of the NRC staffs audit will focus on the following subjects:
Understand how the licensees proposed program conforms to NRC-endorsed guidance in NEI 06-09, Revision 0-A.
Confirm the NRC staffs understanding of the LAR and gain a better understanding of the detailed calculations, analyses, and bases on which it is based, including the probabilistic risk assessment (PRA).
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 whether the proposed changes challenge design-basis functions or adversely affect the capability or capacity of plant equipment to perform design-basis functions.
Information needed to support a safety finding or licensing decision may already be docketed, which can be determined during the audit. Otherwise, it must be submitted under oath or affirmation. The licensee may supplement the LAR with this information. Alternatively, the licensee may respond to a formal request for additional information (RAI). If needed, RAIs will be developed and transmitted separately in accordance with NRR Office Instruction LIC-115, Revision 1, Processing Requests for Additional Information, dated August 5, 2021.7 The NRC staff will audit the PRA methods that the licensee would use to revise completion times for affected TSs. This will include the licensees assessment of internal events (including internal flooding) and fire as well as the licensees treatment of uncertainties and evaluation of defense-in-depth. The NRC staff will also review the quantification of risk from significant external events, whether PRA or bounding methods are used. In addition, the audit team will discuss these topics with the licensees subject matter experts.
5 ML24309A281 6 ML071700658 7 ML21141A238 4.0 Information and Other Material Necessary for the Regulatory Audit The NRC staff will request information and interviews throughout the audit period. The NRC staff will use an audit items list to identify the information to be audited (e.g., methodology, process information, and calculations) and the subjects of requested interviews and meetings.
The NRC staff requests that the licensee have the information referenced in the attachment of this audit plan available and accessible for the NRC staffs review via a web portal within 2 weeks of the date of this audit plan. As additional or supplemental information is requested, it should be available and accessible within 1 week of the date of the NRC staffs notification to the licensee of the new requests. The NRC staff requests that the licensee notify the review team when an audit item is added to its portal by sending an email to the NRC licensing project manager.
The NRC staff acknowledges and will observe appropriate handling and protection of proprietary information made available for the audit. The NRC staff will not remove non-docketed information from the audit site or web portal.
5.0 Audit Team The following table identifies the NRC audit team members and their respective organization:
Name Email Organization Robert Beaton Robert.Beaton@nrc.gov Nuclear Systems Performance Branch Norbert Carte Norbert.Carte@nrc.gov Instrumentation and Controls Branch David Coy David.Coy@nrc.gov Containment and Plant Systems Branch Gordon Curran Gordon.Curran@nrc.gov Containment and Plant Systems Branch Malcolm Patterson Malcolm.Patterson@nrc.gov PRA Licensing Branch A Gokul Vasudevamurthy Gokul.Vasudevamurthy@nrc.
gov Nuclear Systems Performance Branch Khadijah West Khadijah.West@nrc.gov Technical Specifications Branch 6.0 Logistics The audit will be conducted remotely via a secure, online portal, established by the licensee to present supporting documentation and calculations. In addition to the review of documents made available on the portal, the NRC staff will interview the licensees subject matter experts, virtually (by telephone and videoconference). The audit will begin within 2 weeks of the date of this audit plan and last through June 2025. The NRC staff will establish a schedule of audit meetings as appropriate (e.g., a single, multi-day audit meeting with supplemental audit meetings as needed) on mutually agreeable dates and times.
At the meetings, the licensee is to discuss information needs and questions arising from the NRCs review of the application and other material reviewed during the audit. The NRC project manager will inform the licensee of audit meeting dates when they are established, including the date of an audit kick-off meeting.
7.0 Special Requests The following conditions associated with the online portal should be maintained while the NRC staff and contractors on the audit team have access to the online portal:
The online portal will be password-protected, and separate passwords will be assigned to each member of the audit team.
The online portal will prevent the NRC participants from printing, saving, downloading, or collecting any information directly from the online portal.
The licensee should provide username and password information directly to the NRC staff on the audit team listed above. The NRC project manager will provide the licensee the names and contact information of the NRC staff who are added to the audit team. All other communications should be coordinated with the NRC project manager. The NRC project manager will inform the licensee via routine communications when the NRC staff no longer needs access to the portal.
No data accessed by the audit team members will be retained by the NRC following the conclusion of the audit.
8.0 Deliverables The NRC staff will develop any RAIs, as needed, in accordance with NRR LIC-115 and issue such RAIs independent of audit-related correspondence. At the end of the audit, the NRC staff will conduct an exit meeting to inform the licensee of the outcome of the audit. The NRC staff will issue an audit summary report within 90 days of the audit exit.
Attachment:
Audit Items List
Audit Request List Attachment ITEM REQUESTS 1
Technical Specifications Task Force (TSTF) traveler TSTF-505 Revision 2 (ML18183A493) PDF page 113 of 850 states:
The description of proposed changes to the protective instrumentation and control features in TS [Technical Specification]
Section 3.3, Instrumentation, should confirm that at least one redundant or diverse means (other automatic features or manual action) to accomplish the safety functions (for example, reactor trip, SI [safety injection], containment isolation, etc.) remains available during use of the RICT [risk-informed completion time], consistent with the defense-in-depth philosophy as specified in RG [Regulatory Guide] 1.174. (Note that for each application, the staff may selectively audit the licensing basis of the most risk-significant functions with proposed RICTs to verify that such diverse means exist.)}
The license amendment request (LAR) does not seem to include an evaluation to address the above. Please provide for discussion during the audit.
2 The explanation of technical variations (see attachment 4 of the LAR, page 5 of 5 -
PDF page 80 of 160): (a) TS 3.3.1 Condition X, (b) TS 3.3.2 Condition M, and (c)
TS 3.3.2 Condition K (where is the two or more inoperable?); does not state that there is no loss of function. Please explain why there is no loss of function, or if there is a loss of function, please provide adequate justification for discussion during the audit.
3 For probabilistic risk assessments (PRAs) cited in enclosure 2 of the LAR to adopt TSTF-505, reports from full-scope and focused-scope peer reviews, self-and gap assessments (including findings, observations, and dispositions), and closure reviews of facts and observations (F&Os). (These were shared for the previous license amendments.)
4 For PRAs identified under Item No.3 above, plant-specific documentation (e.g.,
uncertainty notebooks) related to:
- a. The review of the PRA model assumptions and sources of uncertainty (generic and plant-specific assumptions/uncertainties) for the TSTF-505 LAR.
5 Other documentation that the licensee determines to be responsive to the NRC staffs information requests.
ITEM REQUESTS 6
Final Safety Analysis Report (FSAR), Single line diagrams -
Figure 8-3 Auxiliary Power Distribution System Figure 8-16 (3 pages) Main Station Buses Figure 8-17 (3 pages) Station Main Buses Figure 8-34 Single Line Diagram 125 VDC 240/120 VAC Auxiliary Power System.
These drawings are related to FSAR, Chapter 8. Equivalent training drawings may suffice.