ML25245A157
| ML25245A157 | |
| Person / Time | |
|---|---|
| Site: | 99902079 |
| Issue date: | 12/03/2025 |
| From: | Vechioli-Feliciano L NRC/NRR/DANU/UAL2 |
| To: | Schoedel A Westinghouse |
| Vechioli-Feliciano L | |
| References | |
| EPID L-2024-TOP-0020, CAC 00431 | |
| Download: ML25245A157 (0) | |
Text
OFFICIAL USE ONLY PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICE OF NUCLEAR REACTOR REGULATION REGULATORY AUDIT REPORT NUCLEAR DESIGN METHODOLOGY TOPICAL REPORT WESTINGHOUSE ELECTRIC COMPANY, LLC.
DOCKET NO. 99902079
1.0 BACKGROUND
By letter dated May 15, 2024, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24137A244), Westinghouse Electric Company, LLC (Westinghouse) submitted Revision 0 of Topical Report (TR) EVR-LIC-RL-002-P/NP, Nuclear Design Methodology Topical Report, for the U.S. Nuclear Regulatory Commission (NRC) staffs review. In this TR, Westinghouse documents the eVinci microreactor nuclear design and the analysis methodology used to characterize their reactor physics. The TR also documents the software verification and validation (V&V) plan for Serpent Monte Carlo Code (Serpent), which is Westinghouses selected nuclear design and analysis software. After initial assessment of the TR, the NRC staff determined that a regulatory audit would assist in the timely completion of the review. The NRC staff shared the audit plan with Westinghouse and the audit kick off meeting was conducted on November 22, 2024 (ML24324A382). During the audit, the NRC staff reviewed supporting documentation to determine if the docketing of additional information was required to develop and support conclusions for the NRC staffs safety evaluation of the TR.
The audit closeout and exit meeting was held on April 23, 2025, at which the NRC staff reiterated the purpose of the audit and discussed the activities conducted. During the exit meeting, Westinghouse committed to resolving the issues that were identified during the audit by making revisions to the TR or via future licensing submittals. Westinghouse and the NRC staff agreed that the proposed TR revisions will be reflected in the -A version of the TR. The revisions identified during the audit are mentioned in section 5.0, Closure Path, of this audit report.
2.0.
SCOPE OF THE AUDIT AND AUDIT ACTIVITIES The NRC staff conducted the audit virtually using Westinghouses electronic reading room platform. The regulatory audit followed the guidance in NRR Office Instruction LIC-111, Regulatory Audits (ML24309A281).
OFFICIAL USE ONLY PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION Members of the audit team included the NRC staff below:
Name Division Branch Patrick Boyle NRR-DANU UAL2 Michelle Vega Rodriguez NRR-DANU UAL2 Lucieann Vechioli Feliciano NRR-DANU UAL2 Ayesha Athar NRR-DANU UTB1 Robert Jake Mikouchi-Lopez NRR-DANU UTB3 Andrew Bielen RES-DSA FSCB NRR: Office of Nuclear Reactor Regulation RES: Office of Nuclear Regulatory Research DANU: Division of Advanced Reactors and Non-Power Production and Utilization Facilities DSA: Division of Systems Analysis UAL2: Advanced Reactor Licensing Branch 2 UTB1: Advanced Reactor Technical Branch 1 UTB3: Advanced Reactor Technical Branch 3 FSCB: Fuel and Source Term Code Development Branch During the audit, the NRC staff also reviewed supporting documentation to determine if the docketing of additional information was required to develop and support any conclusions for the NRC staffs safety evaluation of the TRs.
The NRC staff reviewed portions of the following documents:
Westinghouse Commercial Grade Dedication Process Document No. W2-9.5-102 rev2 Commercial Grade Dedication of Serpent 2 for Nuclear Design Analysis Document No.
EVR-RXS-GL-008 procedure MCNP6 Version 3 Commercial Grade Dedication (CGD) Document No. SW-REAC-CN-NA-000001 Proposed revisions of the TR as a result of the audit discussion 3.0
SUMMARY
OF OBSERVATIONS The NRC staffs observations noted and discussed during the audit are summarized below:
- 1. Subsequent license applications for the eVinciTM microreactor design should provide the level of information necessary to demonstrate how it meets the principal design criteria scope.
- 2. During the audit, Westinghouse and NRC discussed and agreed about the limited information provided in the topical report regarding design tools presented in this topical report. It was established that subsequent license applications will provide that the level of information and that the safety evaluation report will reflect the limited safety determination.
- 3. The NRC staff requested clarification regarding the critical characteristics of the Serpent code which are to be evaluated in the V&V suite. Westinghouse stated that further V&V details will be provided in future TRs.
OFFICIAL USE ONLY PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION
- 4. The NRC staff requested clarification regarding the use of ((
)) to verify the depletion capabilities of Serpent. Westinghouse committed to providing revisions in the approved -A version of the TR.
- 5. The NRC staff identified editorial inconsistencies during the review and discussed them with Westinghouse. Westinghouse addressed these inconsistencies in the TR for clarification.
As a result of the audit, the NRC staff identified information required to make a safety determination for the TR. Consequently, Westinghouse docketed the following supporting document:
Commercial Grade Dedication of Serpent 2 for Nuclear Design Analysis Document No.
EVR-RXS-GL-008 procedure 4.0 REQUESTS FOR ADDITIONAL INFORMATION RESULTING FROM THE AUDIT Based on the scope presented in the TR, the NRC staff determined that no requests for additional information were necessary to complete its review of this TR. However, the NRC staff does anticipate future submittals and interaction related to this topical area.
5.0 CLOSURE PATH The NRC staff identified some specific aspects of the TR during the audit that can be addressed by revisions to the TR. Westinghouse confirmed that the following revisions to the TR will be reflected in the -A version of the TR:
- 1. Westinghouse will provide justification for using comparisons to experiments with ((
] as the basis for determining biases and associated uncertainties in safety-related calculations. The staff expects the explanation of the validation application in a future licensing submittal.
- 2. Westinghouse will revise the value of the ((
)) in table 4.1-1, Design Specifications, of the TR.
- 3. Westinghouse will be making text changes to the -A version of the TR to clarify the use of ((
)) models in benchmarking Serpents depletion capabilities.