ML25230A055
| ML25230A055 | |
| Person / Time | |
|---|---|
| Site: | 99902079 |
| Issue date: | 08/21/2025 |
| From: | Vechioli-Feliciano L NRC/NRR/DANU/UAL2 |
| To: | Schoedel A Westinghouse |
| Vechioli-Feliciano L | |
| Shared Package | |
| ML25190A670 | List: |
| References | |
| EPID L 2024-TOP-0028, CAC 00431 | |
| Download: ML25230A055 (1) | |
Text
OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICIAL USE ONLY - PROPRIETARY INFORMATION OFFICE OF NUCLEAR REACTOR REGULATION REGULATORY AUDIT REPORT TRISO FUEL DESIGN METHODOLOGY TOPICAL REPORT WESTINGHOUSE ELECTRIC COMPANY, LLC.
DOCKET NO. 99902079
1.0 BACKGROUND
By letter dated July 31, 2024, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24214A277), Westinghouse Electric Company LLC.,
(Westinghouse) submitted Revision 0 of topical report (TR) EVR-LIC-RL-003-P/NP, Westinghouse TRISO Fuel Design Methodology for the eVinci' Microreactor Topical Report, to the U.S. Nuclear Regulatory Commission (NRC) staff for review. The TR provides an overview and description of the design methodology and analytical tools used to assess the performance of uranium oxycarbide (UCO) tristructural isotropic (TRISO) fuel for the eVinciTM microreactor core being developed for the eVinciTM microreactor. On September 12, 2024, the NRC staff found that the material presented in the TR provides technical information in sufficient detail to enable the NRC staff to conduct a detailed technical review (ML24256A093).
Westinghouse requested the NRC staffs review and approval of the Evaluation Model (EM) presented in the TR for use by future applications utilizing the fuel kernel and compact design.
The applicants overall methodology follows NUREG-2246, Fuel Qualification for Advanced Reactors (ML22063A131).
The NRC staff provided its audit plan for the subject TR to Westinghouse via the electronic reading room and later sent the audit plan by e-mail on January 28, 2025 (ML25022A004). The audit kick-off meeting was held on January 27, 2025, and the audit was conducted from January 27, 2025, through July 9, 2025, using Westinghouses electronic reading room (eRR).
2.0 AUDIT PURPOSE AND ACTIVITIES The purpose of the audit was for the NRC staff to gain a more detailed understanding of Westinghouses verification and validation (V&V) processes to evaluate the development of a TRISO fuel particle falling outside of historic operating envelopes with little supporting data or framework for model validation. A secondary purpose of the audit is to identify any information that will require docketing to support the NRC staffs safety evaluation.
The audit followed the guidance in the Office of Nuclear Reactor Regulations Office Instruction LIC-111, Regulatory Audits, (ML24309A281). Audit activities included virtual meetings to discuss questions, the review of files shared via its electronic reading room, and code demonstrations via videoconference.
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001
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Members of the audit team included the NRC staff listed below:
Walter Williams, Reactor Systems Engineer, Audit Technical Lead Ayesha Athar, Nuclear Engineer, Technical Reviewer Vince Voltaggio, Reactor Systems Engineer Kenneth Geelhood, Pacific Northwest National Laboratory, consultant Lucieann Vechioli, Project Manager Patrick Boyle, Project Manager Michelle Vega, Project Manager On July 9, 2025, the NRC staff held the audit exit meeting with Westinghouse, summarized the audit findings, and provided an opportunity to clarify any issues related to the audit results. The NRC staff did not identify any supplementary documents or additional information required to be submitted to complete its review.
3.0
SUMMARY
OF OBSERVATIONS As indicated in the NRC staff's audit plan, the audit was focused on clarification of and needed justification for information in the TR pertaining to irradiation testing plans and scope to benchmark[.)). model V&V methods, justification for extrapolation of models outside of presented opera mg envelopes, scalability of fuel swelling and buffer layer scaling, and general clarification. Key audit observations include:
- 1. The NRC staff requested that Westinghouse either revise the scope of some areas of the review to be more specific or provide the necessary details that support the safety determination. During the audit, the NRC staff and Westinghouse discussed and agreed that the scope of the review will not be revised, and the safety evaluation report will reflect the limited safety determination.
- 2. Westinghouse has clarified that, consistent with limits posed in the TR, the methodology proposed in the TR is not meant to address conformance with Principal Design Criteria.
Such activities are deferred to future submittals.
- 3. Westinghouse proposed edits throughout the TR to clarify information in response to the audit questions. Some of these revisions are related to references to comparable Advanced Gas-cooled Reactor (AGR) fuel program data. Westinghouse addressed these inconsistencies in the TR for clarification and confirmed those revisions will be part of the -A version.
- 4. Westinghouse stated their intent to develop a benchmarking and validation case similar to RG 1.203 'T ransient and Accident Analysis Methods" (ML053500170) to be used with the implementation of this TR. The NRC staff noted that this is an acceptable methodology but does defer regulatory risk since the specifics of the approach were not shared.
- 5. Westinghouse has clarified that the outlined data in the TR is to be used for benchmarking, verification, and validation. There will also be a transient test of its design to further assist this effort.
- 6. Westin house has clarified that the osed fuel desi n OFFICIAL USE ONLY - PROPRIETARY INFORMATION
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- 7. Both the NRC staff and Westinghouse discussed and agreed that several items noted in the audit will be further evaluated during the implementation of the methodology described in the TR.
Prior to the audit exit, the NRC staff also reviewed the proposed revisions to the TR provided by Westinghouse through the eRR. During the audit exit meeting, the NRC staff informed Westinghouse that the NRC staff intends to impose limitations and conditions in the SE based in part on the material contained in the proposed revision. The limitations and conditions must be addressed by any licensee or applicant referencing the TR. The NRC staff summarized that the limitations and conditions will relate to demonstrating credibility of assumptions, operating conditions in the TR remain valid, code benchmarking and V&V.
4.0 REQUESTS FOR ADDITIONAL INFORMATION RESULTING FROM THE AUDIT As a result of the audit, the NRC staff determined that no requests for additional information related to this TR were necessary. However, the NRC staff does anticipate future submittals and interaction in this topical area.
5.0 CLOSURE PATH Westinghouse confirmed that the TR revisions agreed to during the audit will be reflected in the
-A version of the TR.