ML25303A299
| ML25303A299 | |
| Person / Time | |
|---|---|
| Site: | Kemmerer File:TerraPower icon.png |
| Issue date: | 11/06/2025 |
| From: | NRC/NRR/DANU |
| To: | |
| References | |
| Download: ML25303A299 (1) | |
Text
THIS NRC STAFF DRAFT SE HAS BEEN PREPARED AND IS BEING RELEASED TO SUPPORT INTERACTIONS WITH THE ACRS. THIS DRAFT SE HAS NOT BEEN SUBJECT TO FULL NRC MANAGEMENT AND LEGAL REVIEWS AND APPROVALS, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS.
OFFICIAL USE ONLY - PROPRIETARY INFORMATION 3
LICENSING BASIS EVENTS 3.1 Probabilistic Risk Assessment 3.1.1 Introduction Section 3.1 of the Kemmerer Unit 1 (KU1) preliminary safety analysis report (PSAR) describes the KU1 probabilistic risk assessment (PRA) and the use of PRA as the primary tool for implementing the risk-informed, performance-based methodology established under the Licensing Modernization Project (LMP). This methodology is outlined in Nuclear Energy Institute (NEI) 18-04, Risk-Informed Performance-Based Technology Inclusive Guidance for Non-Light Water Reactor Licensing Basis Development, Revision (Rev.) 1 (ML19241A472), and is endorsed with clarifications by the NRC in Regulatory Guide (RG) 1.233, Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors, Rev. 0 (ML20091L698).
The KU1 PRA serves as a key input to several elements of the LMP framework, including:
Identification of licensing basis events (LBEs);
Classification of structures, systems, and components (SSCs), along with the determination of their associated special treatment requirements; Derivation of design basis accidents (DBAs); and Evaluation of the adequacy of defense-in-depth (DID) measures.
The KU1 PRA is also used to evaluate overall plant risk against the following risk evaluation criteria described in section 3.2.2, step 7b of NEI 18-04 and addressed in PSAR section 4.1:
The total frequency of events resulting in a site boundary dose exceeding 100 mrem should not exceed 1/plant-year; The average individual risk of early fatality within 1 mile of the exclusion area boundary (EAB) should not exceed 5x10-7/plant-year; and The average individual risk of latent cancer fatality within 10 miles of the EAB should not exceed 2x10-6/plant-year.
As part of its safety review, the staff evaluated how USO developed the construction permit (CP) stage PRA, used it to develop the preliminary KU1 licensing basis following the LMP approach, and applied specific risk insights throughout the KU1 PSAR. The staff followed the guidance in Appendix A of RG 1.253, Guidance for a Technology-Inclusive Content-of-Application Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light-Water Reactors, Rev. 0 (ML23269A222) to review the KU1 CP stage PRA within the context of the LMP framework. Appendix A provides guidance on the expected scope, level of detail, and quality of a PRA suitable for the CP stage,