Document: NRC Regulatory Guide
Document ID: 22ccfd5e-c5d8-4615-a02c-32369aa9f533
Document Type: regulatory_guide
Title: Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1930/ML19308B636.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.200
CFR Part: 
CFR Title: 

Content:
for updating the model periodically to reflect changes that impact the significant accident sequences. The various national consensus PRA standards and industry documents that provide guidance on the development, performance, and peer reviews of PRAs are discussed, in regulatory positions C.2 through C.2.2.4 of this RG. Details of the staff’s clarifications and qualifications that support regulatory positions are provided in Appendices A, B, and C. DG-1362, Page 49 When the exceptions and clarifications raised by the staff are taken into account, the national consensus PRA standard or PRA peer review process in question is considered to be acceptable for the purpose for which it was intended. If the portions of the PRA can be shown to have met the requirements of these documents, with attention paid to the NRC’s objections, it can be assumed that the analysis is technically correct. Therefore, the staff should be able to focus on the assumptions and approximations relevant to the application (as discussed below in regulatory position C.3.3.2), and other than an audit, a detailed review by NRC staff of the base model PRA should not be necessary. When deviations from these documents exist, the applicant should demonstrate either that its approach is equivalent or that the influence on the results used in the application are such that no changes occur in the significant accident sequences or contributors. Assessment of Assumptions and Approximations Since the standards and industry PRA programs are not (or are not expected to be) prescriptive, there is some freedom on how to model certain phenomena or processes in the PRA; different analysts may make different assumptions and still be consistent with the requirements of the standard or the assumptions may be acceptable under the guidelines of the peer review process. The choice of a specific assumption or a particular approximation may influence the results of the PRA. For each application that calls upon this RG,