Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
te either that its approach is equivalent or that the influence on the results used in the application is such that no changes occur in the risk contributors. As discussed in Regulatory Position C.2.2 of this RG, a peer review is performed to determine whether the requirements established in a national consensus standard, as endorsed by the NRC with exceptions, have been met. The peer review includes assessing the appropriateness of assumptions and approximations used in the PRA. This helps ensure that the technical aspects of the PRA have been developed in a technically correct manner and consistent with industry practices. In addition to assessing the PRA against an NRC-endorsed national consensus standard, the peer review also assesses whether the methods used to develop the PRA were applied correctly and that the probabilities and frequencies used are estimated consistently with the definitions of the corresponding events in the PRA logic model and based on the best information available. The PRA model is compared against the plant design and procedures to validate that it reflects the as-designed, as-to-be-built, or as-to-be-operated plant or the as- built and as-operated plant, depending on the stage of the plant life cycle. The results of a peer review should be used to help ensure that the PRA was developed in a technically correct manner as it relates to whether the technical requirements in a national consensus standard have been met. PRA models rely on the use of approximations and assumptions that may reflect a lack of information, that may be used to address uncertainties related to specific modeling issues, or that make the models more tractable. The impact of these assumptions and approximations on the results used in support of the application should be understood. For a given PRA, different analysts may use different assumptions and approximations but still be consistent with the requirements of the national consensus standard, or the assumptions