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:
results of the peer review, resolution of the Facts and Observations (F&Os), and how the PRA conforms to the requirements in the national consensus PRA standards. Use of the ASME/ANS NLWR PRA standard and NEI 20-09, Revision 1, as endorsed by the NRC in this RG, reduces the need for an in-depth staff review of the PRA. C.2.1 National Consensus Probabilistic Risk Assessment Standards National consensus PRA standards provide requirements for an acceptable PRA. However, it is recognized that a PRA may not always need to satisfy each technical requirement to the same degree. The NLWR PRA standard features two capability categories (CCs), CC-I and CC-II, which are used to distinguish between greater and lesser scopes, levels of detail, plant representation, and realism needed for a given technical requirement. When a supporting requirement (SR) provides a different requirement for each capability category, the CC-I requirement generally fosters identification of the most risk- significant event sequences at a functional or systemic level. The CC-II requirement fosters the development of a realistic assessment of risk. The CC achieved for the different technical requirements may vary. In terms of the staff position in this RG, this variation can range from the minimum capability needed to meet the characteristics and attributes for each PRA element (i.e., CC-I) to the minimum capability needed to meet current good practice (i.e., state-of-practice) for each PRA element (i.e., CC-II). Further, the capability category that needs to be met for each technical requirement depends on the application. In general, the staff anticipates that meeting CC-II should result in an acceptable scope, level of detail, and realism for most applications. However, for some applications, CC-I may be acceptable for some requirements. The requirements in an ASME/ANS PRA standard are either process related or technical. Process-related requirements address the process for development,