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:
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 and approximations may be acceptable under the guidelines of the peer review process, as endorsed by the NRC. The choice of a specific assumption or a particular approximation or assumption is considered to be key if it can influence the results of the PRA and, therefore, influence the application under consideration. For each application that uses this RG to meet regulatory requirements, the assumptions and approximations relevant to that application and those that are key to that application are identified. The key assumptions are used to identify sensitivity studies that RG 1.247, Page 62 inform the decision-making associated with the application. When a key assumption is shown to be consistent with a consensus method or approach, that key assumption is not likely to be subject to additional sensitivity studies in the context of an application, as determined on a case-by-case basis. Based on an understanding of how the PRA model is to be used to achieve the desired results, the licensee should have identified the parts of the PRA for each hazard group required to support a specific application. This includes the following two categories of items: (1) the PRA logic model elements onto which the cause-effect relationships are mapped (i.e., those directly affected by the application), and (2) all the events with mapped cause-effect relationships that appear in the event sequences. For some applications, this may be some subset of all items in the PRA, but for others (e.g., risk-informing the scope of special treatment requirements), all parts of the PRA model may be relevant. The current state-of-practice in PRA technology reflects that there are issues where there is no consensus on the method of analysis. However, in the context of risk-informed regulatory decisions,