Document: NUREG-0800
Document ID: e32f0820-4e33-476e-aa36-4ca8c2c64af0
Document Type: srp
Title: Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking:
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0119/ML011940192.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
e frequency of the given event, the plant systems or other features available to mitigate the event, and the consequences of the event if unmitigated. Proposed plant changes could affect the frequency of initiating events, the probability of mitigating event initiators and, in some cases, event consequences. In addition, plant changes could potentially introduce new initiating events or increase the importance of events that were previously screened out. b. Review Guidance and Procedures SRP 19-Al For risk-informed applic'ations, reviewers should determine if the licensee followed a systematic approach to determine if initiating events and anticipated plant response are affected by the proposed changes. Reviewers should also determine if the licensee's process includes provisions to evaluate whether the proposed changes can (i) increase the frequency of an initiator already included in the PRA; (ii) increase in the frequency of initiators that were initially screened out in the PRA; (iii) introduce new initiating events; or (iv) affect the grouping of initiating events. These considerations are discussed in more detail in the following paragraphs. Applications that change the frequency of an initiator or the ability of the plant to respond to event initiators are relatively easy to model in the risk analysis if the initiators are already included in the base analysis. In such cases, the licensee should have evaluated the impact of the changes directly from the risk model. In cases where initiators are not included in the original risk analysis based on screening analyses, the licensee should have determined if initiating events previously screened out because of low frequency might now be above the screening threshold as a result of a proposed application. Plant changes could increase the frequency of initiating events that were relatively infrequent to begin with, or these changes could affect SSCs or operator actions that were credited with the satisfactory