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:
ion regarding categorization of SSCs or human actions, it should be supported and supplemented by an evaluation based on traditional engineering considerations. This will require using the qualitative insights obtained from the PRA, and considering the maintenance of the defense-in-depth philosophy and sufficient safety margins. One important element of this integrated decisionmaking can be the use of an "expert panel." This section provides guidelines for reviewing the licensee's integrated decisionmaking process in the area of importance categorization, and it supplements the general guidance in Appendix B to this SRP chapter. b. Review Guidance and Procedures Identification of functions, systems, and components important to safety: The PRA can provide significant qualitative insights that emerge simply from considering whether and how systems are invoked in particular scenarios. If a front-line system is credited in success paths, it is "important" in some sense, and at least some of its SSCs must also be important in some sense, even if a given single-event importance measure does not reflect this. However, the real importance of a system is a function of whether alternative, diverse systems that could fulfill the same function. Those systems which are the only means of providing the function would be considered more important than those for which there are viable alternatives. A system that supports an important front-line system could also be considered important. This does not mean that all such systems cannot be candidates for relaxing current requirements; however, it does mean that components in system trains credited in the PRA should be explicitly considered during the integrated decisionmaking process. Either by evaluating the licensee's documentation or by conducting an independent verification, reviewers should complete the following steps: * Identify all systems that are relied upon in plant response to an initiating event, whether explicitly modeled