Document: NUREG-0800
Document ID: ac43f632-9db1-4857-9f56-bfba45965456
Document Type: srp
Title: * These are modifications to a plant’s design, operations, or other activities that require NRC approval. These modifica
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0232/ML023250195.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19
CFR Part: 
CFR Title: 

Content:
ined. • The information provided to the integrated decisionmaking process with regard to determining the risk importance of contributors for a specific application is robust in terms of model inputs and assumptions, including issues like the use of both CDF and LERF, completeness of the risk model, and sensitivity of the results to data uncertainties, common cause failure modeling, modeling of human reliability, and truncation limits used. SRP 19-C5 • The categorization addresses the effect of the change on groups of components in a way that is compatible with the risk acceptance guidelines. C.2 Role of Integrated Decisionmaking in Component Categorization a. Areas of Review While probabilistic importance analysis can provide valuable information 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