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:
the proposed change and quantification of the expected change in risk using plausible models of the impact on SSC unavailability to the extent that the affected components are included in the plant's PRA. For other risk-informed applications, however, it may not be feasible to explicitly model the cause-and-effect relationship because the resulting actual impact on component unavailability is not clearly understood. For such applications, the use of risk categorization techniques provides a useful way to identify groups of SSCs that are less risk important to risk and, as such, are possible candidates for a graded approach to regulatory requirements. Using such a categorization approach, however, it is still necessary to understand the potential or bounding impact of the proposed change, and to assess the risk impact through appropriate sensitivity studies. In either the detailed quantification approach or the risk categorization approach, risk results should be derived from analyses of appropriate quality. Section 111.2.2.4 and Appendix A to this SRP chapter present guidelines to help reviewers evaluate PRA quality as a function of the application. Finally, Appendix C to this SRP chapter discusses review issues related to the determination of risk contribution and component categorization. SRP 19-13 111.2.2.1 Characterization of Change in Terms of PRA Model Elements Where quantitative PRA results are used as part of a risk-informed evaluation of a proposed change, the licensee should define the change in terms that are compatible with the risk analysis, i.e., the risk analysis should be able to effectively evaluate the effects of the change. The approach to risk characterization should establish a cause-effect relationship to identify portions of the PRA affected by the issue being evaluated. This includes (i) identifying the specific PRA contributors for the particular application, (ii) assessing the portions of the model that should be modified for the