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:
human actions, it is reasonable to expect that the categorization could be different for different applications. Thus, the question being addressed by the application is, for which groups of SSCs and human actions can the change be made such that there will be no more than an insignificant increase in the risk to the health and safety of the public. This impact on overall risk should be related back to the criteria for acceptable changes in the risk measures identified in Regulatory Guide 1.174. It is those groups for which changes can be made that satisfy these criteria that can be regarded as low safety-significant in the context of the specific application. Thus, the most appropriate way to address the categorization is through a requantification of the risk measures. However, the feasibility of performing such risk quantification has been questioned for those applications for which a method for evaluating the impact of the change on SSC unavailability is not obviously available. In such instances, an acceptable alternative to requantification of risk is to categorize SSCs and human actions using an integrated decisionmaking process (such as the use of an Expert Panel), with PRA importance measures as input. This appendix discusses the issues that reviewers should address for this approach. Section C.1 discusses the technical issues associated with the use of SRP 19-C2 PRA importance measures, and Section C.2 discusses the use of the importance measures by the decisionmaking panel. C.1 Use of Importance Measures a. Areas of Review In the implementation of the Maintenance Rule and in many industry guides for the risk-informed applications, the measures most commonly identified for use in the relative risk ranking of SSCs and human actions include the Fussell-Vesely Importance, Risk Reduction Worth, and Risk Achievement Worth. However, in using these importance measures for risk-informed applications, several issues should be addressed. Most of these issues relate