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:
modifications to the existing basis. It is expected that some applications will seek to modify the LB in risk-informed submittals. Applications that seek to make qualitative changes to the LB (such as moving components out of the scope of a required program) should be reviewed in greater detail with respect to defense in depth and safety margins when compared to applications that seek to make parametric changes (such as incremental changes to surveillance interval). SRP 19-13 III.2.2 Risk Assessment For effective implementation of risk-informed regulatory approaches, reviewers should ensure that the licensee has demonstrated that the plant’s design and actual operating conditions and practices are properly reflected in the risk insights derived using the plant-specific PRA model. Otherwise, the risk assessment may provide inaccurate or misleading information that will require careful scrutiny before use in any regulatory decisionmaking process. Development of a plant-specific, risk-informed program also requires the availability of information to identify the SSCs and human actions that contribute most significantly to the plant’s estimated risk. In addition, it is necessary to be able to capture the impact of the proposed change on the elements of the PRA. Section III.2.2.1 of this SRP chapter discusses the characterization of the proposed change in terms of PRA model elements. The results of this determination of the cause-effect relationships between the proposed application and the PRA models will help define the scope and level of detail required for the PRA to support the application. Sections III.2.2.2 and III.2.2.3 discuss these topics. Many applications, such as those involving changes in component test intervals, allow explicit PRA modeling of the impact of 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