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
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CFR Title: 

Content:
rectly reflected in the choice of the value of the measure used to determine whether an SSC should be classified as being of high or low safety significance. This i!3 a concern whether importances are evaluated at the component or group level. Therefore, the criteria for categorization into low and high significance should be related to the acceptance guidelines for changes in CDF and LERF. This implies that the criteria should be a function of the base case CDF and LERF, rather than being fixed for all plants. Thus. reviewers should determine how the choice of criteria relates to, and conforms with, the acceptance guidelines described in RG 1.174. If component level criteria are used, they should be established taking into account the fact that the allowable risk increase associated vwith the change should be determined on the basis of simultaneous changes to all members of the category. c. Evaluation Findings The SER should incorporate language equivalent to the following, and exceptions (if any) should be noted and explained. 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 the use of both CDF and LERF, completeness of the risk model, and sensitivity of the results to SRP 19-C4 data uncertainties, common cause failure modeling, modeling of human reliability, and truncation limits used. 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 Decisionmakincq 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