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:
, since they play a role in preventing core damage or large early release. These SSCs and human actions may include those that do not necessarily appear in the final quantified model because they have initially been screened, are assumed to be inherently reliable, or have been truncated from the solution of the model. In addition, there may be SSCs or human actions not modeled in the PRA that have the potential to be safety significant because they play a role in preventing core damage or large early release. In reviewing the categorization, it is important to recognize its underlying purpose. Categorization is generally intended to sort the SSCs or human actions into two general groups; those for which some change is proposed, and those for which no change is proposed. It is the potential impact of the application on the particular SSCs and human actions and on the measures of risk which ultimately determines which SSCs and human actions should be regarded as safety-significant. Since different applications impact different SSCs and 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 RG 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