Document: NRC Regulatory Guide
Document ID: 2459a562-8984-421c-8058-d096dbb9617c
Document Type: regulatory_guide
Title: Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to Their Safety Significance
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0314/ML031430373.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.201
CFR Part: 
CFR Title: 

Content:
ation Guideline.” (ADAMS Accession No. ML021910534). Section numbers refer to those of Draft Revision C of NEI 00-04, dated June 2002. A. Quality Attributes. As discussed in Regulatory Position 6 of DG-1121, applicants for implementation of 10 CFR 50.69 will need to prepare arguments about the quality and adequacy of the methods to be used for external events and non-probabilistic risk assessment (PRA) analyses. To facilitate these reviews, the NRC staff recommends that the industry develop guidance as to the expected quality attributes of the external events PRA and non-PRA type analyses that are required for use in the Option 2 categorization process. B. Determination of Potential Risk Increase with Non-PRA Methods. In Draft Revision C of NEI 00-04, the final step in the allocation of SSCs into the different risk-informed safety classes (RISC) categories is to show that the reduction in treatment of low safety-significant (LSS) structures, systems, and components (SSCs) will not result in a significant increase in risk. This is done by performing the risk sensitivity study, discussed in Section 8, based on increasing the failure probabilities of those SSCs for which treatment is proposed to be relaxed. This risk sensitivity study is a very important part of the categorization process. The choice of the factor to use in increasing the failure probabilities of LSS SSCs with reduced treatment must be based either on some reasonable expectation that it is bounding or that it is such that the change in unreliability that it represents will be detected and corrected by the monitoring, corrective action, and feedback processes. The NRC staff recommends that the industry develop a method to determine the appropriate factor to be used in the risk sensitivity study and provide the appropriate guidance for implementing the monitoring, feedback, and corrective action processes to ensure that potential performance degradations will not invalidate the factor used in the risk