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:
rors, CCFs, and maintenance unavailabilities) are simultaneously modified and the importance measures of the SSCs recalculated. These studies are performed to ensure that assumptions in these types of analyses are not masking SSC importance. The NRC finds the identified sensitivity studies reasonable and they are to be used in the categorization of SSCs. Therefore, if based on any of these sensitivity studies, an SSC is identified as being safety-significant, then this basis must be documented and the SSC must be considered safety-significant. SSCs must be categorized according to the highest safety significance determined, including these sensitivity study results and the results of any other pertinent considerations (e.g., defense-in-depth, shutdown risks, etc.). 9. Section 5.1 The NRC has not formally endorsed ASME Code Cases N-577 and N-578. The NRC staff review of the ASME Code Cases is expected to be completed prior to promulgating 10 CFR 50.69. The NRC staff notes that staff positions on the ASME Code Cases are provided in regulatory guides referenced in 10 CFR 50.55a. If and when endorsed by the NRC, the ASME risk-informed Code Cases on categorization and treatment will satisfy the applicable portions of the proposed 10 CFR 50.69. However, at this time, a licensee cannot assume that using the methods described in these code cases will be acceptable. The NRC has endorsed WCAP- 14572 and EPRI TR-112657, which include guidance for the categorization of piping segments, but not individual SSCs, for the purpose of reducing the number of inservice inspections on piping welds. NEI 00-04 does not provide a description of a methodology for categorization that addresses the passive pressure boundary (i.e., pressure retention capability) for the purpose of exempting SSCs from special treatment requirements in sufficient detail for the staff to endorse. Therefore, the endorsement of NEI 00-04 does not adopt any method to categorize the safety significance of the passive