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:
orm its safety functions will be detected in a timely fashion 9. Relaxing the requirements will have a minimal impact on the expected onsite occupational or offsite doses from transients and accidents that do not contribute to CDF or LERF. The specific considerations that permit a LSS determination of an SSC in a safety-significant functional flow path must not be limited to just active failure modes, but must consider all potential failure modes for the subject SSC. The NRC staff does not generically endorse the examples provided under the specific considerations that permit a LSS determination of an SSC in a safety-significant functional flow path. The specific conditions and criteria must be justified and documented for the specific SSCs under consideration. For example, a 1-inch diameter line off a small diameter pipe might create a large enough diversion path that would impair the system from meeting its safety- significant function. Thus, such a criteria would not be appropriate in determining that the SSC is LSS. 22. Sections 11.1 and 11.2 This section discusses the expansion of the licensee’s design/configuration change control process to provide reasonable assurance that the safety-significant beyond design basis functions under 10 CFR 50.69 will be satisfied following a facility change. The NRC staff agrees with the need for the licensee’s implementing 10 CFR 50.69 to expand their design/configuration change control process, as above, but also requires that this expansion include an evaluation to ensure that the categorized SSCs, considering both their design basis and beyond design basis functions, also are maintained within the assumptions of the categorization process (i.e., reliability of LSS SSCs is maintained within the potential reduction in reliability assumed in the risk sensitivity study of Section 8 of NEI 00-04 and the reliability of safety-significant SSCs is maintained in accordance with their reliability assumed in the analysis) and must