Document: NRC Regulatory Guide
Document ID: b3da4d67-03d8-4f52-b04b-8e76d142c857
Document Type: regulatory_guide
Title: Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors + HISTORY - HISTORY 05/2019 – Issued DG-1353 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1831/ML18312A242.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.233
CFR Part: 
CFR Title: 

Content:
ed capabilities have helped to mitigate the consequences of the LBE. The safety classification process and the corresponding special treatments to ensure reliabilities and capabilities of SCCs thereby serve to control the frequencies and consequences of the LBEs in relation to the F-C target and ensure that the cumulative risk targets are not exceeded. SSC safety margins play an important role in the development of SSC design requirements for reliability and performance capability. NEI 18-04 describes how a designer sets acceptance limits on SSC performance with safety margins between the level of performance that is deemed acceptable in the safety analysis and the level of performance that would lead to damage or adverse consequences for all the LBEs in which the SSC performs a preventive or mitigative function. The magnitudes of the safety margins in performance are set considering the uncertainties in performance, the nature of the associated LBEs, and criteria for adequate DID. The ability to achieve the acceptance criteria, in turn, reflects the design margins that are part of the SSC capability to mitigate the challenges reflected in the LBEs. C.2 Staff Position: NEI 18-04 provides an acceptable method for assessing and classifying non-LWR SSCs as SR, NSRST, or non-SR with no special treatment. The staff offers the following clarifications: a. The SSC classifications and logic outlined in NEI 18-04 are part of an integrated methodology, which includes a defined relationship among LBEs, equipment classification, and assessments of DID for non-LWRs. The classifications and related outcomes may not apply for alternative approaches that do not follow the other parts of the NEI 18-04 methodology. The staff expects that SSCs that provide essential support (including required human actions) for SR or NSRST SSCs will be classified in a manner consistent with the higher-level function, even if the supporting SSC is not explicitly modeled in the PRA. b. The SSC