Document: NRC Regulatory Guide
Document ID: db0c5d18-2d27-4720-8935-40b402e52f9a
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:
sk metrics selected for evaluating the total risk from all analyzed LBEs o non-SR SSCs relied on to perform functions requiring special treatment for DID adequacy • nonsafety-related with no special treatment: o all other SSCs (with no special treatment required) Within the methodology used in NEI 18-04, safety-significant SSCs include all those SSCs classified as SR or NSRST. None of the non-SR with no special treatment SSCs are classified as safety significant, but they may have requirements to ensure that failures following a design-basis internal or external event do not adversely impact SR or NSRST SSCs in their performance of safety-significant functions. The methodology in NEI 18-04 includes defining performance criteria for the reliability and capability of the SSCs fulfilling safety-significant functions for non-LWRs. Table 4-1, “Summary of Special Treatment Requirements for SR and NSRST SSCs,” in NEI 18-04 gives examples of such requirements. For SSCs classified as SR, required functional design criteria (RFDC) and lower-level design criteria are defined to capture design-specific criteria that may supplement or may not be captured by the principal design criteria for a reactor design developed using the guidance in RG 1.232. These criteria are used within the methodology to frame specific design requirements as well as special treatment requirements for SR SSCs. NEI 18-04 states that NSRST SSCs are not directly associated with RFDC but are subject to special treatment as a result of risk significance or assessments of DID. The RFDC, design requirements, and special-treatment requirements that result from the methodology in NEI 18-04 also define key aspects of the SSCs that will be described in safety analysis reports. NEI 18-04 describes some non-LWR SSCs as having specific “barrier functions,” in which the SSC serves as a physical or functional barrier to the transport of radionuclides. “Barrier functions” can also include indirect