Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
nt inventory, containment isolation, and containment integrity) are examples representative of operating light-water reactors. Other types of reactors may have different critical safety functions. The identification of these critical safety functions is a plant-specific activity performed by applicants that is based on the reactor design safety analysis and may be risk-informed. Risk-informed approaches may be used to identify the most important safety functions to be accomplished or maintained to prevent a direct and immediate threat to public health and safety. Section 4 of this BTP provides acceptance criteria for the implementation of diverse and independent displays and manual controls for actuation of critical safety functions. 2. Safety Significance and Effects of Failure Principle 3 of SECY-18-0090 explains that the D3 assessment “may not be necessary for some low-safety-significance l&C systems whose failure would not adversely affect a safety function or place a plant in a condition that cannot be reasonably mitigated.” Point 1 of SRM-SECY-22-0076 states that the D3 assessment must be commensurate with the risk significance of the DI&C system, as described further below. Furthermore, Point 3 of SRM-SECY-22-0076 states that the level of technical justification demonstrating the adequacy of design techniques, prevention measures, or mitigation measures, other than diversity, credited in the assessment to address potential CCFs must be commensurate with the risk significance of each postulated CCF. This section provides guidance for reviewing (1) the relative safety significance of the functions performed by an SSC and (2) an application that does not include a detailed D3 assessment for an SSC of lowest safety significance based on the potential effects of the SSC’s failure. 2.1 Safety-Significance Determination For the purposes of this BTP, a safety-significant function is one whose degradation or loss could have a significant adverse effect on