Document: NUREG-0800
Document ID: f4b8f0c1-9a14-46be-88c9-a6cb74d64dff
Document Type: srp
Title: Rev. 4 — June 1997
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500499.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
irements. Most of these items identify deterministic criteria that, if met, will normally provide the level of reliability needed for safety systems. These criteria may be relevant for both individual system elements, as well as the system as a whole. 6. Section 5.1 — Single-Failure Criterion This section requires that any single failure within the safety system shall not prevent proper protective action at the system level when required. The applicant/licensee's analysis should confirm that the requirements of the single-failure criterion are satisfied. Guidance in the application of the single-failure criterion is provided in Reg. Guide 1.53, "Application of the Single-Failure Criterion to Nuclear Power Plant Protection Systems," which endorses ANSI/IEEE Std 379, "Standard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems." Where it is determined that the spatial dependence of a parameter requires several sensor channels to ensure plant protection, the redundancy requirements are determined for the individual case. In certain designs, for example, adequate monitoring of core power requires a minimum number of sensors arranged in a given configuration to provide adequate protection. This aspect of redundancy is dealt with in coordination with the Reactor Systems Branch (SRXB) to establish redundancy requirements. Components and systems not qualified for seismic events or accident environments and non-safety-grade components and systems are assumed to fail to function if failure adversely affects safety system performance. These components and systems are assumed to function if functioning adversely affects safety system performance. All failures in the safety system that can be predicted as a result of an event for which the safety system is designed to provide a protective function are assumed to occur if the failure adversely affects the safety system performance. In general, the lack of equipment qualification may