Document: NUREG-0800
Document ID: 9b1d30d6-5422-403a-bfae-ffa674dbbb75
Document Type: srp
Title: B-6
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A091.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
CFR Part: 
CFR Title: 

Content:
Revision 6 – August 2016 Staff acceptance of system reliability is based on the deterministic criteria described in IEEE Std 279-1971 rather than on quantitative reliability goals. The NRC staff does not endorse the concept of quantitative reliability goals as a sole means of meeting the requirements for reliability of protection systems. Quantitative reliability determination, using a combination of analysis, testing, and operating experience can provide an added level of confidence in the reliable performance of the I&C system. The applicant/licensee should justify that the degree of redundancy, diversity, testability, and quality provided in the protection system design is adequate to achieve functional reliability commensurate with the safety functions to be performed. 4.2. Single-Failure Criterion (IEEE Std 279-1971, Clause 4.2) Clause 4.2 of IEEE Std 279-1971 requires in part that any single failure within the protection system shall not prevent proper protective action at the system level when required. The applicant’s or 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 RG 1.53, “Application of the Single-Failure Criterion to Safety Systems,” which endorses IEEE Std 379, “IEEE 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 organization responsible for the review of reactor systems to establish redundancy requirements. Components and