Document: NUREG-0800
Document ID: 012eaab8-824c-49d3-b5d8-7cb652f166f0
Document Type: srp
Title: B-5
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550087.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
CFR Part: 
CFR Title: 

Content:
Revision 5 - March 2007 4. REQUIREMENTS 4.1. General Functional Requirements (IEEE Std. 279-1971 Clause 4.1) Clause 4.1 of IEEE Std. 279-1971 requires in part that the protection system shall, with precision and reliability, automatically initiate protective action for the range of conditions and performance enumerated in Clauses 3(7) through 3(9) of IEEE Std. 279-1971. The applicant/licensee's analysis should confirm that the protection system has been qualified to demonstrate that the performance requirements are met. The evaluation should confirm that the general functional requirements have been appropriately allocated to the various system components. Automatic initiation is required for all protective functions; a manual initiation capability is also a requirement (see Clause 4.17 of IEEE Std. 279-1971 and Regulatory Guide 1.62, "Manual Initiation of Protection Actions"). The evaluation of the precision of the protection system is addressed to the extent that setpoints, margins, errors, and response times are factored into the analysis. The topic of reliability is addressed in the following paragraphs. 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