Document: NUREG-0800
Document ID: e427eac9-c153-4d33-b744-70711f982d6e
Document Type: srp
Title: B-9
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 4.6. Channel Independence (IEEE Std 279-1971, Clause 4.6) Two aspects of independence should be addressed: • Physical independence. • Electrical independence. Guidance for evaluation of physical and electrical channel independence is provided in RG 1.75, “Criteria for Independence of Electrical Safety Systems,” which endorses IEEE Std 384, “IEEE Standard Criteria for Independence of Class 1E Equipment and Circuits.” The applicant or licensee should confirm that the protection system design precludes the use of components that are common to redundant channels, such as common switches for actuation, reset, mode, or test; common sensing lines; or any other features that could compromise the independence of redundant channels. Physical independence is attained by physical separation and physical barriers. Electrical independence shall include the utilization of separate power sources. The organization responsible for the review of electrical systems reviews power source requirements. Reviewers in the organization responsible for the review of I&Cs should coordinate with the electrical systems reviewers to confirm that I&C protection system power sources are adequate. Transmission of signals between independent channels should be through isolation devices. SRP BTP 7-11, “Guidance on Application and Qualification of Isolation Devices,” provides guidance for the application and qualification of isolation devices. 4.7. Control and Protection System Interaction (IEEE Std 279-1971, Clause 4.7) Control and protection system interaction involves more than examining the electrical isolation and interconnection. The functional performance of control systems must be such that a control system cannot prevent proper action of a protection system. Clause 4.7 of IEEE Std 279-1971, with regard to isolation devices and multiple failures resulting from a credible single event, is explained by example in Clause 4.2 of IEEE Std 279-1971. The