Document: NUREG-0800
Document ID: 4b0fa4a0-ce32-4f59-9360-9426826a668c
Document Type: srp
Title: Rev. 4 — June 1997
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500496.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
es to confirm that I&C safety system power sources are adequate. The review of channel integrity should confirm that the design provides for protection systems to fail in a safe state, or into a state that has been demonstrated to be acceptable on some other defined basis, if conditions such as disconnection of the system, loss of energy, or adverse environments are experienced. This aspect is typically evaluated through evaluation of the applicant/licensee's failure modes and effects analysis. The analysis should justify the acceptability of each failure effect. RTS functions should typically fail in the tripped state. ESFAS functions should fail to a predefined safe state. For many ESFAS functions this predefined safe state will be that the actuated component remains as-is. 7. Section 4.6 — Channel Independence Two aspects of independence should be addressed: • Physical independence. Rev. 4 — June 1997 SRP 7.1-B-7 • Electrical independence. Guidance for evaluation of physical and electrical channel independence is provided in Reg. Guide 1.75, "Physical Independence of Electrical Systems," which endorses IEEE Std 384, "IEEE Standard Criteria for Independence of Class 1E Equipment and Circuits." The applicant/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. (EELB and SPLB review power source requirements. HICB reviewers should coordinate with these branch requirements to confirm that I&C safety system power sources are adequate.) Transmission of signals between independent channels should be through isolation devices. BTP HICB-11 provides guidance for the