Document: NRC Regulatory Guide
Document ID: 30181e34-3bc1-46b8-8de9-ef073c34bc13
Document Type: regulatory_guide
Title: Bypassed and Inoperable Status Indication for Nuclear Power Plant Safety Systems + HISTORY - HISTORY 10/2008 – DG-1205 , Proposed Revision 1 (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0821/ML082140114.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.47
CFR Part: 
CFR Title: 

Content:
system. Regulatory Guide 1.53, “Application of the Single-Failure Criterion to Safety Systems” (Ref. 6), endorses IEEE Std 379-2000, “IEEE Standard Application of the Single-Failure Criterion to Nuclear Power Generating Station Safety Systems” (Ref. 7), as an acceptable method to meet the regulations concerning the application of the single-failure criterion to the electrical power, instrumentation, and control portions of nuclear power plant safety systems. Digital system common-cause failures are not treated as a single failure with respect to the single-failure criterion. IEEE Std 7-4.3.2-2003, “IEEE Standard Criteria for Digital Computers in Safety Systems of Nuclear Power Generating Stations” (Ref. 8), provides guidance on using diversity to address common-cause failures in computer-based safety systems. In addition, NUREG/CR-6303, “Method for Performing Diversity and Defense-in-Depth Analyses of Reactor Protection Systems” (Ref. 9), describes a method for analyzing computer-based nuclear reactor protection systems to identify design vulnerabilities to common-mode failure. In addition to meeting the single-failure criterion, if bypass and inoperable status indication is deemed to be part of a safety system, then maintaining independence between redundant portions of the safety system is essential to the effective utilization of the single-failure criterion. Regulatory Guide 1.75, “Independence of Electrical Safety Systems” (Ref. 10), provides guidance through the application of IEEE Std 384-1992, “IEEE Standard Criteria for Independence of Class 1E Equipment and Circuits” (Ref. 11), to meet the regulations with respect to the physical independence requirements of the circuits and electric equipment that comprise or are associated with safety systems. Regulatory Guide 1.152, “Criteria for Digital Computers in Safety Systems of Nuclear Power Plants” (Ref. 12), endorses IEEE Std 7-4.3.2-2003 as an acceptable method for addressing high