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:
n should aid the operator in recognizing the effects on plant safety of seemingly unrelated or insignificant events. Therefore, the indication of bypass conditions should be at the safety group level, whether or not it is also at the channel, component, or module level. Clause 5.8.3.1 of IEEE Std 603-1991 states that “this display instrumentation need not be part of the safety systems.” The indication system should be designed and installed in a manner that precludes the possibility of adverse effects on plant safety systems. The bypass and inoperable status indications may be provided via operator workstations or hardwired indicators and analog signal processing circuits. DG-1205, Page 5 However, Clause 5.6.3.1(1) of IEEE Std 603-1991 specifies that “equipment that is used for both safety and nonsafety functions shall be classified as part of the safety systems.” Therefore, if the bypassed and inoperable status indication is used for both safety and nonsafety functions, then the indication system will require classification as part of safety systems. Unless the indication system is designed in conformance with criteria established for safety systems, it should not be used to perform functions that are essential to safety, and administrative procedures should not require immediate operator action based solely on bypass indications. Therefore, if the design or administrative procedures establish the bypassed and inoperable status indication as an element of the safety system, then the following paragraphs addressing single failure, independence, and qualification would apply. If bypass and inoperable status indication is deemed to be part of a safety system, then the single- failure criterion of IEEE Std 603-1991, Clause 5.1, would apply to the indication 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