Document: NRC Regulatory Guide
Document ID: bcbe26a0-004f-4616-b7f4-b32b2bfe4909
Document Type: regulatory_guide
Title: Setpoints for Safety-Related Instrumentation (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2005/ML20055G823.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.105
CFR Part: 
CFR Title: 

Content:
1. Reason for Revision This revision of RG 1.105 describes a method that is acceptable to the staff for use in complying with the agency’s regulations to ensure that: a) setpoints for safety-related instrumentation are established to protect plant safety and analytical limits, and b) the maintenance of instrument channels implementing these setpoints ensures they are functioning as required, consistent with the plant technical specifications. This revision endorses ANSI/ISA S67.04-2018, which provides a basis for establishing setpoints for nuclear instrumentation for safety systems. 2. Background 2.1 Introduction Safety analyses and design bases for systems and components used in a nuclear power plant demonstrate or provide reasonable assurance that safety limits will be adequately protected under normal and anticipated conditions. Safety analyses and design bases include assumptions that important protective actions will be initiated when key process parameters exceed preanalyzed limits. It is important that those analyses and design bases adequately bound both actual plant conditions and actual equipment operation; otherwise, the conclusions of the safety analyses might not be valid, or the protection intended by the design bases might not be attained. The ability of plant safety systems to achieve their required functional performance depends, in part, on proper selection of instrument setpoints. Therefore, assumptions contained within the analyses concerning the capabilities of instrumentation equipment to achieve required setpoints and other aspects of instrument operation should be verified through setpoint analyses to ensure the conclusions of the safety analyses bound the actual operation of the safety-related instrument channels. Also, licensees should monitor the performance of safety-related instrument channels to ensure that the instrument channel performance during operations is consistent with those assumptions. This RG provides guidance to address