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:
for all expected performance uncertainties. RIS 2006-17 and TSTF-493, Revision 4, address this concern by identifying the as-found tolerance (AFT) limit as a benchmark for assessing instrument channel operability, rather than an allowable value. RIS 2006-17 states that if the as-found setpoint measured during a surveillance is outside predefined limits (double-sided acceptance criteria band), the instrument channel equipment being tested shall be immediately evaluated to determine whether the channel is functioning as expected for operability before returning it to service. If it is found to be not operable, then the licensee should take appropriate action as required by the plant corrective action program and/or the plant technical specifications. Sections 3, 4.5.5, and 4.6 of ANSI/ISA 67.04.01-2018 provide definitions that the NRC staff finds useful for establishing and accounting for AFT and as-left tolerance (ALT) when performing setpoint analyses, as well as acceptance criteria that the staff finds useful for performing technical specification-required surveillances. The definitions and use of these concepts are consistent with staff positions on the use of AFT and ALT presented in NRC RIS 2006-17 and TSTF-493, Revision 4. Under 10 CFR 50.90, “Application for amendment of license, construction permit, or early site permit,” a licensee may submit a license amendment request (LAR) that revises its technical specifications to implement a setpoint control program, as described in TSTF-493, Revision 4, Option B. Once the NRC staff approves the setpoint control program in the LAR, the program would allow for controlling the setpoint values outside of the technical specifications. The setpoint control program would ensure instrumentation will function as required and provide the licensee flexibility to revise setpoints without requiring a license amendment. The setpoint control program should implement a setpoint calculation methodology that the NRC has reviewed