Document: NRC Regulatory Guide
Document ID: 30e6fa68-c7c1-4266-ba45-e06d1bbc07a0
Document Type: regulatory_guide
Title: Criteria for Accident Monitoring Instrumentation for Nuclear Power Plants (Rev. 5)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1708/ML17083A134.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.97
CFR Part: 
CFR Title: 

Content:
aking for support of the mitigation strategy or for support of emergency preparedness functions. If redundant instrumentation is provided, or where spatial orientation and distribution is required for measuring the same parameter, the equipment must be sufficiently accurate to preclude ambiguous trend information. In addition, IEEE Std. 497-2016, Annex A, Clause A.3 states, in part, “Historically, the required accuracy for instrument channels relied upon to monitor containment pressure and hydrogen concentration has been ±10% of full span.” The licensee should base the accuracy of the instrument channels on the plant’s licensing basis or the severe accident analysis and not the example provided in this section. 6. IEEE Std. 497-2016 does not mention the number of measurement points for each variable (with the exception of redundancy requirements). The number of measurement points for each variable should be sufficient to adequately characterize the variable. DG-1335, Page 10 For example, containment temperature may require several measurement points, spatially distributed. 7. The design of instrumentation should incorporate diversity and defense-in-depth as part of addressing common cause failures. Clause 6.2, “Common cause failures” in IEEE Std. 497-2016 states: Design of Type A, Type B, and Type C instrumentation shall address common cause failures, as described in IEEE Std. 379-2016 and IEEE Std. 603-2009/ IEC 62340:2007 consistent with the plant’s LBD [licensing basis document]. For instrumentation using digital devices, guidance to address common cause failures can be found in IEEE Std. 7-4.3.2-2016/IEC 60880:2006. The licensee or applicant should verify the acceptability of endorsed IEEE or International Electrotechnical Commission (IEC) standards identified in Clause 6.2 of IEEE Std. 497-2016; alternately, applicants should consider NUREG-0800, Chapter 7, Branch Technical Position 7-19, “Guidance for Evaluation of Diversity and Defense-in-Depth