Document: NRC Regulatory Guide
Document ID: 37f53017-d71c-4f3c-a2a4-ab67a8270066
Document Type: regulatory_guide
Title: Pre-Earthquake Planning, Shutdown, and Restart of a Nuclear Power Plant Following an Earthquake (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1826/ML18268A185.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.166
CFR Part: 
CFR Title: 

Content:
or by writing the International Atomic Energy Agency, P.O. Box 100 Wagramer Strasse 5, A-1400 Vienna, Austria. DG-1337, Appendix A, Page A-1 APPENDIX A OPERATING-BASIS EARTHQUAKE EXCEEDANCE GUIDELINES IF INSTRUMENTATION IS DEGRADED OR INOPERABLE If the seismic instrumentation or data-processing equipment is degraded or inoperable, the following should be used to determine whether the operating-basis earthquake (OBE) ground motion has been exceeded: • For plants at which instrumentally determined data are available only from an instrument installed on a foundation, the cumulative absolute velocity (CAV) check does not apply. In this case, the determination of OBE exceedance is based on a response spectrum check described in Section 6.4.1 of American National Standards Institute/American Nuclear Society (ANSI/ANS)- 2.23-2016, “Nuclear Power Plant Response to an Earthquake” (Ref. 1). A comparison should be made between the foundation-level design response spectra and data obtained from the foundation-level instruments. If the response spectrum check at any foundation is exceeded, the OBE is exceeded, and the plant must be shut down. At this instrument location, it is inappropriate to use the 0.2g spectral acceleration limit or the spectral velocity limit of 6 inches per second (15.24 centimeters per second) in Section 6.4.1 of ANSI/ANS-2.23-2016. • For plants at which no free-field or foundation-level instrumental data are available or the data-processing equipment is inoperable and the response spectrum check and the CAV check cannot be determined, the OBE will be considered to have been exceeded, and the plant must be shut down if one of the following two conditions apply: (1) If instrumental intensity information is not available, the earthquake with moment magnitude M specified in Table B-1 occurred within a distance less than or equal to that specified in Table B-1. Table B-1 Maximum Distance from an Earthquake with Moment Magnitude M at which the OBE Can