Document: NRC Regulatory Guide
Document ID: 99fe445b-c440-4921-ba8f-841c8f236046
Document Type: regulatory_guide
Title: Nuclear Power Plant Instrumentation for Earthquakes + HISTORY - HISTORY 09/2016 – DG-1332 , Proposed Revision 3 04/2015 – Periodic Review on Revision 2 – Revise 02/1995 – DG-1033, Third Proposed Revision 2 11/1992 – DG-1016, Second Proposed Revision 2 07/1981 – Draft MS 140-5 , First Proposed Revision 2 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1610/ML16104A220.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.12
CFR Part: 
CFR Title: 

Content:
en exceeded. RG 1.166 provides useful information for determination of OBE exceedence. The instruments located at the foundation level and at elevation in the structures measure responses that are the input to the equipment or piping and will be used in long-term evaluations. Additional expectations are discussed in RG 1.167 which provides useful information on plant restart following and earthquake. Foundation-level instrumentation provides data on the actual seismic input to the containment and other Seismic Category I structures and is used to quantify differences between the vibratory ground motion at the free-field and at the foundation level. Instrumentation is not located on equipment, piping, or supports since experience has shown that data obtained at these locations are obscured by the vibratory motion associated with normal plant operation. The guidance in RG 1.166 is based on the assumption that the nuclear power plant has functional seismic instrumentation, including the equipment and software needed to process the data within 4 hours after an earthquake. This is necessary to determine whether plant shutdown is required. This determination is made by comparing the recorded data against OBE exceedance criteria and by evaluating the results of the plant walkdown inspections that take place within 8 hours of the event. An NRC staff evaluation of seismic instrumentation noted that instruments have been out of service during plant shutdown and sometimes during plant operation for extended durations. The instrumentation system needs to be functional and operated at all times. There are guidelines in Appendix A to Regulatory Guide 1.166 to address non-functional or degraded seismic instrumentation or data processing hardware and software necessary to determine whether the OBE has been exceeded. The type, location, operating modes, characteristics, installation, activation, remote indication, and maintenance of the seismic instrumentation are described in this