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:
cord is stored on computer memory, provisions should be made to transfer the record to a permanent medium during the processing phase to prevent accidental loss. The documentation and retention of all earthquake records should be commensurate with the recordkeeping for other plant equipment. 4.12.5 Timing Data on the time of the earthquake occurrence should be adequate to differentiate the main shock from any foreshock and aftershock with absolute timing accuracy of not less than 5 millisecond (msec) of absolute Universal Time Coordinated (UTC) time. 4.13 Seismic Trigger 4.13.1 Actuating Level The seismic trigger should be set to actuate at a maximum of 0.01 g. 4.13.2 Frequency Range The frequency range of the seismic trigger should include the range of 1 Hz to 10 Hz. DG-1332, Page 12 4.13.3 Output The seismic trigger output should be compatible with the device to be actuated. 4.13.4 Proximity The seismic trigger may be integral to or separate from the time history recorder. 5. Instrumentation Installation 5.1 Mounting The instrumentation should be designed and installed so that the mounting is rigid and remains so over time. In addition, all instrument components should remain tight over time. Installation at open ground locations requires constructing a reinforced concrete mounting pad with a lightweight enclosure. It is recommended on using commercial power plant type fiberglass or aluminum lightweight enclosure (instrument shelter or T-hut) not exceeding 50 in. x 50 in. x 50 in. and weighting less than 200 lbs. If a special, light instrument hut is used, the pad should be approximately 4 ft. square, with 6 in. x 18 in. piers to ensure effective coupling. A small concrete slab/pad and a lightweight enclosure will help meet the goal that the transmissibility of the installed strong-motion station be 1.0 over the frequency range 0-50 Hz; see Ref. 12, the “Guidelines for Installation of Advanced National Seismic System Strong-Motion Reference Stations.” for