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:
32, Page 13 at least 24 hours. The central recorder should be able to withstand flooding of its remote sensors without compromising its operation or the integrity of any stored data. 5.4 Accessibility Instrumentation stations should be accessible for maintenance during full-power operation. Seismic instrumentation with sensors located in inaccessible areas should contain provisions for data recording and certain maintenance operations at an accessible location, and the instrumentation should provide for an external remote alarm to indicate actuation. The free- field station should be accessible immediately following an earthquake. 5.5 Accuracy Installed instrumentation should maintain timing and recording accuracy throughout the design range of environmental conditions, such as temperature, humidity, pressure, vibration, and radiation. 5.6 Instrumentation Station Environment Instruments and their interconnections should be installed in accordance with the manufacturer’s recommendations consistent with the COSMOS “Guidelines for Installation of Advanced National Seismic System Strong-Motion Reference Stations.” 5.7 Interconnection of Instruments All time history recorders at the plant should be interconnected to be activated at the same time. All instruments on the site should maintain a common time scale with relative timing accuracy not less than 1 millisecond and absolute timing accuracy better than 5 milliseconds of absolute Universal Time Coordinated (UTC) time. 6. Instrumentation Actuation 6.1 Ground Motion Actuation Both vertical and horizontal input vibratory ground motion should activate each time history recorder. Since the time history recorders are interconnected, they should be activated by the same trigger. In this case, the trigger should be located with the time history recorder nearest to the free-field ground station. 6.2 Spurious Triggering Spurious triggering should be avoided. 6.3 Threshold Ground Motion Acceleration The seismic trigger