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:
he 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 supporting information. The downhole instrument package should be securely attached to the bottom of the downhole to move with the medium it is embedded in. In addition, the sensor package should not, due to lose component rattling during strong shaking, add noise to the signal. 5.2 Orientation The instrumentation should be oriented so that the horizontal components are parallel to the orthogonal horizontal axes assumed in the seismic analysis of the structure. Triaxial acceleration sensors should be mounted orthogonally with no more than 2 degrees out of orthogonality. The downhole sensor orientation should be controllable, and known without the use of data recordings. Downhole electronic compasses have become available to measure orientation, which makes orientation easier to achieve. Also, if the downhole sensor locking device includes a pin to control orientation relative to the casing, orientation repeatability is obtained. 5.3 Protection Protection should be provided against accidental impacts due to earthquake-induced failures of structures, nonstructural elements, equipment, or other features. Strong motion instrumentation installed in areas prone to flooding should be adequately protected from water damage. Recorders and associated components that can be damaged by water should be installed above the highest water level predicted to occur, increased by a factor of 1.3. Sensors, cabling connectors and any other components installed at lower levels should be sealed against water intrusion, and be able to withstand immersion to a depth of three meters for DG-1332, 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