Document: NRC Regulatory Guide
Document ID: ad61f8a3-1cce-4446-9542-dcdda55c1ec6
Document Type: regulatory_guide
Title: Comprehensive Vibration Assessment Program for Reactor Internals During Preoperational and Initial Startup Testing + HISTORY - HISTORY 07/2015 – DG-1323 , Proposed Revision 4 03/2013 – Periodic Review of Revision 3 – No Issues Identified 11/2006 – DG-1163 , Proposed Revision 3 (Rev. 4)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1508/ML15083A390.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.20
CFR Part: 
CFR Title: 

Content:
ment in which it will operate. b. Bench testing of sensors in representative environments and on structures similar to those in the plant is necessary to establish guidelines for installation and data acquisition. Sensitivities need to be confirmed via the bench testing. c. Strain gages that are welded to a base structure need to be installed according to vendor guidelines as modified by lessons learned from bench testing, by trained welders using appropriate welding procedures to ensure the functionality of the sensors. Past installations of strain gages to reactor internals and MSLs have not always been consistent with vendor guidelines or have been of poor quality. In particular, strain gages mounted to pressurized MSLs have not always produced measurements consistent with those on other nominally identical MSLs and locations. In some cases, additional guidance beyond nominal vendor guidelines has been necessary based on specialized laboratory tests on structures of similar size and materials. DG-1323, Page 30 d. Strain gage signals might be affected by static preloading when mounted to pressurized surfaces, and can be significantly affected if the welds on the gage edges crack. Periodic shunt calibration is recommended to confirm strain gage sensitivities and performance. e. Surface pressure measurements can be affected by strong sensor vibration and result in “measuring” vibration rather than surface pressure. f. All sensor signals can be affected by electrical noise, particularly when inadequately shielded sensor wiring passes close to strong electromagnetic fields. Tonal harmonics of electrical supply frequencies are commonly observed, but broad-band signal corruption has also been observed in previous plant data. All instrumentation wiring needs to be properly shielded and, if possible, routed through reactor penetrations that do not include electrical supply lines. g. Data acquisition systems need to be calibrated to ensure that signals are not altered