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:
e peak loading conditions might not be included in the analysis. In this case, additional frequency-dependent bias errors and uncertainties need to be determined by comparing the time increment subset used to the total time history dataset. Linear structural response may be assumed, so that statistical assessments of the measured time histories may be related to corresponding statistical assessments of the resulting structural vibrations and stresses. The bias errors and uncertainties need to be included in the analysis results from the limited time history subset. DG-1323, Page 23 When using a structural dynamic analysis approach with the Rayleigh damping method, peak responses at various frequencies need to be evaluated to ensure nonconservative damping has not been applied. In particular, below and above the “anchor frequencies” where damping is specified, structural damping might be higher and artificially reduce the resonant peak response. Deviation from the accepted 1 percent damping ratio needs to be justified in determining final peak vibration and stress levels. Benchmarking of Overall (End-to-End) Computed Response Dynamic benchmarking of flow-, acoustically, or mechanically- induced structural response simulation procedures and structural vibration monitoring is preferable using end-to-end measurements, such as alternating surface strains on the structure. End-to-end benchmarking encompasses bias errors and uncertainties associated with loading estimates (including unknown loading mechanisms), mapping of surface loading models to structural dynamic models, and structural dynamic modeling. When multiple simulations are performed spanning a range of frequency-shifted loads (for example, +/-10 percent in increments of 2.5 percent), the upper bound of the simulations needs to be compared to the corresponding measurements. Any differences need to be addressed by frequency-dependent bias errors and uncertainties, which are applied to all subsequent dynamic