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:
ximum tensile stress directions), as well as cumulative stress spectrum plots. The cumulative plots show the integration of a stress spectrum over frequency, and identify dominant frequency peaks. The FRFs described in Section C.2.1.1 and forcing functions described in Section C.2.1.2 have a computational uncertainty associated with the frequencies of the response peaks attributable to resonant modes, the vibration and stress calculations need to address those uncertainties by shifting either the FRFs or the forcing functions in frequency to span the uncertainty in the response peak frequencies. An acceptable approach to resolving the uncertainty associated with natural frequencies is to align any forcing function peaks with all modal peaks within the range of frequency uncertainty, and to determine the worst-case vibration and stress. All uncertainty and bias associated with natural frequencies is eliminated with this approach. The uncertainty and bias associated with the FRF amplitudes are not eliminated by aligning all forcing function and modal peaks. An alternative approach is to perform several analyses in which the FRFs or forcing functions are shifted by increments within the frequency uncertainty range. Once again, the worst-case vibration or stress needs to be identified because the frequency uncertainty might lead to a negative (non-conservative) bias in the vibration and stress when modal peaks are misaligned with forcing function peaks. Forced response calculations may be performed using time-domain or frequency domain approaches, provided they are verified to be accurate against computational benchmarks. When using a time-domain structural analysis approach over a limited subset of time history data acquired to infer SSC loading, it is possible that the 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