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:
intermediate frequencies. Alternate Rayleigh damping anchor frequencies need to be quantitatively justified. For components other than BWR steam dryers, higher values of damping may be appropriate if justified. If a frequency domain analysis procedure is selected, then FRFs at sufficient locations, for a sufficient number of frequencies, up to the highest frequency of interest, need to be calculated. It is necessary to ensure that the FRF data are sufficiently complete to achieve solution accuracy. Comparison to a time domain solution is an acceptable method to address this aspect. Modal damping of 1 percent is acceptable for BWR steam dryers. For components other than BWR steam dryers, higher values of damping may be appropriate if justified. b. Applying Dynamic Loads to the Structural Model The excitation mechanisms that might cause dynamic loading are described in the previous section of this regulatory guide. Application of the dynamic loading to the structural model is within the scope of the structural analysis. The loading file for dynamic analysis of rapidly changing surface pressure, with time-varying spatial distribution comprises a very large data set. The input time increment needs to be sufficiently small to capture the highest frequency input pressure fluctuations of interest. Typically, the input time increment should be no larger than 0.25 times the shortest period of interest. For example, if 250 Hz is the highest frequency of interest, then the input time increment should be no larger than 0.25/250 = 0.001 sec. Also, the mesh in the model used for load generation usually does not coincide precisely with the mesh in the model used for structural analysis. Interpolation procedures are used to define the load at nodes in the structural model. In such cases, checks on localized loading distributions, particularly in areas of expected high stress, need to be conducted to ensure conservative load mapping has occurred. c. Fatigue Analysis of Two-Sided