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:
ne fluid-structure interaction mechanisms needs to be conducted on dynamically similar scale models based on all relevant dimensionless parameters of the full-scale installation. Scale models based on conservative assumptions are recommended for which the fluid-elastic parameter is higher, and the vibration damping coefficient is lower, than in the full scale installation. The fluid-elastic parameter relates the dynamic fluid force to the structural elastic force. d. When SMTs are performed at transient conditions of pressure, temperature or flow velocity, repeated test runs of the same test conditions are necessary to obtain reliable averaged test data with reasonable uncertainties. e. The model geometry needs to replicate the details of the full-scale geometry accurately, particularly at critical locations that are sensitive to flow excitation mechanisms, such as the locations of flow separation. For example, when modeling the geometry of a closed side-branch representing an SRV standpipe, the edge radius of the standpipe inlet can strongly influence the onset flow velocity and the sound intensity of acoustic resonances DG-1323, Page 18 in the standpipe. Therefore, the size of the scale model needs to be sufficiently large to allow the evaluation of small relevant geometrical details. f. SMTs performed under transient test conditions are often associated with fast temperature variations during the tests. For example, fast depressurization of a limited capacity tank results in fast temperature variations with time. The resulting changes in the speed of sound and acoustic resonance frequencies can affect the acoustic response during transient tests (e.g., producing artificially wide acoustic resonance peaks in the pressure power spectral densities (PSDs)). Sensitivity analyses of the effect of the sample length of the pressure signal on the PSDs need to be performed to ensure bounding estimate of the loading functions. g. When evaluating the growth rates of