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:
ant forcing functions which are not described here. The applicant or licensee should determine the excitation mechanisms that are relevant to the various structural components and evaluate the forcing functions for each component. The applicant or licensee should justify the methodologies for determining pressure fluctuations and vibration in plant systems. Experience indicates that computational fluid dynamics (CFD) analyses might not provide sufficient quantitative information regarding unsteady pressure loading. If applicable, bounding analyses may be used where justified. Full-scale testing, along with SMT and analysis, may also be used to evaluate potential adverse effects of flow and mechanically excited resonances and verify the alternating loads predicted by CFD or bounding analyses. Testing and analysis may also be used to ensure appropriate bias error and uncertainties are properly addressed. Proper application of bias and uncertainties ensures that evaluation approaches lead to verified bounding simulations of vibration and alternating stress. When using SMT, the applicant or licensee should quantify the effects on the measurements because of (1) reduced Reynolds Number, (2) differences between working fluids and structural components (materials and dimensions), and (3) other differences between the SMT model and full-scale conditions. For example, of particular concern for BWR steam dryers are the following flow- induced forcing functions: a. separated, impinging and reattached flows in the reactor dome, including low-frequency hydrodynamic loading on BWR steam dryers. b. boiling water excitation of the immersed lower portion (skirt) of BWR steam dryer. c. flow turbulence and narrow-band excitation in MSLs in BWRs. DG-1323, Page 16 Flow Excitation with Feedback and Lock-In Mechanisms The applicant or licensee should evaluate forcing functions that might be amplified by lock-in with an acoustic or structural resonance (referred to as self-excitation