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:
on and FEI focused primarily on structural vibration in the lift direction. However, experiences from nuclear power plants revealed thermowell failure because of streamwise vibration excited by vortex shedding from the thermowell. Therefore, the applicant/licensee should develop the CVAP to include possible streamwise (or in-plane) vibration because of FEI and vortex shedding excitation. As previously noted, studies of past failures have determined that flow-excited acoustic resonances within isolation valves, in standpipes of safety relief valves (SRVs), and dead-end branch lines in the MSLs of BWRs can produce mid- to high-frequency pressure fluctuations and vibration that can damage MSL valves, the steam dryer, and other reactor internals and steam system components. In addition, hydrodynamic loading acting directly on a steam dryer (caused by flow turbulence and boiling water rumbling) can result in undesirable dynamic stresses. b. AIV caused by reactor pump pressure pulsation or pressure waves emanating from acoustic resonators such as the standpipes of SRVs in MSLs. RRPs generate pressure pulsations at multiple frequencies, including the pump shaft speed, the impeller VPF, and their harmonics. These pressure pulsations are caused by hydrodynamic forces induced by the rotating impeller interacting with distorted in-flow. The hydrodynamic forces act as acoustic dipole sources within the working fluid. These pressure pulsations could excite the acoustic modes of the water/steam system inside the RPV, causing significant acoustic loads on reactor internals. Depending on the number and arrangement of the pumps and the relative phase between their respective drive frequencies and resulting forcing functions, local pressure pulsations could reach several times those of a single pump. For RRPs that are driven with a variable frequency drive, the excitation frequencies vary as the drive frequency varies, leading to potential interactions with structural and acoustic