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:
f 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 resonances in the plant. The enhancement and propagation of resonant acoustic waves can exert substantial acoustic loading on structures such as BWR steam dryers. DG-1323, Page 12 c. MIV of reactor internals and other structural components caused by structure- borne vibration transmission from RRPs and other machinery. As stated in (b) above, RRPs generate dynamic forces at the pump shaft speed, impeller VPF, and their various harmonics. These forces act directly as acoustic dipoles on upstream and downstream fluid, but also act on the pump mounting structures and can be mechanically transmitted through the reactor wall to other components connected to the feedwater and steam piping, or to other components inside the reactor. MIV is exacerbated when pumps are mounted directly to the reactor vessel instead of connected to the RPV through external piping. As previously noted, studies of past failures in nuclear power plants have determined that the steam dryer in a BWR plant experienced fatigue failure caused by vibration transmission from the reactor pumps at the VPF. The CRDS in some SMRs are not part of the pressure boundary, and therefore the areas of review are different than those for conventional light water reactors. In some SMRs, all internal CRDS components, including the CRDMs, are exposed to primary coolant flow, and corresponding temperature and flow-induced loads. Therefore, all components in a fully immersed CRDS need to be evaluated for FIV, AIV, MIV, and the potential generation of loose parts. Also, in some SMRs that consolidate all major reactor components into a single modular system, additional dynamic excitation might be imparted on the CRDS components. Dynamic excitation because of fluid flow, flow-excited acoustic resonances, and mechanical