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:
Operating RRPs generate various exciting forces at multiples of their drive frequency, including those induced by electromagnetic oscillations within motor cores, by imbalance and misalignment (which can be caused by steady hydraulic side forces), and by hydrodynamic forces at multiples of impeller VPFs. The hydrodynamic forces are induced by the impeller vanes rotating through DG-1323, Page 21 non-uniform in-flow. These forces act on both the acoustic waves within the piping, as well as on the mechanical bearing systems, and therefore on the piping structures. For reactors with multiple pumps, the forces can be amplified when synchronized. For worst-case conditions, the pump forces are perfectly synchronized, and the total force is the product of a single pump force and the number of pumps. When not synchronized, excitation tones with time varying amplitude commonly known as a “beating phenomenon,” can also occur as discussed below. Any of the tones, when aligned with a structural or acoustic resonance, can lead to strong vibrations of reactor components. These pump sources are combined with computational acoustic and structural models of the reactor internal (water) domain to determine the excitation forces acting on the internal structures, such as control rod drive housing, control rod guide tube, differential pressure lines, and the housing system, guide tubes, and stabilizers for in-core monitors. Acoustic and mechanical pulsations generated by RRPs and their effects on reactor internals might be more intense in some SMRs because of the close proximity of the pumps to reactor internals. The applicant for new BWRs, PWRs, and SMRs should address the following issues, as applicable for the specific design: a. The acoustic and mechanical forcing functions of individual pumps need to be based on data obtained from full-scale experiments performed on pump test stands (e.g., at the pump supplier facility). Tests of sub-scale pumps may be acceptable if full-scale