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:
length and phase distributions of the fluid dynamic forces on structures exposed to fluid flow. j. Past review of EPU applications indicated that variability in reactor operating parameters can affect flow rates, working fluid mass density, pressures, and other quantities. These variations need to be addressed when assessing reactor internals and other safety-related components at worst-case operating conditions. DG-1323, Page 20 Force Inference Approaches In some BWR EPU requests, licensees have employed inverse acoustic models to estimate fluctuating pressures within the RPV and on BWR steam dryers. These pressures are inferred from measurements of fluctuating pressures either (a) on dryer surfaces, or (b) within the MSLs connected to the RPV. Benchmarking of these procedures on plants and systems similar to the plant being designed or licensed is acceptable. All uncertainties and bias errors associated with the on-dryer or MSL pressure measurements and modeling parameters need to be clearly defined. The bases for the uncertainties and bias errors, such as experimental evaluation of modeling software, need to be described. There are many approaches for measuring MSL pressures and computing fluctuating pressures within the RPV and the MSLs. Although some approaches reduce bias and uncertainty, all approaches have a finite bias and uncertainty that need to be addressed. In particular, it is challenging to fully quantify all alternating loads acting on SSCs (including steam dryers) within complex environments (surrounded by moving steam with varying wetness, partially immersed in boiling water), especially using remote measurements and inference techniques. Based on experience, the following guidance provides approaches that minimize uncertainty and bias error (MSL pressure measurement details are provided in Section C.2.2 of this regulatory guide): a. At least two measurement locations need to be used on each MSL. However, using three measurement locations on each