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:
mulations needs to be compared to the corresponding measurements. Any differences need to be addressed by frequency-dependent bias errors and uncertainties, which are applied to all subsequent dynamic analyses. It is also necessary to validate the simulation of intermediate quantities, such as loads acting on the structure. In such cases, any revisions to simulation procedures need to adhere to previously validated assumptions and measurements. For example, artificially adjusting the speed of sound or damping to achieve agreement with measured data is inappropriate. Best engineering estimates of modeling parameters need to be used, and any errors evaluated in the final end-to-end bias errors and uncertainties. Benchmarking of FIV or MIV methodologies will produce statistical estimates of bias errors and uncertainties. The estimates need to be based on comparisons of measured and simulated acoustic and structural responses at sufficient locations to reasonably characterize all critical regions of an SSC. Standard practice is to specify uncertainties based on two standard deviations of a dataset. When a single standard deviation is used, the methodology outputs need to bound those at all measurement locations at critical peak frequency regions. If the methodology results, combined with bias errors and uncertainties, are not bounding, the discrepancies need to be used to estimate the effect of the underprediction on fatigue life such that SSC replacement will be planned before failure. In some cases where structures are subdivided into clearly divisible sections, spatially- dependent bias errors and uncertainties may be computed over those regions. Frequency-dependent end-to-end bias errors and uncertainties computed from experimental benchmarking of simulation procedures are not universally applicable to a class of structures. For example, a steam dryer of different size, geometry, location, orientation, or construction from the prototype will be driven by flow- or