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:
forcement action (i.e., an order) would be necessary to halt power ascension if the NRC staff’s evaluation determined it was warranted. (4) Power ascension acceptance limit checks may be of in-plant instrumentation frequency spectra (often called “limit curves”), or of peak or RMS quantities. However, if peak or RMS limits are used, (a) a sufficient number and types of sensors and locations are needed so that all critical peak stress regions on a structure are monitored, and (b) accompanying confirmations are performed to ensure that all important resonance and forcing function frequency peaks at the peak stress locations are bounded by simulation methods. DG-1323, Page 33 (5) If an instrumentation limit is exceeded during power ascension, triggering a reanalysis of structural alternating stress, the reanalysis may be performed using approximate methods that have been shown to be reasonable and conservative in previous benchmarking. The final structural analysis after the completion of power ascension needs to be conducted using the full analysis procedures. (6) During power ascension, structurally mounted instrumentation may be used to re- benchmark design analyses. As discussed previously, this instrumentation needs to be chosen and located so that all key peak vibration and stress locations are properly monitored. Any re-benchmarking needs to use data from a power level that is sufficiently high for unsteady loading and dynamic response to be well above any noise floors of the measurements, and representative of the forcing functions that will occur at full power. Generally, power levels of at least 75 percent of full power are specified. (7) As a reactor ascends in power, limits on spectra (limit curves) or peak/RMS values need to be continuously updated based on the most recent data acquired. Also, corresponding estimates of full-power levels need to be continuously updated using trending analysis. The trending needs to be based on a reasonable number of