Document: NUREG-0800
Document ID: 6b7eddf4-f7ce-4821-9f11-e37070221e57
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, STRUCTURES, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1613/ML16133A418.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
de shapes should be similar, and corresponding resonance frequencies should be used to establish the bounds of modeling accuracy over frequency. Subsequent response calculations should include forcing functions conservatively shifted upward and downward in frequency to span the accuracy range of the models. Many recent applications have adopted an uncertainty range of ±10% over frequency. (ii) The damping factors for different modes should be properly identified and substantiated. In prior submissions, applicants/licensees have referenced 3.9.2-21 Revision 4 – March 2017 NRC damping guidance for very low frequency seismic analyses as justification for high damping factors for mid-to-high frequency analyses. RG 1.20 corrects this guidance and states that damping factors used in structural dynamic modeling needs to be based on mid- to high-frequency measurements or rigorous analyses conducted on structures typical of the reactor internal structure modeled. In general, any assumed damping greater than 1% of critical needs to be substantiated with measurements. Also, if Rayleigh damping is used, its ‘anchor’ frequencies need to span the range of dynamic analysis to ensure excessive damping above and below the anchor frequencies is not applied. (iii) The uncertainties and bias errors of the amplitudes of the FRFs also should be provided, and based on specific comparison of simulated and measured data. The uncertainties and bias errors may be estimated from comparisons of simulations to measurements made on structures similar in construction to the reactor internal being modeled. The results of dynamic vibration response tests with known force inputs are expected for replacement steam dryer analyses. B. Comprehensive forcing function lists should be provided for all reactor internals. The forcing functions should account for the effects of transient flow conditions and the corresponding frequency content. Any potential amplification of a forcing function caused by