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:
es 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 mechanically induced forces that are shifted in frequency or amplitude from those of the prototype. Therefore, frequency-dependent negative bias errors should not be applied to different-sized structures or structures driven by different flow fields. In these cases, loads (or structural response functions) need to be shifted in frequency during the analysis to ensure bounding worst-case interactions between loads and response are identified. The benchmarking of vibrations or surface strains does not ensure that peak stresses are properly calculated in a numerical structural model. Peak stresses usually occur near corners and welds and other stress concentration locations. Separate convergence studies may be necessary for these locations to ensure peak stresses are properly determined. DG-1323, Page 24 Stress Convergence and High-Cycle Fatigue Evaluation For BWR and PWR reactor internals, and in particular for BWR steam dryers, the potential for high-cycle fatigue cracking at fillet-welded joints and other locations of stress concentration needs to be evaluated in detail and eliminated at the design stage. To account for uncertainty, an alternating peak stress design limit should be selected that provides a design margin compared to the ASME BPV Code allowable alternating peak stress limit. Pressure, acceleration, and strain data collected during power ascension testing are used to confirm or adjust the analytical peak stress predictions. After adjustment based on measured data during power ascension testing, the revised alternating peak stress intensity prediction is limited to the ASME BPV Code allowable alternating peak stress intensity at the material endurance limit. Developing conservative predictions of peak stress involves three elements. First, the structural