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:
calculated from the solid element stress output. The adequacy of the solid element mesh in the submodel needs to be verified by a stress convergence study. The converged, linearized stress prediction at the root of the fillet weld is multiplied by a factor of 3, to obtain the peak stress estimate for use in the fatigue evaluation. From this point, the evaluation follows the first method. Because the second method involves isolation of a local region of the global model, it is necessary to verify that (1) the local model is sufficiently large to preclude boundary effects on the response of interest; (2) the boundary conditions applied to the local model properly simulate the behavior of the local region in the global model; and (3) the pressure loading is properly applied to the local model. An acceptable method to verify this is to create an intermediate local submodel, with grids and elements identical to the global model, and analyze the intermediate local submodel with the appropriate boundary conditions extracted from the global model analysis, before making any mesh refinement and local geometry changes using solid elements. The intermediate local submodel results will match the global model results if items (1), (2), and (3) have been properly implemented. The intermediate local submodel, after further mesh refinement and addition of the fillet weld solid elements, will become the final local submodel. Operational Vibration and Stress Limits DG-1323, Page 27 Computed vibrations and stresses need to be compared to allowable levels, such as the fatigue criteria specified by ASME, or other criteria substantiated by testing and analysis. For steam dryers, minimum factors of safety below allowable levels need to be specified and justified. The ASME stress limits are to be used to establish operational limits on monitoring instrumentation to be applied to the structure for in-plant testing (see Section C.2.2). Steam dryer vibration and alternating stress simulation