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:
ited 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 model needs to be an accurate representation of the actual structure, in terms of geometry, material properties, and boundary conditions, with sufficient model refinement to respond to the applied dynamic loads and to provide appropriate stress output for the fatigue analysis. Second, the applied dynamic loads need to be known and properly applied to the structural model. Third, the relationship between the model stress output and a conservative prediction of the peak stress needs to be known. a. Structural Model Development To conduct the structural analysis, a widely-used, well-verified finite element computer code (e.g., ANSYS) needs to be applied. In the current context, the analysis is linear elastic. Modeling of reactor internals (including BWR steam dryers) typically entails using solid, plate/shell, and beam elements. Limited use of other element types may also be appropriate. Connecting plate/shell elements and beam elements to solid elements involves special modeling techniques to ensure rotational compatibility and moment transfer. Various techniques have been developed and successfully applied. It is the applicant’s responsibility to verify that such connections have been appropriately modeled. This is significant because two-sided (or double) fillet welds are often used to provide a connection between a thin plate type sub-component and a heavy section, as in a BWR steam dryer. The predicted stress in the thin plate element at the connection is used in the fatigue evaluation of the connecting double fillet weld. The implemented connection modeling technique is not allowed to result in a reduction or distortion of stress in the plate at the connection. The next step is developing a suitable finite element mesh, consistent with the loading, the expected