The heat transfer tubes of steam generators (SG) should not be damaged in an earthquake. The current seismic integrity assessment uses a simple model that integrates multiple pipes. In order to cover the increasing seismic loading conditions under Japanese regulations, more current and realistic estimates are needed than the conservative existing assessment methods.
In this study, all SG components, such as heat transfer tubes and anti-vibration bars (AVB), were modeled, and linear and nonlinear models were developed in order to evaluate more realistic responses and strains.
The natural frequency of the developed linear model and the strain distribution in the tube of the nonlinear model agreed well with the test results in the past. The effect of the AVB stiffness on the strain distribution of the tube has been evaluated by altering the thickness of the AVB.