Investigation about Effect of Thickness in Stress Classification of Components

Abstract

In current practices, stress analyses of Class 1 vessels with internal pressure of nuclear power plants have been carried out using the minimum thickness of the component. In this paper, influences of thickness on stresses have been investigated by comparing stress analyses for two kinds of 3D-FEA models of a typical nozzle of a pressure vessel with minimum thickness and nominal thickness. Since variations of stresses between minimum and nominal thickness models are small, nominal thickness can be employed in the stress analysis. In order to conduct more conservative evaluation, a correction method to multiply primary membrane stress by the thickness ratio and primary bending stress by the square of thickness ratio can also be used.