An Investigation of Thermal Stress Ranges Under Stratification Loadings

This paper deals with a unique and severe stratification phenomena in the pressurizer surge line piping system. The methodology used in the calculation of total stress state includes pressure stresses from internal pressure, global thermal stresses from the constraining of the system by supports, local thermal stresses from hot/cold stratified condition, and transient thermal stresses in the pipe and at structural discontinuities. Special discussion on the interpolation to obtain moment loadings from one state of thermal condition to the next with nonlinear gapped support system is presented. Finally, the thermal cycling associated with operating transients in the surge line system is also addressed.