Stress Analysis Of Pipeline In Nuclear Power Plant With Fluid-Structure Interaction Method

The main function of pipeline in nuclear power plant (NPP) is to transport fluid and heat, and the equipments in NPP form a complete are connected by pipelines. However, the thermal fatigue accidents often occur in pipelines, because of the non isothermal flow existing in the pipeline. Especially, thermal fatigue accident is easy to occur in the T-shape pipes in the primary circuit, because they are subjected to not only the high pressure and high temperature, but also of the cold and hot fluids are mixed here with high-speed. The safety operation is always the most important in NPP, but thermal fatigue accident has seriously influenced the safety of NPP.This paper studies the thermal fatigue phenomenon of T-shape pipelines in the primary circuit of nuclear power plant using fluid-structure interaction numerical simulation method, and commercial software ANSYS-Workbench. We study the fluid flow in the pipelines and the stress of pipe wall by numerical calculation. The influences of different working conditions on pipe wall stress are studied, such as variety of velocity and temperature. It is found that the maximum stress in the pipe wall changes with the velocity ratio of cold water and heat water, and it reaches the minimum when the velocity ratio is1.15. The stress in pipe wall is not influenced very much by the absolute temperature, but is seriously influenced by the difference in temperature. And the maximum stress is approximately linearly increased with the temperature difference. We also study the influence of some others parameters on pipe wall stress, such as the wall thickness, the thermal expansion coefficient of pipe wall and the constraint conditions. It is found that the maximum stress in the pipe wall will decrease with the increase in the wall thickness and the decrease in the thermal expansion coefficient.The influence of working conditions and material parameters of pipe wall on the pipe wall stress is studied. This work can provide important references for NPP design, installation and operation.