Study On The Performance Of Thermal Shock Protection Of The Microstructure Based On Bionic Surface

Nuclear reactor coolant pump (RCP) which is called as the "heart" of the nuclear reactor is the main cooling device of the first circuit within the reactor. As the core of RCP, the RCP primary shaft is very important for the safe and reliable operation to RCP, which is working under the environment of high-temperature, high-pressure and strong-radiation. The problem of thermal fatigue crack caused by the impingement cooling repeatedly always restricts the development of nuclear power equipment in China even all over the world. This paper focuses on the research of this issue.To prevent the nuclear power facilities from crack caused by the thermal shock at the primary pump shaft, a new method for thermal shock protection is proposed. The proposed thermal shock protection technique is based on bionic surface with microstructure covered with a layer of water film. Due to the low thermal diffusivity of the water film, the thermal stress at the surface caused by the thermal shock is reduced and the probability of the thermal fatigue failure of the structure will be decreased. In the present paper, using COMSOL multi-field coupling analysis software, the temperature field and thermal stress distribution of microstructure at the solid surface are analyzed combining finite elements method with infinite elements method. Effects of thermal shock time, the transition corner radius between microstructure and bulk material, the thickness of viscous boundary layer and the boundary temperature difference on the surface thermal stress are studied. Based on the simulation results, it is found that the surface microposts or microtubes can remarkably reduce the thermal stress resulting from the water thermal shock. The thermal stress generated in the surface is released due to the surface microstructure, and there is an optimal shape of transition surface between microstructure and bulk for minimizing the thermal stress. Moreover, this paper investigates the effect of geometric parameters on the best shape of transition surface.