The numerical simulation of dead leg phenomena in residual heat-removal system

"Dead leg phenomena" is that the high-temperature fluid in primary loop heat the low-temperature static liquid in dead leg by convection heat transfer and heat conduction, and then the static fluid in dead leg is heated to evaporate or produce thermal stratification, which leads to the corrosion of pipe's inner wall and valve. In this research, we use FloEFD which is a well-known CFD software to simulate the thermal stratification in residual heat-removal system's inlet pipeline and the heat exchanger's outlet pipeline to get the fluid's temperature distribution. The stream line in the pipe and the process of thermal stratification was investigated and the temperature distribution of the fluid was displayed. The calculation results show that the temperature in dead leg is lower than its saturation temperature and the design of this dead leg is appropriate. In addition, the calculation results prove that the thermal stratification exists in the dead leg. Finally, the formation mechanism of dead leg was speculated. The calculation results can provide a theoretical basis for the layout plan of residual heat-removal system's inlet pipeline and heat exchanger's outlet pipeline. The calculation and analysis results are of great importance for nuclear power plant operation safety and reliability. (author)