Design and Experimental Verification of Passive Residual Heat Removal System for a Alkali-Metal Heat Pipe Cooled Reactor

Abstract The high-temperature heat pipe (HTHP) cooled reactor has the advantages of compact, safety and reliability, rendering it a promising technology for application in Unmanned Underwater Vehicles (UUVs). In this paper, a Passive Residual Heat Removal (PRHR) system is designed for a marine nuclear power plant proposed by the Chinese Academy of Engineering Physics (CAEP). The PRHR efficiently utilizes the space of the adiabatic section of the heat pipe bundle as Emergency Cooling Chamber (ECC) to establish natural circulation. The CFD model of the ECC was established and the geometric parameters of the system were optimized. The results indicate that a hexagonal baffle around the adiabatic section of heat pipe bundle is superior to no baffles. The inlet and outlet widths of the hexagonal baffle has a negligible impact on the heat removal power during the natural circulation process. Furthermore, the analysis shows that the residual heat removal power requirement can be conservatively met when the axial length of the ECC is 100.0 mm. Subsequent experimental investigations were conducted to analyze the characteristics of heat removal power and the wall temperature distribution of the heat pipe under various cooling conditions. The results reveal a logarithmic rise in heat removal capacity with the mass flow rate, a linear decline in cooling water temperature with increasing inlet temperature, and a negligible impact of pressure fluctuations on heat removal capacity. Furthermore, the mass flow rate, temperature, and pressure of the cooling water demonstrate minimal effects on the temperature of the heat pipe wall.