A study of system pressure and temperature distributions in pressurizer and estimation of sensitivities for design variables during heat-up period of integral reactor SMART

SMART, an integral reactor currently under development at KAERI, adopts an in-vessel pressurizer that maintains stable pressure by the principle of self-pressurization. The gas space of the pressurizer is filled with nitrogen and saturated steam. The volume of the pressurizer relative to the total system is large in comparison with those of the current commercial PWRs. The total pressure in the pressurizer is determined by the sum of partial pressures of the gases. Since the rate of change of pressure with temperature increases with temperature for steam, the temperature in the gas space needs to be kept low to prevent rapid pressure change. However, because the pressurizer is located inside the reactor vessel and surrounded by hot primary coolant, it receives heat continuously. Thus, it was necessary to design a cooling circuit to remove heat and a thermal insulator to minimize heat transfer for installation. In this study, changes in the system pressure and the pressurizer temperature during the heat-up period of SMART have been analyzed, and the effects of thermal insulator size and cooler capacity on the system pressure and temperature have been investigated