Investigation of the safety limits and the limiting safety system settings on a super carbon-dioxide cooled micro modular reactor

Abstract

The supercritical CO2 (S-CO2), with the low critical pressure and temperature, shows excellent potential, as the coolant of the nuclear reactor, with improved thermal efficiency and reduced structure material requirements. One-dimensional thermal–hydraulic analysis code is developed for the S-CO2 cooled nuclear reactor. The thermal licensing and safety analysis are performed on the KAIST proposed S-CO2 cooled micro modular reactor (MMR) concept design. The safety limits (SLs) and the limiting safety system settings (LSSSs) are obtained. The temperature limit types that restricts the SL and LSSS power are achieved for the conditions of low flow rate, medium flow rate and high flow rate, respectively. Based on the assumption of core outlet temperature at its LSSS limit, the LSSS reactor power is 57.511 MW, 1.5 times of the rated value. The flow distribution factor, heat transfer coefficient and S-CO2 thermal conductivity are the three main factors affecting the LSSS power uncertainty.