Experimental analysis on passive residual heat removal in molten salt reactor using single cooling thimble test system

An experimental setup has been designed and fabricated for the analysis of the passive residual heat removal system as applied to molten salt reactor. The main characteristic of this test facility is the presence of two natural circulation loops and a cooling thimble with double-wall barrier. The objective is to investigate the thermal performance of the drain tank cooling system, as well as further understand the heat transfer process. It is observed that the passive cooling system with single cooling thimble is capable of removing 2175 W at the desired temperature of 699 °C. Due to the large temperature difference, radiation heat transfer plays a significant role between the thimble and the bayonet tube. The contributions of several constituent thermal resistances in the heat flow path, together with the overall thermal resistance, have been obtained at various boundary conditions. It is also found that the operating mode is quite unstable with periodical oscillations at relative low temperature. From this study, valuable reference data and useful information are provided for practical applications. - Highlights: • Experimental study on passive residual heat removal system for molten salt reactor. • The heat removal rate of the system is 2175 W at the desired temperature of 699 °C. • The thermal resistance of the air gap is quantitatively analyzed. • The feasibility and practicality of the passive cooling system is validated. • Periodical oscillations are suggested to be induced by flashing in the riser.