Design and Test Study on a High Temperature Molten Salt Loop

The Thorium Molten Salt Reactor (TMSR) project plans to construct a 2 MWt liquid fuel molten salt reactor. After successful R&D of the proto-type equipment like pump, heat exchanger and freeze valve, construction of a high temperature fluoride loop is designed and constructed to test them. The rated power of heat exchange is designed to be 200 kW, and the flow rate is set as 15 m3/h by the caloric equation. Hence the pipe caliber chose to be DN50. The numerical computation by Fluent revealed that the pressure drop of the loop system is about 155 kPa, and the overdesign of the pump head is set as 20 m accordingly. To avoid thermal stress concentration of the pipeline, both the electric heater and radiator are designed to be fixed on a flexible universal sphere support, except the pump which is anchored on steel support directly. The structural design of the equipment and the loop hase been verified by several tests with an accumulated operating time near 4000 hours. The actual pressure drop of the loop is about 110~120 kPa, which still needs to be accurately measured by differential manometer in future. The analysis of the impurity of the molten salt shows that the contents of Cr and Mo increased by two orders of magnitude after loop operation, which means that an obvious material corrosion occurs. The level of moisture and oxygen, which is the main reason that cause fluoride corrosion, should be controlled considerably lower than the original design level of 100 μL/L.