Design and Analysis of Fast Response Freezing Valve for EAST Liquid Lithium Limiter Loop

Lithium which can be served as first wall material in tokamak has the function of improving the plasma parameters. Liquid lithium limiter (LLL) system has been planned to be installed in EAST and applied in next campaign of physics experiment. To avoid the large pressure drop of liquid lithium caused by the long distance of feeding pipe in the central shaft, the lithium tank is planned to be installed in the vacuum vessel (VV) and moved with the limiter. A valve will be installed between the lithium tank and the limiter which can stop the lithium feeding immediately if accidents like coolant leaking in the VV occurred. Restricted by the large magnetic field, common valves can’t work normally, and at last freezing valve was chosen to be used. In this paper, the mechanical design of the freezing valve is introduced and the thermal–hydraulic properties of the valve are analyzed. Helium gas (80 K) and water (300 K) can be used as the coolant for the valve. Based on the analysis results, to satisfy the design requirement for the response time of shutting down, the flow rate of the helium gas must be large than 4 g/s (15 m/s), while, for water 2 m/s is enough. Besides, using water for cooling, the thermal affected area is much little than helium gas. At last, water with velocity of 2 m/s is chosen for the freezing valve used in EAST LLL loop, and the thermal-structural analysis shows that the thermal stress is safe for the current design.