Conceptual Design And Analysis Of A High-temperature Molten-salt-cooled Divertor Target For Fusion Reactor

Divertor is one of the key components which directly facing the plasma in the fusion reactor.The main function of the divertor is to control the impurity content in the plasma and exhaust the high heat load on the first wall.Sufficient cooling technology is necessary to maintain the normal running status of the divertor.With the increase of the fusion power,the divertor target plate has to withstand higher heat load.The neutron irradiation dose expected for the fusion divertor will be an order of magnitude higher than that of the ITER divertor.Neutron irradiation will result in the degeneration of the mechanical performance.For finding a solution suitable for the environment of high neutron irradiation in future fusion reactor,we need to design a divertor with resistance to neutron irradiation and high heat transfer capacity,reduce the radioactive effects on the environment and improve the efficiency of fusion plant.Based on the above requirements,a molten-salt-cooled(MSC)divertor target was proposed in this paper by comparing the advantages and disadvantages of different coolants and structural materials.FLiNaK is selected as the coolant,it can operate at a wide temperature window and has a strong heat transfer capacity.The MHD loss is almost negligible because of its low electrical conductivity.With the experience getting from the development of the helium-cooled divertor,the MSC divertor target adopts tungsten as armor material,tungsten alloy(W-1.0%La203(WL10))as heat sink material,the preliminary design for the cooling structure of divertor target was carried out.The heat transfer characteristics,pressure drop characteristics and the MHD effect of FLiNaK were analyzed by numerical calculation.The geometrical structure of divertor target was optimized within the limit of allowable temperature and stress.The influence of different inlet velocities on the heat transfer capacity was also evaluated.Then,the cooling system of divertor is designed by theoretical analysis and numerical calculation.The flux distribution among different modules and the pressure drop in the circuit were optimized.The final optimized divertor target can effectively withstand a steady heat flux of 15.7 MW/m2 and a transient heat flux of 20 MW/m2.The MSC divertor target design will be a solution of the development of a divertor target with a sufficient capability of power exhaust in fusion reactor.