ON THE DESIGN OF LIQUID-METAL DIVERTORS

The divertor technology has become the focus of concern for prospective steady state tokamak reactors. The imposed heat flux and particle flux conditions cast doubt on the feasibility of any solid surface divertor. The aim of this work is to evaluate the existing concepts of liquid metal divertors from the physics, engineering, and safety points of view. Lithium metal is found to relatively suffer from a large tritium inventory that may develop in the form of solid hydride LiH, in addition to the fire hazard potential. Gallium does not form hydride within the temperature range of interest and is inactive with oxygen, therefore it is considered a more favorable metal. The flowing film and pool type divertors are found to suffer from the possible blistering erosion and resulting plasma contamination. The self-cooled liquid metal film divertor suffers also from a linear MHD instability, in addition to complicating factors such as the variation of the liquid metal electric property, dynamics of halo current, and the possible incompatibility with the insulator coating. The liquid gallium droplet curtain divertor appears to be the most feasible and robust, but its high temperature vapor is corrosive to most structural materials.