Compatibility Tests of Insulating Materials in Pb-17Li Alloy

Abstract

The liquid alloy Pb-17Li is used as breeder material and as coolant in the concept of a self-cooled liquid metal blanket of a fusion reactor [1]. The circulation of the eutectic has to be performed at relative high flow velocity in order to get a good heat-exchange. One serious problem of this concept is the pressure drop due to the magneto-hydrodynamic (MHD) forces in the flowing liquid metal under the influence of the magnetic field [2]. This pressure drop has to be drastically reduced. An electrical insulation of the flowing liquid alloy against the metallic tube walls may suppress the effects of MHD forces. There exist three different methods to insulate the tube walls. The so called “laminated walls” and the “flow channel inserts” are described elsewhere [3]. The direct insulating of the tube walls by means of a coating is a third method. The insulating coating on the wall surface performs the easiest way to reduce the MHD pressure drop. In this case electrical currents could only flow inside the liquid metal itself, and the result is a reduction of the MHD pressure drop by some orders of magnitude. However, the insulating coating has to be compatible with Pb-17Li over the whole lifetime of the blanket and has to withstand wear, crack formation, or peeling off. The electrical resistance should remain above a certain limit even under irradiation.