ELECTRICALLY INSULATING COATINGS FOR V - Li SELF - COOLED BLANKET IN A FUSION SYSTEM

The blanket system is one of the most important components in a fusion reactor because it has a major impact on both the economics and safety of fusion energy. The primary functions of the blanket in a deuterium/tritium-fueled fusion reactor are to convert the fusion energy into sensible heat and to breed tritium for the fuel cycle. The liquid-metal blanket concept requires an electrically insulating coating on the first-wall structural material to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Based on the thermodynamics of interactions between the coating and the liquid lithium on one side and the structural V-base alloy on the other side, several coating candidates are being examined to perform the insulating function over a wide range of temperatures and lithium chemistries. INTRODUCTION Liquid lithium is being considered as a coolant/tritium-breeding blanket for the magnetic fusion device. The structural material considered for this application is a V-base alloy with 4-5 wt.% each of Cr and Ti. In fusion applications, the structural material must be (a) compatible with the liquid metal; (b) capable of maintaining structural integrity for long periods while exposed to moderately elevated temperatures, thermal cycling, and intense irradiation; and (c) amenable to low magnetohydrodynamic (MHD) pressure losses during flow in the magnetic field. Key performance variables of importance in application of liquid metals in firstwall/blankets include: • Liquid-Metal Compatibility. Corrosion due to mass transfer of metallic elements. Mass transfer of nonmetallic elements (O, C, and N). Influence of corrosion on mechanical properties. • Minimization of MHD Pressure Drop. Candidates for electrical insulators.