Recent progress in the development of electrically insulating coatings for a liquid lithium blanket

Electrically insulating coatings on the first wall of magnetic confinement reactors are essential to reduce the magnetohydrodynamic (MHD) force that would otherwise inhibit the flow of the lithium coolant. There are very few candidate materials because Li dissolves most oxides and many carbides and nitrides do not have sufficient electrical resistivity for this application. Based on thermodynamic considerations and testing of bulk ceramics, the most promising materials are Y2O3, Er2O3 and AlN. Coatings of these materials are being fabricated by a variety of processing techniques and their resistivity and microstructure characterized. Electrical resistivity results from Y2O3 coatings as-deposited and after exposure to Li are presented. Self-healing and in situ coatings are being investigated based on CaO from Li–Ca and Er2O3 from Li–Er. Because there are likely to be cracks in any coatings, a dual-layer system with a thin outer layer of vanadium appears to be a more attractive MHD coating system.