Lithium Compatibility with Metallic and Coated Substrates for Nuclear Fusion Applications

Lithium has the ability to improve plasma performance, but its application is often limited by material compatibility issues. Corrosion of useful materials along with wettability concerns pose challenges for the widespread use of lithium. The University of Illinois (UIUC) and General Fusion have been working to study and overcome these issues. A dynamic corrosion testbed has been constructed to allow for rotation of samples submerged in lithium for extended periods. Material properties are observed before and after lithium exposure via 3D confocal microscopy and tensile testing. Up to now, many common materials have been tested at UIUC, including titaniums, steels, and stainless steels. Testing of advanced materials, such as Inconels, coated substrates, and 3D printed alloys is ongoing. With our experience in plasma coatings, we look to develop coatings which can protect important incompatible materials, such as copper, from lithium attack. The ability to use lithium with previously unusable materials and in 3D printed geometries will open up many pathways for lithium use in fusion devices. Along with material corrosion, wetting behavior is being investigated by measuring lithium droplet contact angles on substrates. Preliminary results indicate the ability to use yttria coatings to prevent wetting of insulators, however, coating reactions seem to occur. Work is ongoing to determine the wetting behavior of coated and surface modified stainless steels.