The chemical compatibility of oxide ceramic candidates in static PbLi for advanced breeding blanket channel components

Abstract

The use of a PbLi eutectic alloy is extended in the Dual Coolant Lead Lithium (DCLL) and Water Coolant Lead Lithium (WCLL) Breeding Blanket (BB) design concepts in future fusion reactors. However, the reactivity of PbLi is a challenging problem, as the flow liquid metal can damage metallic and ceramic materials. For the development of BB technologies, to conduct chemical compatibility studies of materials that will be exposed to the liquid metal is therefore critical. The advanced DCLL concept considers the use of ceramic channels, which could help to extend the BB operating window above 550 °C while improving the tritium-breeding ratio. Since BB components will be highly exposed to neutrons, the influence of PbLi in neutron-like damaged components is also of high concern as compositional changes may modify properties and functionality of the exposed material. Consequently, selected ceramics were submitted to long-term chemical compatibility experiments using COES, a lab-scale facility located at the Liquid Metal Laboratory at CIEMAT, Spain. Commercial Al2O3 ceramics were tested in the as-received and light-ion-implanted conditions, the resultant surfaces after static PbLi exposition being studied by SEM-EDX microstructural and SIMS analytical techniques. The conclusions after the long-term chemical compatibility experiments suggest that the use of bulk alumina ceramics in contact with PbLi is promising. Although lithium diffuses inside the ceramic transforming the initial alumina stequiometry, the surface structural damage is limited to the first 50 µm in the worst case, and could be still considered as a candidate ceramic material for the advanced DCLL BB.