The behaviour of bulk ceramic materials under DCLL BB operational conditions

Ceramic compositions are being examined at within the EUROfusion as volumetric channel elements in the Dual Coolant Lithium Lead (DCLL) concept of a fusion Breeding Blanket (BB). This paper reviews the results obtained in compatibility experiments with PbLi and the mechanical and electrical measurements of ceramics immersed in PbLi as part of a down-selection exercise of single-phase and composite ceramics. Commercially available oxides and carbides characterized by high electrical resistivity were initially considered. The evolution of the original microstructure was analyzed in surface after 1000–500 h of static or dynamic PbLi testing at 550–700 °C. The influence of an applied 5 T magnetic field and prior irradiation with high-energy ions of selected samples was specially pondered. The required insulating functionality of the channel element was assessed by monitoring the electrical resistance of ceramic probes immersed in PbLi as a function of thermal cycling. Considering the most relevant factors, the ceramic mechanical resistance at temperature and in contact with PbLi was evaluated. In conclusion, oxides (such as alumina, yttria-stabilized zirconia and zirconia-toughened composites) and SiC meet the minimum requirements for operation under DCLL BB conditions without deterioration of their functionality over time in contact with the breeding alloy.