Large-scale behavior of sandwich-like FCI components within the EU-DCLL operational conditions

Abstract The Dual Coolant Lithium Lead breeding blanket concept being developed by EUROfusion uses PbLi to breed tritium and to refrigerate the blanket. The location of electrically insulating Flow Channel Inserts (FCIs) as tubes floating inside the liquid is considered a good solution to minimize the magnetohydrodynamic (MHD) drop. A steel-alumina-steel sandwich-like FCI was here analyzed. Neutronic studies provide an estimation of the FCI impact on the tritium breeding performance of the blanket while its behavior under irradiation was estimated under representative DEMO pulsed operational scenario for activation and transmutation assessments. The generated flow velocity profile due to MHD simulations suggests the formation of high jets in the 2mm-gap near the side-walls. The mechanical stability and the insulation properties of the FCIs were tested after submitting commercial alumina ceramic tubes to several thermal cycles and thermal gradients between surfaces. The thermomechanical analysis anticipates tolerable stresses in the alumina part under a representative temperature distribution, whereas the restriction to freely expand originates important peak stresses in the internal steel jacket. Results indicate the moderate viability of these steel protected ceramic structures as insulating devices for FCI applications, although the advantages of introducing the naked ceramic tube have been also pointed out.