Innovative Design and Material Solutions of Thermal Contact Layers for High Heat Flux Applications in Fusion Draft

One of the most critical issues associated with the design and development of sacrificial plasma facing components that have to handle the high heat and particle fluxes in ITER is achieving the necessary contact conductance between the plasma protection material and the high-conductivity material in contact with the coolant. This paper presents a novel bond idea which is proposed as one of the options for the sacrificial energy dump targets located at the bottom of the divertor legs and provides armour thermal and electrical contact with the cooled sub-structure while promoting remote, in-situ maintenance repair and an easy replaceability of the armour part without disturbing the cooling pipes or rewelding neutron irradiated materials. To provide a reliable and demountable adhesion the bond consists of a metal alloy, treated in the semi-solid region in such a way as to lead to a fine dispersion of a globular solid phase into a liquid matrix (rheocast process [1]). This thermal bond layer could be made working in the solid state during normal operation and could be brought reversibly in the semisolid state during the armour replacement simply by heating it slightly above the solidus temperature. The results of some preliminary thermal-mechanical analyses carried out to assess the heat transfer performance of these joints are reported in this paper together with some highlights on the key design, material, and remote maintenance issues which need to be rapidly addresses in the course of a R&D program.