Full scale electrical insulation coating development

Abstract

A de-mountable mechanical system has been designed by ITER-IT for the attachment and the remote handling of the blanket modules. The modules are attached to the supporting structure by bolting using four flexible radial supports (cartridges) which are electrically insulated from the vacuum vessel to avoid high-value circulating currents. The hydraulic coaxial connectors also electrically connect the blanket to the module and straps are used to provide an electrical path for halo currents. Coating the contact surfaces with alumina provides the required electrical insulation. The objective of this work was to test the performance of the electrical insulation coatings specified for the ITER blanket attachment design. The testing campaign required the manufacture of mock-ups and the application of alumina coating by plasma spray technique. The flexible attachment system was mechanically tested with a 500 kN push/pull load for 1000 cycles. Another assembly was thermally cycled between 150 and 300 °C for 1000 times in inert gas atmosphere and then mechanically cycled. The activity included mechanical testing of two pairs of wedged coated keys under an impact load of 500 kN applied 1000 times. No failures and damages occurred on the alumina coatings, which preserved good insulating and mechanical properties confirming suitability for the ITER blanket system.