Progress in manufacturing and testing of a first wall mockup for NET/ITER

The proposed first wall (FW) for the NET/ITER (Next European Torus/International Thermonuclear Experimental Reactor) consists of a box structure, made of stainless steel, with an active cooling of the side facing the plasma by a flow of water through the tubes inserted into it. An innovative brazing process to improve the quality of the brazed joints between cooling tubes and plates has been developed and optimized within the framework of NET technological task PDT 1.2. The brazing technique is based on creep expansion of the tubes during the high-temperature holding time of the brazing treatment, which minimizes the gap that was initially present around the tubes. A flat, mockup FW panel with plate dimensions 622×216×33 mm and with eight cooling tubes was built using this technique. Thermal fatigue tests are scheduled to be carried out in the near future on this mockup. An automatic, computerized procedure for the nondestructive examination, of the brazed joints using ultrasonic probes has also been developed