Fabrication Process Qualification of TF Insert Coil Using Real ITER TF Conductor

JAEA is fabricating the toroidal field insert coil (TFIC) in cooperation with Hitachi, Ltd. This solenoidal coil has about 50 m of ITER TF conductor wound in a 1.44-m diameter. In preparation for fabricating the TFIC, fabrication trials of windings, removal of Cr plating of the cable and welding of the terminal sleeve were performed for process qualification. The winding trials were accomplished without breaking any of the superconducting strands. In the trials to remove the Cr plating from the cable, HCl-soaked unwoven cloth was used, and the surface of a strand selected from the cable was confirmed by magnification to be free of Cr plating. In trials to fabricate termination, using electron beam welding (of OFHC copper and SS316LN) and fillet-welding (of SS316LN and SS316LN using JK2LB weld wire), tensile tests of the welds were conducted at room temperature and 4 K, and ultimate tensile strength values equivalent to that of the base metal of the weld were obtained. Also these welds passed test items of JIS Z3040 code, so the weld procedures were qualified. During fillet-welding the maximum temperature of the cable under the weld was 120 °C, not high enough to damage the cable. From the results obtained, the main processes involved in TFIC fabrication were established and qualified.