Cold Removal of Inner-Outer and Outer Inter-Coil Structure Components for ITER TF Coils

Insulated inter-coil structure components are installed to ITER TF coils to fix the aliment of the coils. In the cases of Intermediate Outer Intercoil Structures (IOIS) and Outer Intercoil Structures (OIS), custom machined sleeves (CMSs) with Al2O3 coating are installed in the holes of TF coil structure. The IOIS/ OIS CMSs are possibly stacked in the IOIS/ OIS holes during their cold installation, and surface of their Al2O3 coating would thermally contact with the IOIS/ OIS holes tightly. Thus we propose a method to remove the CMS without damaging its insulation. In the method, the IOIS/ OIS CMSs are removed by cooling with liquid nitrogen (cold removal). The gaps of the IOIS/ OIS CMSs and holes ( increment ) are influenced by contact thermal resistance between them (Rct). Thus, in this study, we first numerically estimated the gap between the IOIS/ OIS CMSs and holes. Then, the cold removal was experimentally demonstrated with mock-ups of IOIS/ OIS holes and CMSs. In addi-tion, an insulation test of the Al2O3 coating to confirm their soundness after the cold removal. It was numerically shown that increment became > 57 & mu;m, which was sufficiently large considering the manufacturing tolerance of IOIS/ OIS holes, even if Rct is 0. The experimental result showed that IOIS/ OIS CMSs were successfully removed from the IOIS/ OIS holes. Moreover, the insulation test demonstrated that the cold removal did not influence on the insulation resistance of the IOIS/ OIS CMSs.⃝c 2023 The Japan Society of Plasma Science and Nuclear Fusion Research