Cryogenic structural materials for the ITER superconducting magnets

Okuno, Kiyoshi; Nakajima, Hideo; Hamada, Kazuya; Kawano, Katsumi; Takano, Katsutoshi; Tsutsumi, Fumiaki

The ITER superconducting magnet system consists of 18 Toroidal Field (TF) coils, one Central Solenoid (CS) and six Poloidal Field (PF) coils. The TF coil has a D-shape with a height of 14 m, a width of 9 m and a weight of 310 tons. In order to sustain large electromagnetic forces, the TF coil has a massive coil case that contains a winding pack The total weight of stainless steel required for the 19 TF coils (18 + one spare) amounts to 3,800 tons in finished shape, which corresponds to more than 10,000 tons in raw materials. Trial fabrications of the TF structures are underway at full scale in extensive collaboration with industries. Complete database on mechanical properties of these materials is being established. Technologies for the machining and welding of these materials into coil case segments are also under development and successful results have so-far been obtained.