Technical aspects and manufacturing methods for JT-60SA toroidal field coil casings

JT-60SA is a superconducting tokamak machine to be assembled in Naka site, Japan, designed to contribute to the early realization of fusion energy by supporting the exploitation of ITER and research toward DEMO.In the frame of the Broader Approach Agreement a contract between ENEA and Walter Tosto (Chieti, Italy) started on July 2012 for the construction of 18 TF coil casings for JT-60SA. Two different sets of 9 casings each will be progressively delivered, from 2013 to the end of 2015, to ASG Superconductors (Genoa, Italy) and to Alstom (Belfort, France), where the integration of the winding pack into the casing will be carried out.Each TF coil casing (height 7.5 m and width 4.5 m) consists of four main components: one “Straight Leg Outboard” and one “Curved Leg Outboard” both with their own covers, “Straight Leg Inboard” and “Curved Leg Inboard”. The casing components are segmented in forgings and plates made of FM316LNL. The straight leg outboard is composed of two wings welded to a central core and two elbows welded at the ends with a cooling channel installed inside. Elbows of straight leg outboard are segmented in two half-elbows machined from 1 rough forging and welded to the central core made by plate. Welding of wings to the central core is performed in EBW (electron beam welding) and the straight part is welded to the elbows by NGTIG (TIG narrow gap) process. The curved leg outboard is composed of two wings welded to a central core for a final shape of “D”. Other supports are welded by TIG or Electrode process.This paper describes the technical design solutions, the manufacturing methods defined and the particular processes adopted, such as welding (EB, TIG), non-destructive examinations (NDE), vibration stress relief (VSR) and laser tracker survey, most of which have been validated by the construction of two different sets of full scale mock-ups representing the straight and the curved legs.