Toroidal Field coils manufacturing gains momentum

Ever since Dr Heike Kamerlingh Onnes walked the pace of superconductivity back in 1911, there have always been scientists endeavouring to exploit its tremendous properties through powerful;  high magnetic field magnets.

These endeavours are turning into a reality at ITER, as the largest and most powerful superconductive magnets ever designed, with an individual stored energy of 2.2 Gigajoules (GJ), are being manufactured.

The Toroidal Field Coils is the ITER magnet system responsible for confining the plasma inside the Tokamak vacuum vessel, using Cable-In-Conduit niobium-tin-based conductor technology.

Procurement for the 19 Toroidal Field Coils (TFCs) is shared between the Japanese Domestic Agency (JA-DA), and the European Domestic Agency Fusion for Energy(EU-DA).

Following the last call for tender in August 2012, the first of a series of procurement contracts of the nine Japanese TF coils has been awarded to Mitsubishi Heavy Industry as a main contractor, with Mitsubishi Electric Corporation (MELCO), as a sub-contractor — a well-known stakeholder in superconducting magnet world.

_To_39_Tx_TF Coils are encased in large stainless steel structures. The nineteen encasing stainless steel coil structures (TFCS) procurement is the responsibility of the Japanese Domestic Agency (JA-DA) who recently placed two contracts respectively for First of Series European TFCS with Hyundai Heavy industry  in Korea and for Japanese TFCS with Mitsubishi Heavy Industry in Japan.

With a total weight of 3400 tons, the „superstructure” of TF coils is pushing the limits of manufacturability. Millimetric tolerances require state-of-the-art welding techniques (plate thickness on 316LN is up to 180 mm) to reach high quality requirements. As a result it is necessary to use specialists in heavy industry.

From 1 to 3 October 2012, the Collaboration Toroidal Field Coil Working Group met in NAKA (Japan) after visiting Hyundai Heavy Industry, Mitsubishi Heavy Industry and MELCO manufacturing premises. This meeting was attended by TFC and TFCS Technical Responsible Officers (TROs) from the ITER Organization, the European Domestic Agency and JA-DA. Several specialists from JA-DA supplier Mitsubishi Heavy Industry were also invited to participate in the meeting.

Such meetings are essential for resolving common Toroidal Field Coil system issues between both DAs and their multiple suppliers, and to manage the interfaces and tolerances between the winding packs and the coil structures.

It goes without saying that regular contact with the Domestic Agencies industry, through meetings with TROs will guarantee the prompt solving of any issues that may arise within such a challenging production environment.

The manufacturing of the first series of double pancakes as part of first Winding packs by both DA is planned to start in September 2013, with delivery of the first winding pack in 2014 bringing up to full speed the.series production.

Given that the knowledge-based coil fabrication will be very dynamic, improving insight in those magnets tolerances will be essential as discussed with JA-DA TRO Norikiyo Koizumi and EU-DA TRO Alessandro Bonito Oliva.

Alexandro Bonito Oliva reported additionally on recent progress concerning the commissioning of the European TF winding tooling facility, the heat treatment oven and ongoing qualification tasks on joint, helium inlet and impregnation trials.

In spite of the difficulties of coordinating fabrication work with such a vast logistic and high production rate, the ITER Organization is confident in the ability of the DA suppliers and of the ITER TF IO-DA team project capacity to continue working in a cooperative and synergetic manner in order to reach our common goal.”

The TF Collaboration Meeting is also an opportunity to showcase the work done in the Japanese and European DAs. The substantial progress achieved by both European and Japanese domestic agencies would not have been possible without an effective collaboration with the TF team.