Toroidal field coils
First cold test in Europe
14 May 2018
The first ITER toroidal field coil winding pack has spent nearly 20 days in a specially conceived cryostat at minus 193 °C (80 K), in a cold testing operation that confirmed the integrity of the insulation system.
The first toroidal field winding pack (110 tonnes) fabricated in Europe is lowered into a specially designed cryostat for cold testing. © SIMIC
The first cold testing operation of the European toroidal field coil program was successfully carried out by European contractor SIMIC near Venice, Italy, last month. Cold testing, which involves submitting the coil winding pack to a thermal cycle between room temperature and 80 K, is the penultimate step in the toroidal field coil fabrication process—intervening before the magnet inner core is inserted into a structural case.
The first toroidal field winding pack produced in Europe was shipped from its manufacturing location last November. Reception teams at SIMIC first performed a series of dimensional and electrical inspection tests, before lifting the component into a specially constructed cryostat, where the winding pack was cooled to 80 K (193 °C) for nearly 20 days using a combined cycle of nitrogen and helium. Electrical connections placed at the exits of the chamber were tested with a current of 1000 amps.
Cold testing allows the magnet teams to ensure that the coil insulation is robust and that the component can be cooled to superconducting temperatures without cracks forming. The winding pack will now be inspected again through dimensional and electrical tests, before transfer to the assembly rig for insertion.
The final industrial operation for ITER's toroidal field coils is the insertion of the winding pack into a structural steel coil case. The case elements will be fitted over the winding pack with millimetric precision, before closure welds of up to 12 centimetres in thickness are realized. Each weld will be verified through ultrasonic testing, and the gap between the inner core and the case will be filled with reinforced resin to ensure the mechanical continuity of the coil.
In the final step of the manufacturing process, the winding pack will be inserted into a steel jacket. The elements of the first coil case, procured by Japan, have arrived at the SIMIC facility. © SIMIC
At SIMIC the cooling chamber, the specialized tooling and the laser measuring equipment took almost one year to assemble, explains the company's commercial manager Marianna Ginola. "... We have invested in the infrastructure of our plant, collaborated extensively with our subcontractors, and trained our workforces for the delicate operations that we will have to carry out." SIMIC is collaborating with subcontractor Babcock Noell GmbH for some of the tooling and technologies.
Japan is procuring all coil cases, as well as nine of the toroidal field winding packs. Europe is procuring the other nine toroidal field winding packs plus a tenth, as a spare.
The ITER magnet procurement program—six participating Domestic Agencies, four superconducting magnets systems—has been the longest-lead and most international of all ITER procurement packages.
Read the full report on the European Domestic Agency website.