Success for ITER Poloidal Field coils manufacturing

The momentum in the impressive Poloidal Field (PF) coils facility is growing as works are accelerating. In ITER’s first industrial on-site hub some of the most powerful magnets will be manufactured. A range of bespoke equipment, heavy cranes, a vacuum chamber and assembly stations are already in place to produce the coils that will maintain the shape and stability of the ITER plasma. Due to their impressive size and weight, four out of the six gigantic coils ranging between 17 and 25 m in diameter, and weighing between 200 and 400 tonnes, will be made in this facility. F4E is responsible for another coil, currently fabricated in China, under an agreement signed between the two ITER Domestic Agencies, and Russia will also produce one.

With all F4E contracts signed in the area of PF coils and contractors working hard, there is visible progress. In the PF coils facility, where temperature needs to be rigorously controlled, there is confidence in the air. First, a large part of the tooling is fully assembled. Second, the successful manufacture of the first complete layer of the dummy coil, in which all main winding activities have been carried out, open a new chapter for the six ITER magnets. Which are the main fabrication stages so far? First, the conductor was unspooled, straightened, cleaned with in a ultrasound bath, bent to the correct radius and then sandblasted, washed and dried before being finally insulated with five layers of glass/polyimide. A team of ten people from F4E, CNIM, Sea Alp and ASG, has been involved in this task.

The second coil layer of conductor is expected to be completed early next year in order to form, as it is known in the ITER jargon, the first dummy Double Pancake (DP) for the fifth poloidal field coil which has a diameter of 17 m and weighs roughly 30 tonnes. When the production of the second layer begins, it will be placed on top of the first layer in a controlled manner, after performing a “layer joggle” using a tool specifically designed by Sea Alp, F4E’s supplier for winding tooling. Two Helium Inlets will also be welded on these inter-layer joggles to supply the DP with helium at a temperature close to -269 °C. Then, the DP will be insulated and prepared to be electrically tested. When the second layer is completed, the dummy DP will be lifted and moved to the next working station in order to prepare the electrical connections between conductors and add further insulation. Subsequently, the DP will be moved to the next station where it will be impregnated with epoxy resin. Finally, the DP will be sliced in eight sections and stacked to reproduce a mock-up of the entire PF coil.

For Pierluigi Valente, Technical Responsible Officer for the supply of the European share of PF coils, the installation of tooling and the development of engineering processes are of great importance. “What you see today in the PF coils Facility is the result of the work which started almost three years ago. We have been collaborating with ASG to integrate all these manufacturing stages and seeing them in practice is extremely gratifying” he explains. “All these stages are essential and need to be carried out carefully in order to validate the manufacturing processes. For example, it is challenging to control the exact length of conductor that we need to unspool and then accurately measure the turns wound on the table” explains Pierre Gavouyere-Lasserre, F4E’s Technical Officer overseeing the PF coils’ winding. The progress of tooling has also been an important achievement for F4E’s Technical Officer, Gian Fachin, who has been following this task. “We started almost a year ago the assembly of the winding table, which was produced by the SEA Alp consortium, and today nearly 80% of the equipment, manufactured by Elytt Energy, Alsyom and Seiv has been delivered” he explains. By the end of this year, the tooling for the stacking of the DPs and the final fabrication stages will be in place. In case you are wondering how many DPs will be produced for each PF coil, manufactured in Europe, the answer is between 6 and 8. So rest assured that the workforces in the facility will be busy for a while making some of the biggest magnets ever made in history.

A similar scenario is unfolding more than 8 000 km away from Europe’s PF coils facility in China’s Hefei province. PF 6, the sixth and one of the smallest in diameter, is being manufactured through a collaboration agreement signed in 2013 between F4E and ASIPP (China’s Institute for Plasma Physics). The first full layer using a dummy conductor is coming along nicely. The team of technicians has been working hard to complete the first layer and work is ongoing for the second. Peter Readman, F4E’s Technical Officer, highlights the extremely good collaboration between F4E and ASIPP and praises the high quality of work. “Thanks to the good team spirit between the two organisations, we have managed to stick to our schedule and carry out the technical work with rigour and precision. When we carried out a pre-qualification test of a joint at the Sultan facility in Switzerland, the centre of excellence where conductors are tested to their limits, the technicians there acknowledged that the work was of high quality” he explains.

In overall terms the production of the two dummy coils for the fifth and sixth PF coils, although sited on different continents, are neck and neck as we head towards the end of 2016. Kevin Smith, F4E’s Poloidal Field coils Manager, gives his impression and offers a forecast: “We have made great progress with both coils this year, a clear testament to the very good work and diligence of the teams in Cadarache and Hefei. As we go into 2017, we are excellently positioned for handing over the two coils to the ITER Assembly team in the first half of 2019!”