Overview of the ITER project, and our variable experiences in the development of some critical components of the magnets

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ITER has now reached the stage where about half of the large magnet components have arrived on site and many more are nearing completion at manufacturing locations distributed throughout the ITER partners. Although we still have several years of challenging on-site assembly ahead, the acceptance tests and first-of-a-kind assembly are teaching us a lot about the magnet quality and possible improvements for future tokamaks.

The webinar, presented by Neil Mitchell, will summarise the present status of manufacturing and assembly. Neil will then chose three areas, critical to magnet and tokamak performance, to describe in more detail:

1. Development of Nb₃Sn strands for fusion applications started in the 1980s and the selection of the material for the Toroidal and Central Solenoid Coils in the first phase of ITER 1988–1991 was a key driver of the overall tokamak parameters. The development, qualification and procurement, both before and after the decision to use it, gives us an unusual opportunity to look at the implementation of a novel technology in its entirety, with the expected and unexpected problems we encountered and how they were solved – or tolerated.

2. High-voltage insulation in superconducting magnets is a frequently overlooked area that demands many new technologies. It is the area in the ITER magnets that has created the most quality issues on magnet acceptance and is clearly an area where more engineering attention is required.

3. The need for improvements in overall integration of the magnets into the tokamak, and in particular maintainability and repairability, is being demonstrated as we assemble components into the cryostat. The assembly is proceeding well in terms of quality but at the same time, the complexity shows that for a nuclear power plant, we need improvements.

After completing his PhD at Cambridge University on the fluid mechanics of turbomachinery, Neil Mitchell entered the nuclear fusion world in 1981 during the completion of the JET tokamak, and participated extensively in the early superconducting strand and conductor development programme of the EU in the 1980s, as well as in the design/manufacturing of several small copper-magnet-based magnetic fusion devices, including COMPASS at UKAEA. He was involved in the prototype manufacturing and testing of the superconductors that eventually became the main building blocks of the ITER magnets, and participated in the development and first tests of facilities such as Fenix at LLNL and Sultan at PSI. He has filled several positions within the ITER project after joining as one of the founder members in 1988, in particular, as the section leader for the ITER conductor in the 1990s with the highly successful construction and test of the CSMC in Japan and TFMC in Europe, and then after as division head responsible for the magnet procurement. He was responsible for finalising the magnet design, negotiating the magnet in-kind procurement agreements with the ITER Home Institutes and direct contracts, following and assisting the industrial production qualification and ramp up in multiple suppliers in EU, Japan, Korea, China, US and Russia. The ITER conductor production was completed in 2016 and now with the completion of the first-of-kind magnets, the delivery to the site of several coils and the placement of the first PF coil in the cryostat, he is working as an advisor to the ITER director. He is deeply involved in problem solving in the interfaces to the ITER on-site construction as the ITER magnets are delivered, contributing to the magnet control and commissioning plans, and advising the EU on the design of a next-generation fusion reactor.