ITER’s massive high-voltage boxes manufactured

At ITER, trucks carrying Neutral Beam power supplies have become a familiar sight, part of the usual traffic on-site. Each week, a new convoy rolls in to bring the European-made equipment that will feed with 1MV ultra-high voltage the two injectors heating ITER’s plasma. Yet, the amount and sheer size of the pieces leave no doubt—these are no ordinary deliveries.

The power supplies started arriving last May, becoming the first systems for the Neutral Beam injectors to reach the site (while the assembly of the MITICA prototype carries on in Italy). The shipments accelerated in autumn, with the equipment that will make up the High Voltage Deck (HVD) and Bushing Assembly (HVBA). These huge components, procured by F4E, were manufactured in Germany by Siemens and its subcontractors Andreas Karl and HSP. There are two units of each, one per injector. In total, it will take 40 truckloads to deliver the equipment, with the last ones envisaged for March 2025.

The HVD is often described as a large Faraday insulated cage. What does this mean? Essentially, it is a steel box designed to isolate the ion source power supplies from the ground and cancel electromagnetic interference. The cage rests at 6 m high, supported by eight insulated pillars. Inside this 80-tonne structure, there will be 50 tonnes of transformers, converters, control cubicles and other high voltage equipment, distributed in two floors.

“These power supplies in ITER are beyond industrial standards. There are few electric applications working at this voltage level (-1 MV) and with these dimensions,” explains Gerard Gómez, F4E Technical Responsible Officer. This was the hardest challenge in the design: the HVD must withstand the heavy load whilst keeping a perfect electromagnetic insulation. Then, the bushings will allow the safe transmission of the current out of the box and towards the injector, protecting with insulating gas the cables provided by Japan.

F4E’s contract with Siemens started a decade ago with the fabrication of a first unit for the MITICA real-size prototype. The electrifying success of the tests proved that the concept worked. “MITICA helped us to polish our knowledge about the design and behaviour of the systems, minimising the risk of events such as electrical discharges. We have capitalised on this experience for the ITER units,” asserts Michael Krohn, Project Manager at Innomotics, formerly part of Siemens.

“The partnership we developed with our suppliers over ten years, marked by adaptability and trust, has been pivotal to this contract’s success,” adds Gómez. As the lorries keep coming, ITER is placing the equipment in storage. Next autumn, when the high voltage building is completed, they will be assembled into the two metallic towers, ready to channel their power into ITER’s heating beams.