Europe delivers ITER vacuum vessel Sector 9 on schedule

Sector 9’s double-walled vacuum vessel shell takes shape at Westinghouse Mangiarotti ahead of its Adriatic shipment to ITER.

(Image courtesy of Fusion for Energy)

Europe’s AMW consortium has shipped its third vacuum vessel sector for ITER, meeting a deadline set three years ago and closing out what the teams involved describe as one of the most demanding fabrication campaigns in the project’s history. Sector 9 left the Westinghouse Mangiarotti plant in Monfalcone, sailed out of the Adriatic, and is now heading to Fos-sur-Mer before the final road leg to Cadarache. It will join Sector 5, already installed in the tokamak pit, and Sector 4, currently in sub-assembly.

The vacuum vessel is a double-walled stainless steel torus that will ultimately measure 19.4 metres across and 11.4 metres high, weighing around 5,200 tonnes once all nine sectors are welded together. Each sector accounts for roughly 440 tonnes of that total. The structure has to maintain ultra-high vacuum conditions while taking the full thermal and electromagnetic loading of a burning plasma, which puts the manufacturing tolerances somewhere between aerospace and nuclear pressure vessel work. Each sector runs to approximately 150 kilometres of weld beads, and it is that welding burden that created the problems on Sector 9.

Late in the fabrication sequence, inspections flagged defects in a number of joints. The repair required opening sections of the completed structure, grinding out the affected material through restricted access, reheating, and rewelding, all while keeping the overall dimensional envelope within specification. With each segment of Sector 9 having been produced at a different facility, ENSA in Spain, Belleli and Walter Tosto in Italy, and Westinghouse Mangiarotti itself, the logistics of coordinating repairs across a distributed supply chain added another layer of difficulty. Helium leak testing at 10⁻⁹ mbar·l/s and ultrasonic scanning confirmed the repaired joints before the sector was cleared for shipment.

The on-schedule delivery matters beyond the milestone itself. Vacuum vessel sectors from other Domestic Agencies have not fared as well. Korea’s sectors ran into dimensional non-conformities that required extensive remediation work at the ITER site, with Sector 8 completing a 20-month repair campaign only recently and returning to sub-assembly tooling ahead of pit installation. Those delays reshuffled the in-vessel assembly sequence and put pressure across the entire critical path.

Against that backdrop, AMW delivering Sector 9 on time is a meaningful data point for F4E’s remaining two European sectors. Both are advancing and are expected to complete later this year. If that holds, F4E will have turned around five vacuum vessel sectors through a single industrial consortium without a programme-level slip, which is a different outcome to what other parts of the ITER supply chain have experienced. Whether the pace translates to first plasma by 2034 depends on a lot more than vessel completion. In-vessel components, the divertor, and the blanket installation sequence all carry schedule risk. But closing out the vessel fabrication without adding to the project’s delay count is a prerequisite for anything else falling into place.

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