ITER tokamak assembly passes halfway as fifth sector module lands in pit

Five of nine vacuum vessel sectors now in place inside the ITER tokamak pit, with 200 degrees of the plasma chamber assembled and two further sector module installations scheduled before the end of 2026

(Image courtesy of ITER)

Five of nine vacuum vessel sectors are now seated in the ITER tokamak pit following the successful installation of sector module #4 on the 27th of May. The 36-hour operation brought the plasma chamber past the halfway mark and continued a tightening learning curve that has ITER’s assembly teams completing sector modules faster than the project’s own baseline schedule projected.

ITER vacuum vessel assembly reaches critical midpoint

The lift of sector module #4 unfolded in three distinct phases spanning 26 to 27 May. Nine hours of pre-lift tests and verifications began at 6:00 a.m. on Tuesday, covering metrology confirmation and sequential test lifts to 90 mm and then 500 mm. Transfer to the tokamak pit then took 12 hours, with the module arriving 500 mm above its final landing position at 3:00 a.m. on Wednesday.

From there, 15 hours of ultra-precise landing manoeuvres followed. Teams reconnected sensors, verified alignment with gravity supports, and brought the 1,400-tonne lift (including rigging) into contact with the TIPI tables – the toroidal field coil in-pit installation tools used for adjusting and positioning components later in the assembly process. The overhead cranes released the full weight shortly after 6:00 p.m.

Mathieu Demeyere, the principal construction manager who supervised the operation for ITER, credited the outcome to preparation and team responsiveness, saying the ability to adapt to challenges as they arose made a safe landing possible. Tokamak assembly at ITER now encompasses five vacuum vessel sectors standing side by side in the pit, with 200 degrees of the plasma chamber in position.

Tokamak assembly learning curve accelerating ahead of schedule

Each sector module installation has delivered measurable gains in assembly efficiency, and sector module #4 marks the clearest evidence yet. Sector module #7, the first to be assembled under the current programme, took 7.4 months from the time its vacuum vessel sector entered tooling to the moment it landed in the pit in April 2025. Sector module #4 completed the same process in 5.5 months, a reduction of nearly two months.

Sector module #4 landed ahead of the ITER Baseline schedule, as have its predecessors in the pit, with lessons learned continuing to drive greater efficiency at each successive installation. The CNPE Consortium, the international industrial partnership serving as principal contractor for tokamak assembly, worked alongside ITER Organisation teams through rotating shifts over the full 36-hour operation.

Nicolas Sapet, the ITER project leader for sector module sub-assembly, said the learning curve effect had been expected but was materialising more quickly than anticipated, with progress driven by experience accumulated across teams.

A sixth sector module is scheduled for installation this summer on the opposite side of the machine. A seventh is expected before the end of 2026, keeping plasma confinement hardware on track as the project works toward a complete nine-sector vacuum vessel.

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