ITER vacuum vessel sector modules continue to be installed in the tokamak pit

Vacuum vessel fabrication and module build

ITER’s plasma chamber, the vacuum vessel, is the structure that houses fusion reactions and serves as a first safety containment barrier. With an interior volume of 1,400 cubic metres, the chamber will be formed from nine wedge-shaped steel sectors measuring more than 14 metres in height and weighing 440 tonnes each. When assembled, the ITER vacuum vessel is described as having an outer diameter of 19.4 metres, a height of 11.4 metres, and an approximate weight of 5,200 tonnes. After installation of in-vessel components including the blanket and the divertor, the vacuum vessel total weight is stated as 8,500 tonnes. Each sector module includes a vacuum vessel sector, two toroidal field coils, thermal shields, and auxiliary components, with lifting equipment and stabilising beams attached for the lift operation.

Core sector-module installation progress

The fabrication of the vacuum vessel sectors is shared between Europe (five sectors) and South Korea (four sectors). South Korea’s initial responsibility covered producing two vacuum vessel sectors, and an additional agreement in 2016 extended its scope to produce two more sectors originally assigned to the EU. Sector modules that make up the ITER core have been progressively installed within the tokamak pit since April 2025. The sixth tokamak sector module, #1, weighing about 1,100 tonnes, was transferred from the Assembly Hall and lowered into the pit in a coordinated lifting operation that mobilised more than 100 people, took 30 hours, and concluded on 28 July. The suspended load, including its lifting rig, is described as nearly 1,400 tonnes. The latest sector installation is said to bring two-thirds of the torus-shaped core into place. With sector module #1 now complete, it joins the five others already in the tokamak pit: #4, #5, #6, #7 and #8.

Schedule outlook for remaining modules and torus joining

ITER states that it is on track to install the final sector module in mid-2027, with teams continuing to identify opportunities for further schedule optimisation. The project says it expects a seventh sector module to be transferred before the end of the year. Once all nine sector modules are positioned in the pit, teams will proceed with the work of joining the sectors to complete the torus.