€22 billion nuclear build in France in key phase of machine assembly
The sixth of nine tokamak sector modules has been installed in the tokamak pit at the International Thermonuclear Experimental Reactor (Iter) at Cadarache in southern France, bringing two-thirds of the machine’s torus-shaped core into place.
The Iter Organisation, which oversees the world’s largest nuclear fusion project, said the approximately 1,100-tonne sector module was transferred from the assembly hall and lowered into the pit in a carefully coordinated lifting operation, which took 30 hours and concluded on 28 July, almost six months ahead of schedule.
Together with its lifting rig, the suspended load weighed nearly 1,400 tonnes.
The Iter assembly teams have been installing progressively the sector modules that form the machine’s core since April 2025 and are on track to position the final module in 2027.
Experience gained from each successive module assembly and lifting operation has increased the pace, efficiency and predictability of the work, the Iter Organisation said.
Iter director-general Pietro Barabaschi said Iter teams have translated lessons learned from each operation into greater efficiency, stronger coordination and a more predictable assembly sequence.
“With six modules now in place, we are demonstrating that this technical approach is delivering tangible results on the project’s critical path.”
The sixth module is built around vacuum vessel sector “#1,” which is the fourth and final sector manufactured in South Korea.
The Iter vacuum vessel is one of the most technically demanding components of the tokamak. Its nine double-walled stainless-steel sectors will form the ultra-high-vacuum chamber in which fusion reactions take place and will support many of the systems needed to operate the machine.
The vacuum vessel will provide the primary confinement boundary for the fusion plasma. The completed vessel will measure approximately 19 metres across and 11 metres high and will weigh about 5,200 tonnes before the addition of in-vessel components. Its double-wall structure will accommodate shielding and cooling water and provide support for equipment used to heat, diagnose and control the plasma.
Iter is designed to demonstrate the scientific and technological feasibility of fusion power. As host, Europe contributes almost half of the cost of construction, while China, India, Japan, South Korea, Russia and the US contribute equally to the remaining costs.
In May, Barabaschi said Iter was in a key phase of machine assembly and both on budget and on schedule.
He said lessons had been learned following multiple delays that set the project back and sent its costs to over €22bn ($25.1bn).
Technicians at a control desk lower the tokamak sector module into place. Courtesy Iter Organisation.
