Assembly of the ITER fusion device in Saint-Paul-lez-Durance, France, has reached a significant structural milestone with the successful installation of the sixth of nine vacuum vessel sectors. The operation, completed on 29 July 2026, means two-thirds of the core toroidal structure of the tokamak is now in place. This achievement places the assembly process approximately six months ahead of the revised project schedule, demonstrating a notable acceleration in construction and integration activities at the site. Each sector, a massive D-shaped steel component, forms a 40-degree segment of the vacuum vessel that will ultimately contain the fusion plasma. The successful lowering and positioning of this component into the tokamak pit is a critical step toward completing the machine's primary confinement boundary. Source: ITER

The vacuum vessel is a hermetically sealed, double-walled stainless steel container that houses the fusion reactions. Its nine sectors, once welded together, will form a torus with a total plasma volume of 840 cubic meters. The space between the double walls will be filled with cooling water and in-vessel shielding blocks to protect external components, such as the superconducting magnets, from intense heat and neutron flux. The precision required for the placement of these multi-hundred-tonne components is extreme, with tolerances in the millimeter range, to ensure the magnetic fields can accurately shape and control the plasma. This phase of assembly is a complex logistical and engineering challenge, coordinating the delivery and preparation of components from international partners before the final on-site lift. Source: ITER

The vacuum vessel is a hermetically sealed, double-walled stainless steel container that houses the fusion reactions.

This progress follows a period of schedule re-baselining and focused efforts to overcome earlier delays related to component manufacturing and the global pandemic. The accelerated pace is attributed to refined assembly sequencing and improved workflow efficiencies developed by the ITER Organization and its industrial partners. The installation of a sector module is not a singular event but the culmination of a multi-stage process of pre-assembly. Each sector arrives on site and is then fitted with thermal shielding and two toroidal field coils in the main Assembly Hall before being designated as a sector module, a combined load weighing over 1,200 tonnes. The successful integration of these complex sub-assemblies is a testament to the collaborative framework of the international project. Source: ITER

With six of the nine sectors now installed, the project's focus will shift to completing the toroidal structure and beginning the intricate process of welding the sectors together to form a single, vacuum-tight chamber. The final three sectors are expected to be installed in the coming months, followed by the closure of the torus. Subsequent major assembly steps will include the installation of the central solenoid, the remaining poloidal field coils, and the cryostat lid. Achieving this two-thirds milestone is a critical prerequisite for these future activities and keeps the project on track for the start of integrated commissioning and eventual First Plasma operations. The demonstrated momentum is a positive indicator for investors and partner governments monitoring the project's progress toward its ultimate goal of demonstrating a net energy gain, or Q_plasma > 10. Source: ITER