Tokamak assembly

Why the removal of the first radial beam is a good sign of progress

12 Oct 2026

Vacuum vessel sector #5 and its radial beam—a critical element of support during Assembly Hall activities and the first few months in the tokamak pit—have parted ways.

In a first-of-its-kind operation at ITER, a radial beam is extracted from the tokamak pit, an essential step towards welding readiness and the start of other key assembly activities.

Radial beams are temporary lifting tools that support and stabilize sector modules weighing more than 1,000 tonnes as they are lifted from Assembly Hall tooling and lowered into the tokamak pit. After the modules are in position, these 80-tonne beams rest between the central column and the bioshield wall, holding vacuum vessel sectors securely in place for months while they are precisely aligned, stability clamps are attached, and their load is transferred to gravity supports and the tokamak’s underlying support system, the crown.

Only once these engineering tasks are completed and metrology confirms that a sector is stable can its radial beam be removed. This operation was carried out for the first time at ITER on Wednesday 7 October as the beam for sector module #5 was successfully extracted from the pit.

“The removal is an important milestone because it is the last step to demonstrate that the structure is now sufficiently stable,” says Sébastien Koczorowski, ITER’s Deputy Program Manager for the machine assembly. “This marks a major transition in the assembly process as it opens the way for welding and ex-vessel assembly activities in the tokamak pit that cannot proceed while the radial beams remain in place.”

Lifting engineer Gael Hardy checks the hooks and slings on the crane before it moves to the tokamak pit to extract the first radial beam.

The operation to remove the radial beam involved a team of more than 20 people and took a little less than two hours.

“This operation has real importance because it shows the progress we are making in assembly,” says Colin Smith, the tokamak assembly engineer who oversaw the radial beam extraction. “Now that the first one has been successfully removed, three others will follow in rapid succession.”

The extraction of the radial beams is the first step in a longer sequence that will transform the tokamak pit. The final sector module is scheduled to be lowered into the pit in spring 2027, with the last radial beam expected to be removed in September 2027.

Once all nine beams have been removed, the central column that has served as a temporary support and alignment structure during sector installation can also be dismantled and extracted from the pit—an operation that is expected to take place over approximately six weeks at the end of 2027.