Inside the arena
17 Apr 2017
A visit to the deep "well" where the ITER Tokamak assembly will begin next year begins with a journey underground ... through a maze of giant pillars, omnipresent scaffolding and spiral staircases.
All of the openings in the bioshield will allow access to the tokamak for all of the auxiliary systems needed to run the machine (fuelling, power, cooling, diagnostics, etc.). But the four ovoid-shaped openings that stand out in this picture are reserved for particular equipment—the powerful neutral beam injectors that will provide the bulk of ITER's heating power and the neutral beam used for diagnostics.
This is a place where one can get easily lost. Access, safeguarded pathways, and metal staircases move as work progresses and once-familiar itineraries often turn into dead ends.
But there's a reward to this erring. Having found (and climbed) the proper staircase, the view opens at last to what we have come to see: a concrete arena, bristling with steel rebar. The scene that sets the stage for one of the most awesome experiments in human history.
Soon, though, the view will change. The installation of a temporary steel cap—whose purpose is to protect teams below while allowing work to continue on the bioshield, above—will hide the lowest level of the Tokamak Pit from our view.
Inside the huge well of the ITER bioshield, teams are working on different levels simultaneously. The worker in yellow stands at B1 level, where the base of the cryostat will one day be supported on a concrete crown. At L1 level a temporary structure has been erected to support some of the tools and equipment needed for concrete pouring and, just above, work continues to finalize the L2 level which hosts the multi-tonne steel plates that will anchor the main assembly tool in the Tokamak Pit.
A temporary cap will soon be installed at B1 level, where you see the red line in this picture. The cap will allow workers to work safely below, while work on the bioshield continues above up to the final level: L4.
In the bowels of the Tokamak Building, this technician is patiently smoothing rough edges of concrete with a specialized tool.
Special openings for neutral beam injectors
The concrete has dried and the formwork has been removed from the special openings that have been created for ITER's neutral beam injectors.
One of the most spectacular features of the ITER site is the perfectly circular bioshield, which will rise up to the L4 level and then be capped. The bioshield will surround the cryostat, which in turn surrounds the steel vacuum vessel.