Subscribe options

Select your newsletters:

Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Port cells | All 46 doors in place

    In ITER, ordinary objects and features often take on an awesome dimension. Take the doors that seal off the port cells around the Tokamak for instance. Doors th [...]

    Read more

  • Toroidal field coils | Two make a pair

    One of the essential 'building blocks' of the ITER Tokamak is the pre-assembly of two toroidal field coils, one vacuum vessel sector and corresponding panels of [...]

    Read more

  • Industrial milestone | Cryostat manufacturing comes to an end in India

    With a flag-off ceremony on 30 June, India's L&T Heavy Engineering marked the end of an eight-year industrial adventure—the manufacturing of the ITER cryost [...]

    Read more

  • Local partners | A celebration for ITER's "vital artery"

    ITER is made possible through the work of thousands of scientists, engineers, workers of all trades and industries across the globe. It is also made possible by [...]

    Read more

  • Photo reportage | Travelling with a coil

    From the salt marshes of the inland sea Étang-de-Berre to the rolling hills around the ITER site (with a view of some of the highest alpine summits) an ITER con [...]

    Read more

Of Interest

See archived entries

Trying on the Tokamak crown

R.A.

On the very place where the ''B2 slab'' mockup was standing just a few months ago, a new Tokamak support system (''crown'') mockup has been under construction since the end of 2014. (Click to view larger version...)
On the very place where the ''B2 slab'' mockup was standing just a few months ago, a new Tokamak support system (''crown'') mockup has been under construction since the end of 2014.
A crown usually sits on a king's head, or on the top of prestigious buildings such as cathedrals or skyscrapers.

In ITER, the "crown" sits under the machine: it is the structural element that supports the combined mass of the cryostat, vacuum vessel, magnet system and thermal shield—in short, the support system for the 23,000-tonne machine. From both a structural and safety perspective, it is one of the most strategic parts of the installation.

Designing the ITER crown has proved an utterly complex and challenging task, involving several ITER departments as well as experts from the ITER European agency and its architect-engineer Engage.

The crown's complexity stems from the fact that the huge mass that it will support will not be an idle one. In the course of operation, the ITER Tokamak might slightly "up-lift", wobble, or shrink...causing considerable load transfers from the machine to the Tokamak Building basemat.

In late 2012, following some ten months of collaborative effort, the crown design was finalized: it will consist of a thick, circular concrete structure connected to the three-metre-thick bioshield by radial concrete walls. 

The mockup will consist in a 20° segment of the Tokamak crown, complete with a one-metre-thick radial wall and a three-metre-thick section of the bioshield. (Click to view larger version...)
The mockup will consist in a 20° segment of the Tokamak crown, complete with a one-metre-thick radial wall and a three-metre-thick section of the bioshield.
In order to allow for the smooth transfer of horizontal and rotational forces generated by the movement of the Tokamak, 18 spherical bearings acting like ball-and-socket joints will be installed between the concrete crown and the steel ring that acts as the interface with the cryostat.

Actual construction, however, is a long way from 3D design documents. When a structural element is as complex and as strategic as the ITER crown, an intermediate step is necessary to demonstrate constructability.

"Just like for the Tokamak Complex basemat slab, we need to be certain that the rebar principles we have opted for are constructible, and we need to qualify the bespoke concrete formula," explains ITER's Nuclear Buildings Section leader Laurent Patisson. "And there's only one way to do this: by trying it first on a real-size mockup."

On the very place where the "B2 slab" mockup was standing just a few months ago, a new mockup has been under construction since the end of 2014. When completed, the large structure will reproduce a 20° segment of the Tokamak crown, complete with a one-metre-thick radial wall and a three-metre-thick section of the bioshield.



return to the latest published articles