Subscribe options

Select your newsletters:


Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Heating | A pinch of moondust in the ITER plasma

    One day in the distant future, fusion plants might be fuelled by helium 3—an isotope that is extremely scarce on Earth but reputed to be abundant on the Moon. B [...]

    Read more

  • Delivery | 2,000 km through canals, locks and tunnels

    When the thruway is closed, one takes the back roads. And when it's low-water season on the Rhine-Rhône canal, a barge leaving Switzerland for the Mediterranean [...]

    Read more

  • Monaco Fellows | A hand in shaping ITER

    For the sixth time, ITER is welcoming a group of five young researchers as part of the Monaco-ITER postdoctoral fellowship scheme. Working alongside experienced [...]

    Read more

  • On site | Drone survey on a perfect day

    There are days in winter when the skies over Provence are perfectly transparent. Snowy peaks 200 kilometres away appear close enough to be touched and farms, co [...]

    Read more

  • AAAS conference | ITER on the world science stage

    With more than 120,000 members globally, the American Association for the Advancement of Science (AAAS) is billed as the world's largest scientific society. The [...]

    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