Subscribe options

Select your newsletters:

Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Component delivery| A jewel in a box

    Sailing under the flag of Germany, the Regine is a mighty ship, strengthened for heavy cargo and equipped on its portside with two 750-tonne on-board cranes. Ha [...]

    Read more

  • Education | Make your own tokamak with 3D printing!

    It's not Lego, but it is definitely 'hands-on.' To offer a tangible device to illustrate the workings of magnetic confinement fusion in a tokamak, the ITER Orga [...]

    Read more

  • Worksite | Europe's Fusion for Energy is building the ITER installation

    Anyone driving to ITER can take full measure of the enormity of the project a few kilometers before reaching the destination. Gigantic cranes can be seen from a [...]

    Read more

  • Disruption mitigation | Experts in plasma disruptions gather online

    On 20-23 July, 120 international experts participated in the 1st IAEA Technical Meeting on Plasma Disruptions and their Mitigation, jointly organized by the Int [...]

    Read more

  • Start of assembly | World dignitaries celebrate a collaborative achievement

    Due to the constraints imposed by the COVID-19 pandemic, the crowd in the ITER Assembly Hall was small. But thanks to live broadcasting and video feed, the audi [...]

    Read more

Of Interest

See archived entries

Concrete pouring

The "slump test" ritual

R.A.

Like ancient priests bent over the entrails of a sacrificial bull, a group of men in hard hats are carefully examining a bucketful of semiliquid concrete as it slowly expands on a perfectly flat steel slab.

At night, under artificial light, the slump test procedures are evocative of an ancient ritual—like reading the future in the entrails of a sacrificial bull... (Click to view larger version...)
At night, under artificial light, the slump test procedures are evocative of an ancient ritual—like reading the future in the entrails of a sacrificial bull...
A strategic operation, one for which no chance can be taken, is set to begin—the pouring of the tokamak "crown," the massive structure that will support the combined mass of the Tokamak and its encasing cryostat (23,000 tonnes) while transferring the forces and stresses generated during plasma operation to the ground.

The "slump test" will determine if pouring operations can begin. Up until that moment, the pumps had been fed with slurry, which acts as a lubricant for the interior surfaces of the pipes. Now, operators need to make sure that the concrete coming out of the pumps is slurry-free and consistent with the required formulation.

On the steel slab, the concrete sample has stopped expanding—it is now perfectly circular and looks like an oversized grey pancake. This is the moment of truth: if the circle's diameter corresponds to a pre-established number, the concrete that comes out of the pumps matches the expected fluidity; if the diameter is larger, it means that slurry is still present and must be evacuated.

Slump tests are systematically performed when the concrete-mixing trucks leave the batching plant to deliver their load to the pumps. When using special-formulation, self-compacting concrete—like in the crown's case—slumps tests are performed again on the very site of the pouring, minutes before actual operations begin.

In the basement level of the bioshield, the ancient priests in hard hats are at last satisfied with what they see: the circle is perfect, its diameter precisely matching the right figure. Operations can begin—another long night of pouring for one of the most important structures of the whole Tokamak Complex.


return to the latest published articles