Assembly preparation

The ballet of the Titans

27 Nov 2017 - R.A.

The stage is ready, some of the props are already in place, and the show will soon begin. It will be a grand production served by an international cast of highly skilled performers. The central theme? Twin Titans, in the form of giant tools dancing a mechanical ballet to contribute to the assembly of one of the most complex machines ever conceived.

The rafters of the Assembly Hall are the catwalk of this oversized theatre. They offer a breathtaking view of the ongoing work on the stage floor some 45 metres below.

To the right side of the 6,000-square-metre open space, technicians are busy preparing for the Titans' arrival, bolting semi-circular rail tracks to steel plates anchored deep into the floor, adjusting torque, and verifying alignment with laser optics.

The Twin Titans, SSAT-1 and SSAT-2 (for vacuum vessel Sector Sub-Assembly Tool), will travel along these tracks, opening and closing their arms to bring together and pre-assemble a vacuum vessel sector with a pair of toroidal field coils plus thermal shielding—for a total mass of 1,200 tonnes. The operation will be repeated nine times, once for each of the nine vacuum vessel sectors.

The Titans will operate in close cooperation with another giant tool—the double overhead crane that will deliver the sub-components to be assembled and, when completed, will carry each sub-assembly to the Tokamak well.

The Titans will operate in close cooperation with another giant tool—the double overhead gantry crane whose lifting capacity exceeds 1,500 tonnes.

Load tests for the 1,500-tonne overhead crane will begin next week. But the dummy loads are already in place, stacked in the centre of the stage ... approximately 40 steel-and-concrete blocks that will stand in the place, for the time of the trials, of ITER's massive components.

Several tests will be performed: a static test at nominal capacity, followed by a dynamic test at 10 percent over-capacity (reproducing all of the operational movements of the crane) and a final test at 25 percent over-capacity to verify that the flexion of the 43-metre-long girders remains within specifications.

The actual production on stage will open in a little more than a year. It is expected to be one of the most spectacular in the history of science and industry.

Pour certains sur le site ITER, la journée de travail commence au bout d'une échelle de 65 mètres. Photo : Engage-AP

A truly international operation

Procured by Korea, the twin SSATs are being assembled by technicians from the French company CNIM. The operation is being closely monitored by quality insurance specialists from the ITER Organization, by ITER's Construction Management-as-Agent contractor MOMENTUM, and by a representative of the manufacturer Taekyung Heavy Industries (THI).

Trolleys and cranes of various capacities fill most of the space in the Assembly Hall rafters. Like a catwalk in a theatre, they host the invisible machinery that makes the production possible.

All the props are oversized: this massive hook is one of four, each with a lifting capacity of 375 tonnes, that belong to the double overhead bridge crane installed 43 metres above the floor in the Assembly Hall.

Load tests are scheduled to begin in the first week of December. A final test at 25 percent over-capacity (1,875 tonnes) will verify that the flexion of the 43-metre-long girders remains within specifications.