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Tokamak assembly

The "module" has landed

23 May 2022

This "module" was not designed to land on the Moon. But it was as complex a piece of technology, requiring as much precision in its handling as the famed "lunar modules" of the Apollo project that made history more than 50 years ago. In the ITER world, a "module" is an assembly of one vacuum vessel sector, two vertical D-shaped coils and corresponding thermal shield panels, plus all kinds of piping and appendices that bring the sub-component's total mass to 1,380 tonnes—the equivalent of four fully-loaded Boeing 747s. On 11-12 May, the first of the nine modules required for the tokamak's torus-shaped vacuum vessel was slowly extracted from the sub-assembly tool, lifted and transported over the wall separating the Assembly Hall from the machine assembly pit, and positioned with sub-millimetric precision on its supports. Although the machine assembly sequence has offered many spectacular operations since May 2020, the lifting and landing of this first sector module eclipsed them all. It was both a magnificent performance and a unique demonstration of technological mastery.

VSM6_Approach_1.jpg
The 1,380-tonne load has just passed the wall separating the Assembly Hall from the machine assembly pit. Vertical clearance does not exceed 20 centimetres and will be much less during the component's descent to its near final mooring at the bottom of the pit.
The long-expected operation was more than a year in planning. It tested the limits of the building's structure, of the overhead crane's lifting capacity, of the complex rigging's manoeuvrability and, perhaps most of all, of the coordination of a 50-person team belonging to half a dozen different companies and organizations. At each and every stage of the component's journey—from the pre-assembly tool to the final resting position in the assembly pit—clearances were minimal. It was indeed an extraordinary spectacle to watch: the massive load practically grazing the different structures it encountered on the way to its final destination. Four centimetres of lateral clearance during the extraction procedure from the sub-assembly tool, 20 centimetres vertically as it passed over the pit wall, 7 centimetres during lowering ...

Due to the inevitable "swing" created by the pendulum effect, the clearance throughout the whole operation was reduced, down to 5 centimetres in a few positions.

VSM6_Port_Cell-14_screens_2.jpg
Members of the "landing team" monitor the movement of the load, both directly through one of the port cells opening onto the assembly pit, and on computer screens relaying data and images from strategically positioned sensors and video cameras.
One of the main challenges, considering the composite nature of the load, was to determine its centre of gravity—an essential parameter in guaranteeing the safety and fluidity of the transfer operation. "What we had in fact were two loads in one, each with its own centre of gravity," explains Daniel Coelho, the ITER assembly engineer who coordinated the lifting. "Long before we started the operation, when the module was still inside the pre-assembly tool, we precisely characterized its dimensions and weight, performed calculations, and established 3D models in order to obtain theoretical alignment targets. Theoretical data however, is only a starting point. You don't have an absolute certainty before actually starting to lift, and this is why the pre-lift operation a few days ago was so important."

Like Daniel, the operators involved all have experience in heavy, precision lifts in demanding environments, mostly nuclear. "The difference here is that we are in a first-of-a kind context. We have the quality constraints of the nuclear world, but with highly specific components and extremely tight clearances that require unique lifting equipment, techniques and procedures." How did they overcome such a daunting challenge? "We compensate with thorough calculations and models, the qualification of operations, and exceptional safety measures," smiles Daniel.

VSM6_in_Pit_Day_2_Fisheye_1.jpg
Although only one-ninth of the Tokamak's torus-shaped vacuum vessel, the sector module dwarfs everything around it. Eight other similar operations, plus welding, will be necessary to close the torus.

But the outcome of such an operation does not rest on technology only. Men and women, working as a perfectly coordinated team—Daniel calls it "a family"—were instrumental in its success. "The contractors had prepared extremely well for every action, and the integration with the ITER Organization teams was faultless."

At the close of the day on Wednesday 11 May, the module, still attached to its rigging, was hovering a few centimetres above its supports. More metrology, some further meticulous adjustments ... and by the following day, the sector module was solidly and precisely moored in its near-final position. Inside the assembly pit, the view was striking. Although only one-ninth of the vacuum vessel torus, the component seemed to dwarf everything around it.

The operation was coordinated by the ITER Organization construction team and its management-as-agent contractor MOMENTUM, and executed by tokamak assembly contractor DYNAMIC SNC (Ansaldo Nucleare; Endel Engie; Orys Group ORTEC; SIMIC; Ansaldo Energia; and Leading Metal Mechanic Solutions SL), crane operator Foselev, and GEATOP metrologists, with the support of APAVE health and safety officers.

Read the press release in English or French. 

See the related video in this issue.

The daylong operation is almost over. Still attached to its rigging, the module is immobile a few centimetres above its supports. More metrology, further meticulous adjustments ... by the following day, the sector module was solidly and precisely moored in its near-final position.
The complex rigging required for the lifting of the sector module is clearly visible is this view from high above: the yellow structure is the Dual Crane Heavy Lifting Beam (DCHLB) that synchronizes the four hooks of the cranes into a single lift point, enabling the rotation of the load. The grey device below is the Sector Lifting Tool. Connected to both the DCHLB and the radial beam, this tool can precisely align the load with the cranes.
On the second day, disconnected from the crane's hooks, the sector module is in its close-to-final position. At the bottom, it is resting on three "TIPI tables" (Toroidal Field Coil Pair Installation Tool) while supported high above by the radial beam.
Seven centimetres of clearance
During the descent to its mooring position, at the bottom of the Tokamak assembly pit, the distance between the vertical section of the D-shaped component and the central column never exceeded 7 centimetres.
The pit and the pendulum
The sector module is now passing the circular opening of the 30-metre deep, 30 metre-in-diameter Tokamak assembly pit. The last and most delicate phase of the operation begins. The pendulum effect generates a slow swinging that is clearly visible on time-lapse videos.
Coordination
The perfect coordination of a 50-person team belonging to half a dozen different companies and organizations was key to the operation's success.
Feet (almost) touching the ground
Over the bioshield wall that circles the Tokamak pit, the clearance at the base of the sector module does not exceed 20 centimetres.
Extracted from the sub-assembly tool, the component has rotated 90 degrees and is now heading towards the wall separating the Assembly Hall from the Tokamak pit.
From whatever side one looks at it, a sector module is an impressive structure. This is particularly true of this image from the component's "underbelly"...
A very slow lift-off
As one of a dozen "spotters" communicates by walkie-talkie with the operators in charge of the lift, the 1,380-tonne sector module commences its journey to the assembly pit.
Eyes everywhere
As the sector module is slowly lifted from the sub-assembly tool, an operator closely monitors the feedback from three of the seven video cameras positioned at strategic locations inside the tool.
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