ITER project: how are cranes helping to build a new sun?
By Lucy Barnard06 September 2022
At the ambitious ITER project in southern France, scientists are hoping to demonstrate nuclear fusion as a safe, plentiful and commercially viable source of energy for the Earth. Lucy Barnard finds out about the cranes being used to harness the power of the sun.
Towering over the picturesque countryside of hills and vineyards at Cadarache in Provence, southern France, a machine capable of emulating the power of the sun is slowly being assembled.
If all goes to plan, when its first phase is fully assembled, some time after 2025, ITER, the International Thermonuclear Experimental Reactor, will be able to heat gases to temperatures of more than 100 million degrees Celsius to help scientists demonstrate the power of nuclear fusion as a clean and abundant source of energy.
Funded and run by seven member parties – China, the EU, India, Japan, Russia, South Korea and the USA – the ITER machine will become the largest tokamak or nuclear fusion reactor in the world, comprising around a million components and weighing around 23,000 tonnes.
According to the ITER foundation, if you include the foundations and buildings too, the lot will weigh 400,000 tonnes – more than the Empire State Building in New York, USA.
Components include: the vacuum vessel, the 5,200 tonne doughnut-shaped core of the machine and the chamber in which the fusion reaction will take place; the cryostat, the largest stainless-steel high-vacuum pressure-chamber ever built, which will hold the vacuum vessel in place and act like a giant fridge maintaining the low temperatures needed to cool the machine down again; and a magnet system including 18 D-shaped super-conducting magnets, known as Toroidal Field Coils which create a cage to confine and control the plasma inside the vacuum vessel and will generate a magnetic field 200,000 times greater than the Earth.
The huge weights involved, coupled with the need for precise alignment of ITER’s largest and heaviest components to within tolerances of 2 or 3 millimetres, mean that ITER assembly teams have had to develop 128 custom-designed tools to assemble, lift and manoeuvre ITER’s super-sized components into place.
Central to the machine’s assembly are two sets of enormous yellow bridge cranes designed and manufactured by a consortium of German crane manufacturer NKMNoell Special Cranes and French manufacturer Reel, which have the capacity to lift ITER’s heaviest components.
The remotely-operated cranes which run on 170 metres of rail, were commissioned by The European Domestic Agency Fusion for Energy in 2013 as part of a €31 million contract. They are being used both to help handle the machine components and then to help assemble the tokamak machine.
The ITER bridge cranes
Installed at a height of 46 metres above the giant assembly hall and tokamak pit where engineers are putting together the enormous machine, the two 750 tonne cranes can work together to lift loads of 1,500 tonnes or the approximate weight of four jetliners, in a system complemented by two smaller auxiliary cranes with a capacity of 50 tonnes each.
The cranes are designed to travel 175 metres on rails and their main beams span 47 metres.
In May 2022 the ITER assembly team completed one of its most complex lifts to date, using the bridge cranes to extract the first 1,380 tonne wedge-shaped pre-assembled segment of the vacuum vessel from a specialist Sub Sector Assembly Tool and slowly move it into the tokamak pit to its final resting position with accuracy within a fraction of a millimetre.
Eventually the vacuum vessel will comprise nine sectors made of special grade stainless steel. Each sector is 13 metres high, 6.5 metres wide and 6.3 metres deep.
As part of the main assembly, each vacuum vessel sector has to be first lifted to a vertical position on a specially adapted “upending cradle” and then transferred to a standing tool capable of docking the vacuum vessel sector in its centre where it is fitted with two specialist magnets known as toroidal field coils and three thermal shield panels which will prevent heat escaping from the vessel to the ultra-cold super-conducting magnets.
For Daniel Coelho, the ITER assembly engineer charged with executing the entire operation, the lift was the culmination of more than a year’s worth of preparation and co-operation.
Although Coelho spent nearly six years of his career co-ordinating complex nuclear projects for French nuclear reactor business Framatome and most of the team hailed from similar backgrounds, Coelho says the ITER project was still very different.
“We are in a first-of-a-kind context,” he says. “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.”
He says that well before the module had even been fully assembled, the team had spent hours calculating exactly how the lift would be achieved using 3D models.
“What we had in fact were two loads in one, each with its own centre of gravity,” Coelho says.
“Long before we started the operation, when the module was still inside the pre-assembly tool, we precisely characterised its dimensions and weight, performed calculations and established 3D models to obtain theoretical alignment targets,” he adds.
“Theoretical data, however, is only a starting point. You don’t have an absolute certainty before actually starting to lift.”
As a final precaution, the team also staged a real-life trial the previous week, lifting the real plasma chamber load just 50 centimetres above its supports to test the equipment and to enable metrology experts to measure the most minute dimensional deviations to ensure that the load remained within tolerance.
How was the ITER lift carried out?
Although Coelho and the ITER team were in charge of co-ordinating the lift, the team of 50 men and women who came together to complete the manoeuvre came from at least 12 different contractors and organisations.
Coelho was assisted on the ground by the organisation’s management-as-agent contractor, Momentum, a joint-venture entity comprising engineers UK-based Amec Foster Wheeler, France-based Assystem and Korea-based KEPCO Engineering & Construction.
Meanwhile tokamak assembly contractor Dynamic SNC, another consortium which includes Italian specialists Ansaldo Nucleare and SIMIC, France-based firms Endel Energie and Ortec Group, and Spanish engineer Leading Metal Mechanical Solutions, were in charge of execution. French crane specialist Foselev acted as crane operator.
An hydraulic lifting system, comprising four, double acting, push-pull cylinders manufactured by Enerpac, was suspended by a header beam from the ITER assembly hall’s overhead crane to enable pinpoint accuracy with the lift.
The SyncHoist system connected to the object’s four lifting points to assess the exact centre of gravity. In addition to synchronous lifting and lowering, the operator is able to lift and lower each cylinder independently for balancing, tilting and positioning loads.
For repetitive hoisting tasks, the controller can also be pre-programmed for positioning, tilting and aligning of loads. The wireless controller allows the operator to work at a safe distance. No cables are needed, so there is no risk of entanglement or tripping hazards.
“It is essential that we hold the vacuum vessel sector in the plane during lifting. SyncHoist allows us to know the load at each lifting point and control the lift precisely with a one millimetre accuracy,” adds Jarl Buskop, assembly engineer, Sector Modules Delivery & Assembly Division, ITER.
We will update this story with news of lifts and moves of components as they are manufactured, moved and installed. If you are involved with the ITER project and would like to be included in this story, please contact the editor. To find out more about ITER visit ITER or F4E
ITER is a collaboration between China, the European Union, India, Japan, South Korea, Russia and the USA. All members share the costs of construction. After it is finished, the facility will be able to test whether nuclear fusion will be commercially viable and whether it is really the ‘clean’ source of energy scientists hope.
Existing nuclear power plants rely on fission where the nuclei of heavy chemical elements are split apart to produce lighter elements, creating dangerous nuclear waste as a by-product. Fusion, on the other hand, works by forcing together the nuclei of two lighter elements to produce a heavier element, producing lots of energy and very little radioactivity.
This process, however, requires very high temperatures and densities. In the Sun, huge gravitational pressures and temperatures of around 10 million degrees Celsius mean that hydrogen atoms can fuse into helium, releasing energy which makes the sun shine.
On Earth, lower atmospheric pressure mean scientists need to heat gases to temperatures of more than 100 million Celsius to achieve fusion. Because no materials exist on Earth which can withstand such high temperatures, scientists have designed a structure called a tokamak to confine the super-hot gas or “plasma” inside a magnetic field. Scientists plan to use the ITER tokamak to fuse two hydrogen isotopes deuterium and tritium. Deuterium can be extracted from sea water and therefore is in limitless supply – unlike the uranium used in nuclear fission reactors.