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Cryostat top lid

Big muscle for a huge load

11 Apr 2023

It takes a lot of muscle to move a 900-tonne load. On Thursday 6 April, no less than six self-propelled modular transport platforms, each equipped with a 500 HP power pack, worked in unison to move the cryostat top lid and its massive support frame from the workshop where it was assembled and welded to an exterior storage area a few dozen metres away.

Top_lid_into_storage_0_small.jpg
Looking a lot like a flying saucer, the 665-tonne cryostat top lid has been removed from the Cryostat Workshop (left) and placed in a long-term storage area on the platform.
At 665 tonnes, the cryostat top lid is the second-heaviest¹ component of the ITER machine. Its main elements, manufactured by ITER India contractor Larsen & Toubro Ltd, were delivered to ITER in the fall of 2020. The onsite assembly and welding of this fourth and last section of the 16,000-cubic-metre cryostat took a little more than one year. By February 2023, the top lid had been sealed away in tight wrapping and was ready to be placed in outdoor storage.

The perception of size depends on the environment. Sitting at the far end of the Cryostat Workshop, the top lid certainly felt like a large component. But as it slowly came out of the building, amidst the roar of the power packs, it seemed to have dramatically grown in size. The 30-metre-in-diameter, 10-metre-tall load dwarfed everything around it.

It will be some years before the top lid "closes" the giant vacuum chamber that surrounds the ITER Tokamak at the end of core machine assembly. In the meantime, the flying-saucer-shaped component will sit securely on a bespoke heavy-duty slab protected from dust and moisture by leak-tight wrapping, its surface monitored by strategically positioned cameras.

¹ At 1,250 tonnes, the cryostat base, which was installed in the Tokamak assembly pit in May 2020, is the heaviest single machine component.

On its way to the storage location, some 50 metres away from the Cryostat Workshop, the flying saucer-shaped component passes the Cleaning Facility and adjacent Assembly Hall, whose architectural design add a futuristic touch to the scene.
A heavy duty, 50-centimetre-thick reinforced slab was recently constructed to accommodate the combined load of the top lid, support frame and transport platforms in the last phase of the operation. At approximately 900 tonnes, their total weight is equivalent to that of three Airbus A380s.
As it sat at the far end of the Cryostat Workshop, the top lid certainly felt like a large component. But as it slowly came out of the building amidst the roar of the power packs, it seemed to have dramatically grown in size. The 30-metre-in-diameter, 10-metre-tall load dwarfed everything around it.
Success was achieved through the close collaboration and coordination of the ITER Organization, global logistics provider DAHER, and transport platform operator Mammoet; Cegelec played an important role in designing systems and processes to synchronize the movements of the six individual transport platforms, and risk manager Apave was responsible for the safety of the transfer.
Coordination and anticipation are key for a successful, smooth and safe operation. As the transport trailer power packs warm up, a last briefing brings together the operators and responsible officers from the dozen companies and organizations involved in the top lid transfer.
Wrapping operations for the cryostat top lid begin in January 2023, close to one year after the massive component was finalized. Sealed in an environment saturated with corrosion inhibitor molecules and wrapped in a succession of protective layers, the top lid will remain in outdoor storage until installation at the end of core machine assembly.
February 2021: The major elements of the cryostat top lid are aligned on the workshop floor, waiting to be positioned inside the supporting frame to be assembled and welded.
November 2018: At the Larsen & Tourbo's Hazira manufacturing complex on the northwestern coast of India, work is underway on the "ribs," "flanges," "knuckles," and "crown" that make up a top lid segment.
June 2020: Upon completion of the segments for the fourth and last section of the ITER cryostat in India, ITER India contractor Larsen & Toubro marks the end of an eight-year industrial adventure to manufacture the world's largest steel vacuum chamber (16,000 m³).
June 2021: Two welders from MAN Energy Solutions, working in parallel on opposite sides of the top lid's skin, produce the ''first arc'' of a welding campaign scheduled to last four to five months. The cryostat top lid is made of twelve 30-degree sections that require approximately 300 metres of deep welds (50 millimetres deep on average, but up to 280 millimetres at the flange levels) and more than 4 tonnes of filler metal.
March 2022: In the onsite Cryostat Workshop, the finalized top lid is being prepared for a long hibernation. Because it seals the cryostat, the 665-tonne, circular structure will be the last machine component to be lowered into the assembly pit.
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