How to cool down the ITER Vacuum Vessel housing the hottest fusion reaction

The ITER plasma is expected to reach 150 million °C -it will be ten times hotter the core of the Sun. Can a container sustain such high temperatures and if so, how? The vacuum vessel will house the fusion reaction, and with the help of powerful superconducting magnets, the gas will be confined, avoiding any contact with its walls. To protect the 1400 m³ of the vessel from the heat, 440 panels will be fixed on its surface to form a wall, otherwise known as a blanket- a protective layer that will face the superhot plasma. Beneath the blanket, in a network of pipes running along 10 km, pressurised water will circulate to remove up to 736 MW of thermal power. Fire and water will be deployed on both sides of the vacuum vessel to even out blazing temperatures with cooling power.

Illustration of Blanket Cooling Manifolds procured by F4E ©F4E

Europe is responsible for the procurement of the blanket cooling manifolds, the system of tubes that will embrace from top to bottom the device to cool it down in various locations. In summary, F4E will finance the manufacturing of several types of pipes such as inboard and outboard bundles, in-vessel and lower port bundles, connectors, chimney, upper port and branch pipes to name few.

Works are expected to run over a period of seven years with a budget that could reach 100 million EUR. The successful conclusion of the tender has resulted to a Framework Contract, which allows F4E to breakdown operations in smaller task orders and procure parts of the system step by step. Three bidders have been selected for the signature of the task orders: i) Dockweiler-Tecnalia-Leading, ii) Altrad Babcock Europe, iii) SIMIC. Through competitive calls between them, and depending on the price, quality, expertise, availability and resources, different contracts will be signed to manufacture these components.

In the kick-off meeting of the Framework Contract, F4E outlined the overall strategy and informed the successful bidders of the first two task orders to be launched. The first concerns the qualification of one prototype bundle, and the production of one inboard and one outboard bundle. Meanwhile, the second task order aims towards the fabrication of the remaining inboard/outboard bundles, expected to be launched towards the end of this year.

Georges Dellopoulos, F4E Project Manager for this contract, has identified some of the main challenges and lessons learnt from earlier prototypes. "First, we would need to make sure that there are no leaks. Given the location of the manifold bundles behind the shield modules, any repair once operation has started would be extremely difficult. Second, the design of the supports is a complicated matter. Due to their operating conditions, they need to establish a reliable thermal path, together with the piping they are supporting, to avoid overheating. Currently, several designs are being considered. When the qualification phase is completed in Task Order 1, the final design will be concluded. Last, the manifold bundles need to fit in the device and match the geometry of the different components in the vicinity. The available envelope for the manifolds is +/- 2.5 mm."

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