ENSA is no stranger to the vacuum vessel welding project; since 2012 the company has been working under a phased contract with the ITER Organization to first develop
The contract covers the welding of ITER's 9 vacuum vessel sector sub-assemblies and 54 ports. The work will take place inside of the Tokamak pit, as sector sub-assemblies are lowered one by one and welded according to a plan than aims to minimize deformation.
The ENSA team will face a challenging task, evolving in a crowded Tokamak pit environment with co-activity on every side. The weld robots will have access from inside the vessel only, as the thermal shield panels and the toroidal field coils block access to the vessel's outer shell. Weld thickness is consequential—up to 60 mm—and weld shrinkage will have to be managed at every step of the process to ensure the correct shape of the final vessel assembly. Finally, stringent volumetric examination protocols will be required to comply with French nuclear regulations.
Mockups built by ENSA during the development of welding processes and tools (like this one at ENSA's Special Projects workshop in the outskirts of Santander, Spain) will be used at ITER to train operators. Welding activities will begin as soon as two sectors are side by side in the ITER Tokamak pit (2022).