Europe’s fourth Vacuum Vessel sector is ready for ITER

The ITER Vacuum Vessel, the massive stainless-steel container that will house the fusion reaction, is made of nine slices, known as sectors. Europe is responsible for providing five of them. To manufacture these components, Fusion for Energy (F4E) is collaborating with the AMW consortium, formed by Ansaldo Nucleare, Westinghouse, and Walter Tosto. This week, the teams completed the fourth of the series: Sector 3, ready to set sail from the Italian port of Ortona towards ITER. Despite its scale and pressing timeline, Europe delivered once more on schedule and even went the extra mile.

The component is one-of-a-kind, in both scale and quality requirements. When fully assembled, the Vacuum Vessel will form a torus—a doughnut shape—measuring 19.4 meters in diameter by 11.4 meters high and weighing around 5200 tonnes. It is engineered to provide a clean, sealed environment for the plasma to float in, kept away from the walls by the magnetic field of the superconducting coils. As a first safety barrier, the Vacuum Vessel complies with strict standards set by France’s Nuclear Safety Authority.

Each sector is made up of four segments (see the breakdown in this poster). The segments for Sector 3 were machined by different specialised firms across Europe: ENSA (Spain), Belleli (Italy), Westinghouse Electric Italy and Walter Tosto (Italy). All the pieces then came together at the workshop of Walter Tosto in Chieti, where they were assembled and welded.

The manufacturing process is an intensive test of skill and task coordination. Engineers, welding technicians, metrology experts and quality inspectors worked daily side by side to ensure each interface met the strict geometrical requirements. In total, there are at least 150 professionals and 15 companies directly involved in the supply chain of a sector.

Being the fourth sector, F4E and its partners built on lessons learned and the strong relationship among them, which proved key. Given the acceleration of the ITER assembly plan, the teams had to adapt to a tighter deadline. But the project did not crack under pressure; quite the contrary: “We sat with our contractors and agreed to expedite the delivery. This commitment was effectively transferred to the work floor. Thanks to a clear strategy and teamwork, we managed to parallelise activities and cut three weeks off a three-month plan to completion,” recounts Boris Bellesia, F4E Programme Manager.

A critical aspect of the fabrication is the nearly 150 km of welding beds. They rely on a delicate, one-shot operation in which precision is non-negotiable. Weld after weld, the team ensured the conformity of the entire sector and did so in record time. Arturo Fernández, F4E Project Manager, followed the process directly from Chieti. He shared his recipe for success: “Anticipating challenges, finding joint solutions, monitoring progress and coordinating daily are essential in a nuclear factory. As F4E, we were always close to the action and developed a one-team attitude with the suppliers,” he said

Despite the condensed schedule, the European teams also took on more activities beyond the initial scope. This included re-machining the field joints, the edges where different sectors will be welded together, to prevent non-conformities. In addition, the technicians welded 200 bosses, the supports to attach diagnostic sensors onto the vessel’s inner surface. This task, typically carried out at ITER, will help streamline the sector’s assembly on site.

“Sector 3, completed ahead of the reference schedule, fully meets the stringent high quality requirements of ITER. It is an outstanding achievement, and for it we thank our staff for their dedication and efforts, as well as the close collaboration with F4E and ITER Organization,” commented Luca Ascione, Project Director for the AMW Consortium.

Sector 3 is now travelling by sea towards ITER, in the south of France. With its delivery, Europe is entering the final stretch in the production of the most iconic components of ITER, the world’s largest fusion experiment. The completion of the fifth and last one, Sector 2, is expected next autumn.