The first of five vacuum vessel sectors under the responsibility of Fusion for Energy - the Iter Organisation's European domestic agency - is undergoing factory acceptance tests. The component has already passed leak testing and its dimensions will now be checked.

ITER vacuum vessel sector No.5 (Image: F4E)

ITER's plasma chamber, or vacuum vessel, houses the fusion reactions and acts as a first safety containment barrier. With an interior volume of 1400 cubic metres, it will be formed from nine wedge-shaped steel sectors that measure more than 14 metres in height and weigh 440 tonnes. The ITER vacuum vessel, once assembled, will have an outer diameter of 19.4 metres, a height of 11.4 metres, and weigh approximately 5200 tonnes. With the subsequent installation of in-vessel components such as the blanket and the divertor, the vacuum vessel will weigh 8500 tonnes.

The fabrication of the vacuum vessel sectors is shared between Europe (5 sectors) and Korea (4 sectors). Vacuum vessel sector No.6, at the centre of the assembly, and associated thermal shielding has already been manufactured and delivered by the Korean Domestic Agency.

The first sector, No 5, being supplied by Europe has now been manufactured at the Westinghouse/Mangiarotti facility in Monfalcone, Italy, and is undergoing factory acceptance tests prior to being shipped to the construction site.

The precise measurements of the vacuum vessel sector will be checked (Image: F4E)

"Years of teamwork in developing the procurement strategy, agreeing on the design, the technical specifications, and following up its manufacturing, have come down to this make-or-break moment in the lifecycle of the component," F4E said. "The valuable lessons learnt from sectors delivered by Korea, and the knowledge accumulated from the collaboration between F4E and the AMW consortium (Ansaldo Nucleare, Mangiarotti and Walter Tosto) have fed into this exercise."

The factory acceptance tests consist of hydraulic and dimensional checks.

The hydraulic testing of sector No 5 was successfully completed on 16 January. These tests - using nitrogen and helium - examined how the component responds to pressure and vacuum. Their objective is to make sure that there are no leaks in the structure. "Checking these parameters is of paramount importance because the fusion reaction requires an environment which is completely tight," F4E noted. "Furthermore, the vacuum vessel is classified as a nuclear component that needs to comply with the strict prerequisites set by the French Nuclear Safety Authority." It said the results were "solid proof that the welding, assembly and manufacturing met the highest standards".

"The successful outcome of these operations results from years of cooperation between F4E, ITER Organisation and AMW," said Joan Caixas, F4E Assembly Project Manager. "The results give us a lot of confidence for the next tests and ultimately for the delivery of Europe's first sector."

The dimensional tests - which will require more time given the volume of the component - essentially measure with accuracy the component using sophisticated probes, lasers, and other tooling to scan the surface, spot any deformations, etc.

Once the factory acceptance tests are completed, the component will be transported to the ITER construction site. According to the current schedule, the component is expected to depart from Mangiarotti later in the year. It will leave on a boat and be shipped to the port of Marseille. From there, it will be loaded onto a large track, and by applying the protocol of a heavy exceptional convoy, it will be transported to the ITER site.

ITER is a major international project to build a tokamak fusion device in Cadarache, France, designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy. The goal of ITER is to operate at 500 MW (for at least 400 seconds continuously) with 50 MW of plasma heating power input. It appears that an additional 300 MWe of electricity input may be required in operation. No electricity will be generated at ITER.

Thirty-five nations are collaborating to build ITER - the European Union is contributing almost half of the cost of its construction, while the other six members (China, India, Japan, South Korea, Russia and the USA) are contributing equally to the rest. Construction began in 2010 and the original 2018 first plasma target date was put back to 2025 by the ITER council in 2016. In June last year, the ITER Organisation was expected to reveal a revised timeline for the project but instead put back by a year an announcement on an updated timeline.