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Today’s contribution to tomorrow’s energy revolution

Thirty five nations; more than one million components assembled in factories around the world; over €20 billion of investment; one of the most complex scientific and engineering projects ever seen. The International Thermonuclear Experimental Reactor (ITER) is a project of superlatives. In southern France, a multinational cast of thousands is building the world’s largest tokamak, a magnetic fusion device that could change the future of sustainable energy production. And MAN is playing a major role.


ITER construction site

Using the same principle that powers our sun and stars, ITER aims to fuse atoms in a controlled way that releases almost four million times more energy than burning coal, oil or gas, and four times as much as nuclear fission reactions. Housing this incredible experiment is a huge seven-story machine weighing 23,000 tons, the tokamak. Its name is an acronym based on the transliteration of the Russian words describing the “toroidal chamber and magnetic coil”.

MAN’s ITER contribution

In MAN Diesel & Turbo’s Deggendorf plant in southwest Germany, MAN specialists are fabricating essential parts for this ground-breaking undertaking. “We currently have contracts for three ITER sub-projects,” says MAN Project Manager Armin Kroiss, who has been involved in all three, gaining a few gray hairs in the process, as he adds with a laugh.

The first of these was signed in 2012. MAN will deliver 18 of the tokamak’s upper ports to an ITER subcontractor, the Efremov Institute of Electrophysical Apparatus in Russia. Each measuring 3.8 m meters high, the ports form the upper openings of the 8,000-ton steel vacuum vessel, which will house the fusion reaction. 

What happens inside the tokamak

cryostat iter-organization

The cryostat being constructed for ITER measures Ø29 x 29 m.

The fusion reaction occurs when deuterium and tritium are heated to an astonishing 150 million degrees Celsius, ten times hotter than the sun’s core, forming a plasma, a gas-like matter that contains huge amounts of energy. The energy is absorbed as heat into the walls of the vessel, which is used to create steam and then electricity via turbines and generators.  

Surrounding the vacuum vessel is the huge cryostat. Measuring 29 meters in diameter and 29 meters in height, weighing 3,550 tons, it is the largest vacuum chamber ever built and provides an ultra-cool environment for the vacuum vessel. This limits heat exchange with the surroundings.

Indian company Larsen & Toubro is producing 54 individual components for the cryostat, which is the largest part of the entire reactor. They are delivered to the ITER site in France and assembled and welded by a team of experts from MAN Deggendorf – a ten-year process in total.


A MAN welder working on the ITER site in France.

Planning ahead for the energy of the future

“The number of countries involved, combined with the sheer level of detail and need for the utmost accuracy make the timelines on this project very long – unlike anything else we have ever worked on,” says Kroiss. “According to current planning the machine won’t be powered on until 2025, with full experiments starting in 2035.”

ITER may be unique, but MAN does already have experience in this area. It worked with the Max Planck Institute on Wendelstein 7-X, a multinational fusion experiment completed in 2015 to evaluate the suitability of certain components for a fusion power plant. The company supported the project for 15 years, supplying the plasma and outer vessel, the machinery foundation, the superinsulation, as well as performing the assembly of the aforementioned components – valuable experience for the even greater challenge posed by ITER. 

This experience and expertise was rewarded again in 2017 when MAN was commissioned by the Italian equipment supplier Walter Tosto to fabricate 13 ‘port stubs’, each weighing up to 5.5 tons. These act as connectors between the vacuum vessel and the tokamak’s ports, which provide access to installations such as diagnostics and heating.

Unprecedented projects call for innovative approaches

The demands of the ITER project have led MAN to develop well-elaborated assembly strategies and enhanced welding techniques, which are now utilized across the company. “We’re preparing and performing high-precision welds to gain the stringent tolerances on the large-size and heavy-weight components. The necessary accuracy is on a new level,” explains Kroiss. 


The seven-story tokamak building with the circular opening for the cryostat at the center.

As if the technical challenges weren’t enough, the global nature of the project adds an extra hurdle. Thousands of scientists and engineers from the seven ITER members – China, the European Union, India, Japan, Korea, Russia and the United States – have contributed to ITER ever since the initial idea was launched in 1985. Each of the seven members is responsible for producing a significant part of the tokamak. “It unites a lot of different countries, cultures and companies, which can make things complex as well as interesting,” Kroiss says. “But everyone is learning and improving as the project progresses – we are proud to be part of this mega-project, working towards the goal of finding a new, clean energy solution.”


Size of the ITER site in southern France
Weight of the world’s largest tokamak, which is being built for ITER
million °C
Temperature inside the tokamak’s vacuum vessel

The timelines on this project [are] unlike anything else we have ever worked on

Armin Kroiss, Project Manager, MAN 

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