ITER: assembly finally complete for the world's most powerful fusion reactor

The assembly of the last magnetic coil for the world's most powerful fusion reactor is finally complete, but it is not expected to be operational for another 15 years. The ITER reactor, the core of this colossal project, raises as many hopes as it does challenges.


Initially scheduled to begin its first tests in 2020, the ITER fusion reactor, composed of 19 massive coils forming several toroidal magnets, is not expected to produce energy until 2034, with a positive energy balance anticipated in 2039. This new timeline further delays the potential arrival of nuclear fusion as a solution to current climate issues.

The ITER project is the result of a collaboration between 35 countries, including all European Union member states, Russia, China, India, and the United States. The reactor houses the most powerful magnet in the world, capable of producing a magnetic field 280,000 times stronger than Earth's own protective field. However, these technological feats come with a high cost: the initial budget of $5 billion has soared to over $22 billion, with an additional $5 billion to cover unforeseen expenses.

Nuclear fusion, the process that powers the stars, has been pursued for more than 70 years. By fusing hydrogen atoms to form helium under extremely high pressures and temperatures, stars generate immense amounts of energy without producing greenhouse gases or lasting radioactive waste. However, replicating these conditions on Earth has proven to be complex.

Tokamak reactors, the most common design, work by superheating plasma and trapping it in a donut-shaped chamber using powerful magnetic fields. Keeping this turbulent and superheated plasma stable long enough for fusion to occur is a monumental challenge. Since the first tokamak was designed by Natan Yavlinsky in 1958, no reactor has succeeded in producing more energy than it consumes.

The main difficulty lies in handling plasma hot enough to fuse. Fusion reactors require temperatures far higher than those of the Sun, as they must operate at much lower pressures than those found at the cores of stars.

Achieving these temperatures is relatively easy, but containing the plasma so that it doesn't burn away the reactor or disrupt the fusion reaction is extremely complicated, requiring the use of powerful magnetic fields.