Marseilles (AFP)
A weight of 1,000 tons and the size of a seven-story building: the first part of a gigantic magnet, announced as the most powerful in the world, will arrive on Thursday at the site of the experimental nuclear fusion reactor Iter, in Saint-Paul -lez-Durance (Bouches-du-Rhône).
This magnet called "Central Solenoid" constitutes a major milestone of Iter, an international program bringing together 35 countries which aims to control the production of energy from the fusion of hydrogen, as in the heart of the Sun.
Manufactured by General Atomics in California, it consists of six modules, the first of which is due to arrive overnight from Wednesday to Thursday at the construction site of the future reactor, launched in 2010.
Transported by sea from the United States, this first 66-tonne piece arrived at the port of Marseille and is currently on its way to the Iter site, on the banks of the Durance, about a hundred kilometers away.
The other five magnet modules will complete the puzzle "no later than 2024", Bernard Bigot, CEO of Iter Organization, told AFP.
Once assembled, the "Central Solenoid" will weigh nearly 1,000 tons and be 18m high.
The superconducting magnet will be placed in the heart of the tokamak fusion reactor, a huge ring-shaped magnetic chamber where the temperature can reach 150 million degrees.
By heating the plasma (a hydrogen gas), it allows the hydrogen nuclei to collide and merge into heavier helium atoms, releasing colossal energy.
The magnetic fields make it possible to confine the plasma in the enclosure, to prevent it from coming into contact with the walls and from cooling.
But the more its volume increases, the more difficult it is to stabilize it.
It is to overcome this problem of scale that the magnet will be installed: "beating heart" of the tokamak, it will produce a variable magnetic field, going from zero to 13 tesla, "ie 300,000 times the value of the earth's magnetic field", details Bernard Bigot.
It will therefore be the "key element" of stabilization.
Iter plans to inject an unprecedented volume of 830 m3 of plasma.
"This is the condition for the plasma current to be self-sustaining and for more energy to be recovered than it is injected", up to ten times more, according to the expert in nuclear physics.
The first plasma production should take place in 2026 and Iter should reach full power in 2035.
Nuclear fusion is considered by its supporters as the energy of tomorrow because it could be virtually unlimited and non-polluting.
Iter is nevertheless criticized, especially among environmentalists, who see it as Greenpeace a "scientific mirage" and "a financial pit".
The initial budget has tripled to almost 20 billion euros now.
"It is likely that it will be revised" due to delays due to the Covid-19 pandemic, according to Mr Bigot.
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