Saint-Paul-lès-Durance (France) (AFP)

A gigantic puzzle officially began on Tuesday in the south of France, with the launch of the assembly of the Iter project reactor, an international program aimed at harnessing the production of energy from the fusion of hydrogen, as in heart of the sun.

"With fusion, nuclear can be a promise for the future" by offering us "non-polluting, carbon-free, safe and virtually waste-free energy," said President Emmanuel Macron, in a pre-recorded video broadcast during the ceremony organized at the Iter site in Saint-Paul-lès-Durance (Bouches-du-Rhône).

Commenting on this international project launched by a 2006 treaty and bringing together 35 countries, i.e. the entire European Union (with the United Kingdom), Switzerland, Russia, China, India, Japan, South Korea and the United States, South Korean head of state Moon Jae-In also hailed in a video message "the greatest science project in the history of mankind" and this "shared dream of creating clean energy and safe by 2050 ".

A dreamed alternative to fossil fuels such as oil, gas or coal, which emit CO2, hydrogen fusion could also replace nuclear energy: if the fission of the atom produces radioactive waste for tens of thousands of years. 'years, the fusion of hydrogen does not generate long-lived waste, insisted Bernard Bigot, the CEO of Iter.

Another advantage: the fuels necessary for this fusion, extracted from water and lithium, are available and, according to Mr. Bigot, able "to ensure the supply of a fleet of reactors for millions of years, one gram of fuel releasing as much energy as eight tons of oil ".

In recent months, several components of this experimental reactor called "Tokamak" - some as tall as a four-storey building and weighing several hundred tons - have been delivered to the site from India, China, Japan, from South Korea or Italy.

And the size scales make you dizzy. By itself, the most powerful of Iter's magnets, the one that will initiate the electric current within the plasma, could thus lift an aircraft carrier.

- 150 million degrees -

The elements arriving little by little, it remains to assemble the million pieces of this three-dimensional puzzle, a job which should last until 2024 for the 2,300 people present on the site.

This gigantic reactor will make it possible to reproduce the hydrogen fusion reaction that occurs naturally in the heart of the sun and the stars: concretely, this fusion will be obtained by bringing to a temperature of the order of 150 million degrees a mixture of two isotopes of hydrogen transformed into plasma.

Iter could produce its first plasma at the end of 2025 at the beginning of 2026 and the reactor could reach full power in 2035.

An experimental reactor, Iter will not actually produce electricity. And it is 2060, at best, that it will be necessary to wait to have the first connection to the electrical network of a fusion reactor derived from Iter.

To generate electricity, these future commercial fusion reactors will simply use the heat produced on the walls of their "tokamak" by the bombardment of neutrons born from the fusion: this heat will be evacuated by a pressurized water circuit to go to supply, in the form of steam, a turbine and an alternator.

Iter, if connected to the electricity grid, would produce only 200 MW of electricity, enough to power some 200,000 homes. Future fusion reactors would have a volume of plasma to supply two million homes.

This for a construction cost and an operational cost "equivalent to those of a conventional nuclear reactor", according to Mr. Bigot.

These "artificial suns" are however the subject of recurring criticism from environmentalists, especially French, who see "a financial pit" and "a scientific mirage". The project has already taken five years late, with a tripling of the initial budget, to nearly 20 billion euros now.

© 2020 AFP