Passing through the entrance to the building where the future Tokamak of Iter is currently assembled, the gigantism and the power suggested by this installation are disconcerting. “This is where we will light the little sun”, presents Robert Arnoux, Iter’s communications director. If the journey of humanity had its terminus, perhaps this is what it would look like. Because it is in this tank 30 meters high and 30 meters in diameter that the international community intends to artificially reproduce the nuclear reaction that occurs in the heart of the sun of the stars. Behind what could appear as the ultimate vanity of a humanity of masters and possessors of nature, this research program aims “to offer humanity a source of clean energy, without nuclear waste and virtually inexhaustible”.
20 minutes takes you into the bowels of the greatest experimental research program mankind has ever known.
Iter, what is it?
Iter is an international organization whose research and experimentation site is located in the north of Bouches-du-Rhône, on the border of Var, Vaucluse and Alpes-de-Haute-Provence. About 1,200 researchers and 2,500 people on the sites work there. It is financed by seven members, representing 35 countries (the European Union, the USA, China, India, Russia, South Korea and Japan), and comprising more than half of the world’s population. and 80% of GDP.
The site extends over 180 hectares – 42 of which are buildings, on which some fifty industrial buildings are located. The centerpiece of this facility, the Iter tokamak (a spherical magnetic confinement chamber in which nuclear reactions are produced), is currently being assembled. This started in May 2020 and should be completed in 2025. With a volume of 850 m3 (30 meters high and 30 meters in diameter), it has unparalleled dimensions.
Fusion, how does it work?
The nuclear reactors we know today operate on the principle of fission, which consists of breaking atomic nuclei of uranium and plutonium by projecting a neutron onto them. Nuclear fusion, on the contrary, aims to bring together two nuclei of deuterium and tritium (variants of hydrogen) under the effect of very high pressure and dantesque heat (150 million degrees Celsius, or 10 times that of the sun). Conditions in which matter is in the state of plasma, that which is found in the heart of stars. This fusion leads to the release of a neutron which, by hitting the walls of the tokamak, releases heat. This is then recovered to power a turbine, like conventional electrical installations.
What are the difficulties?
No known material withstands such a temperature. So the scientists have recourse to monumental magnets cooled by cryogenics which encircle the interior of the building and contain the heat there by the force of their magnetic field.
For now, scientists have already succeeded in using very small tokamaks (30 m3) to generate non-nuclear plasmas by fusing hydrogen nuclei. But the scientists come up against various pitfalls, starting with the instability of this reaction which has for the time being maintained at a maximum of 17 minutes and 36 seconds, on January 6 in the Chinese tokamak. During this sequence, the scientists managed to produce almost as much energy as that consumed during the pulse to reach the plasma state.
Also, the small volume of these hydrogen tokamaks makes it impossible to envisage the creation of nuclear plasma. Pitfalls that the size of the tokamak should overcome.
It’s for when ?
Assembly of the Iter tokamak, construction of which began in May 2020, should produce its first plasma in 2026. 60% of the parts, built in the various member countries, have already been delivered.
The scientists then give themselves ten years to take control of the machine and check the alignment of the magnetic fields before launching the first nuclear plasma. “Iter’s objective is to demonstrate the technical, scientific and industrial feasibility of nuclear hydrogen fusion. This will be achieved when the reactions produce ten times more energy than that injected to launch the reaction”, explains Robert Arnoux. “In one gram of hydrogen, there is the energy equivalent of eight tons of oil. But those who laid the first stones of this adventure will not see its industrial application,” concludes the man who often compares the Iter project with that of the cathedrals; a cathedral for the 21st century.