On Thursday, the Joint European Torus teams announced that their device had broken a new energy production record during its latest experiment. This major international program based in England is bowing out with a bang, and will now pass the baton to even more ambitious programs like ITER after more than forty years of good and loyal service.
Like ITER, JET is a tokamak, a large donut-shaped reactor designed to mimic the thermonuclear reactions that take place in the hearts of stars. The objective is to fuse hydrogen isotopes in a plasma trapped by a powerful magnetic field, in order to produce a phenomenal amount of energy in a fraction of a second. And that’s exactly what happened on January 8.
69 MJ for five seconds
With just 0.2 grams of a mixture of tritium and deuterium, the same pair of isotopes used by the Cadarache tokamak, JET managed to produce a reaction that generated 69 megajoules for five seconds.
In absolute terms, this quantity of energy is not revolutionary. For reference, it takes roughly 2.6 MJ of energy to boil a liter of water at room temperature. Suffice it to say that we are still very far from the performance of a real operational power plant. What is more impressive is that this represents a gain of 17% compared to its previous record, set in December 2021. An increase far from negligible, knowing the technical challenges hidden behind it.
Experimental fusion, a matter of compromise
Indeed, to allow two atoms to fuse, they must be forced to come close enough to each other so that their positively charged nuclei are able to overcome the electrostatic repulsion that normally keeps them at a good distance. The only way to do this is to make them collide with extreme violence. These collisions are made possible by a very high temperature (around 15 million degrees Celsius at the center of the Sun) which gives massive kinetic energy to the atoms.
But the problem is that our star has a huge advantage at this level: the phenomenal density of his heart. Until proven otherwise, it is practically impossible to reproduce it in the laboratory. It is therefore necessary to compensate with a significantly higher temperature, typically of the order of 150 million degrees in experimental tokamaks. To reach this threshold, the reactor contents must be bombarded with high-energy particles and electromagnetic waves using immense superconducting coils — a diet that is very difficult to maintain over long periods of time.
Operators must therefore juggle these parameters to produce as much energy as possible for as long a time as possible. Some tokamaks instead seek to push the temperature as high as possible for a fraction of a second; at the opposite extreme, others are content with more modest energy production, but maintained over a longer period.
It’s here combination of these two factors which makes the JET record impressive. Maintaining a temperature of 150 million degrees to produce energy for five seconds — an eternity in this context — is a sacred technical feat.
Place at ITER
Unfortunately, the JET has now reached the extreme limits of its capabilities. It was the very last major fusion experiment, more than forty years after its beginnings in 1983. But the good news is that all its successors, starting with ITER, will be able to draw inspiration from this storied career .
“ Throughout its life cycle, JET has been remarkably useful as a precursor to ITER. It made it possible to test new materials, to develop new innovative components, and above all to generate data on deuterium-tritium (DT) operations. », underlines Pietro Barabaschi, Director General of ITER. So many precious elements which will help the immense European tokamak to achieve its objectives.
But it’s best not to be in too much of a hurry. The first plasmas from the reactor located in the south of France will not arrive before 2025. The transition to the concrete phase, with the first DT operations, is not expected before 2035. And it will still take years, or more likely decades of work before arriving at the DEMO project, which will finally try to recover all this energy today sacrificed on the altar of experimentation. It will therefore be necessary to arm ourselves with the power to follow the development of this technology which could completely transform our civilization.
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