Thanks to several groundbreaking innovations, the young start-up has strong ambitions to simplify and accelerate the deployment of this promising technology for the ecological transition.
One step forward, one step back. Nuclear fusion advocates no longer know which foot to dance on. Last November, their enthusiasm was dampened by the announcement of a delay of at least five years in the manufacture of the Iter experimental reactor, an international project at Cadarache in the Bouches-du-Rhône department. A few weeks later, however, her smile returns when the public research center National Ignition Facility (NIF) in the USA succeeds for the first time in using fusion technology to generate more energy than the 192 laser beams fed into the plasma where the reaction takes place. A big step forward, albeit tempered by the greed of these lasers, which required nearly a hundred times more power to operate than was ultimately produced.
It must be said that the hopes that nuclear fusion has raised since the 1930s are in line with the potential of this technology. It is based on a physical reaction similar to that of the Sun or other stars, namely the fusion of lighter nuclei, often deuterium and tritium, into a heavier element. The process then releases energy. Another approach to the process at the heart of all current nuclear power plants, nuclear fission, which, on the contrary, consists in breaking large uranium nuclei to form smaller elements. Nuclear fusion thus promises to retain the advantages of nuclear fission – carbon-free, controllable and non-intermittent flow – without retaining the main disadvantages: no risk of devastating chain reactions, no radioactive waste for hundreds of thousands of years, without even talking about the abundance in nature of one of the two necessary elements, deuterium.
But there is still a lot to be done. In order to force the marriage between these molecules, they must bathe in a plasma heated to almost 150 million degrees – much more than the sun! – to ensure the continuity of the reaction. “ There are still many challengeslists Simon Belka, project manager at Renaissance Fusion, a French start-up dedicated to building a fusion reactor. We need to find the right materials to withstand these very high temperatures, we need to reduce the size and price of the reactors, and most importantly, we need to show that we can generate much more energy than we put into the plasma to heat it , including the operation of the facility. » At the moment, neither of the two majority technologies today, the inertial confinement tested in the NIF or the “tokamak-type” magnetic confinement used by Iter, is able to meet these challenges. To solve them, Renaissance Fusion took a third approach.
Stellarator vs Tokamak
Founded in Grenoble in 2019, the start-up is based on the work of its founding President, the Italian physicist Francesco Volpe. “ For 25 years he was able to experiment with the various devices used in nuclear fusion and make his choice.says Simon Belka. The “stellarator” seemed to him the most suitable for commercial production of fusion energy. »
Under that barbaric and somewhat futuristic name, this technology is somewhat similar to the tokamak-type magnetic confinement used by Iter. In both cases, the plasma is confined in a magnetic field that isolates it from the reactor walls to protect them. So the whole structure can be thought of as a big donut lined with superconducting magnets to create the magnetic field and circulate the plasma in its heart.
But the tokamak has several difficulties: “The tokamak is inherently pulsed: its energy production is intermittent. It creates fusion for a few minutesexplains Simon Belka. In addition, the current circulating in the plasma creates instability and disturbances, electron beams can emerge, hit the walls of the reactor and damage them. »
So many problems that the principle of the stellarator can solve. The use of complex-shaped magnets means that the plasma can theoretically circulate continuously and the reaction cannot be interrupted. A major advance over laser or tokamak technologies. But until now the stellarator, as tested in Germany for example, has been very difficult to design and build because of its peculiar magnets.
Renaissance Fusion has developed two technologies protected by a number of patents to overcome these obstacles. The first is to laser engrave magnets with complex shapes directly onto the reactor body. Thus, there is no need to give the structure a complicated shape, and the presence of these magnets ensures a continuous process.
The second is based on the construction of liquid metal walls inside the reactor, which circulate thanks to a magnetic field. “This brings us several advantages, says Simon Belka. Liquid lithium protects the solid walls of the reactor, absorbs neutrons much better, conducts the heat generated by fusion into the secondary circuit and the power-generating turbine, and finally, by reacting with the plasma, produces the tritium necessary for operation. »
In addition, by using a new generation of superconducting materials, Renaissance Fusion enables the construction of fusion reactors four to five times smaller than those currently planned, and therefore less expensive. Finally, the continuity of the process provided by the complex-shaped magnets makes it possible to eliminate instabilities in the reaction and send most of the electricity to the grid instead of being reused to sustain fusion. As a result, the start-up announces electricity production at an estimated cost of between 40 euros and 80 euros per MWh, that is between solar energy and new generation nuclear fission. Now it’s time to put theory into practice.
A first reactor within ten years
By 2024, Renaissance Fusion intends to complete the development of its two flagship technologies, the etching of superconducting magnets and its liquid metal wall, in order to be able to start manufacturing and, above all, its commercialization in sectors where they represent a real added value such as medical imaging, Energy storage or particle accelerator. “ For this first step, we have completed a fundraising of several million euros from private investors, which allows us to finance ourselves to a large extent », let Simon Belka know without revealing the amount of the operation. The company’s team is expected to grow from 23 employees to around 60 next year.
After completing these proofs of concept and starting commercialization, the start-up will work on building a first experimental reactor, in particular to demonstrate its ability to produce more energy than it needs. Finally, in the early 2030s, it is scheduled to inaugurate its first 1 GW reactor capable of feeding electricity into the grid.
“Compared to major international public projects, start-ups offer an interesting alternative: we bring new ideas, take more risks to create disruption, and are less dependent on public funding. The two complement each other, I am convinced that the emergence of merger will go through public-private partnerships », assures Simon Belka. A new perspective to hope that catching the sun in a box is not just a dream of Icarus.