by Future fusion reactions inside tokamaks could produce much more energy than previously thought, thanks to groundbreaking new research that found that a fundamental law for such reactors was wrong.
The research, led by physicists from the Swiss Plasma Center at the École Polytechnique Fédérale de Lausanne (EFPL), has determined that the maximum density of hydrogen fuel is about twice the “Greenwald Limit” – an estimate derived from more than 30 years.
The discovery that fusion reactors can actually operate at hydrogen plasma densities well above the Greenwald limit for which they were built will affect the operation of the huge ITER tokamak made in southern France and greatly influence the designs of successors. of ITER, called Demonstration Power Plant Fusion Reactors (DEMOs), said physicist Paolo Rizzi at the Swiss Plasma Center.
“The exact price depends on the power,” Ricci told Live Science. “But as a rough estimate, the increase is in the order of a factor of two on ITER.”
Ricci is one of the leaders in the research project, which combined theoretical work with the results of nearly a year of experiments on three different fusion reactors across Europe – EPFL Tokamak à Configuration Variable (TCV (opens in new tab)), the Common European Torus (JET (opens in new tab)) in Culham in the United Kingdom and the Axially Symmetric Divertor Experiment (ΑΣΔΕΞ (opens in new tab)) Tokamak upgrade at the Max Planck Institute for Plasma Physics in Garching, Germany.
He is also one of the lead authors of a study on the discovery published May 6 in the journal Physical Review Letters (opens in new tab).
Future fusion
Donut-shaped tokamaks are one of the most promising designs for nuclear fusion reactors that could one day be used to generate electricity for power grids.
Scientists have been working for more than 50 years to make controlled fusion a reality. Unlike nuclear fission, which makes energy from the crushing of very large atomic nuclei, nuclear fusion could produce even more energy by joining very small nuclei together.
The fusion process generates much less radioactive waste than fission and the neutron-rich hydrogen it uses to fuel it is relatively easy to obtain.
The same process empowers stars as The sun, which is why controlled fusion is likened to a “star in a jar”. but because too high a pressure on a star’s heart is not possible Earththe fusion reactions below require temperatures higher than the sun to operate.
The temperature inside the TCV tokamakfor example, it can be over 216 million degrees Fahrenheit (120 million degrees Celsius) – almost 10 times the temperature of the sun’s fusion core, which is about 27 million F (15 million C).
Several fusion energy projects are now at an advanced stage, and some researchers believe the first tokamak to generate electricity for the grid could be operational by 2030previously reported by Live Science.
More than 30 governments around the world are also funding ITER tokamak (“Iter” means “road” in Latin) which is set to produce its first experimental creatures in 2025.
ITER, however, is not designed to generate electricity. but ITER-based tokamaks, called DEMO reactors, are being designed now and could be operational by 2051.
Plasma problems
At the heart of the new calculations is the Greenwald boundary, named after MIT physicist Martin Greenwald, who set the limit in 1988.
The researchers were trying to figure out why their fused plasma became virtually uncontrollable (it expanded beyond the magnetic fields contained in the tokamak chamber) when they increased the fuel density beyond a certain point and Greenwald drew an experimental limit based on tokamak’s small radius (the size of the donut’s inner circle) and the amount of electricity passing through the plasma.
Although scientists have long suspected that the Greenwald limit could be improved, it has been a fundamental rule of fusion research for more than 30 years, Ricci said. For example, it is a guiding principle of ITER design.
The latest study, however, extends to both the experiments and the theory used by Greenwald to derive its limit, resulting in a much higher fuel density limit that will increase the capacity of ITER and affect the designs of DEMO reactors that they will follow. he said.
The key was to discover that a plasma could maintain a higher fuel density as the output power of a fusion reaction increased, he said.
It is not yet possible to know how such a large increase in fuel density will affect the output power of tokamaks, Ricci said, but it is likely to be significant. and research shows that higher fuel density will make fusion reactors easier to operate.
“It makes it easier to achieve safe, sustainable fusion conditions,” he said. “It allows you to get to the mode you want, so that the fusion reactor can work properly.”
Originally published in Live Science.
