The power of the sun has always impressed people. Even on Earth, a good 150 million kilometers away, their tremendous energy can still be felt. The fire of the sun is fed by the nuclear fusion inside the star. Under the pressure of gravity, hydrogen melts into helium – at around 15 million degrees Celsius.
Researchers have long been working on artificially mimicking this energy principle. Such nuclear fusion reactors should one day generate almost emission-free electricity. But so far, such star machines have primarily been expensive experiments that are still a long way from being ready for series production.
In South Korea, however, experts have now come a step further. With the KSTAR (Korea Superconducting Tokamak Advanced Research), a fusion reactor in the city of Daejeon, scientists were able to set a world record. For the first time, a temperature of the ion plasma of over 100 million degrees Celsius was maintained over a period of 20 seconds. This was announced by the Korean Institute for Fusion Energy. So far this has not been successful on any other system.
This means that the reactor has more than doubled its record from 2019. Back then, the team managed to hold the temperature for eight seconds. Such high temperatures are considered to be one of the prerequisites for atoms to fuse.
Si-Woo Yoon, the director of KSTAR, spoke of an “important turning point” in the race for technologies for longer and more powerful plasma operation. In the long term, the researchers want to achieve longer and longer stable plasma states. By 2025, the KSTAR is expected to achieve continuous operation for 300 seconds with an ion temperature of more than 100 million degrees.
Heat, plasma and huge magnets
The hydrogen isotopes deuterium and tritium are used for fusion reactors. Very high temperatures are needed to bring the repelling nuclei together. Ions and electrons can only be separated in the plasma state – they have then become an electrically charged gas.
In the end, the heat generated by nuclear fusion is supposed to drive steam turbines, just like in a nuclear power plant, where nuclei are split. Conventional generators then take over the generation of electricity.
In Korea, the researchers are working with a tokamak device. The plant is shaped like a donut. As the plasma rotates inside the circular tube, it is held on its path by a strong, superconducting magnetic field. However, this technology is considered technically complex, as many control and regulation systems are required. The magnets have to be cooled to minus 269 degrees Celsius, for example.
Cost trap or future technology?
Nuclear fusion research has recently made progress in other countries. Huge plants like Iter in the south of France are about to be completed. The reactor, in which researchers from South Korea are also involved, is to be switched on for the first time in December 2025.
Start-ups are also researching the technology, for example in the USA or Great Britain. In China, a reactor was recently able to fuse atomic nuclei for ten seconds at 150 million degrees Celsius.
Supporters of nuclear fusion see technology as a climate-friendly, almost infinitely available energy source. Critics argue that with the rise of renewable energies, the technology is coming too late. In addition, the costs are too high. The reactor in France will cost more than 20 billion euros.