If we want to rely on nuclear fusion to power the world’s homes, the first step is to make reactors that can run as hot and for as long as possible.
Now an experimental reactor called KSTAR in Daejeon, Korea, has set a new world record.
The enormous doughnut-shaped device, dubbed “Korea’s artificial sun,” operated at 100 million °C (180 million °F) for 48 seconds.
To put that into perspective, that’s seven times hotter than the core of the sun!
The record-breaking test brings us one step closer to the ultimate goal of limitless clean energy.
How Nuclear Fusion Works: This image shows the inside of a nuclear fusion reactor and explains the process by which energy is produced. At its heart is the tokamak, a device that uses a powerful magnetic field to hold the hydrogen isotopes in a spherical shape, similar to a cored apple, while they are heated by microwaves into a plasma to produce fusion.
Engineers in South Korea have pushed the boundaries of nuclear fusion by setting a new record for sustaining plasma. Plasma is one of four states of matter – the others are liquid, gaseous and solid – with examples including lightning and the sun
Nuclear fusion reactors around the world are in a race to operate at higher temperatures and for longer, to extract as much energy as possible from the fusion process.
They work by colliding heavy hydrogen atoms to form helium, releasing enormous amounts of energy – mimicking the process that occurs naturally at the center of stars like our Sun.
KSTAR already set a record of 100 million degrees for 30 seconds in 2021, but has now broken this record.
The nuclear fusion reactor of the rival Chinese ‘artificial sun’ operated for more than seventeen minutes, but at a lower temperature: 70 million degrees Celsius.
Korean experts achieved this between December 2023 and February 2024 by using tungsten instead of carbon in the diverters.
These diverters remove impurities from the fusion reaction while also being able to withstand incredibly high temperatures, thanks in large part to the fact that tungsten has the highest melting point of all metals.
“Thorough hardware testing and campaign preparation have enabled us to achieve results that surpass those of previous KSTAR records in a short time,” said Dr. Si-Woo Yoon, director of the KSTAR Research Center.
Like other fusion reactors, KSTAR is a ‘tokamak’, a kind of doughnut-shaped chamber that creates energy through the fusion of atoms.
Hydrogen gas in the tokamak vessel is heated into ‘plasma’: a soup of positively charged particles (ions) and negatively charged particles (electrons).
Plasma is often referred to as the fourth state of matter, after solid, liquid and gas, and comprises more than 99 percent of the visible universe, including most of our sun.
In the tokamak, the plasma is collected and pressurized by magnetic fields until the activated plasma particles begin to collide.
As the particles fuse into helium, enormous amounts of energy are released, mimicking the process that occurs naturally at the center of stars.
The Korean ‘artificial sun’, the Korea Superconducting Tokamak Advanced Research (KSTAR) device, at the Korea Institute of Fusion Energy (KFE) in Daejeon
It successfully maintained plasma with ion temperatures of 100 million degrees Celsius for 48 seconds during the last KSTAR plasma campaign that ran from December 2023 to February 2024
In a tokamak, the energy produced by the fusion of atoms is absorbed as heat in the walls of the vessel. Pictured: the KSTAR vacuum vessel
While the use of nuclear fusion to power homes and businesses may still be a long way off, KSTAR proves that the combustion of star-like fuel can be achieved and contained using current technology.
“To achieve the ultimate goal of KSTAR’s operation, we plan to sequentially improve the performance of heating and power driving devices and also secure the core technologies required for high-performance long-pulse plasma operations,” added Dr . Si-Woo Yoon added.
Like many other reactors around the world, KSTAR was built as a research facility to demonstrate the promising potential of nuclear fusion to produce energy.
Others include China’s experimental advanced superconducting tokamak (EAST) in Hefei and Japan’s reactor, called JT-60SA, recently switched on in Naka, north of Tokyo.
In the meantime, the $22.5 billion (£15.9 billion) The International Thermonuclear Experimental Reactor (ITER) in France will be the largest in the world once construction is completed next year.
Other smaller reactors are being built and tested – including the ST40 in Oxfordshire, which is more compact and compact compared to other ‘doughnut-shaped’ reactors.
And the Joint European Torus (JET), also based in Oxfordshire, produced a total of 69 megajoules of energy in five seconds before it was recently decommissioned.
The holy grail of clean energy: Pictured is how a reactor works, based on one developed by Tokamak Energy, based in Milton, Oxfordshire
They could all be precursors to fusion power plants that feed power directly into the grid and deliver electricity to people’s homes.
These power plants could reduce greenhouse gas emissions from the power generation sector by moving away from the use of fossil fuels such as coal and gas.
Fusion differs from fission (the technique currently used in nuclear power plants) because the former fuses two atomic nuclei together instead of splitting one (fission).
Unlike nuclear fission, fusion poses no risk of catastrophic nuclear accidents — such as the one at Fukushima, Japan, in 2011 — and produces far less radioactive waste than today’s power plants, its exponents say.