If we want to rely on nuclear fusion to power the world’s homes, the first step is to build reactors that can operate at the highest temperature and for the longest time possible.
Now, an experimental reactor called KSTAR in Daejeon, Korea, has set a new world record.
The huge donut-shaped device, which has been dubbed “Korea’s artificial sun,” operated at 100 million degrees C (180 million degrees F) for 48 seconds.
To put it into perspective, it is seven times hotter than the core of the sun!
The record-breaking test brings us one step closer to the ultimate goal of unlimited clean energy.
How Nuclear Fusion Works: This graphic 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 confine hydrogen isotopes in a spherical shape, similar to the core of an apple, while they are heated by microwaves into plasma to produce fusion.
South Korean engineers have pushed the limits of nuclear fusion by setting a new record for plasma maintenance. Plasma is one of the four states of matter (the others are liquid, gas and solid), examples being lightning and the sun.
Nuclear fusion reactors around the world are in a race to operate at higher temperatures and for longer periods of time, to extract as much energy as possible from the fusion process.
They work by colliding heavy hydrogen atoms to form helium, releasing large amounts of energy, mimicking the process that occurs naturally in the center of stars like our sun.
KSTAR already set a record in 2021 of 100 million degrees for 30 seconds, but has now surpassed it.
Rival China’s ‘artificial sun’ nuclear fusion reactor ran for more than 17 minutes, but at a lower temperature: 126 million °F (70 million °C).
Korean experts achieved the feat between December 2023 and February 2024 by using tungsten instead of carbon in their derailleurs.
These diverters remove impurities from the fusion reaction while withstanding incredibly high temperatures, thanks in large part to tungsten having the highest melting point of all metals.
“Extensive hardware testing and campaign preparation enabled us to achieve results that surpassed KSTAR’s previous records in a short period,” said Dr. Si-Woo Yoon, director of the KSTAR Research Center.
Like other fusion reactors, KSTAR is a ‘tokamak’, a type of doughnut-shaped chamber that creates energy by fusing atoms.
The hydrogen gas inside the tokamak container is heated to become “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, plasma is trapped and pressurized by magnetic fields until the energized plasma particles begin to collide.
As the particles fuse to form helium, they release enormous amounts of energy, mimicking the process that occurs naturally at the center of stars.
The Korean ‘artificial sun’, the Korea Superconducting Tokamak Advanced Research Device (KSTAR), at the Korea Institute of Fusion Energy (KFE) in Daejeon
It successfully sustained plasma with ion temperatures of 100 million degrees Celsius for 48 seconds during KSTAR’s latest plasma campaign conducted between December 2023 and February 2024.
Inside a tokamak, the energy produced by the fusion of atoms is absorbed as heat into the walls of the container. In the photo, the KSTAR vacuum container.
While using nuclear fusion to power homes and businesses may still be a ways off, KSTAR demonstrates that star-like fuel burning can be achieved and contained using current technology.
“To achieve the ultimate goal of KSTAR operation, we plan to sequentially improve the performance of heating and current drive devices and also secure the basic technologies necessary for high-performance long-pulse plasma operations,” added Dr. Si-Woo Yoon.
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 fired up in Naka, north of Tokyo.
Meanwhile, the $22.5bn (£15.9bn) 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 ST40 in Oxfordshire, which is more squished and compact compared to other doughnut-shaped reactors.
And the Joint European Torus (JET), also located in Oxfordshire, released a total of 69 megajoules of energy in five seconds. before being recently discharged.
The holy grail of clean energy: Pictured is how a reactor works, based on one developed by Tokamak Energy, based in Milton, Oxfordshire.
All of them could be precursors to fusion power plants that supply power directly to the grid and electricity to people’s homes.
These power plants could reduce greenhouse gas emissions from the power generation sector by avoiding the use of fossil fuels such as coal and gas.
Fusion differs from fission (a technique currently used in nuclear power plants) because the former fuses two atomic nuclei instead of dividing one (fission).
Unlike fission, fusion carries no risk of catastrophic nuclear accidents – such as the one that occurred in Fukushima, Japan, in 2011 – and produces much less radioactive waste than current power plants, its proponents say.
HOW A FUSION REACTOR WORKS
Fusion is the process by which a gas is heated and separated into its constituent ions and electrons.
It involves light elements, such as hydrogen, breaking down to form heavier elements, such as helium.
For fusion to occur, hydrogen atoms are placed under high heat and pressure until they fuse.
The tokamak (artist’s impression) is the most developed magnetic confinement system and is the basis for the design of many modern fusion reactors. The purple color in the center of the diagram shows the plasma inside.
When the deuterium and tritium nuclei, found in hydrogen, fuse, they form a helium nucleus, a neutron, and a lot of energy.
This is done by heating the fuel to temperatures above 150 million°C and forming a hot plasma, a gaseous soup of subatomic particles.
Strong magnetic fields are used to keep the plasma away from the reactor walls, so that it does not cool and lose its energy potential.
These fields are produced by superconducting coils surrounding the vessel and by an electrical current driven through the plasma.
For energy production, the plasma must be confined for a period long enough for fusion to occur.
When ions get hot enough, they can overcome their mutual repulsion and collide, fusing.
When this happens, they release about a million times more energy than a chemical reaction and three to four times more than a conventional nuclear fission reactor.
