Nuclear Fusion Reactor Sustains Plasma at 100 Million C for 30 Seconds

Scientists in South Korea have managed to get a nuclear fusion reactor to operate a stable plasma for 30 seconds, marking another promising step toward unlimited clean energy.

Nuclear fusion, a process that physicists and engineers have been working on for decades, involves merging two atomic nuclei to form one larger nucleus under intense heat and pressure. The single larger nucleus that results from this merger is not quite as heavy as the combined weight of the two individual nuclei before they fused together, and this leftover mass is converted to energy.

Creating a nuclear fusion reaction isn't actually the hard part. Scientists have devised all sorts of ways to do this, such as compressing matter with lasers or running superheated gas in a circle. The problem is maintaining this reaction so that the energy can be harnessed in power stations.

One of the leading candidates for a stable nuclear reactor is the tokamak—a doughnut-shaped device that contains a ring of hot gas, known as plasma, that is contained using strong magnets. Plasma is the name given to matter in which electrons have been stripped from their atoms, forming a charged gas.

Several advancements and refinements to tokamak technology have been made over the years, from size decreases to temperature increases. However, engineers still struggle to get tokamaks to circulate plasma at high temperatures for a long period. If instabilities in the plasma occur, it can touch the walls inside the reactor, disrupting the reaction and damaging the equipment.

South Korean scientists working with the KSTAR (or Korea Superconducting Tokamak Advanced Research) tokamak have made steady advancements in this area. In 2018, they reached the crucial plasma temperature of 100 million degrees Celsius—one of the core conditions for fusion—for the first time and held that temperature for eight seconds the following year.

In 2020, this was extended significantly to 20 seconds. Now, experts at Seoul National University in South Korea have managed to extend that to 30 seconds. Their method essentially involved using a low-density plasma, enabling the charged atoms within to travel quickly at the plasma's center, resulting in higher stability.

The research was published in the journal Nature on September 7. The study says that the 100 million degrees C conditions were reached for only 20 seconds, but the study's author, Yong-Su Na at Seoul National University, subsequently told New Scientist that the researchers had actually reached 30 seconds.

Despite frequent minor advancements—China's EAST reactor sustained fusion at 126 million degrees Fahrenheit (70 million C) for 17 minutes this year—it's generally accepted that a working nuclear fusion reactor on the grid is not a realistic prospect for a couple of decades.

Correction 9/8/22, 8:20 a.m. ET: An earlier version of this story gave the incorrect temperature for the plasma temperature reached by the South Korean scientists. It was 100 million Celsius.