The long-standing dream of using nuclear fusion to create a safe, efficient supply of energy has come closer to reality. Scientists at the Joint European Torus (JET) near Oxford, UK, have used their reactor to generate the largest-ever amount of energy in a sustained fusion reaction.


In an experiment carried out in December 2021, the team used JET to produce a total of 59 megajoules of heat energy over a five-second period. The previous record of 22 megajoules was set by JET in 1997.

“The record, and more importantly the things we’ve learned about fusion under these conditions and how it fully confirms our predictions, show that we are on the right path to a future world of fusion energy," said Prof Tony Donné, EUROfusion programme manager. "If we can maintain fusion for five seconds, we can do it for five minutes and then five hours as we scale up our operations in future machines."

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Fusion is the process that is ongoing inside stars such as the Sun. It smashes together lighter atoms such as hydrogen at incredibly high temperatures to form heavier elements and release huge amounts of energy as heat.

The success of the experiment now sets the scene for the International Thermonuclear Experimental Reactor, or ITER, a larger, more advanced version of JET, the researchers say.

ITER is a global fusion project based in Saint-Paul-lès-Durance, southern France that involves scientists from China, the European Union, India, Japan, South Korea, Russia and the USA. Although it is much larger than JET, ITER plans to use the same deuterium-tritium fuel source and operate under similar conditions when it goes online in 2025.

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“This is a big moment for every one of us and the entire fusion community. Crucially, the operational experience we’ve gained under realistic conditions gives us great confidence for the next stage of experiments at ITER,” said Donné.

It is hoped that nuclear fusion will play an important role in addressing the effects of climate change thanks to the low amounts of carbon it generates, the researchers say.

“It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential,” said Prof Ian Chapman, The UK Atomic Energy Authority’s CEO.


“We’re building the knowledge and developing the new technology required to deliver a low-carbon, sustainable source of baseload energy that helps protect the planet for future generations. Our world needs fusion energy.”


Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.