A lab in the U.K. has set a new record for the most amount of energy made from a fusion reaction. It lays the groundwork for the next generation of fusion reactors and is a tiny step closer to the dream of boundless clean energy.
The donut-shaped Joint European Torus (JET) reactor managed to squeeze out 69 megajoules of output at the end of 2023, in a reaction lasting 5.2 seconds. That’s about as much as burning two kilograms of coal and is better than the 59 megajoules the reactor produced in 2021. Since then, the reactor has been decommissioned.
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It’s the last hurrah for a multi-nation experiment that’s been described as “the heart of global fusion research”, dating all the way back to 1983. “Beyond setting a new record, we achieved things we’ve never done before and deepened our understanding of fusion physics,” said Ambrogio Fasoli, Programme Manager at EUROfusion, the consortium of research institutions that ran JET.
JET is a tokamak reactor, which restrains plasma (superheated matter) inside a ring using magnetic fields. It’s one of the two favorite designs when it comes to practical fusion tech—along with the similar ring-shaped stellarator—because they keep plasma particles confined and constantly spinning around to create a lasting reaction.
Like many other fusion reactors, JET combines two types of hydrogen, deuterium and tritium, to make helium and energy. It’s hoped this reaction could be the cornerstone of fusion power plants in the future—plants that could provide massive amounts of energy without all the radioactive waste.
That ultimate goal of powering the planet using fusion tech is still a long way off, even as records are smashed. In September 2023, the National Ignition Facility (NIF) in California generated 3.88 megajoules using a different technique of blasting a ball of hydrogen with lasers.
A boasting point for this and other fusion reactions is that the reaction creates more energy than it takes in. This definition, however, only applies to the reaction itself and not the vast amounts of energy needed to power the lasers or heat the plasma to a whopping 150 million degrees celsius—the hottest thing in the solar system at that time. NIF’s lasers for example used 322 megajoules of energy and JET uses between 700–800 megajoules when it runs.
So, for now, experiments like JET are just that. Experiments designed to yield data. The move from lab to commercial plant will come down to overcoming engineering challenges, experts say, such as making sure the swirling plasma doesn’t come in contact with any solid material as it whirls around its donut enclosure.
JET’s final few experiments brought researchers one step closer to meeting those challenges. “Not only did we demonstrate how to soften the intense heat flowing from the plasma to the exhaust, we also showed in JET how we can get the plasma edge into a stable state thus preventing bursts of energy reaching the wall,” said Emmanuel Joffrin, EUROfusion Tokamak Exploitation task force leader in a press statement. “Both techniques are intended to protect the integrity of the walls of future machines. This is the first time that we’ve ever been able to test those scenarios in a deuterium-tritium environment.”
The reactor will now be decommissioned and repurposed to make way for the International Thermonuclear Experimental Reactor, or ITER—a larger fusion project run by 37 countries, scheduled to get underway in late 2025.
“Our successful demonstration of operational scenarios for future fusion machines like ITER and DEMO [The DEMOnstration power plant], validated by the new energy record, instill greater confidence in the development of fusion energy,” said Fasoli.
“JET has operated as close to powerplant conditions as is possible with today’s facilities, and its legacy will be pervasive in all future power plants,” added UK Atomic Energy Authority CEO, Sir Ian Chapman. “It has a critical role in bringing us closer to a safe and sustainable future.”
