A 40-year-old nuclear fusion reactor in the UK has set a world record for energy output in its final run before permanent shutdown, scientists have announced.

The Joint European Taurus (JET) in Oxfordshire began operations in 1983. During its operation, it briefly became the hottest point in the solar system, reaching 150 million degrees Celsius.

The reactor's previous record was in 2021 for a reaction that lasted five seconds and produced 59 megajoules of thermal energy. However, it surpassed this in its final test in late 2023, using just 0.2 milligrams of fuel to sustain the reaction for 5.2 seconds, reaching an output of 69 megajoules.

This corresponds to an output of 12.5 megawatts, enough to power 12,000 homes, Mikhail Maslov of the UK Atomic Energy Agency said at a press conference on February 8.

Today's nuclear power plants rely on nuclear fission reactions, in which atoms are shattered to release energy and small particles. Fusion works in reverse, pushing smaller particles together into larger atoms.

Nuclear fusion can produce more energy without any of the radioactive waste produced by nuclear fission, but there is still no practical way to use the process in power plants.

JET trains atoms of two stable isotopes of hydrogen, deuterium and tritium, together in a plasma to create helium, releasing a huge amount of energy at the same time. This is the same reaction that powers our sun. This is a type of fusion reactor known as a tokamak, which uses rings of electromagnets to contain plasma in a donut shape.

Scientists conducted the final experiment using deuterium and tritium fuel on JET in October last year, and other experiments continued until December. However, the machine is now permanently closed and will be decommissioned over the next 16 years.

Juan Matthews Researchers at the University of Manchester in the UK say many secrets will be revealed during JET's dismantling. For example, how the reactor lining deteriorated from contact with the plasma, and where in the machine the precious tritium, worth around £30,000 a gram, is embedded. You can recover. This will be important information for future research and commercial reactors.

“It's great to have a little bit of a bang,” Matthews said. “It has a noble history. Now that it has served its purpose, we plan to squeeze out more information during the decommissioning period as well. So it's not sad. It's something to be celebrated.”

France's larger, more modern replacement for JET, the International Thermonuclear Experimental Reactor (ITER), is nearing completion, with first experiments scheduled to begin in 2025.

ITER construction project deputy director Tim Luce told a news conference that ITER plans to expand its energy output to 500 megawatts and possibly 700 megawatts.

“These are what I normally call power plant sizes,” he said. “They are at the lowest level of cost required for a power generation facility. Moreover, to obtain high fusion power and gain the timescale needs to be extended to at least 300 seconds, but from an energy production point of view it is probably less than an hour. So what JET has done is exactly a scale model of what we need to do with the ITER project.”

Another reactor using the same design, the Korea Superconducting Tokamak Advanced Research (KSTAR) device, recently succeeded in sustaining a reaction for 30 seconds at temperatures above 100 million degrees Celsius.

Other approaches to creating practical fusion reactors are also being pursued around the world, such as the National Ignition Facility at Lawrence Livermore National Laboratory in California. It fired a very powerful laser into the fuel capsule, a process called inertial confinement fusion, and was able to release almost twice the energy that was put into it.