Double the energy! The 24-year-long nuclear fusion record was broken

Original author: Elizabeth Gibney

The experimental Joint European Torus reactor has doubled the amount of energy produced by fusion, the process by which the sun releases energy.

The 24-year-long nuclear fusion record has been broken. On Feb. 9, scientists at the European Union Ring (JET) near Oxford, England, announced that they had produced the highest ever sustained pulse of energy through atomic fusion, more than twice as much as their 1997 experiments had recorded.

The European Joint Tokamak reactor near Oxford, England, is the test site for the world's largest fusion experiment (France's International Thermonuclear Fusion Reactor Program, ITER) | Christopher Roux (CEA-IRFM)/EUROfusion (CC BY 4.0)

"These results are milestones and a big step forward in solving one of the biggest challenges of science and engineering." Ian Chapman said in a statement that he is the head of the Kalam Fusion Energy Center (CCFE), JET's base. JET is hosted by the UK Atomic Energy Authority (UKAEA), but its scientific projects are managed by a European partnership called eurOfusion.

If researchers can harness nuclear fusion reactions (the process that powers the sun) — it promises to provide a near-limitless supply of clean energy. But so far, no experiment has produced more energy than the energy it has entered. JET's findings don't change that, but they show that a follow-up fusion reactor project using the same technology and fuel blends — the ambitious , $22 billion ITER , which plans to begin fusion experiments in 2025 — should eventually reach that goal.

"JET did achieve its prediction goals, and the same model now means it's successful." Josefine Proll, a nuclear fusion physicist at Eindhoven University of Technology in the Netherlands, says he's working on another type of reactor called a star-replicator. "It's a very, very good sign and I'm very excited."

Twenty years of work

The experiment, the culmination of nearly two decades of work, is extremely helpful for scientists to predict how ITER will behave and guide its operational settings, Says Anne White. She is a plasma physicist at the Massachusetts Institute of Technology and works on tokamak reactors that are as circular as JET. "There must be many people in the fusion research community who, like me, sincerely congratulate the JET team."

JET and ITER use magnetic confinement to plasmas in the tokamak ( a superheated gas composed of hydrogen isotopes ) . At high temperatures and pressures, isotopes fuse to form helium, which releases energy in the form of neutrons.

To break the energy record, JET used a fuel made up of equal amounts of tritium and deuterium — which would also be a mixture to drive ITER, which is under construction in the south of France. Tritium is a rare radioactive isotope of hydrogen: when it is mixed with the isotope deuterium, the reaction produces far more neutrons than deuterium fusion alone. This increased the amount of energy output, but the JET would take more than two years to revamp to prepare the machine for shock. Tritium was last used in the Tokamak fusion experiment in 1997, when JET set its last record.

Record-breaking pulses move in the JET ring-shaped internal pipe | UKAEA

In an experiment on December 21, 2021, JET's tokamak produced 59 megajoules of energy in a 5-second fusion "pulse," more than double the energy released in 1997 at 21.7 megajoules in 4 seconds. While the 1997 experiment still holds the record for "peak power," the peak lasted only a fraction of a second, and the average power of the experiment is less than half of the most recent test, said Fernanda Rimini, a plasma scientist at CCFE who managed last year's experimental activity. The improvement, she said, came after 20 years of experimental optimization, as well as hardware upgrades, including replacing the inner walls of the tokamak to reduce fuel waste.

Power ratio

Generating energy in seconds is critical to understanding the heating, cooling and motion inside the plasma, Rimini said, and is critical to the operation of ITER.

Five seconds is "remarkable," Proll added. "It's really quite remarkable."

Last year, the U.S. Department of Energy's national ignition device set a different fusion record: The researchers used laser technology to produce the highest fusion output power relative to the input power, a value called Q, which when it is 1 means to produce the same power as the input. The device's Q value reached 0.7, a milestone in laser fusion, breaking the record set by JET in 1997. But the event was extremely short-lived, producing 1.3 million joules of energy in less than 4 billionths of a second.

RIMINI said JET's latest experiment maintained the Q value at 0.33 for 5 seconds. JET is a scaled-down version of ITER that's only one-tenth the size of ITER — like comparing a bathtub to a swimming pool, Proll said. It's easier to lose heat than ITER, so no one expects it to break even. If engineers adopt the same conditions and physical approach to ITER as JET, she said, it may be able to achieve the goal of Q=10, which is to produce 10 times the amount of energy invested.

Fusion researchers are far from having all the answers. For example, another challenge is dealing with the heat generated by the exhaust zone of the ITER reactor. ITER's emissions area will be larger than JET's, but the increased area is disproportionate to the surge in power it has to deal with. Proll said research is currently being made on which design is best able to withstand the high temperatures, but the researchers are still far from that goal.

JET's record-breaking run comes on the final day of the 5-month campaign, from which Rimini said scientists have gathered a wealth of information that will be analyzed over the next few years. The final experiment pushed the device to an "absolute maximum," Rimini added, adding that she witnessed the milestone test in real time. "We didn't jump up and down to hug each other – we were two metres apart – but it was so exciting."

The tritium experiment may be jet's last stop. Last year, EUROfusion decided to end JET operations at the end of 2023, 40 years after JET began working. UKAEA has said they plan to stop the experiment; JET's hardware and operational expertise will find a home in other projects there.

The original article was published in the news section of Nature on February 9, 2022, under the title of the Nuclear-fusion reactor smashes energy record

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