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posted by hubie on Monday February 12, @09:20AM   Printer-friendly

Arthur T Knackerbracket has processed the following story:

The UK’s 40-year-old fusion reactor achieved a world record for energy output in its final runs before being shut down for good, scientists have announced.

The Joint European Torus (JET) in Oxfordshire began operating in 1983. When running, it was temporarily the hottest point in the solar system, reaching 150 million°C.

The reactor’s previous record was a reaction lasting for 5 seconds in 2021, producing 59 megajoules of heat energy. But in its final tests in late 2023, it surpassed this by sustaining a reaction for 5.2 seconds while also reaching 69 megajoules of output, using just 0.2 milligrams of fuel.

[...] JET forged together atoms of deuterium and tritium – two stable isotopes of hydrogen – in plasma to create helium, while also releasing a vast amount of energy. This is the same reaction that powers our sun. It was a type of fusion reactor known as a tokamak, which contains plasma in a donut shape using rings of electromagnets.

Scientists ran the last experiments with deuterium-tritium fuel at JET in October last year and other experiments continued until December. But the machine has now been shut down for good and it is being decommissioned over the next 16 years.

“It’s great that it’s gone out with a little flourish,” says Matthews. “It’s got a noble history. It’s served its time and they’re going to squeeze a bit more information out of it during its decommissioning period as well. So it’s not something to be sad about; it’s something to be celebrated.”

A larger and more modern replacement for JET, the International Thermonuclear Experimental Reactor (ITER) in France, is nearing completion and its first experiments are due to start in 2025.

[...] Another reactor using the same design, the Korea Superconducting Tokamak Advanced Research (KSTAR) device, recently managed to sustain a reaction for 30 seconds at temperatures in excess of 100 million°C.

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  • (Score: 4, Informative) by Rosco P. Coltrane on Monday February 12, @11:38AM (2 children)

    by Rosco P. Coltrane (4757) on Monday February 12, @11:38AM (#1344064)

    69 MJ is the same energy as half a gallon of gasoline. The whole site probably goes through that in 5 seconds too just to keep the lights on.

    In other words, while it was probably a great technical success, it's nowhere near unity.

    • (Score: 4, Interesting) by VLM on Monday February 12, @12:58PM (1 child)

      by VLM (445) on Monday February 12, @12:58PM (#1344072)

      Yeah that Q value is relative solely to heating current. Its a arc welding transformer, pretty much, where the heater coils have many turns and the donut is a single shorted turn. IIRC the heating coils run around "forty KW" max.

      You'll notice the tokamak people VERY carefully avoid reporting the highest Q ever was at JET IIRC and was well under 1 whereas the laser-boys have been running above 1 for "some time". Of course the secret squirrel bomb people have been running WAY over a Q value of 1 for some decades now, although the instantaneous peak would be an engineering challenge to contain LOL.

      • (Score: 1) by khallow on Monday February 12, @04:27PM

        by khallow (3766) Subscriber Badge on Monday February 12, @04:27PM (#1344106) Journal

        whereas the laser-boys have been running above 1 for "some time".

        Keep in mind that there's huge power inefficiency in the lasers that aren't being reported in that Q value. They presently run well under Q=1 too. Still these values are nice in that if they were to greatly reduce the inefficiencies in the ignition/containment systems, they'd be running close or even above Q=1.

  • (Score: 3, Interesting) by VLM on Monday February 12, @01:04PM

    by VLM (445) on Monday February 12, @01:04PM (#1344073)

    Modern innumeracy is a given so doing math is a revolutionary act.

    Now I just woke up and no tea yet and I often F up posts under these conditions, but I'll give it a try anyway.

    So if time t = energy J divided by power W that would imply the total operation time is about 1.5 seconds because about sixty megajoules of fusion / about forty megawatts of ohmic heating coil power = about 1.5 seconds amirite or not?

    Something I've never been entirely clear about is how they calculate the fusion power output. IF reactions were stable and continuous-ish and smoothly distributed you could look at the neutron flux in just one detector and extrapolate, but if its all unstable and blah then how do they do it and if it was stable we'd have Mr. Fusion in our cars right now and they wouldn't be doing research anyway. The mass of JET is immense so I can't imagine them doing simple calorimetry like wave a thermometer over the donut.

    Its easy to measure the power in, LOL, the flywheels are near a kiloton of spinning steel (which in itself is pretty impressive) and its pretty easy to measure rotation and even directly measure electric current and magnetic fields etc.

  • (Score: 2) by VLM on Monday February 12, @01:07PM (1 child)

    by VLM (445) on Monday February 12, @01:07PM (#1344075)

    being decommissioned over the next 16 years

    Anyone know why? Its an inconvenient length. Half life of tritium is 12 years and the journalism filter is too good to mess up 12 to 16, but not good enough to notice 16 isn't that many half lives. So they're not saving much from primary contamination. In a century or two essentially all the H3 will be gone but they're in a hurry so only waiting 16 years.

    My guess is neutron irradiation causing secondary radiation from "stuff". They probably had to order special low-cobalt steel etc but the whole thing is probably still kind of hot for awhile.

  • (Score: 2) by c0lo on Monday February 12, @02:38PM

    by c0lo (156) Subscriber Badge on Monday February 12, @02:38PM (#1344088) Journal

    doi:s41598-023-49432-3 [] in Sabine's translation [] (7mins vid)

  • (Score: 5, Informative) by quietus on Monday February 12, @04:37PM

    by quietus (6328) on Monday February 12, @04:37PM (#1344111) Journal

    Claiming it's the UK's fusion reactor is a bit a stretch. While it's located in the UK, it was actually funded and run by originally Euratom since 1978, with the European Consortium for the Development of Fusion Energy (Eurofusion), headquartered in Germany, later took over the experiments.

    That little nitpick aside, those JET experiments weren' t about the energy output, but rather about controlling the created plasma, developing the expertise to continuously feed that plasma, harnessing (converting) the heat exhaust from the plasma, and studying the effect of fusion-born high energy neutrons on the cooling system and electronics (in collaboration with CERN [] (no direct info, just interesting link).

    Researchers focused on dispersing energy at the plasma edge while maintaining high energy levels in the plasma core, a critical balance for reactor feasibility. This included minimizing or eliminating energy outbursts from plasma edge instabilities and implementing innovative heat load management techniques like feedback-controlled impurity gas injections to create a localised radiator plasma zone around the X-point. Additionally, the team demonstrated real-time control of the D-T fuel mix by injecting gas and frozen deuterium pellets, a key method for controlling fusion reactions.

    For those interested, more info here [].