The UK’s ST40 Spherical Tokamak Achieves Crucial Plasma Temperatures

As the race towards the first commercially viable nuclear fusion reactor heats up, the UK-based Tokamak Energy has published a paper on its recent achievements with its ST40 spherical tokamak. Most notable is the achieving of plasma temperatures of over 100 million Kelvin, which would put this fusion reactor firmly within the range for deuterium-tritium fusion at a rate that would lead credence to the projection made by Tokamak Energy about building its first commercial fusion plants in the 2030s.

The ST40 is intended to provide the necessary data to construct the ST80-HTS by 2026, which itself would be a testing ground for the first commercial reactor, called the ST-E1, which would be rated at 200 MWe. Although this may seem ambitious, Tokamak Energy didn’t come out of nowhere, but is a spin-of of Culham Centre for Fusion Energy (CCFE), the UK’s national laboratory for fusion research, which was grounded in 1965, and has been for decades been involved in spherical tokamak research projects like MAST and MAST-Upgrade, with STEP as its own design for a commercial fusion reactor.

The advantage offered by spherical tokamaks compared to regular tokamaks is that they favor a very compact construction style which puts the magnets very close to the plasma, effectively making them more efficient in retaining the plasma, with less power required to maintain stable plasma. Although this makes the use of super-conducting electromagnets not necessary, it does mean that wear and tear on these magnets is significantly higher. What this does mean is that this type of tokamak can be much cheaper than alternative reactor types, even if they do not scale as well.

Whether or not Tokamak Energy will be the first to achieve commercial nuclear fusion remains to be seen. So far Commonwealth Fusion’s SPARC and a whole host of Western and Asian fusion projects are vying for that gold medal.

23 thoughts on “The UK’s ST40 Spherical Tokamak Achieves Crucial Plasma Temperatures

  1. It’s too early to say whether _anyone_ will achieve commercial nuclear fusion.

    Nobody, anywhere, has ever run a laboratory system continuously with an energy gain. Not to mention a commercial product.

    The best records so far are for single “shots”, causing fusion in one tiny hohlraum, among many failed shots. The record is held by the National Ignition Facility at Lawrence Livermore laboratories, using 192 tremendous weapons-grade lasers together.

    Solicitations for investment in these companies should be looked at with great doubt. This is most likely a 20-year timeline and It is unlikely that they will reach the target of commercial product shipment within the lifetime of patents that they’re filing now.

    1. “Nobody, anywhere, has ever run a laboratory system continuously with an energy gain”

      The main reason for this is that if they did, they’d deplete the world’s supply of tritium in extremely short order. They *have* generated energy on macroscopic scales – JET had a Q of over 2.5 on a timescale of 5 seconds a little over a year ago. Part of the reason why everyone’s timescales for an actual fusion reactor are still fairly far off is that no one’s actually done tritium breeding yet.

      An interesting side point to fusion is that being able to large-scale generate tritium might be economically more valuable than the actual electricity itself, considering its cost.

      These are all primarily plasma research devices at this point. Tritium’s too expensive to play around with.

      1. The Wikipedia article on JET says Q=0.67, are you wrong twice? :-)

        And isn’t this a chicken-egg problem? Nobody is breeding tritium because there isn’t a need for it yet. Especially given that the bio people turned to gene engineering after the totally irrational uproar about the tritium lab at UC Berkeley.

        It won’t stay expensive. Fusion reactors can make it, once they need it. Nuclear reactors until then.

        1. Only couple types of nuclear reactors that use heavy water actually produce meaningful amounts of tritium that can be extracted. Making it out of lithium in substantial amounts would require a working fusion reactor, which needs tritium to run, so it’s a bootstrapping problem.

          1. Yup. It’s not an impossible one, since the tritium gain is very high in theory. But because the plasma problem is “harder” and decoupled from the fusion part, it makes more sense to focus on getting the plasma part figured first. Actually generating power by injecting D-T can be studied in small bursts, like JET is doing. Studying breeder blankets requires a different setup, which is part of the ITER research umbrella (again: ITER is both a facility *and* a research program).

            That’s why I bring this up when people say “oh, but they still haven’t…” Yes, they haven’t, because they don’t need to yet. It’s not linear development, it’s parallel.

        2. No, I was giving the older value because I thought I remembered the in/out and of course both typed it wrong *and* effed up the math.

          Tritium’s prices are controlled: you literally can’t buy it freely. If it could be more expensive, it would be. It’s useful for a ton of research.

    2. Yes, they had an excess of energy just a few months ago and could run the chamber for 30 mins. Another attempt was to add 2.35MW in energy. They had 2.65 MW in return.
      This is big break throughs both of them.
      It means we within 5 years will have fully working tokamaks with a surplus of energy.

    3. The secret sause is the AI that controls the plasma fluctuations via control of the magnetics, that neural network structure can only be trained on years of test shots that get longer and longer. Patents are irrelevant in that scenario. You can probably apply that to a lot of areas where AI is applicable. The new “land grab” is not patents but neural network configurations, and that favours those with already deep pockets. So the rich will get richer unless you can liberate that knowledge somehow. Do you fully appreciate the paradigm shift you face?

  2. We need some Randian eccentric billionaire with a slightly crazy streak to dump insane amounts of resources into fusion and finally finish it off. I’m not particularly fond of that as a driver of society, but clearly it needs all the help it can get. Very sick of it being 15 years away for the entire lifetime of myself and almost the entire life of my parents, but it seems to actually be drawing closer.
    I’m fine seeing renewables continue to advance (when they aren’t complete scams, which is depressingly common) but fusion could be the lynchpin of the recovery of our environment. Well, that and eradicating 98% of plastics, which would be helped by not having a huge surplus of petroleum byproducts demanding a market because of the material’s primary use in energy.

    1. You won’t get rid of plastic – and in the end, what’s the big deal?

      A big objection is that animals eat it; well, animals eat dirt and other inedible macroscopic particles such as bits of wood floating around – why should plastic make a difference? Next point is, it absorbs toxic chemicals and carries it up the food chain – well that’s a problem from other pollution, not plastic. Next point is, “It’s forever, it doesn’t decay”; it does when exposed to UV and mechanical forces, and when broken down sufficiently it does get eaten by micro-organisms – and what harm does it do down there in the landfill? The next point is, “It’s litter! An eyesore! There’s whole islands of plastic floating in the ocean!” – well, don’t throw it in there. You think anything that replaces plastic wouldn’t get thrown around just as carelessly?

      When you start looking at it critically, what exactly is the problem with plastic itself?

        1. First good point I’ve heard in years.

          >Plasticosis has been compared to asbestosis and silicosis, where plastic acts a similar persistent irritant leading to fibrosis.

          Question is, why? Birds eat rocks because they use them for grinding stones in their stomach – why does plastic cause irritation and the fine silica dust (and asbestos in some cases) that comes off the stones doesn’t? This might be linked with the additives in plastic, and the absorbed chemicals rather than the plastic itself.

        2. > if there is a major impact, there is no way to quickly undo what we are doing to the world.

          And if we try, the replacement to plastics would cause similar issues because it is also unknown. For example, think of the logistics of replacing all plastic packaging (and clothes) with natural fibers and paper: chop chop goes the axe to all the forests in the world.

    2. > We need some Randian eccentric billionaire with a slightly crazy streak to dump insane amounts
      > of resources into fusion and finally finish it off. I’m not particularly fond of that as a driver of society,
      > but clearly it needs all the help it can get.

      Actually, there is no point in being a millionaire or even billionaire, if you don’t use all that money for something worthwhile. So, you *should* actually be fond of that as a driver of society, and so should the millionaire/billionaire.

      If you’re a millionaire or billionaire who just keeps your money to yourself, you’re nothing more than a hoarder, hoarding money instead of whatever else. The only thing that would make you different is that you’d live in less dirty stinking living conditions. :)

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