What about nuclear fusion? – New press headlines again and again

In the last few months we have been hearing more and more news from the press on a topic that for decades was rather characterized by long silences. Does this show that we will soon see the real breakthrough in what is probably the most exciting energy production of all, the controlled generation of the sun’s enormous energy here on earth: Nuclear fusion? Advances in nuclear fusion may one day actually allow us to generate safe and (nearly) climate-neutral energy, unlike the nuclear fission which today’s highly controversial nuclear power generation is based upon, which we have been able to control to generate peaceful energy since the 1950s.

So this week (12 December 2022) almost every press outlet states that scientists had achieved another important milestone in the use of fusion energy. For the first time, they had succeeded in generating more energy with an experimental fusion reactor than what was used during the process. A “net energy gain” of 120 per cent was achieved. That does sound revolutionary: After all, there have been numerous experimental reactors for this purpose for about 70 years, but nowhere has it been possible to generate more energy than what has to be put into the reactors to produce nuclear fusion.

This also made it far into the German-language press:

• Der Spiegel titles its article on it with Is this the breakthrough at the nuclear fusion ?
• In the Neue Zürcher Zeitung it says: Nuclear fusion: Has more energy been released in an experiment than the researchers put into it? That would be a milestone
• The Süddeutsche Zeitung writes: Breakthrough in research on nuclear fusion.

But how exactly can this energy be produced – on the sun, the gravitational force is great enough to bring the nuclei together and cause them to fuse? Physicists have known since the late 1930s that hydrogen nuclei fuse into helium atomic nuclei under very high pressure and temperature. The amount of energy released in this process is much higher than in the reverse process, in which heavy atomic nuclei are split. The basic concept of nuclear fusion, which was already worked out at that time, is still the same today: A deuterium-tritium plasma is heated to several million degrees in a kind of microwave and then confined and controlled with the help of a magnetic field. At a temperature of about 100 million degrees, the mixture ignites and releases the fusion energy – whereby the actual ignition temperature depends on the particle density, i.e. pressure, of the plasma. It is also possible to perform further nuclear fusion with other nuclei, such as protons with boron (¹¹B), but these require much higher temperatures (energies).

The latest headlines are (once again) about the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in Northern California, where, instead of a huge magnetic field holding the plasma in so that the particles fuse at a high enough temperature, it is a high-power laser that brings the deuterium and tritium (both positively charged and therefore repulsive to each other) close enough to each other that they fuse (due to the strong nuclear force, which, however, only has a very short range). With NIF’s technology, however, this reaction only takes place for a (very) short moment. Now the energy from the nuclear fusion achieved has exceeded the energy required to achieve the nuclear reaction – with a net gain of 120%, as written. “For most of us, this was just a matter of time,” as a scientist from Northern California said. But permanent nuclear power generation in the way used here is still very far away. It is even questionable whether this method is even scalable with the short laser pulses (which are currently only possible a few times a day). Most nuclear physicists hardly see the laser method as a way to commercial reactors due to the short duration of the process. And one should not forget: NIF’s main focus is not on clean energy production, but on military interests.

Let us have a look at the NIF process in a little more detail: they specialize in an approach called “inertial confinement fusion” (ICF), where high temperatures are generated in very small spaces by bombarding a tiny sphere with the two hydrogen isotopes (fuel) at its center with 192 high-power lasers. Specifically, this is achieved through careful forming: first for the fuel capsule – a tiny spherical shell of polycarbonate diamond, and second with a “cavity” containing the pellet – a small cylinder of depleted, i.e. not very radioactive, uranium lined with gold. Within 10 billionths of a second(!), the fuel should then be reduced to a minimal fraction of its original volume, bringing its core to a temperature of 50 million degrees Celsius, a temperature sufficient for nuclear fusion under the correspondingly high pressure conditions. However, the lasers themselves consume enormous amounts of energy and can so far only be ignited once or twice a day. This energy, which represents a multiple of the amounts of energy gained, has not even been taken into account in the net gain!

The technology used by the NIF is only one of many possible methods of nuclear fusion. The trigger for a similar wave of newspaper articles a little over a year ago was the Boston-based company Commonwealth Fusion Systems (CFS), a spin-off of MIT, which, as it communicates, has received more than a billion dollars from investors such as Bill Gates and George Soros. The way this nuclear fusion works here is quite different from NIF’s: it is more of a traditional fusion approach, in which they are building a donut-shaped “tokamak” reactor, a “big magnetic bottle” as CEO Bob Mumgaard puts it, in which strong magnetic fields control spheres in a plasma of hydrogen about 100 million degrees hot, which should produce the same fusion of hydrogen isotope nuclei as in the laser-driven reactor (only they are not quite at 100 million degrees yet).

There will pretty much be room for more than one fusion winner. Other companies include Canada-based General Fusion, backed by Jeff Bezos, which received $130 million from investors last year. As with magnetic confinement in CFS, the fusion fuel is held together by magnetic fields as it is heated to form a plasma. However, as with NIF’s inertial confinement, the density required for fusion is then achieved by rapidly compressing the plasma. And finally there is TAE Energy from California, which is probably furthest along with commercially successful nuclear fusion and has already experimented in the last twenty years at a cost of one billion dollars and now, with the successful raising of further money, wants to build the first permanently functional nuclear fusion reactor within the next two to three years, which they are already calling “Copernicus”. Initially, it is also to be operated with hydrogen isotopes and achieve a (permanent) net energy gain ready around the year 2025. Then the scientists want to switch their reactor to the already mentioned fuel p-11B. This reaction has the advantage of being “aneutronic”, i.e. it does not produce the difficult-to-control high-energy neutrons that carry much of the energy produced by fusion of the hydrogen isotopes. TAE’s reactor is one that is an interesting combination of a particle accelerator and an ordinary plasma vessel. The ultra-high temperature in the plasma there is achieved by accelerating beams of fuel particles and then letting them collide with plasma particles. Particle physicists have been doing the latter for decades. The typical magnetically enclosed plasma donuts are replaced by an elongated plasma tube in the shape of a hollow cigar. To improve stability, this tube is rotated around itself in such a way that it becomes much more stable due to the gyroscopic effect. Theoretically, this approach can be used to reach much higher temperatures than the magic 100 million degrees. TAE has found evidence that the induced stability and quiescence in the plasma actually increases with higher temperature! It is precisely the hypothesis that this beneficial scaling property is maintained up to 3 billion degrees that TAE’s approach is based on. Here we will very likely learn a lot more in the near future.

The fact that investors are willing to put up numerous billions of dollars of private capital for the development of nuclear fusion energy machines (with a correspondingly high expected return) shows that they expect to see commercially viable nuclear fusion in five years or little more. Commercially available fusion technology, were it actually available to us one day – and perhaps soon – would mean a societal paradigm shift. If we were actually able to produce energy like the sun, giving us access to the most efficient, safe and environmentally friendly form of energy that nature has to offer, this would certainly not only be another great technological advance, but rather a leap forward in civilization on a par with the invention of the steam engine, which 250 years ago gave us the energy to completely transform our society. The press reports about new results in the generation of controlled nuclear fusion, which are appearing with ever-increasing frequency, could be a sign that we could already achieve this rather soon.