Nuclear fusion: the low-carbon energy of the future?

Nuclear fusion promises monumental energy with extremely little fuel and virtually no radioactive waste. If harnessing the power of the stars in this way seemed utopian just a few years ago, the question now is not if we’ll succeed, but when. It doesn’t seem likely, however, that this will happen before the second half of the 21st century.

What is nuclear fusion?

As far back as 1920, English astronomer Arthur Eddigton envisaged the sun being powered by a fusion reaction that could be replicated on Earth. The first reaction was achieved by Ernest Rutherford in 1934. Classically, a deuterium atom and a tritium atom, two isotopes of hydrogen, are used. The two atoms fuse to form ahelium atom and a neutron, along with an enormous amount of energy. Succeeding in producing more energy than you consume is called ignition. While this is the most common reaction, there are others being considered, such as the one by TAE Technologies, using “normal” hydrogen and a boron atom.

There is no nuclear fuel waste: no uranium, thorium, plutonium… only the reactor itself will become a little radioactive. What’s more, fuel injection is totally controllable, which would prevent any chain reaction.

However, this reaction only occurs in extreme circumstances. On the order of 150 million degrees Celsius. Managing this constraint is one of the major challenges facing fusion.

Nuclear fusion technologies

There are essentially two technologies for harnessing nuclear fusion:

  • magnetic confinement (
  • inertial confinement, which generally uses lasers

You can consult the list of projects here:éacteurs_à_fusion_nucléaire

Magnetic confinement

This is the oldest technology. Essentially, it involves using a magnetic field to confine the plasma. The main exponent of this technology is the tokamak. The principle is to confine the plasma in a donut-shaped field (known as a “torus”). The idea dates back to a patent filed by two British physicists (G.P. Thomson and M. Blackman) in 1946, and was further developed in the 1960s by Soviet scientists, who went on to reveal two tokamaks, T3 and TM3, which enable plasma to reach several million degrees.

Today, its principal representative is the ITER project. Created in 2007, it is based at the CEA Cadarache center, brings together 35 countries and is building a demonstrator at Saint-Paul-Lez-Durance, in the south of France (13). The first experiments were scheduled for 2035, but the project has been delayed due to cracks in crucial parts that became apparent in 2022.

In addition to the ITER Tokamak, there are several major international projects:

Inertial confinement (with lasers)

Another method is to use lasers to heat a fuel ball. A capsule containing deuterium and tritium resides in a tiny cylinder called the hohlraum. Lasers are fired and reflected off the walls, creating an extremely hot plasma. The target is compressed to extreme density, and then fusion is triggered, generating very high electrical power in a matter of nanoseconds.

In a test using this technology, the US project National Ignition Facility (NIF) succeeded in reaching the ignition point in December 2022 at capsule level. However, this does not take into account the power required by the lasers.

hohlraum devant un oeil, plus petit qu'une phallange
The size of the hohlraum. Credit: Wikipedia

Fusion advances

More and more experiments are showing promising results for fusion.

  • In September, Korea’s KSTAR (Korea Superconducting Tokamak Advanced Research) fusion reactor maintained a plasma at 100 million degrees for 30 seconds.
  • For ITER, a plasma was maintained at 50 million°C for 102 seconds in 2016. In 2018, the ITER network tokamak located in China, EAST, raised the plasma to over 100 million °C, 120 in 2021. In December 2021, it succeeded in holding a plasma at 70 million degrees for 17.6 minutes.

The main companies developing fusion

While fusion has long remained a purely public affair, it is increasingly mobilizing private investment, rising from a few tens of thousands of euros in 2015 to 4 billion euros in 2021. The Financial Times published a very interesting article in December 2022: Nuclear fusion: from science fiction to ‘when, not if’. A few companies stand out:

  • Commonwealth fusion systems
  • TAE Technologies
  • Helion Energy
  • General Fusion

Commonwealth fusion systems (CFS)

Commonwealth fusion systems or CFS is developing a model tokamak using a REBCO (Rare Earth Barium Copper Oxide) High Temperature Superconductor magnet. Their aim is to design a very compact tokamak, the demonstrator of which is called SPARC, designed in partnership with MIT. The final model will be called ARC.

The Massachusetts-based company is very new: it was founded in 2018 as a spin-off from MIT’s Plasma and fusion center. Its initial funding was $50 million, then they raised a further $115 in 2019, 84 in 2020 and 1.8 billion in 2021, to build the SPARC tokamak. Their main investors include Italian energy company ENI, Breakthrough Energy Ventures and others.

TAE Technologies

Founded in California in 1998, TAE Technologies is developing an“aneutron” fusion technology (= little energy is released in the form of neutrons, 1% instead of the usual 80%) using a “filed-reversed configuration” plasma, similar to spherical tokamaks. The reaction envisaged is different: an atom of hydrogen and boron fuse into an atom of carbon, which splits into an atom of helium and beryllium, the latter splitting into two atoms of helium.

By 2022, it will have over 250 employees and raised a total of 1.2 billion dollars. Funding came from Goldman Sachs, Vulcan Inc. (VC fund of Microsoft co-founder), Rockefeller Venrock and even Rusnano, a company linked to the Russian government. In 2021, it announced that it had created a stable plasma at 50 million°C.

Helion Energy

Helion Energy was founded in 2013 by a team of researchers and is developing a hybrid process, aneutronic magneto-inertial fusion using deterium and helium-3 as fuels.

The beginnings were slow, starting with a few million euros from the US Departments of Energy and Defense, then Y Combinator and Mithril Capital Management. Total investment reached 77.8 million by 2021. The company had made several prototypes. The 6th, in 2021, reached 100 million degrees. Hélion received 500 million, with the potential for a further 1.7 billion by the end of 2021.

General Fusion

Founded in Vancouver in 2002, General Fusion is developing a process with “classic” magnetic confinement (deuterium-tritium) in a spherical reactor, but with a compact toroid (= donut) plasma. Its originality lies in the use of pistons to compress the plasma.

By 2021, the company had raised a total of $430 million, including $98 million in 2019 and $130 million in 2021.

External appearance of the reactor Credit: Wikipedia

What’s enabling fusion to take off?

According to McKinsey, fusion is experiencing a new boom due to:

  • The development of 3D printing, enabling the design of parts with complex geometric shapes
  • Increased computing capacity, enabling better simulation of the process.
  • An increase in private funding and research: the number of companies has risen from 7 in 2010 to 25 in 2021, and investment from 170 million to 4.44 billion.

Will the merger help combat climate change?

The answer is obviously yes in absolute terms: it’s low-carbon energy. However, the question must specify “by 2050”. In the aforementioned McKinsey article, the merger

In this perspective, it is highly unlikely that fusion will play a major role. Greg de Temmerman, an expert on the subject, tweeted on the subject:

We can see this with renewable energies, which are being deployed very rapidly but remain in the minority in many countries. Imagining a significant share for fusion, an as yet unproven technology, by 2050 is therefore optimistic, to say the least…

However, let’s not forget that the world doesn’t end in 2050. It remains a technology with fantastic promise, which will probably redefine the modern world when it is industrialized.

To find out more:

  • On the ITER project:
  • The Wikipedia article on fusion is very comprehensive:éaire
  • Greg de Temmerman is an expert, scientific coordinator on the ITER project, who communicates on the subject.
    • He makes very pointed threads on the subject. Here are a few of them:
      • On its role in decarbonizing economies:
      • On the principle of fusion and, above all, the Tokamak:
      • On the evolution of progress by year and technology:
      • On the technology of the British tokamak project:
      • SFEN podcast:
      • On China’s fusion program:
      • On materials innovation:
    • On NIF:
  • On cold fusion