Don’t get carried away with fusion talk

Commonwealth Fusion System’s breakthrough in superconducting electromagnets is impressive and represents a significant step forward in fusion research. However, as is always the case when a start-up trumpets its latest achievement, it’s useful to examine such news in a broader context.

Arthur Turrell’s new book, The Star Builders, gives an excellent overview of the nascent international fusion industry. Turrell is himself a nuclear physicist, which enables him to analyze recent developments with an expert eye. He cites at least three other privately funded start-ups that say they expect to cross the elusive net-positive energy threshold — that is, they will produce more energy from a fusion reaction than is required to make it occur —  in the next few years. These include Tokamak Energy and First Light Fusion in the UK, and TAE Technologies in California.

But public prognostications of fusion’s success are historically overoptimistic, and Turrell cites a few such cases in his book. In 2014, Lockheed projected their reactor would be operational in five years; In 2009, Canada’s General Fusion forecasted a working reactor based on inertial confinement within a decade; LPP Fusion of New Jersey expected to be up and running by now. There are numerous other examples of such predictions, none of which have proven accurate.

Today, there are about 25 start-ups competing with CFS in the fusion space, each with its own vision, backers, and secret technological sauce. And there are also large-scale, state-funded fusion projects that have demonstrated advances in the three key components of a fusion reactor, namely extremely high temperature, confinement of the plasma, and achieving high plasma density. According to Turrell, Japan’s JT-60, South Korea’s KSTAR, and the Joint European Torus are “far out in the lead.” All of these are tokamak-based designs, like CFS.

CFS says they aim to have a commercial power plant around 2030. But Turrell describes several daunting hurdles beyond the fusion reaction itself that stand between a successful fusion machine and putting a reactor on the grid.

First, there is the problem of extracting the heat from the plasma, which can be as hot as 150 million degrees Celsius, in order to create steam to power a turbine. This will test the limits of modern material science.

Then there is the radioactivity issue. Most fusion designs fuse two isotopes of hydrogen, deuterium and tritium, which release a torrent of neutrons. Nobody knows yet how the materials that encase the plasma will respond to this much radiation.

Another unexplored aspect of fusion technology is breeding the radioactive tritium fuel in the reactor. Physicists know that bombarding lithium with neutrons will produce tritium, but nobody will know how it works at scale until there is a working fusion machine.

Finally, Turrell notes, there is the cost question. Fusion will have to make economic sense if it is to gain widespread adoption. As prices for wind and solar continue to fall, this will be a challenge.

So, bravo for the brilliant work that CFS is doing. It seems likely that the combination of the urgent need to decarbonize and the intense competition between all the players, both state-funded and privately capitalized, is likely to deliver the dream of fusion power — eventually.

Until then, we need to continue to focus on keeping the transition to renewable energy on track. Ultimately, according to Turrell, fusion is likely to play a complementary role in our energy systems.

Frederick Hewett is a Cambridge-based freelance writer focused on energy and climate issues. His Twitter handle is @fred02138.