The “twisted donut” reactor could help bring nuclear fusion closer

A new reactor design may help commercialize super-fuel

A task force created by the King may have brought nuclear fusion one step closer with a new design of a reactor that looks like a doughnut twisted.

The stellarator reactor offers new methods of controlling white-hot plasmas produced by nuclear fusion.

Fusion plasmas can be so hot they melt all known materials. They must therefore be contained by powerful magnetic fields. It has been 70 years since science was able to maintain a magnetic field for longer than a few moments.

Chris Mowry is the chief executive officer of Type One Energy. He says that Type One Energy expects to install its first stellarator Infinity One in an abandoned power station in Tennessee by 2025.

Mowry said, “The machine is experimental, but it is expected to generate more power than its consumption – opening up the door to commercial development.”

This announcement, together with plans for separate fusion reactors from the UK, and China, signal a possible breakthrough in fusion technology. This announcement also shows that fusion has moved from being a purely scientific endeavor to a race for the first commercially feasible reactor.

The Sustainable Markets Initiative was set up by the Prince of Wales in 2020 to monitor progress. This led to the creation of a task force.

Mowry says that a gram of fusion energy could produce as much power as burning 10,000 kilograms of coal. You could power a city of 250,000 people for an entire year using only a few hundreds kilograms deuterium and Lithium. I expect to see commercial reactors within the next two decades.”

The target is still very ambitious. The first time scientists harnessed fusion energy was nearly 70 years ago, with the development and use of the hydrogen bomb.

It has been impossible to control such reactions in order to produce energy, despite billions of pounds being spent on research.

The temperatures required to create plasma fusion — which are 10 to 15-times hotter than the Sun — would melt any known material.

The magnetic field must contain the plasmas. But designing magnets, and modeling their fields to create a cage that can contain white-hot Plasmas for long periods of time has proven an impossible task.

Mowry, his UK colleagues and the Fusion Taskforce believe now they can solve this and other technical barriers which have kept fusion power “40 years away” in the last seven decades.

The goal of fusion is to create helium by using extremely high temperatures and pressurized hydrogen atoms. This process, that also powers the sun and stars, converts a small fraction of mass into huge amounts of heat energy. This process can be controlled to produce low-carbon electricity.

Mowry says, “The idea may be simple, but the modelling of the physics involved in that process is complex. This is especially true for the magnetic fields. It was impossible to model the process in three dimensions until recently.

Scientists can now calculate the shape and build the machine using supercomputers that have been developed over the past 20 years.

Mowry’s comments are indicative of a wider enthusiasm in the fusion community about hopes for a commercially feasible technology. Fusion research in the US coincided with an increase in interest in the UK, which is partly due to Boris Johnson’s enthusiasm in 2019, when he served as prime minister.

He said that fusion research would be funded with £330m and that the Joint European Torus project (JET), near Oxford, will soon produce “virtually limitless zero-carbon energy”.

The claim of his was exaggerated, but the money helped the UK to remain a leader in the world with plans for a new fusion reactor that will replace JET. The Spherical tokamak for energy production (Step ) will be built inside a disused electricity station in West Burton in Nottinghamshire.

Tokamaks, an older method of fusion, use a simple reactor in the shape of a doughnut. Over the past seven decades, around 200 Tokamaks have been constructed, which has generated invaluable data. However, none of them has proven to be capable of maintaining sustained reactions.

Paul Methven is the chief executive officer of UK Industrial Fusion Solutions which is developing Step. He says that Step will pave a way for commercially feasible fusion, and help to develop the UK’s supply chain. It is a vital opportunity to deliver a new climate solution, and to keep Britain at forefront in the commercial delivery of Fusion.

The UK and US have a friendly rivalry, working together as well as competing for the development of technology. There are also other players.

China announced in 2005 that it would also build a nuclear power station. It has trained 3,000 engineers to work on the project.

Delong Luo is the director-general for China’s Fusion Research Agency. He has stated that he intends to build an experimental fusion power reactor by 2035. Commercial plants would follow a prototype power plant envisioned for 2060.

China and the US also play a leading role in the ITER Project in southern France, where ten nations are building the largest fusion reactor in the world. The tokamak is also designed to produce experimental data. The UK was once a member of the ITER Consortium through its EU membership, but it was kicked out of that consortium after Brexit.

Mowry is of the opinion that fusion research must move beyond tokamak designs. He says it belongs to the 1970s, and won’t be able produce the magnetic fields necessary for sustained fusion.

He says that the tokamak doughnut is a simple geometric design, and because of this, in the 1960s-70s, before high-performance computing was invented, it was easier to create and manufacture these shapes of reactor. The plasma is not stable by nature, so it can’t reach the steady state needed for energy production.

Mowry, along with his colleagues, used the US Department of Defence Exascale Computing Project to attempt to solve these problems. Exascale computing is the ability to perform billions of calculations per second, a pace comparable to that within a nuclear fusion reactor.

The final design looked like a tokamak that had been run over by an army tank, a doughnut twisted. The real power of computing was not in the design, but in figuring out how to create and maintain magnetic fields within the reactor.

Mowry says that the idea behind a stellarator comes from being able to figure out how it turns and control its magnetic field. This brings with it a lot. “Above and beyond, it makes the machine stable enough to produce energy we can use.”

If he’s right, fusion could be within a decade or two. Britain will also share in the benefits. The US and UK signed a joint agreement in December to collaborate on such projects. Whatever design is successful, the science behind it will be shared.

The most important question is, of course, how much will it all cost. Costs for the UK’s latest venture in atomic energy, Hinkley Point C Power Station, have risen from PS18bn up to PS46bn. The UK has a long history of nuclear fission.

The UK Atomic Energy Authority’s chief executive, Sir Ian Chapman points out that dealing with radioactive wastes and materials is one of the largest costs associated with nuclear power plants.

Fusion generates no nuclear waste that can last a long time, so a power plant based on this technology could be as small as a supermarket.

Sir Ian says that Jet, our last machine would have cost £2bn today. The next generation is going to have more technology, so it’s definitely going to cost more. It will cost less than Hinkley’s tens or hundreds of millions. “And it will be clean.”