The UK Government has announced £220m over the next four years towards the design of a commercially viable fusion power station. Known as the Spherical Tokamak for Energy Production (STEP), it will be based on “spherical” tokamak technology that is currently being pioneered at the UK’s Culham Centre for Fusion Energy (CCFE). The design effort – led by the CCFE – will involve over 300 people and be complete in 2024.

The CCFE is owned and managed by the UK Atomic Energy Authority (UKAEA) – which is located at the Culham Science Centre in Oxfordshire. It already houses two world-leading fusion tokamaks – the Mega Amp Spherical Tokamak (MAST) and the Joint European Torus (JET).

Nuclear fusion has the potential to be an unlimited clean, safe and carbon-free energy source and we want the first commercially viable machine to be in the UK Andrea Leadsom

Built in 1983, JET is designed to study the conditions approaching those in a fusion power plant and is the only device that can use a deuterium-tritium fuel mix of the kind that will be used for commercial fusion power. The ITER fusion reactor, which is currently being built in Cadarache, France, is similarly based on such a donut-shaped plasma.

However, since 1999 the UK has been pioneering the use of spherical tokamaks through research on MAST, which contains a spherical plasma, much like a cored apple. This “compact” tokamak allows it to confine highly pressurized plasmas with a lower magnetic field that those used in JET, which could allow for a more cost-effective fusion device.

The UK government has now announced £220m towards a conceptual design report for a fusion power plant based on the spherical tokamak design. To be complete by 2024, the effort will involve the creation of around 300 jobs. “This is a bold and ambitious investment in the energy technology of the future,” notes Andrea Leadsom, UK secretary of state for business, energy and industrial strategy. “Nuclear fusion has the potential to be an unlimited clean, safe and carbon-free energy source and we want the first commercially viable machine to be in the UK.”

It is expected that the money will be used for research that will go into the final integrated design. This will include prototyping components, carrying out materials research and robotics development, as well as computer modelling. The cash will also be used to construct test facilities. “There are a whole series of technical areas that need to be investigated and brought together to reduce risk for the actual power plant,” a spokesperson for the UKAEA told Physics World. “There will also be market analysis and site selection work to make the design as practical and viable as possible”.

The heat is on

The design for a fusion power plant based on a spherical tokamak will take into account the results from MAST. Indeed, the tokamak has just completed a major £45m upgrade with scientists hopeful that the first plasma will be injected into the tokamak by the end of the year. Work on the upgraded facility – known as MAST-U – will also allow scientists to study plasma conditions relevant to ITER.

MAST-U will be able to create a plasma of deuterium with a timespan of around 2–4 s, compared with just 0.5 s before. Indeed, it is hoped that a new exhaust system – known as a divertor – will show that it is able to handle the intense exhaust heat emerging from the plasma more effectively than existing designs, including that used on ITER. The divertor will aim to take a 50 MW/m2 heat load and reduce it to just 5 MW/m2. “The divertor on MAST is truly unique,” says Andrew Kirk, head of MAST-U.

The CCFE has also secured an additional £21m from the European Fusion Research Consortium and the UK’s Engineering and Physical Sciences Research Council to further enhance the upgrade. This will include doubling the neutral beam injection into the plasma from 5 MW with MAST-U to 10 MW. This is expected to be complete around 2022.

UKAEA chief executive Ian Chapman says that the UK has a proud heritage of pioneering developments in fusion research. “This announcement demonstrates the UK government’s commitment to translating that leadership into a working fusion reactor,” he adds. “We are excited to work with our partners to take the next step towards a fusion-powered future.”

Analysis: the race to commercial fusion will likely be won by China “Fusion is always 30 years away.” Fusion researchers have had that comment flung at them for decades now, but in recent years there seems to be some optimism within the community that things are about to change — and that the promise of nuclear fusion could be fulfilled sooner than we think. This is in part due to the ITER fusion reactor, which is finally nearing competition at Cadarache, France, following years of delays and cost hikes. When ITER turns on in 2025, it will first use a deuterium plasma to test all the systems and plasma performance and then only in 2035 use a deuterium-tritium fuel mix to finally demonstrate fusion on a commercial scale. If this is all a roaring success, then the race to build the world’s first fully-fledged fusion power plant will be on. Still, given these timescales, an actual power plant is unlikely to be built before 2040 at the earliest. With the announcement of £220m to design a “commercially viable” fusion power plant, which is a serious amount of money, the UK is firmly entering the race. But rather than basing a design on ITER it is hoping that innovations in “compact” fusion reactors will pay dividends in the coming years. This may come from the spherical tokamak design — being pioneered by the UK and the US – that would allow for much more compact and cheaper power plants. But there is still much more research that needs to be carried out, some of which will be done on the upgraded Mega Amp Spherical Tokamak in the UK and the National Spherical Torus Experiment in the US. For now, though, most eyes in the fusion community will be on ITER, especially from the seven member states of the project that have provided billions in funding for the facility. What will an actual fusion power plant look like? No one knows for sure, but if, or when, ITER is a success then you can expect China to design and build a scaled-up version of ITER and then drive the cost down through volume. They have the energy demand, the know-how and the money to make that happen. This approach, however, won’t work for many other energy markets, including the UK. This is why building a more compact and cheaper design via the spherical tokamak looks promising, although still likely to be decades away.