An artists’ impression of how the Step nuclear fusion reactor would look when built © UKAEA

The UK government is inviting communities across the country to host Britain’s prototype nuclear fusion plant, which aims to “pave the way to a limitless supply of low-carbon clean energy” by taming the reaction that powers the sun and stars.

Public funding for the fusion reactor called Step — short for Spherical Tokamak for Energy Production — will start with £222m for the four-year design phase, followed by a few billion pounds during construction.

The project aims for completion by 2040 when, if all goes well, the reactor and its associated power station will begin to feed hundreds of megawatts into the UK power grid. Then Step would be followed by a fleet of fusion plants providing a substantial proportion of the country’s electricity during the second half of the century.

Ian Chapman, chief executive of the UK Atomic Energy Authority which runs the country’s fusion programme, admits that he frequently faces questions from people who point out that the technology has been touted since the 1950s as the answer to the world’s energy needs, without delivering a single watt of useful power.

“Step will prove that fusion is not a far-off dream but a dawning reality, with the UK leading the commercial development of fusion power and positioning itself as a trailblazer in sustainable fusion energy,” he said.

Ian Chapman © Stephen Kill

The “tokamak” design, which originated in the Soviet Union in the 1950s, has a round reaction vessel that holds the fuel — a plasma of superheated deuterium and tritium — in place with powerful magnets while raising its temperature above 100mC so that the atomic nuclei fuse and release vast amounts of energy.

British fusion research has been based for more than 60 years at UKAEA headquarters in Culham, Oxfordshire, but Professor Chapman said the site did not have space to build the Step reactor. Culham already hosts an EU-funded fusion reactor called Jet (Joint European Torus) which has been running for more than 30 years and is due to be decommissioned from 2025.

“We are asking for a 100 hectare site for the new reactor, power station and its associated infrastructure,” he told the FT. “Although greenfield sites would be considered, there are a lot of brownfield sites — old steelworks for example — that might be suitable.”

Communities have until the end of March to submit bids to host Step, demonstrating that their site has the best blend of social, commercial and technical conditions, including the right ground conditions, water supply and grid connection.

The benefits, according to the government, will include the creation of “thousands of new local highly skilled jobs . . . while creating a new science and technology hub for the UK.”

The world’s largest fusion project is the €20bn International Thermonuclear Experimental Reactor (Iter), a multinational project under construction at Cadarache in the south of France. After many construction delays, it is due to begin operating in 2025.

“Without Iter we would not be able to go on our journey with Step,” said Prof Chapman. “We need Iter to establish a fusion supply chain and demonstrate new technologies. Iter will work but it is expensive.”

UKAEA will also collaborate with the growing number of fusion businesses in Britain and elsewhere, he said. “The private sector is investing in fusion. There are now 40 to 50 fusion companies and we’ll be working with them.”

Business and energy secretary Alok Sharma said: “Communities across the country have an incredible opportunity to secure their place in the history books as the home of Step, helping the UK to be the first country in the world to commercialise fusion and creating thousands of highly skilled jobs to drive our green industrial revolution.”

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Letters in response to this article:

An old hand’s maxim on fusion still holds goodc / From Dennis Jones, West Lulworth, Dorset, UK

Remember nuclear fusion is always 20 years away / From Paul Roberts, London, W5, UK

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