Communities in the UK are being asked to bid to host a prototype nuclear fusion power plant, which a government-backed programme plans to build by 2040. The site does not need to be near existing nuclear power stations but will need 100 hectares of land and a plentiful water supply. Ministers say the project would bring thousands of skilled jobs and be part of its planned “green industrial revolution” to tackle the climate crisis. Nuclear fusion replicates the intense atomic reactions that power the sun and uses a hydrogen isotope found in seawater as fuel. It cannot produce a runaway chain reaction like conventional nuclear fission, which involves splitting atoms rather than fusing them together. The level of radioactive waste is also far lower. No exclusion zone will be needed around the site, officials said. However, the technical challenges are enormous and the programme’s leaders acknowledge it is “hugely ambitious”. This is because fuel heated to 10 times the temperature of the sun has to be magnetically levitated to stop it melting the reactor vessel. Scientists and engineers have pursued the dream of limitless and clean fusion energy for more than half a century, but the first power stations remain decades away. The UK programme is called Step – the Spherical Tokamak for Energy Production – and has been granted £222m to date by the government. Communities have until March 2021 to submit their nominations, with the successful site chosen by the end of 2022. “We want the UK to be a trailblazer in developing fusion energy,” said Alok Sharma, the business and energy secretary. He said communities had an “incredible opportunity to secure their place in the history books” by potentially helping the UK to be the first country in the world to commercialise fusion power. The UK has the largest working fusion reactor in the world – called Jet – at the Culham Science Centre near Oxford. However, a far larger €20bn (£18bn) fusion reactor called Iter is being assembled in France, backed by the world’s biggest countries. It expects to create its first super-heated plasma by 2025 and reach full power by 2035, with the aim of demonstrating that more energy can be taken out than is put in. The goal of Step is to show that a smaller and less expensive plant can create fusion power. Key to this is the spherical shape of the chamber that contains the plasma, which is more compact than the doughnut-shaped chamber being used at Iter. However, this compactness means the Step system must have a much more efficient cooling system. Technology to achieve this is being tested in the Mega Amp Spherical Tokamak (Mast) experiment, also at Culham. But the Culham site is too small to host the Step project. Prof Ian Chapman, the chief executive of the UK Atomic Energy Authority, which is leading Step, said: “Step is about moving from research and development to delivery. It will prove that fusion is not a far-off dream, but a dawning reality.” Tim Luce, the chief scientist at Iter, said: “It is gratifying to see the UK make a firm commitment to continuing its historic leadership in magnetic fusion development. Step promises lower costs but faces various engineering and physics challenges, such as large stresses in the magnet structure and high heat fluxes to the wall. [But] first plasma in 2040 appears to be a realistic goal, assuming favourable and timely results in the present generation of spherical tokamaks.” The UK is a participant in Iter due to its membership of Euratom, but it will leave the group after Brexit. However, officials say they are hopeful that the UK can rejoin Iter as an associate country. The timetable for Step is to have a concept design by 2024, then a detailed engineering design allowing the start of construction in 2032 and operations to begin in 2040.