A giant donut-shaped machine just proved a near-limitless clean power source is possible

By Danya Gainor and Angela Dewan, CNN

There’s no silver bullet to the climate crisis, but nuclear fusion may be the closest thing to it. In the quest for a near-limitless, zero-carbon source of reliable power, scientists have generated fusion energy before, but they have struggled for decades to sustain it for very long.

On Wednesday, however, scientists working in the United Kingdom announced that they more than doubled the previous record for generating and sustaining nuclear fusion, which is the same process that allows the sun and stars to shine so brightly.

Nuclear fusion is, as its name suggests, the fusing of two or more atoms into one larger one, a process that unleashes a tremendous amount of energy as heat.

Nuclear power used today is created by a different process, called fission, which relies on splitting, rather than fusing, atoms. But that process creates waste that can remain radioactive for tens of thousands of years. It’s also potentially hazardous in the event of an accident, such as Japan’s 2011 Fukushima disaster, triggered by an earthquake and tsunami.

Fusion, on the other hand, is much safer, can produce little waste and requires only small amounts of abundant, naturally-sourced fuel, including elements extracted from seawater. This makes it an attractive option as the world transitions away from the fossil fuels driving climate change.

In a giant donut-shaped machine known as a tokamak, scientists working in the English village of Culham, near Oxford, were able to generate a record-breaking 59 megajoules of sustained fusion energy over five seconds on December 21 last year. Five seconds is the limit the machine can sustain the power before its magnets overheat.

A magnetic field is required to contain the high temperatures needed to carry out the fusion process, which can be as high as 150 million degrees Celsius, 10 times hotter than the center of the sun.

“Our experiment showed for the first time that it’s possible to have a sustained fusion process using exactly the same fuel mix planned for future fusion power plants,” Tony Donné, CEO of EUROfusion, said at a press conference.

EUROfusion, a consortium that includes 4,800 experts, students and staff from across Europe, carried out the project in partnership with the UK Atomic Energy Authority. The European Commission also contributed funding.

The potential for fusion energy is enormous. The experiment used the elements deuterium and tritium — which are isotopes of hydrogen — to fuel the fusion. Those elements are likely to be used in commercial-scale fusion, and can be found in seawater.

“The energy you can get out of the fuel deuterium and tritium is massive. For example, powering the whole of current UK electrical demand for a day would require 0.5 tonnes of deuterium, which could be extracted from seawater — where its concentration is low but plentiful,” Tony Roulstone from the University of Cambridge’s Department of Engineering told CNN.

He said the fusion generated by the tokamak — called the Joint European Torus (JET) — was around the same as a wind turbine, and could power one house’s energy for a day.

“But if generated repeatedly, it could power thousands of houses.”

Experts say the results prove that nuclear fusion is possible, and no longer a pipedream solution for the climate crisis.

“These landmark results have taken us a huge step closer to conquering one of the biggest scientific and engineering challenges of them all,” said Ian Chapman, CEO of the UK Atomic Energy Authority.

Mark Wenman, a nuclear materials researcher at Imperial College London, said in a statement that the experiment’s results are “exciting,” and that they show “fusion energy really is no longer just a dream of the far future — the engineering to make it a useful, clean power source is achievable and happening now.”

JET has been subject to such extreme heat and pressure that this experiment is likely the last it will cope with.

But its results are seen as a huge boon for ITER, a fusion megaproject in the south of France supported by the US, China, the European Union, India, Japan, Korea and Russia. The ITER project is 80% built and aims to begin nuclear fusion sometime in 2025-26.

While JET’s goal was to prove that nuclear fusion could be generated and sustained, ITER’s aim is to produce a tenfold return on energy, or 500 MW of fusion power from 50 MW of energy put in.

The results are promising, but mastering nuclear fusion as an everyday energy source is still likely a long way off.

“The JET results are impressive and probably will get better as they proceed through their experiments. They are producing high power 12 MW, but right now just for five seconds. Much longer fusion burn is what is required,” Roulstone said.

The most recent report from Intergovernmental Panel on Climate Change (IPCC) on the latest science shows that the world must nearly halve its greenhouse gas emissions this decade and reach zero net emissions by 2050 to keep global warming in check. That means making a rapid transition away from fossil fuels, like coal, oil and gas.

Those actions are required to have any hope of containing warming to 1.5 degrees Celsius above pre-industrial levels, seen as a threshold to substantially worsening climate impacts, according to the IPCC.

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This story has been updated with additional information.