Energy Transition

Nuclear fusion world record: The science behind the energy technology explained

Nuclear fusion is what happens in the Sun and other stars and involves joining two atomic nuclei to make one larger one.

Nuclear fusion is what happens in the Sun and other stars and involves joining two atomic nuclei to make one larger one. Image: Reuters

Kate Whiting
Senior Writer, Forum Agenda
Simon Torkington
Senior Writer, Forum Agenda
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This article was most recently updated in February 2024.

  • A new world record for nuclear fusion power generation has been set in the UK.
  • At COP28, US special climate envoy John Kerry announced an international plan to boost nuclear fusion as an emissions-free technology.
  • At Davos in January 2023, the lead US government scientist behind a nuclear fusion breakthrough called for more public investment to scale the technology.

In a fitting end to the UK's JET fusion laboratory in Oxford, the lab's final experiment produced a new world record for power generation.

It produced 69 megajoules of energy over five seconds - or enough energy to heat up to five hot baths, according to the BBC, triple what it produced back in 1997.

The UK's Minister for Nuclear and Networks, Andrew Bowie, said: "JET's final fusion experiment is a fitting swansong after all the ground-breaking work that has gone into the project since 1983. We are closer to fusion energy than ever before thanks to the international team of scientists and engineers in Oxfordshire."

The buzz around fusion energy as a way to reduce emissions has been growing over the past year. Emissions-free nuclear fusion technology could be a game-changer in the fight against climate change, if it can be scaled up.

"There is potential in fusion to revolutionize our world," US special climate envoy John Kerry told the UN climate conference, COP28, in Dubai in December 2023.

He was launching an international engagement plan – involving 35 countries – to boost nuclear fusion through research and development. The initiative will also focus on regulation and safety, and look to reduce supply chain issues.

Kerry's announcement comes after Britain and the US signed a cooperation agreement on fusion in November. Australia, China, Germany and Japan are also pursuing fusion, according to Reuters.

Nuclear fusion breakthroughs

In August 2023, scientists at the US Lawrence Livermore National Laboratory in California repeated a breakthrough they first made in December 2022, achieving a "net energy gain" in fusion ignition.

Using laser beams, the amount of energy from the fusion reaction surpassed that concentrated on the target for an instant.

Back in January 2023 at the World Economic Forum's Annual Meeting in Davos, nuclear scientist and Director of the lab, Kim Budil, spoke on a panel, a month after her team made the original breakthrough.

"If we want to take this forward, public-private partnerships are going to be essential," she said.

How the private sector has backed nuclear fusion in the past two decades.
How the private sector has backed nuclear fusion in the past two decades. Image: McKinsey

In May 2023, Microsoft announced a deal with private US nuclear fusion company Helion to buy electricity made using fusion technology in 2028.

Microsoft President Brad Smith said Helion's work "supports our own long-term clean energy goals and will advance the market to establish a new, efficient method for bringing more clean energy to the grid, faster".

Companies have raised around $5 billion in private funding for nuclear fusion, in a quest to replicate the power source that fuels the sun, Reuters says.

Pioneering nuclear fusion

These companies are building on the earlier work of pioneering researchers, including those at the JET fusion lab. The Joint European Torus site, to give it its full name, was a collaboration of European nuclear scientists.

The JET lab, which was the world's largest and most advanced fusion reactor, conducted its first experiments in 1983. Due to its success, it continued for 40 years until the reactor entered the decommissioning stage in October 2023. It conducted its last, ground-breaking experiment in December.

The interior of the record-breaking nuclear fusion reactor at the JET fusion lab in Oxford, UK
The interior of the record-breaking nuclear fusion reactor at the JET fusion lab in Oxford, UK Image: UKAEA, courtesy of EUROfusion

Its successor is a facility called ITER, based in France and due to start operating in 2025, according to the BBC, but without the UK's involvement.

Instead, the UK government announced last year it would commit £650 million to national research programmes, including a plan to build the world's first fusion power plant in Nottinghamshire with operations due to begin in the 2040s.

The nuclear fusion race

Globally, government labs and more than 30 companies are racing to generate power from fusion – including Budil's team in California.

In December 2022, they managed to produce more energy from the reaction than it consumed – a net gain of 1.5 megajoules in less time than it takes light to travel one inch.

"Monday 5 December was an important day for science," said Under Secretary for Nuclear Security and National Nuclear Security Administration (NNSA) Administrator Jill Hruby.

At Davos, Budil explained the experiment involved beaming 192 lasers on a tiny target and heating it to create a self-sustaining reaction.

Have you read?

But she said the timescale to generating power could be "two or three decades away" and urged great collaboration to build a fusion "ecosystem".

"If I look at the private-sector fusion companies that have already been spun out, they have needs for expertise and certain specific skills that it would be cost prohibitive to develop within a start-up framework. So they can partner with the laboratories to get access to that capability and expertise.

"To advance the cause of fusion, we have to create an ecosystem where any private sector players in this area who want to commercialize the technology can work with us to help advance the target designs – think about laser architectures or other driver architectures –to benefit from our expertise and what will be required to operate a facility at this scale.

"I'm hopeful we will start seeing significant public sector investments in the energy application of this technology. We already have several companies formed around inertial confinement fusion that are starting to explore partnerships with us on how to take the technology forward.

"For the next few years, it's essential to work together."

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What is nuclear fusion exactly?

Our current nuclear power stations use nuclear fission – essentially splitting an atom’s nucleus.

Nuclear fusion is what happens in the Sun and other stars and involves joining two atomic nuclei to make one larger one. Both reactions release large amounts of energy, but with nuclear fusion, there is very high energy yield and very low nuclear waste production.

Fusion occurs when two light atoms bond together, or fuse, to make a heavier one. The total mass of the new atom is less than that of the two that formed it; the "missing" mass is given off as energy, as described by Albert Einstein's famous E=mc2 equation.

Nuclear fusion is the holy grail of clean energy.
Nuclear fusion is the holy grail of clean energy. Image: Renato Perillo

There are several "recipes" for cooking up nuclear fusion, which rely on different atomic combinations.

The most promising combination for power on Earth today is the fusion of a deuterium atom with a tritium one. The process, which requires temperatures of approximately 72 million degrees Fahrenheit (39 million degrees Celsius), produces 17.6 million electron volts of energy.

Deuterium is a promising ingredient because it is an isotope of hydrogen. In turn, hydrogen is a key part of water. A gallon of seawater (3.8 litres) could produce as much energy as 300 gallons (1,136 litres) of petrol.

Challenges for nuclear fusion researchers

While nuclear fusion power offers the prospect of an almost inexhaustible energy source for future generations, it has also presented many so-far-insurmountable scientific and engineering challenges.

In the Sun, massive gravitational forces create the right conditions for nuclear fusion in the star’s core, but on Earth they are much harder to achieve.

Fusion fuel – different isotopes of hydrogen – must be heated to extreme temperatures of around 50 million degrees Celsius, kept stable under intense pressure, and dense enough and confined for long enough to allow the nuclei to fuse.

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Energy TransitionChemical and Advanced Materials
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