A controlled fusion reaction has for the first time generated more energy than was put into it. This is a big boost for an alternative route to nuclear fusion as an energy source, in which lasers instead of magnetic fields play the leading role.
For the first time, a controlled fusion reaction has generated more power than was needed to get it going, researchers confirm. The experiment could prove an important step towards commercial fusion power, but experts say significant technological effort is still needed to increase efficiency and reduce costs.
One and a half times as much energy
Rumors of the experiment, conducted at Lawrence Livermore National Laboratory (LLNL) in California, surfaced on December 11. Yesterday the news was officially announced at a press conference.
READ ALSO
A new extraction method for deep geothermal energy
There, scientists announced that in an experiment done Dec. 5, the lab’s National Ignition Facility (NIF) generated 3.15 megajoules of energy from a laser energy of 2.05 megajoules. So about one and a half times as much energy came out as went in. However, that gain is more than offset by the roughly 300 megajoules of energy needed to run the lasers.
Just like in the sun
There are two main approaches to achieving viable fusion power generation. In one case, magnetic fields keep a plasma under control. The other approach is done by lasers. NIF uses that second approach, known as Inertial Confinement Fusion (ICF). In this process, lasers fire at a small capsule containing hydrogen as fuel, causing it to heat up and expand.
This causes an equally large inward reaction that compresses the fuel. The hydrogen nuclei then fuse together to form heavier elements. Part of the mass is released in the form of energy. The same process happens in the interior of the sun.
500 trillion watts
So far, all fusion experiments have consumed more energy than they produced. At NIF’s previous record, confirmed in August this year, an experiment produced an output 0.72 times the energy entering the capsule from the lasers. Yesterday’s announcement confirmed that the researchers now not only the crucial break even-milestone – ‘breaking even’ – have been achieved, but even passed it.
That is, if you ignore the energy it took to power the lasers. At the press conference, Jean-Michel Di-Nicola, group leader at the LLNL, said the lasers consumed 500 trillion watts at their peak power — which NIF only touched for a few billionths of a second. That is more power than the entire American grid can supply together.
‘Superb example’
The result is a “great example of what perseverance can achieve,” said Arati Prabhakar, policy director in the White House Office of Science and Technology. According to her, this brings us a step closer to applicable nuclear fusion.
“It didn’t take one generation to pull this off, but several generations of researchers,” she said. ‘Promoting the interplay of research and building complex technical systems, where both sides learn from each other – that’s how we get really big, difficult things done. And this is a wonderful example of that.’
The hottest point in the solar system
Jeremy Chitterden, a plasma physicist at Imperial College London in England, says the result marks a historic moment for fusion research. “It’s a milestone everyone in the fusion community has been striving for for 70 years. It is a great victory for the method we have been working on for almost fifty years: ICF.’
The largest investments in nuclear fusion are currently going towards tackling magnetic confinement. In particular, the arrows are aimed at a reactor design called the tokamak.
The Joint European Torus (JET), a tokamak near the English city of Oxford, began work in 1983. When it is on, it forms the hottest point in the solar system. It then reaches temperatures of 150 million degrees Celsius. Earlier this year, JET managed to sustain a reaction for 5 seconds. A record amount of energy of 59 megajoules was produced.
A larger and more modern successor, ITER, is currently being built in France. It should start its first experiments in 2027. Another reactor of the same design, KSTAR (Korea Superconducting Tokamak Advanced Research), recently sustained a reaction for 30 seconds at temperatures above 100 million degrees.
Small hordes
LLNL director Kim Budil said at the press conference that the delay between the experiment and the announcement was because a team of independent experts had been asked to review the data. She added that now that the results have been confirmed, it is likely that a power station using lasers can be built “within a few decades”, but that the technology for tokamaks is more advanced.
“There are big hurdles to overcome, not only in the field of science, but also in the field of technology,” said Budil. “This is about one capsule, which ignited once. To get commercial nuclear fusion done, a lot has to happen. You have to be able to make many, many ignitions per minute, and you have to build a robust system of lasers that can do the job.’
Extreme conditions
At the moment, NIF can only do its job for an extremely short time. Then the installation must cool down for a few hours before it can be switched on again. Approaches that try different startups might yield a better way, says Chitterden.
“If we continue to bet on megaprojects that cost billions of dollars and take decades, fusion may well come too late to be of any use in the fight against climate change,” says Chitterden. ‘I therefore think it is important to try different approaches. In this way we can try to find a way that costs less and can be realized faster, so that we will have something in our hands in ten to fifteen years’ time.’
The NIF results can provide valuable data not only for engineers working on reactor designs, says Chitterden. They can also help advance other areas of physics. The observed reactions seem more intense and faster than those in our sun. They have more in common with the reactions that take place in a supernova. “We are reaching pressures, densities and temperatures that we have never been able to study in the lab,” he says. ‘These are processes that allow us to study what happens in the most extreme states of matter in the universe.’
Walk both ways
Gianluca Sarri, who studies the interaction between lasers and matter at Queen’s University in Belfast, Northern Ireland, says the NIF result allows fusion researchers to move forward knowing that it is possible to generate energy from nuclear fusion. ‘Now it’s ‘only’ – in quotes – a matter of fine-tuning things and making technological adjustments. Of course we will not be able to do that today or tomorrow, because there are technical challenges. We’re miles away from a reactor. But we are on the right track. When it comes to clean energy, fusion research is the most ambitious route. But in the end it will prove to be the most rewarding, because the amount of energy you can unlock with it is potentially unlimited.’
Sarri also says he believes tokamaks will be the first working fusion reactors, but that ICF research still has an important role to play. ‘We have to walk both ways, because they can lift each other to a higher level. There is a lot of exchange of information between the two designs. The ways they work are, in concept, similar.’