Nuclear fusion: Has there been a breakthrough at the US National Ignition Facility?

Rumours suggest the US National Ignition Facility has made a significant advance in nuclear fusion, though there are still many hurdles to overcome

By Matthew Sparkes

A nuclear fusion reactor has reportedly created more energy than was put into it, for the first time ever. If the experimental results are confirmed, it will prove that fusion is a viable way to meet the planet’s growing energy demands by replicating the reaction that has been occurring at the heart of our sun for billions of years – with some caveats.

What has happened?

Fusion has long promised abundant, clean energy, but until recently has been a far-off dream. In the past few years, experiments around the world have been increasingly promising, but crucially have all also required more energy input than they have generated.

Now, a report in the Financial Times suggests that researchers at the Lawrence Livermore National Laboratory (LLNL) in California have overcome this major hurdle. The lab’s National Ignition Facility (NIF) fusion reactor uses lasers to create heat and pressure that turns deuterium and tritium into a plasma in which fusion can occur, and the FT reports that an experiment in which the lasers output 2.1 megajoules of energy resulted in the production of about 2.5 megajoules, roughly a 20 per cent increase.

Sources at the lab told the newspaper that data is still being processed, but that the energy output was greater than expected and had damaged some diagnostic equipment.

“Our analysis is still ongoing, so we’re unable to provide details or confirmation at this time. We look forward to sharing more on Tuesday when that process is complete,” an LLNL spokesperson told New Scientist, referring to an announcement by the US Department of Energy expected to take place on 13 December, according to the FT and sources who spoke to New Scientist.

Gianluca Sarri at Queen’s University Belfast says that caution is required until the reports are verified, but that if true it is a huge milestone. “This was not a given, it was not obvious that this could be done,” he says. “We know that now we can get fusion on Earth.”

So has fusion been cracked?

While an energy output higher than that of the lasers that power NIF’s reactor would be extremely positive, there is still much more work to be done.

For a reactor to be generally useful, it would have to produce more energy than was initially put into the lasers. Inefficiencies involved in producing laser light from electricity mean that is currently not the case – Sarri estimates that if 2.1 megajoules of energy was output by the laser then NIF would have had to draw “tens” of megajoules from the electricity grid to achieve it.

Even once a reactor can offset the true energy required by the lasers, it would only be breaking even. For fusion to become a viable alternative to existing power sources, we must be able to extract a large amount of net energy.

“The important point though is that scientifically this is the first time that we they showed that this is possible,” says Sarri. “From theory, they knew that it should happen, but it was never seen in real life experimentally. All the other bits are complicated, but there is no showstopper – it’s only a technical issue.”

What happens next?

One researcher told New Scientist that rumours along the same lines as the FT report have been circulating in academia, along with preliminary data, and that it’s expected that the results will be confirmed officially by the Department of Energy on 13 December.

There is still much work to be done after that. The NIF reactor is a laser-based inertial confinement fusion (ICF) research device, which squeezes plasma with lasers. This is a different approach to the magnetic Tokamak devices which are currently the largest area of fusion research, so it is still unclear whether those machines can achieve fusion.

Overall, a viable, commercial reactor that can generate significantly more energy than it draws as input, reliably, for long periods of time, is still likely decades away.

Will nuclear fusion solve climate change?

Probably not. If we can build efficient, reliable fusion reactors, the world’s energy demands could be easily met, and without unpleasant waste, as the main byproduct of fusion is helium.

But for that to happen we need to perfect the engineering of the reactors and then build them. While the physics of fusion is now well understood, the engineering challenges involved in creating a working reactor are huge, and the costs are currently eye-wateringly high.

Even tried-and-tested nuclear fission plants, the type we’ve relied on for decades, take around five years to build. Fusion reactors could take longer. In order to keep global warming below 1.5°C, the world must immediately cut carbon emissions, reducing them by 43 per cent by 2030. While fusion may be able to play a role in powering the second half of the 21st century, it is unlikely to be a solution to the immediate climate crisis.