Nuclear fusion breakthrough: Have US scientists finally produced cheap, clean energy?


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The US National Ignition Facility uses lasers to compress a fuel capsule

Lawrence Livermore National Laboratory/Shutterstock

A breakthrough fusion experiment has produced a net gain in energy for only the second time ever and with improved performance over the first successful attempt. But before you get excited about the coming era of unlimited clean energy, there are some important caveats to keep in mind.

What’s so good about fusion power?

Today’s nuclear power plants rely on fission reactions, where atoms are smashed apart to release energy and smaller particles. Fusion works differently, by squeezing smaller particles together into larger atoms – the same process that operates within our sun. Fusion can create more energy, with no radioactive waste, but containing and controlling such a reaction has proven to be a monumental problem for both physicists and engineers.

What has happened and what is ignition?

In December 2022, researchers at the Lawrence Livermore National Laboratory (LLNL) in California reached a historic milestone: they got more energy out of a fusion reaction than they put in. The lab’s National Ignition Facility (NIF) fusion reactor used lasers to create enough heat and pressure to turn deuterium and tritium – isotopes of hydrogen – into a plasma in which fusion could occur. These lasers output 2.1 megajoules of energy, but the reactor produced about 2.5 megajoules, roughly a 20 per cent increase. While those numbers are nowhere near the sort of ratio you would need to run a commercial reactor, it offered a vital glimmer of hope that fusion reactors were a viable goal.

Now the lab has reportedly created a second ignition – the term for a reaction that surpasses break-even – and improved on those numbers with the reactor producing around 3.5 megajoules. The experiment occurred on 30 July, according to a report in the Financial Times.

There has been no official confirmation yet, although a spokesperson for LLNL told the FT: “As is our standard practice, we plan on reporting those results at upcoming scientific conferences and in peer-reviewed publications.” New Scientist has contacted LLNL for confirmation.

Does this mean fusion power has been solved?

In short, no.

One problem is that while the reactor’s output is higher than the laser’s output, the lasers themselves are very inefficient. To create 2.1 megajoules of energy they draw 500 trillion watts, which is more power than the output of the entire US national grid. So a significant challenge for the future is to create a reaction that breaks even with its total energy requirements, and not just the final laser stage.

Another issue is that the NIF reactor can fire only once, for a few billionths of a second, before it has to spend several hours cooling its components in order to be switched on once more. A commercial reactor would have to run nearly continuously with multiple ignitions a second.

And, of course, even once a reactor can run for long periods and offset its true energy requirements by the lasers, it would still 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 – enough to make the enormous cost of building it worthwhile.

Will fusion be solved in the future?

While it is still impossible to tell for sure, as there could be insurmountable problems ahead, there is more cause for optimism than ever before. The ignition milestone effectively proves that the science is sound, and makes the problem one of engineering rather than physics.

There are two main research approaches aiming to achieve viable nuclear fusion. One uses magnetic fields to contain a plasma, while the other uses lasers. NIF uses the second approach, known as inertial confinement fusion, where a tiny capsule containing hydrogen fuel is blasted with lasers, causing it to heat up and rapidly expand. But there are a host of startups working on unusual designs that all have the potential to break through. All these experiments are helping us to better understand the problem, and the best way forward.

But one thing is clear: with a working fusion reactor still many years away at the very least, we cannot rely on the technology to solve the climate change crisis. Fusion reactors will be perhaps the greatest pay-off ever received from a coordinated research effort stretching back more than a century, but clean and abundant energy will have to come from renewable sources for the short and medium term.


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