Nuclear fusion lab achieves 'ignition': What does that mean, and why is it so important?

Scientists have been striving to achieve fusion ignition for decades.
Chris Young
An artist's impression showing the hydrogen capsule at NIF.
An artist's impression showing the hydrogen capsule at NIF.


Scientists from the Lawrence Livermore National Laboratory (LLNL) announced a major breakthrough for nuclear fusion on Tuesday, December 13.

In a historic first, they achieved fusion ignition during a nuclear fusion experiment. This means they produced more energy than they put into their fusion experiment, paving the way for practically limitless clean energy production from nuclear fusion.

Here's why that achievement was described as a "history-making" moment by US Secretary of Energy Jennifer Granholm during the announcement event.

What is nuclear fusion?

Nuclear fusion is the method the Sun and stars use to produce energy. For decades, scientists have been striving to harness this energy by developing complex nuclear fusion reactor technology — typically in the form of doughnut-shaped tokamak reactors that utilize incredibly powerful magnets to control the fiery plasma created during the fusion process.

Nuclear fusion lab achieves 'ignition': What does that mean, and why is it so important?
An example of a tokamak reactor, General Atomics' DIII-D, in San Diego.

Nuclear fusion occurs when two atoms are slammed together to form a heavier nucleus. When this happens, a massive amount of energy is released. Crucially, nuclear fusion releases zero carbon emissions, meaning fusion power plants could one day play a vital role in the fight against climate change.

What's stopping us from having a working nuclear fusion plant today?

One of the critical barriers to commercially viable nuclear fusion is that fusion reactors require a massive amount of energy to power. Until now, scientists haven't been able to demonstrate a fusion experiment where they could produce net energy — meaning they produced more energy than was required to power the experiment in the first place.

The LLNL experiment is a major breakthrough in that regard, though there is still a lot of work to be done. During the Tuesday announcement event, LLNL Director Dr. Kim Budil explained that their experiment is "a first fundamental step", but there are still “very significant hurdles” toward realizing commercial nuclear fusion.

Essentially, the process achieved during the experiment must be refined and then produced at a much larger scale.

Why is everyone talking about a new nuclear fusion breakthrough?

The LLNL scientists achieved fusion ignition at LLNL's National Ignition Facility (NIF) during a controlled fusion experiment last Monday, December 5, according to a statement from the US Department of Energy (DOE). The scientists waited for their results to be peer-reviewed before releasing them to the world yesterday, December 13.

The LLNL researchers used a powerful 192-beam laser at the $3.5 billion NIF facility to heat and compress hydrogen inside a capsule the size of a peppercorn. That laser can heat the capsule to 100 million degrees Celsius, which is hotter than the center of the Sun. This also compresses the hydrogen to more than 100 billion times Earth's atmospheric pressure, causing it to implode and for the hydrogen atoms to fuse and release energy.

In its statement, the DOE explained that LLNL’s experiment "surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output, demonstrating for the first time a most fundamental science basis for inertial fusion energy (IFE)."

In other words, they had achieved fusion ignition, or net energy production, for the first time in a nuclear fusion experiment.

Why is it so important?

The LLNL experiment paves the way for practically limitless clean energy. Though the experiment ultimately produced a relatively small amount of energy, fusion ignition has been a long-term goal for nuclear fusion scientists.

Now that it has been achieved, there is still a long road ahead before we can see commercial nuclear fusion plants in action. Essentially, the global scientific community will have to refine and scale up the experiment to produce massive amounts more energy than it currently does, which is not an easy feat.

As Budil pointed out during the announcement event, a "few decades of research could put us in a position to build a power plant." While she didn't want to commit to a more specific timeline, we are now likely talking somewhere in the line of 2-3 decades instead of the 5-6 scientists often cited until recently. She added that the Joint European Torus (JET) in Oxfordshire, which uses an alternative fusion technology, could be ready sooner.

Nuclear fusion power plants are still a long way off, but the scientific community has now overcome a key hurdle by proving beyond a shadow of a doubt that we can produce more energy than is required to power the process in the first place.

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