What is nuclear fusion, and could it change our energy future?

When Secretary of Energy Jennifer Granholm announced Tuesday that the Lawrence Livermore National Laboratory in California had successfully produced a nuclear fusion reaction that creates a net energy gain, she hailed the event as “one of the most impressive scientific feats of the 21st century.”

Nuclear fusion, after all, is the same energy that powers the sun and every other star in the universe. Being able to harness and replicate it means that humankind could one day tap an almost limitless source of energy that wouldn't contribute to the climate crisis caused by the burning of fossil fuels.

But what is nuclear fusion, and how did the team of scientists in California succeed in achieving what Granholm characterized as a breakthrough?

Learning from the sun

Nuclear fusion occurs when two atoms of a light element such as hydrogen are heated and fused together to form a heavier element such as helium. In order for that process to occur, the atoms must be subjected to extremely high temperatures and pressure. When that chemical reaction happens, it gives off energy.

Fission vs. fusion

Nuclear fission is the opposite of nuclear fusion in that the former unleashes energy by splitting heavy atoms apart. While fission and fusion both produce clean energy in terms of greenhouse gas emissions, fission comes with a glaring downside.

“Nuclear fission power plants have the disadvantage of generating unstable nuclei; some of these are radioactive for millions of years,” the International Atomic Energy Agency states on its website. “Fusion, on the other hand, does not create any long-lived radioactive nuclear waste.”

The waste byproduct of a fusion reaction is far less radioactive than in fission, and decays far more quickly.

The upsides to fusion over fission have long been known to scientists.

“Fusion could generate four times more energy per kilogram of fuel than fission (used in nuclear power plants) and nearly four million times more energy than burning oil or coal,” the IAEA says on its website.

Laser energy is converted into X-rays inside the hohlraum
Laser energy is converted into X-rays inside a cylindrical shell known as a hohlraum. (John Jett and Jake Long/Lawrence Livermore National Laboratory/Handout via Reuters)

Star power

In order to replicate the chemical process that powers stars in the universe, researchers at the National Ignition Facility employed the world’s most energetic lasers — 192 of them, to be exact — further compressing their intensity before shooting them into a cylinder the size of a small pebble that contained a small portion of hydrogen encased in diamond.

By blasting the hydrogen pellet with 2.05 megajoules of energy, which the New York Times noted is the equivalent of a pound of TNT, the chemical reaction was achieved, resulting in the release of 3 megajoules of energy.

No small feat

Researchers from 50 countries have been working on the problem of how to re-create and harness the energy of a fission reaction since the 1960s. In 2009, when work began in earnest at the National Ignition Facility, the Livermore laboratory released a video explaining its work.