What is nuclear fusion? A ‘breakthrough’ in clean energy

The U.S. Department of Energy plans to announce Tuesday a “major scientific breakthrough” at Lawrence Livermore National Laboratory, one of several sites around the world where researchers have been trying to exploit the possibility of harnessing fusion energy.

The technology has the potential to one day accelerate the planet’s transition away from fossil fuels, the main cause of climate change. The technology has long struggled with daunting challenges.

Here’s a look at what nuclear fusion actually is, and some of the difficulties in turning it into the cheap, carbon-free energy that scientists think it can be.

What is nuclear fusion?

Look up and it’s happening right above your head – nuclear fusion reactions that power the sun and other stars.

This reaction occurs when two light nuclei merge to form a heavier nucleus. According to the Department of Energy, since the combined mass of this single nucleus is less than the mass of the two original nuclei, the remaining mass is the energy released in the process.

In the case of the Sun, its high temperature — millions of degrees Celsius — and the pressure exerted by its gravity cause atoms that would otherwise repel each other to fuse.

Scientists have understood how nuclear fusion works as far back as the 1930s and have been trying to replicate the process on Earth. According to the U.S. Department of Energy, current efforts are focused on fusing a pair of hydrogen isotopes — deuterium and tritium — a specific combination that the DOE says releases “significantly more energy than most fusion reactions” and requires Fewer calories.

How much will this be worth?

If fusion technology becomes commercially viable, it has the potential to provide “essentially unlimited” fuel, said Daniel Kamen, a professor of energy and society at the University of California, Berkeley. The required elements are available in seawater.

It’s also a process that doesn’t create radioactive waste from nuclear fission, Kamen said.

How do scientists try to do this?

One way scientists are trying to recreate fusion involves a so-called tokamak — a circular vacuum chamber that uses powerful magnets to convert fuel into a superheated plasma (between 150 million and 300 million degrees Celsius) that can fuse. between).

The Livermore lab used a different technique, in which researchers fired 192 laser beams at a small capsule filled with deuterium-tritium fuel. An August 2021 test produced 1.35 megajoules of fusion energy — about 70% of the targeted energy, the lab reported. Several subsequent experiments showed declining results, but the researchers believe they have found a way to improve the mass of the fuel tank and the symmetry of the laser, the lab said.

“The most critical feature in moving fusion from theory to commercial reality is that more energy is output than input,” Kammen said.


AP climate and environment reporting is supported by several private foundations. Find out more about the AP Climate Initiative here.The Associated Press is solely responsible for all content

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