Nuclear Fusion Breakthroughs Bring Near-Limitless Energy Closer

Physicists in the U.S. have overcome two major hurdles in fusion power generation. Their discovery increases the stability of fusion reactions and brings us one step closer to making commercial fusion energy a reality.

Nuclear fusion is a process that creates energy in the same way as our sun does. It involves the smashing together of two atoms with such force that they combine into a single, larger atom, releasing huge amounts of energy along the way.

Unlike nuclear fission—the nuclear reaction that is currently used in the energy sector—fusion does not create radioactive waste. It produces three to four times more energy than fission and does not release carbon dioxide into the atmosphere, unlike burning fossil fuels. Fusion is also a very fragile process that will shut down in a fraction of a second if the correct conditions are not maintained. Therefore, there is no risk of nuclear meltdown from this reaction.

For this reaction to take place, we need to be able to mimic conditions comparable to the sun, which takes a lot of energy.

At these superhot temperatures, atoms exist in a state called a plasma, which is basically a soup of negatively charged electrons and positively charged ions that have been ripped apart by the extremely hot temperature of their surroundings.

These positively charged ions will usually repel each other but, in the sun, a high pressure is created by its intense gravitational forces that thrust the ions together and overcome this repulsion. However, on Earth it is nearly impossible to replicate this, so the plasma has to be heated even more, to temperatures roughly six times hotter than the center of the sun.

In recent years, we have seen some incredible breakthroughs in fusion energy, including getting more energy out of the reaction than we put in. But we are still a long way off from a commercial fusion power source.

One way to bring down the energy demands of this process is to increase the density of the plasma—that way those positively charged hydrogen particles become more closely squashed together. The only problem is that, as the particles become squashed closer and closer together, it becomes harder and harder to contain them, so the reaction becomes very unstable.

However, new research from the DIII-D National Fusion Facility in San Diego, together with collaborators in China, has shown that these high-density systems can actually be maintained for a reasonable length of time.

The team completed their experiments in a device called a tokamak, a donut-shaped contraption that uses super strong magnets to contain the plasma in a dense ring. By using additional magnets and extra hydrogen fuel, the team showed that it was possible to exceed historical predictions for the maximum density in a reactor (known as the Greenwald limit) while also maintaining a steady reaction for 2.2 seconds, which is quite a long time by fusion standards.

The researchers write that their findings demonstrate the feasibility of higher densities in fusion reactors and open "a potential avenue to an operating point for producing economically attractive fusion energy."

Their results were published on April 24 in the journal Nature.