Don’t Get Too Excited About That Nuclear Fusion Breakthrough

It is big, big news that scientists were recently able to perform a nuclear fusion reaction that gave off more energy than it consumed. It is also true that this type of reaction could potentially be a useful energy source in the future. Or as physicists are fond of saying, useful nuclear fusion has been “10 years away” for the last 50 years or so. Read on for more on why scientists are excited, but also why our homes are likely to be powered by the same ol’ power plants for a long time to come.

Is nuclear fusion the same as nuclear power?

Nuclear power plants and nuclear bombs use a fission reaction, which is different from the fusion reaction that made the news recently. Fission occurs when an atom is split apart. Typically you start with a uranium or plutonium atom, smack a neutron into it, and split that atom into multiple pieces which can then break into yet more pieces. Fission produces energy in the form of heat, and nuclear power plants use that heat to boil or vaporize water. There are no emissions from nuclear power, but there is the inconvenient problem of nuclear waste—those smaller atoms that are still radioactive.

Nuclear fusion is the opposite reaction: Smaller atoms are combined into a larger one. It’s an exciting possibility because it doesn’t produce carbon emissions or present issues with radioactive waste.

So fusion could be a waste-free, emissions-free power source?

That’s the dream. We know that fusion reactions can create energy, because that’s what the sun does all day. It fuses hydrogen atoms so that they become helium (helium atoms being twice the size of hydrogen). Fusion reactions are what create the sun’s heat and light. Fusion happens so easily on the sun because of the extreme temperatures and gravity there; getting it to happen on Earth is a lot harder.

Fortunately, hydrogen is easy to come by, at least; it’s the most common element in the universe. Instead of coal that’s been dug out of the earth, a fusion reactor could use deuterium (heavy hydrogen) from plentiful sources like water as its main fuel. As CNN reports, a glass of tap water contains enough deuterium to theoretically power a house for a year. You also need tritium, a rarer form of hydrogen, but finding fuel is not the main problem.

The tricky part is that it takes a lot of energy to get a fusion reaction to happen. Scientists have been able to fuse atoms before, but before this week, the reaction always used more energy than it produced—which is the opposite of what you need a power source to do.

What happened in the National Ignition Facility breakthrough?

For the first time, scientists managed to initiate a fusion reaction that created more energy than it used up. Sort of. Big caveat on that.

Technically, the reaction created more energy than the laser energy that powered it. But if you compare the output of the reaction to the facility’s entire power bill, it’s a different story: The lasers delivered 2.05 megajoules of energy to the reaction, and the reaction produced 3.15 megajoules as output. But those lasers themselves use a lot of electricity—more like 300 megajoules.

The whole setup for the reaction wasn’t cheap or easy to put together, either. In addition to the hydrogen, gold, uranium, and diamonds were also involved, and it took researchers months to figure out the exact shape the diamond portion needed to be.

Scaling this process up to the size of a power plant isn’t likely to be possible anytime soon. Science Magazine reports that a different type of reactor, called a tokamak, is considered to be a better bet for practical power generation, but the major facility in France that is supposed to be working on tokamak fusion is “vastly over budget, long overdue, and will not reach breakeven until the late 2030s at the earliest.” So we’ll be waiting for our space-age power source for a little while longer.