Armed With Lots Of Lasers, American Researchers Just Got Another Step Closer To Fusion Power

Posted on

CREDIT: Lawrence Livermore National Laboratory

In late September, American scientists got more energy out of a fusion reaction than the fuel absorbed in igniting it — the first time that’s been achieved by researchers anywhere in the world. The research team that pulled it off is based at the National Ignition Facility (NIF), in Livermore, California. And in a bitter twist, they were furloughed just days afterward by the government shutdown.

Traditional nuclear power is achieved through controlled fission reactions, which involve firing particles into a fuel made of a heavy element. That sets of a chain reaction as atoms in the fuel split, sending out more particles that in turn split more atoms. Fusion reactions, by contrast, are achieved by, well, fusing two light atoms — usually hydrogen — into a heavier element. As with fission, the fusion reactions release a large amount of energy, which is used to heat water into steam and drive a turbine, generating electricity.

But fusion reactions require a tremendous amount of power to set off. Consider that the fusion reactions powering the sun are ignited by the sheer scale of the gravitational pressure at the star’s core. That’s why getting more energy out of a fusion reaction than is put into setting it off would be such a big deal. But it’s also why technologically and economically feasible fusion-based nuclear power remains so elusive, despite the decades we’ve already sunk into research without producing a commercially viable energy source.

According to the BBC, the NIF team didn’t quite reach that milestone, because “known ‘inefficiencies’ in different parts of the system mean not all the energy supplied through the laser is delivered to the fuel.” So the system, taken holistically, isn’t yet generating an energy gain on net. But the fact that the fuel’s reaction itself resulted in a net gain is still a major step forward.

The team’s methodology used “192 beams from the world’s most powerful laser to heat and compress a small pellet of hydrogen fuel to the point where nuclear fusion reactions take place.”

Like fission power, fusion power is carbon-free, making it a critical part of a renewable energy future should human beings find a way to make it workable. But on top of that, fusion power actually has many advantages over fission, several of them with a distinct environmental flair.

For one thing, the fusion reaction itself actually produces no radioactive waste at all, just helium. That’s in contrast to fission reactions, which leave behind radioactive waste that lasts for hundreds or even thousands of years. This obviously presents a huge storage problem. Fusion reactions do make certain surrounding materials in the reactor radioactive over time, and these have to replaced and stored. Happily, their radioactivity drops off massively after just one hundred years, making storage much less difficult.

Fusion reactions also rely on various isotopes of hydrogen as a fuel, usually deuterium, or on lithium. These are abundant resources that can be obtained with minimal environmental damage. Deuterium can be cheaply extracted from water, and fusion run on it could fulfill 1995 levels of global energy consumption for 150 billion years. (The sun would die out before then.) Known lithium deposits in the Earth would last 3,000 years, and the supply of lithium we could get from seawater would last 60 million years. Fission power, on the other hand, relies on heavy elements like uranium that have to be mined.

Fusion power is arguably less risky. The basic physics mean the reactor’s controls would be built around maintaining the reaction. So should anything go wrong, the reaction would go dead of its own accord. Fission reactions can become self-sustaining, and thus can burn out of control if safety features fail badly enough. The very worst case scenarios with a fusion reactor could see a small release of radioactive material, but nothing requiring an evacuation beyond the immediate vicinity.

Finally, fusion power is significantly harder to weaponize than fission. Fusion reactions don’t produce any materials that can be used in nuclear weapons. A technological modification to a reactor could change that, but experts seem to agree the modifications would be easy to spot by inspectors.