Last December 5, at 1:03 AM in California's National Ignition Facility, 192 lasers fired into a tiny metal can called a "hohlraum" which contained a peppercorn-size fuel pellet consisting of frozen deuterium and tritium. In response, some of the atoms in the pellet fused and released more energy than it took (in the form of laser beams) to start the reaction.
At a news conference afterwards, U. S. Secretary of Energy Jennifer Granholm called the experiment a "fusion breakthrough" and the hundreds of scientists who have labored for years to achieve what is technically called "ignition" were thrilled to learn that they had finally achieved a goal they had worked toward for decades.
They indeed deserve congratulations, because they are the first group in the world to demonstrate ignition with their type of fusion reactor, which is termed inertial confinement. At the same time, it's a little premature to sell all your fossil-fuel stocks and order your Back to the Future fusion-energy car that runs on a glass of water.
Inertial-confinement fusion is one of those simple-sounding ideas that turns out to be fiendishly complicated in practice. Not long after the laser was invented (1960), it occurred to somebody that the short intense burst of energy that certain pulsed lasers could make might be able to heat up deuterium and tritium enough to cause their nuclei to fuse, leading to a fusion reaction. Nuclear fusion has been the pot of gold at the end of the energy rainbow ever since fusion was demonstrated in the first thermonuclear hydrogen bomb test called Ivy Mike in 1952.
The device that made the nuclei fuse in that explosion was a conventional nuclear-fission bomb, of the type dropped on Japan at the end of World War II. So far, bombs are the only reliable way to get a lot of energy out of nuclear fusion, but they are hardly a practical energy source.
Fusion is an attractive source of energy because the raw material—deuterium, mainly—can be extracted from ordinary water, the energy output per weight of fuel is even better than fission reactors, and the waste products tend to be less nasty than those from fission reactors, which is the only way we get practical amounts of energy from nuclear reactions these days. Most efforts in making fusion practical try to work with ways of containing a hot ionized gas called a plasma inside various tricky confinement chambers in a continuous process that would put out a steady flow of energy.
But confining a plasma is a little bit like nailing Jell-O (TM) to the wall: it doesn't want to stay put. So in 1994, the National Ignition Facility (NIF) began to study ways of doing it in a batch process, rather than continuously.
Rather than having to keep the plasma confined constantly, their idea was to shoot a whole lot of laser-beam energy onto a small pellet of fuel, that would then get so hot part of it would fuse, and the burst of fusion energy coming out would be larger than the energy it took to make it. In the meantime, it would be confined by its own inertia—hence the name "inertial confinement."
It sounds simple, but the NIF people have been working for nearly thirty years to do the thing that their lab is named for—namely, achieve ignition. So at last, in December the lab lived up to its name.
Are we home free? Not yet. For one thing, the amounts of absolute energy we are talking about are trivially small. Two megajoules of laser-beam energy went into the pellet and produced fusion energy of three megajoules. A megajoule sounds like a lot until you realize that three megajoules of energy is contained in about a fourth of a measuring cup (100 ml) of gasoline. So the process will have to be scaled up seriously before practical amounts of energy are produced.
Also, the lasers are not 100% efficient. One scientist at the news conference admitted it took "well over 400 megajoules" to charge the lasers that created the 2-megajoule beam. That reminds me of the guy who went into business and admitted he was losing money on each transaction, but he'd make it up in volume. Sometimes you can do that, but sometimes you can't.
So while the NIF folks deserve congratulations for their achievement, one wonders if inertial confinement fusion for practical energy generation will ever see the light of day. It begins to look like one of those things that would work given indefinite amounts of resources, but at some point, other researchers will overtake it and further work will be pointless.
I was once engaged in an engineering project that lost my company six million dollars. Some years later, I ran into the manager I worked for, who said about it, "Well, if we'd just had a little more time and money, I think we could have made it work." Yes, but we didn't, and it was a good thing for the company that we stopped.
A huge project based in France called ITER is pursuing a different approach: a giant "tokamak" style continuous-plasma reactor that is scheduled to make its first plasma (of any kind) in 2025. From what I can tell, ITER's main use so far has been as a way to employ thousands of European physicists, engineers, and auxiliary personnel. But it may turn out to work.
Personally, I hope all these behemoth-like government-funded decades-long projects are shown up by one of the dozens of small startup fusion companies that are pursuing off-the-wall fusion ideas, ranging from boron fusion (with hardly any dangerous waste products) to modifications of a thing called a "fusor" developed by Philo T. Farnsworth, the guy who didn't invent television. Actually, he did invent an alternative approach to the TV camera tube that was not as good as the one RCA and its Vladimir Zworykin came up with, but Farnsworth was an independent inventor and RCA was tied in with the government and dominated the entire radio-electronics sector. Sometimes the big guys win and the little guys lose, but not all the time.
Chances are that I will no longer be around to see the first commercial electric power delivered from fusion energy. But if it ever happens, I hope somebody like Philo Farnsworth invents it.
Sources: USA Today carried a report on the NIF breakthrough on Dec. 13, 2022 at https://www.usatoday.com/story/news/nation/2022/12/13/fusion-energy-advance-clean-power/10883067002/. The energy content of gasoline was from https://www.engineeringtoolbox.com/fossil-fuels-energy-content-d_1298.html and I also consulted Wikipedia's articles on the National Ignition Facility and ITER.
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