Last month the National Ignition Facility at the Lawrence Livermore National Laboratory (LLNL) in California announced a significant breakthrough in nuclear fusion research. Since then, a number of people have asked me what this breakthrough really means.
First, let’s discuss some basics of nuclear fusion. Today’s nuclear power plants are based on nuclear fission, which is the splitting of a heavy isotope like uranium-235 into two smaller isotopes. (Isotopes are just different forms of an element).
In simple terms, nuclear fission is like shooting a tiny bullet at the center of the isotope, which causes it to become unstable and split. When it splits, it releases a tremendous amount of energy (mass and energy are related by Einstein’s famous equation E = Mc2). That energy can then be turned into electricity.
However, one of the primary objections to nuclear fission is that the byproducts of fission are highly radioactive, and many of them are long-lived. In other words, they pose a danger to life unless properly handled. These radioactive byproducts are why some are opposed to nuclear power.
Nuclear fusion, which is the source of the power for stars like our sun, is different. With fusion, you are forcing smaller isotopes together to form larger isotopes. Typically this involves combining isotopes of hydrogen — the smallest element — to form helium. This reaction releases even more energy than the fission reaction, but more importantly it doesn’t produce any long-term radioactive byproducts. That’s why nuclear fusion is often called the “holy grail” of energy production.
So, what’s the problem? Those small hydrogen isotopes are highly resistant to fusing. It takes tremendous pressure and high temperatures (as are present in the sun) to force them to fuse. That’s very different from nuclear fission, which takes place relatively easily. Thus, although fusion can be achieved in nuclear weapons, researchers have spent decades trying to create a controlled fusion reaction that could be used for energy production.
Over the years, many “breakthroughs” have been announced. The one that was announced last month was that for the first time, scientists got more energy out of the fusion process than they had to put in. Previous efforts that had achieved fusion required more energy inputs than the fusion reaction produced.
So, this does mark a significant breakthrough. But how close are we to developing commercial fusion reactors?
Here is an analogy I have used to put it in context. There were many milestones on the way to commercial airline travel. The Wright Brothers flew the first successful powered flight in history in December 1903. It would be another 16 years before the first transatlantic flight. But, the first widely successful commercial airliner, the Boeing 707 wouldn’t be introduced until 1958.
The long-running joke has always been that commercial nuclear fusion is 30 years away. In reality, that simply means we still can’t quite see the complete pathway to get there. The recent breakthrough is certainly a milestone on the path to commercial nuclear fusion, but it’s closer to the flight of the Wright Brothers using that analogy. We may still be 30 years away from seeing commercial realization of nuclear fusion.