There’s an old joke about nuclear fusion: It’s the energy source of the future — and always will be. When headlines blared last month that researchers at Lawrence Livermore National Laboratory had hit on a history-making fusion breakthrough, the future felt one giant step closer. To get a sense of just how much closer, we reached out to Jim Bray, who’s worked for GE Research for 48 years and is now a chief scientist in its electrical power group — and the company’s go-to expert on all things fusion (including that joke). “I can’t tell you exactly when, but I will tell you, it will happen,” Bray said. “I have no doubt in my mind.” Here’s the rest of our conversation.
GE Reports: What is fusion?
Jim Bray: Fusion is the combination of light atoms to make a heavier atom. It’s that simple. And the best example of that is: Look up. The sun is combining hydrogen to make helium. Helium is about twice as heavy as hydrogen (depending on the isotopes used). But if you were to add up the masses of the two light items you started with, you would see that the heavy atom is a little bit lighter. And that difference in mass is converted into energy — a lot of energy. This is the primary energy production process of the entire universe. And it is happening in all stars. Constantly.
Why is it so elusive here on Earth?
When my colleagues ask me that, I say, “Because 100 million degrees is hard!” In order to get fusion to happen, you have to gather the materials you want to fuse and contain them — you can’t let them go all over the place — and then you’ve got to heat them up to a round number of about 100 million degrees. And that’s hard.
Humans have conquered fusion very well, when you don’t care about holding on to it. All thermonuclear weapons are made with fusion. The problem, of course, is we can’t do that if we want to contain it, to use it. There are two basic ways that people are trying for containment. One is to use a force field, usually a magnetic field. The Lawrence Livermore team that just made the news are using a different method called inertial confinement fusion. They’re causing the process to happen so fast that the plasma does not have a chance to blow itself apart. Plasma refers to gases that we are trying to get to fuse at these very, very high temperatures.
What is the significance of this achievement at Lawrence Livermore?
Attempts to do controlled (peaceful) fusion have worked, but they’ve had to put more energy into the plasma than they get out from the fusion happening. And so that’s obviously not a way to solve any of our energy problems. So the big-deal thing that was done at Lawrence Livermore is that they put about 2 megajoules of energy into a little pellet of hydrogen with lasers. And they got out about 3 megajoules, when they calculated all the energy that came out in various forms. And so they got about 50% more energy than they put in. And that’s the first time in human history that that happened, in a repeatable way that everyone can look at the experiment and believe.
And that’s an important threshold despite the fact that it took way more energy to fire up those lasers than the lasers put into the plasma, right?
You’re right. They’re just talking about the energy that goes into the reactor and out of the reactor. They did not count the losses in the peripheral equipment, like how much so-called wall-plug energy did you have to put into the lasers to get the lasers to fire all that energy into the reactor? That wasn’t counted. This is just a statement of what happened in the reactor, which is important and a big deal. But that’s the reason that this is not likely to happen commercially anytime soon.
Why is the idea of fusion energy so important?
Nuclear energy is roughly a million times more energy dense than gasoline or coal. So compared with chemical production of energy, like what happens when we burn things like fossil fuel, or even the energy density of sunlight or wind, it’s much, much, much more energy dense. And the main fuel that people want to use, which is hydrogen, just happens to be the most common element in the universe. So you’re very unlikely, in any future you can possibly think of, ever to run out of fuel. So essentially, fusion would mean an unlimited source of energy that is completely clean. Unfortunately, it’s very difficult to do, but in my opinion, humans will do it eventually.
How does fusion energy differ from the nuclear energy that we know today?
The nuclear energy we know today is fission energy. That’s the opposite process from fusion. It’s where you take heavy atoms and split them into two lighter atoms and that produces energy. The most stable nucleus in the periodic table is around iron. You can get energy by fusing atoms that are lighter than iron, or by splitting atoms that are heavier than iron. Fission and fusion energy have about the same energy density, and they’re both hugely greater than burning coal or oil or gasoline. The U.S. makes about 20% of its electricity with fission. The challenge, of course, is that it does produce a certain amount of nuclear waste that then has to be managed. In a fusion plant, the amount of nuclear waste that you produce is, relatively speaking, minuscule. But so far, we’ve been able to deal with waste from fission pretty well, and I think it’s going to continue to serve humanity quite well in the nearer future than fusion, which is more difficult.
Is GE doing anything in the fusion space?
We don’t do fusion, but we do an awful lot of the other stuff you have to put into the plant to make it work. When you make a fusion reactor, you have to embed it in a plant that takes the heat and turns it into electricity. Making electricity will be just about the same for a fusion plant as a fission plant. There are a lot of peripheral systems, which we call the balance of plant, to do that sort of thing. GE has mastered that for fission plants. And so what GE is looking at in the fusion area is, well, how can we use all of this expertise we have from our fission reactors and other businesses, like power conversion, to make big power supplies to do heating of the plasma, for instance? I believe we have more to offer to companies who are trying to build fusion plants than anybody else in the U.S. We’ve actually written white papers with some of the companies out there doing the fusion reactor work. Some of the research they need to do for what they are planning are things that we can help with. When somebody actually makes a fusion reactor that works, I think GE will have lots of things to build for the rest of the plant.