In this series of interviews. I ask scientists, engineers, and ethicists how technology might change our future. We had these conversations during the research for my book, Welcome to the Future (Quarto, 2021).
Interview 10 – Arturo Dominguez
Dr. Arturo Dominguez is a plasma physicist who studies magnetic fusion at the Princeton Plasma Physics Laboratory (PPPL). He also leads PPPL’s Science Education program. Fusion is a nuclear reaction that merges two elements, typically isotopes of hydrogen, producing heavier elements and lots of energy. Fusion is what keeps the sun and other stars shining. However, here on Earth, it still takes more energy to start and sustain a fusion reaction than that reaction produces. Dominguez and other fusion experts hope to change that. We spoke in August 2019.
How do you envision a future world powered by fusion energy? What would it be like to live in that world?
I think it’s a good vision. We in the fusion community have that vision as our motivator. I think that fusion would be one of a portfolio of energy sources for the world. If you’re in Tucson, AZ, it’s always going to be more cost-effective and easier to put solar panels on your roof and get all the energy you can from there. Fusion energy is an excellent way of getting what we call baseload energy. It’s a high density energy supply, like what’s being done right now by [nuclear] fission plants, by coal, or by natural gas. [A fusion plant would be] one big power plant that supplies energy for a community that is geographically close by.
The ideal future with fusion has a smart energy grid and transportation that is electric. In places where there’s a lot of wind we’d have a lot of wind turbines, in places with a lot of sun we’d have a lot of solar panels, and everywhere else we’d have fusion energy reactors supplying clean, inexhaustible energy.
What makes fusion energy inexhaustible?
The fuel for fusion is deuterium [an isotope of hydrogen] and lithium [a metal]. The reaction [to produce fusion energy] is typically deuterium and tritium [another isotope of hydrogen], but tritium isn’t found in nature. You can breed tritium using lithium.
The fusion energy reactor is so efficient that you need very little fuel to create a substantial amount of energy. Deuterium is already in the ocean. You can also extract lithium from the oceans. If you look at how much would be needed for the energy consumption of the world, you’re looking at hundreds of thousands to millions of years of energy [contained in ocean water]. So that’s why it would be inexhaustible.
Do you think we’ll ever live in this world?
It depends on what day you ask me. I think electricity produced from fusion is going to happen. I think we will get to that point. Having a society that is creative and forward thinking enough to have development of smart grids and electrically powered vehicles, and that can have the fusion reactors built, I’m not sure. I’m really not.
All the markers of climate change are accelerating. It’s a race for time, and I think we have to take that race more seriously as a society.
ITER is a large experimental magnetic fusion reactor being built in France by a group of 35 countries. Simulations show that it should produce more energy than it consumes. How could it help lead to fusion energy, and when might that happen?
If ITER is getting first plasmas around 2025, then in the meantime someone has to design and develop a demonstration plant, then build a pilot plant. I think that’s all reasonable, and I think that will all happen. There might be some years delay, but ITER is already more than halfway built. There are a lot of designs for power plants from different countries. I think that timeline will happen and that would lead to electricity around 2050 or 2050-something.
Don’t quote me on this, but I think by 2060 we will already have fusion [energy] in the grid. I’m optimistic that there’s a lot of interest in private industry already. Some ideas are a little out there and some are much more down-to-earth. It only takes one to succeed. Just the fact that they’re there, exploring markets, looking into business questions — they’re making the zeitgeist [society’s idea of how the world should be] move further along to what is required to have a fusion future. That’s been very exciting, both within and outside the community.
Do you think ITER will work? Will it get to breakeven [meaning it produces as much energy as it consumes] or produce excess energy?
I think it will. There are intrinsic problems about doing an experiment that’s so large and so complex with so many cooks in the kitchen. You’ve got so many countries with a vested interest. That is a problem even harder than the space station was in the past. So there are some challenges with it, but a lot of thought has gone into the design and they’re flexible enough with new research to make modifications, that I think it will work. There might be issues, but it’s an experiment. I think it will get to breakeven and beyond.
ITER is not intended to be a power plant. It’s intended to be proof that breakeven and beyond is possible, and then you could build power plants based on the design.
Exactly. ITER will not produce a single iota of electricity. It’s going to produce neutrons. It’s going to test the technology and it’s going to test the physics. It’s a good place for us to put a lot of these ideas and materials and techniques to the test.
How would you describe the type of fusion ITER is trying to achieve, magnetic confinement fusion, to a teenager?
It takes a while. It starts with, we know fusion happens. It’s what happens in every star. It’s small positive nuclei — the nucleus of atoms — combining together and releasing energy. It doesn’t just happen naturally since they’re both positively charged, they don’t want to combine. If it’s hot enough and energetic enough, some of them collide together and hit each other [and fuse]. That’s what we’re trying to do. We’re trying to recreate that process here on Earth.
It turns out that if we were to do what the star does, which is proton chains, or protons combining with protons, it takes a lot of steps to get to the final product of helium. It would take forever for that process to happen here on Earth. It is a very slow process. So what we do is we use deuterium and tritium, which are isotopes of hydrogen. It turns out that reaction is more energetic. It’s energetic enough that it’s worthwhile doing in a lab. But the downside is that we have to make it ten times hotter than center of the sun. The sweet spot is at around 150 million degrees. We heat it by shooting neutral particles at it, we heat it by sending microwaves into it, but the hard thing is to keep it in place without it melting the walls!
Why don’t we do it like the sun? The sun does it with gravity, We can’t do that because we don’t have enough. We have to find another way of doing it. By the time the particles are this hot, they are 100% plasma, or charged particles. You can see the answer close to North and South pole. You see it at night in the auroras, the Northern Lights. What you’re seeing there is the same thing that happens in a tokamak [a magnetic confinement fusion device], or at least the same principle.
Plasma comes from the sun, and when it sees the magnetic field lines of the Earth, it gets attached to them and goes streaming to the North and South. Auroras are the consequence of Earth’s magnetic field confining plasma from the sun
We use that idea. We make a machine that has a magnetic field. You should watch the PhD comic fusion video. They say it’s like a donut. The jelly in the donut is the plasma. The crispy crème outer layer is the machine. The jelly doesn’t touch the outer layer. Is that a good explanation?
Yes, thank you! I have written about fusion in the past and I like to think I understand it pretty well, but it always helps to hear someone else’s explanation.
Sometimes I don’t remember what is obvious and what isn’t obvious.
So what are the biggest technical problems with this process?
There’s so much we still don’t know! If you throw a lot of money at the problem, we could build ITER much faster, we can build machines that output more neutrons, but it wouldn’t make sense to do it that way. There are still a lot of questions we haven’t tested. What happens when you are shooting 14 mega electron volts (MeV) of neutrons towards materials? We have to build these machines out of something. That material is going to be bombarded by very energetic neutrons. At the moment we don’t have a way of making neutrons at a high enough rate to be able to test these materials. There are a lot of simulations and extrapolations, but we haven’t put materials in an environment that reproduces what a fusion energy machine is going to deliver.
This is what ITER is going to help with?
ITER will help somewhat with that. If we’re going to build a pilot plant, we need to do more thorough testing. We also don’t have a working blanket system.
A blanket? What is the blanket for?
Let me go through the whole process. Let’s say we have a working tokamak in which deuterium and tritium combine to make very energetic neutrons and very energetic helium. It ignites the plasma and becomes the main source of energy for maintaining a hot plasma. The neutrons leak with most of the energy. 14 MeV per reaction. That is the energy we’re relying on [to make electricity with].
That energy hits the blanket — if you think of the donut, it’s the crispy crème outer layer. This blanket would contain vessels with molten lithium lead flowing through it. The neutrons hit this lithium and most of the energy heats up the blanket — which is good. It’s what we want. Some of the neutrons have a nuclear reaction with lithium to produce the tritium, which is what we need to put back into our machine [as fuel]. So the hot liquid lithium lead gets piped out of the enclosure surrounding the machine and it goes somewhere where the tritium is extracted from it and the heat is extracted and used to heat up water or something which ultimately turns turbines [to make electricity]. That’s how we get fusion energy into the grid.
None of that exists. There’s research going into all of that, but we don’t have a functioning prototype that’s just ready to go. That’s a huge engineering issue. How do you make efficient tritium extractions? How do you do the piping? Some of the problems are solved, but not as an integrated system. After that, we are not certain about materials and how they are going to react to the neutrons. We still have a lot of engineering challenges to go.
For this material testing, what we really need is a high energy neutron source, and what you’re talking about is a fusion power plant. So we need to have a fusion power plant just to test the materials to construct a fusion power plant.
It’s a bit of a Catch-22! When I was researching fusion a couple years ago, it seemed like high temperature superconducting magnets were a really big deal in the world of magnetic confinement fusion. Is that still the case?
Not only is that the case, that is one of the drivers of the conversation right now. I would associate high temperature superconductors with this private company coming out of MIT, the CFS. The Commonwealth Fusion Systems. The short term goal is to construct a machine that will get us to right about breakeven using high temperature superconductors. High temperature superconductors can really change the game for fusion. The reason is pretty straightforward.
If you can make a stronger magnetic field, you can decrease the size of your machine. That is less expensive while still having the same performance.
Has there been any other big, exciting news in the fusion or plasma science community in the last year or two?
What I would say is pretty exciting is there’s this alternative concept called stellarators. They were actually invented here in this lab [at Princeton University]. The flagship stellarator called W7X is in Germany, but we helped design it. They recently reached some very high values of density and temperature and I think energy confinement time, to the point of being competitive with tokamaks, which is a really big deal. So we’re making sure that we’re putting a lot of effort into stellarators. Stellarators have a lot of advantages. They’re more difficult to design and to build. But they’re more robust. When you have a plasma in a tokamak you can have disruptions happen because there’s a very high current and any loss of the energy in the device can lead to a strong fall of the energy in the machine. Whereas with a stellarator, it’s more robust to these perturbations. If we get to a stellarator that’s constantly running and that’s fusion relevant, it could actually be a better long-term solution. I think we’re still maybe a couple decades away from stellarators being fusion relevant. But they’re making some very good strides forward.
The main difference between a stellarator and a tokamak is the geometry of the space you’re sending the plasma around, right?
Right, the tokamak is very symmetric. But it turns out that the magnetic field has got to spiral. It has to turn. To do that a tokamak uses an induced current inside. The central solenoid in tokamak is like the inner core of a transformer. It induces a current inside of the plasma, and that creates the magnetic field that we need. In a stellarator, we make that spiraling magnetic field entirely through external coils. If you do that, it can’t be very symmetric. You have to incorporate some swirliness into it. The result ends up being these magnets that are all weird. In the last 20 years, there was a real renaissance for stellarators. Super computers came into the conversation – you could design things by iterative process. We got to this next generation of stellarators, of which W7X in Germany is the big one.
How do you think fusion energy might help with climate change? Will it help alleviate the risk?
I think so. I think we need to hurry up. I think we haven’t put enough eggs in any of the baskets. [When it comes to investing in solutions for climate change.] But let’s assume we have a bunch of eggs. I don’t think we should put them all in the fusion basket. We should develop better [versions of every energy technology], including fission. As a society we need to realize that if we’re serious about [combatting] climate change, fission has to be part of the solution, at least to help us get to fusion. Once fusion is out there, it doesn’t create greenhouse gases. It doesn’t pollute. It would be like a utopia in terms of energy. But I’m very conscious that it’s a race against time. We need to be serious as a society about what this actually means in terms of sacrifices that we need to do.
I’m a big fan of fission. I wish more people knew that it’s become so much safer than it was in the past.
It’s much safer. In terms of deaths per kilowatt of electricity, it’s much lower than anything else.
It’s much safer than the zeitgeist believes.
What do you wish more people knew about fusion?
Really, about our existence! If I could make one wish come true – it would be getting people to know about us. Fusion has been this thing you hear in science fiction. You hear it in the media about cold fusion [which was debunked]. People confuse cold fusion with fusion. There’s lots of misunderstanding about fusion, about how many advances there have been in the past decade, and the fact that we’re very much ahead in developing this source. We haven’t solved all problems, but we haven’t gotten to the point where we’ve proven this won’t work. We do have ideas to get us ahead in all the issues that we have.
You want people to know that it’s not a joke or a myth – it’s true and you’re really doing it.
Right. It’s not a myth. It’s not a long shot. We’ve solved a lot of the most difficult problems and we feel we’re almost there.