The Star Builders Page 5
Of course, those regulations may be there for good reasons. “When something does go wrong, it really goes wrong,” Jonathan Carling says of fission, “to the point where you’ve got to evacuate portions of the population and for that reason there are lots of places in the world that just don’t want to do that.” He also brought up the proliferation risk and that not many people want a fission reactor, which could melt down, in their backyard.
Too often, renewables and nuclear fission are viewed as either/or options. Honestly, looking at the scale of the challenge we face, we’re going to need both. But we should take people’s concerns and the risks seriously. Star builders are, and they don’t think we can rely on fission alone to fill the gap between what energy renewables alone can provide and how much energy we’ll need.
The Star Power Rescue Plan
What of the star builders’ grand plan? How would building a star help save the planet? On paper, nuclear fusion combines many of the advantages of other power sources.
Ian Chapman is clear. “It’s going to change the world,” he told me, adding that preventing catastrophic climate change with star power is what gets him out of bed in the morning. “If I didn’t believe that fusion was important for that I’d stop doing it and go do something else with my life,” he said. “The imperative to tackle climate change is only escalating and I could see that back in 2000.” Since that point, he says, we’ve “burned 80 percent more oil and gas. We need a seismic change in how we provide clean, affordable, safe, carbon-free energy, and fusion will be a big part of that, I’m convinced of it.”
His colleague, and the physics coordinator of one of Culham’s experiments, Dr. Fernanda Rimini, agrees. She told me that the planet would go on after a climate catastrophe, but she’s trying to bring star power to Earth for the next generation, for our way of life. I ask about alternatives, but she points out that fission just isn’t acceptable, and renewables aren’t enough. She sees a future that combines renewables and fusion. “Fusion could replace fission,” she says, “but be more environmentally friendly.”
Why are the star builders so in love with fusion? In short, they believe it will solve in one fell swoop many of the problems of the other power sources. The greatest problem of energy production is climate change: fusion will produce no more carbon dioxide than fission. How much carbon dioxide is that? Solar photovoltaics have life-cycle emissions that are 50 percent higher than fission and wind. Everything else, including biomass and hydro, has emissions that are at least twenty-five times that of fission and wind.38
Fusion also looks promising with respect to land use and scale. The star builders say that fusion plants will take up just a fraction of the space of an equivalent-power renewable plant. They’ll need a land area similar to what is taken up by fission plants today. And fusion neatly solves the problem of consistency. The star builders say that, once cracked, fusion will provide a steady supply of energy come rain or shine.
Yet another argument for fusion is that it produces a lot less radioactive waste than fission, and what is produced won’t last as long. Star builders say that it’s impossible for a nuclear fusion reactor to melt down or undergo a runaway reaction. The amount of regular waste would also be vastly less than fossil fuels produce.
Given that the most devastating nuclear weapons are based on fission and fusion, it’s rational to ask whether fusion power plants would pose even more of a risk of nuclear proliferation than nuclear fission plants. Seeking the perspective of someone who works at a site where the US’s nuclear arsenal is maintained, I talked to NIF’s Jeff Wisoff about this. He was clear: “Fusion is less of a nuclear weapons proliferation risk than fission.” I’ll revisit these claims later in the book.
And while energy security due to possible restrictions in fuel supply is a problem for oil, coal, gas, and the fissile material used in today’s nuclear reactors, it’s not a problem for fusion because almost every nation on Earth has direct access to it: the supply can be found in plain old seawater.
Fusion is a fuel-based power source, like fission or fossil fuels, so, in principle, it could run out. The fuel is a finite resource. It would be reasonable to wonder whether, if fusion is perfected, humanity could run out of fusion fuel and be right back in another energy crisis in a few years’ time. But, as the star builders point out, we won’t be running out of fusion fuel any time soon.
The two reactants needed for the simplest form of fusion (which requires the lowest temperatures) are the special types of hydrogen known as deuterium and tritium. Deuterium is outrageously common, with every briny bathtub of seawater containing five grams of the stuff. We know how to extract it too.39
The other ingredient for the simplest fusion reaction, tritium, is very mildly radioactive and, because it decays, doesn’t exist in significant quantities on Earth. However, it can be made from another element that is extremely plentiful: lithium. Lithium exists in ores and in seawater. It’s around fifty times more common in seawater than uranium, the raw ingredient for nuclear fission. While it’s not currently extracted at scale, if any metal is economical to extract from seawater, it’s lithium.40
Figure 2.2 shows how long different types of fuel would last if we relied on them, and only them, to provide everyone on the planet with the same energy use as the average US citizen. In the figure, the clear columns are the non-fusion fuels. The gray columns show how long the fusion fuels would last. The clear columns show that, by going all out on any one of oil, gas, coal, or existing reserves of uranium (assuming no new reserves were found), the planet would run down its energy supplies in fewer than one hundred years. Uranium extracted from seawater would enable fission to go on a lot longer.
Figure 2.2: The number of years of energy left if we used just one type of fuel. Clear columns are non-fusion energy sources. The gray columns are types of fusion—deuterium-tritium fusion (using lithium from either the ground or the sea) and deuterium-deuterium fusion (which just requires seawater).41
The gray columns for fusion are labeled by the limiting factor in how long each type of fusion would last. Deuterium-tritium fusion is limited by the amount of lithium, either from ores or from seawater, because lithium must be used to create tritium. Deuterium-deuterium fusion is limited only by the amount of deuterium in the oceans. The simplest form of fusion, using mined lithium, would last two thousand years. Lithium extracted from seawater42 would stretch the fusion energy supply to 30 million years. Deuterium-only fusion would last over a billion years.
Our planet’s supply of fusion fuel is effectively limitless. Deuterium-tritium fusion would last long enough for continents to move, and species to rise and fall. That’s a geological timescale. Energy from fusion using deuterium alone would last for astrophysical timescales—long enough for the Sun to exhaust its own hydrogen fuel supply and expand to swallow the Earth. Fusion is a power source that could go on until the planet itself is uninhabitable.
Fusion buys the planet time. But in another sense, time is running out. When I visited Ian Chapman at the Culham Centre for Fusion Energy, a crop of fresh PhD students just beginning their star-building careers was presenting posters on their work and discussing it over a modest buffet lunch of sandwiches and potato chips. I had some time to kill before I went upstairs to meet their boss, so I asked a group of them about their motivations for working on fusion. I was especially interested if, as people likely to inhabit the planet longer than their older peers, they were drawn to fusion because of its potential to help with climate change. One or two said yes, fusion was going to help stop climate change. But the majority were skeptical that fusion energy would be ready in time to meet the IPCC’s dramatically short deadline for averting a climate catastrophe. They still believed that fusion could and should be an essential part of Earth’s energy supply in the future, but they didn’t believe it would arrive quickly enough to keep climate change in check. I was taken aback by their view, which was so different from that of more senior-ranking star builde
rs. But given that the development of star machines has taken decades so far, I thought it was a good challenge, and I decided to put it directly to their boss. Upstairs, I asked Ian Chapman if fusion would be ready too late to make a difference; he shook his head emphatically.
“I don’t think it’s true. We don’t just get to 2050 and there’s a cliff edge and the world just stops or we’ve saved it,” he told me. “We’ll be on the right path, but there’ll still be a whole load of carbon technology we’ll need to displace.”
He also said that the IPCC deadline wasn’t a reason not to pursue nuclear fusion.
“You’ve got to remember that 80 percent of our energy is oil and gas. You can’t just say by 2050 we’ve got to be net zero—how are you going to deliver that? Eighty percent! That’s a huge challenge, and to be honest we’re not going to meet it with current technology.”
He’s strongly pro renewables, and pro investment in renewables. But he doesn’t think they’ll be enough on their own. “People are totally blasé about it,” he says. He is concerned, angry even. “We’re not behaving like it’s an emergency, and at some point that will bite.”
Other star builders agree that the quicker fusion energy is delivered, the better for the climate.
“I feel that in many ways, time is our biggest enemy. If we want fusion to be a big factor in combating climate change—tick tock, tick tock,” the director of MIT’s Plasma Science and Fusion Center, and cofounder of fusion start-up Commonwealth Fusion Systems, Dennis Whyte has said.43 Another star builder told me that eventually—whatever the specific timescale—the world will be driven to star power.
Star builders at start-ups were among the most bullish about the potential of fusion to defeat climate change. Scientists at both Tokamak Energy and First Light Fusion talked about building multiple net-energy-gain reactors in the 2020s or 2030s.
Given the long history of star building and the frustratingly slow progress thus far, it may seem surprising that so many star builders are so upbeat about the prospects of stopping climate change with fusion energy. In subsequent chapters, I’ll explain why they’re so strongly convinced they can get it working in time.
Nuclear fusion isn’t the only energy source that’s taken its sweet time to come to fruition, by the way. The utopian John Adolphus Etzler had the bright idea of solar power in a visionary 1833 book, and the inventor Charles Fritts’s first solar cell appeared in 1883. Newspapers in 1891 jubilantly promised that “the day is not unlikely to arrive before long” when economical solar power would be driving “all the engines on the Earth.” Forty years later, in 1931, they assured readers that “use of solar energy is near a solution.” Close to two centuries after the idea was proposed, the cost of solar power has become competitive with fossil fuels, although installed capacity is comparatively tiny. Maybe there’s hope for fusion yet.44
And yet… nuclear fusion is qualitatively different. Even Charles Fritts’s first solar cell managed a net energy gain, harvesting 1 percent of the sunlight energy that fell on it. Ignoring the energy cost of creating the cell in the first place, that first cell produced energy. So far, the only widely known artificially triggered fusion reactions that have produced net energy gain have been the ones in hydrogen bombs.
Nuclear fusion has always been essential for life on Earth to exist and to flourish. Essentially, all of our energy comes directly or indirectly from the massive, fiery nuclear fusion reactor in the sky that we know as the Sun. After all, solar power, the most promising renewable, is just indirect nuclear fusion energy. The star builders want to cut out the intermediary. They recognize the difficulty of their quest and that the stakes are as high as any we as a species have faced. But to have a hope of building a star and saving the planet, they need to understand nuclear fusion’s secrets.
I. There are surprisingly large number ranges for renewable energy density; these are based on renewable sites that were generating in the US in 2016.
CHAPTER 3 ENERGY FROM ATOMS
“A star is drawing on some vast reservoir of energy by means unknown to us. This reservoir can scarcely be other than the sub-atomic energy which, it is known, exists abundantly in all matter; we sometimes dream that man will one day learn to release it and use it for his service. The store is well-nigh inexhaustible, if only it could be tapped.”
—Arthur Eddington, “The Internal Constitution of the Stars,” 19201
This book is about scientists’ attempts to unlock energy from within the atom, and the star builders owe a great debt to the person who did more than anyone else to show the world this was possible.
That person is the physicist Ernest Rutherford, who, in the first decades of the twentieth century, discovered the structure of the atom, carried out the first nuclear reaction (without realizing it), and led the teams that discovered both nuclear fusion and nuclear fission reactions. But even the first ever artificial fusion experiment performed by Rutherford would show that achieving net energy gain was going to be very, very hard.
Ernest Rutherford was a brilliant, innovative, and hardworking physicist whose character and creativity won him many successes throughout his career. He helped to develop an early form of sonar; he built a world record–beating device for detecting radio waves at a distance; and his sensational early discoveries in radioactivity won him the 1908 Nobel Prize for Chemistry. He’s so important to the history of science that the UK’s Royal Society has kept some bizarre personal effects of his, including a potato masher. He was generous of spirit and, also, averse to affectation. His fellow physicist Niels Bohr said, “Although Rutherford was always intensely occupied with the progress of his own work, he had the patience to listen to every young man, when he felt he had any idea, however modest, on his mind.” Bohr also observed that Rutherford had “little respect for authority and could not stand what he called ‘pompous talk.’ ”2
Rutherford’s work on the atom began with his move to the University of Cambridge’s Cavendish Laboratory, from New Zealand, in 1895. Rutherford’s supervisor at the Cavendish was the great physicist Joseph John “J. J.” Thomson, the discoverer of the electron: the smallest distinct particle that makes up the atom. In 1904, Thomson had put forth a theory that could explain the facts about atoms as they were then known: the “plum pudding” model, a Christmas pudding–like dessert containing raisins (rather than plums). The model posits that atoms are made up of a positively charged “pudding” embedded with negatively charged “raisins” (electrons).3
In 1909, Rutherford moved to the University of Manchester, where he came up with experiments that tested his former supervisor’s theory. Rutherford ingeniously showed that—rather than a plum pudding—most of the atom was made up of empty space, with a concentrated lump of positively charged matter right in the middle. We now call this lump the nucleus (from which we get the word “nuclear”).4
The basic structure of Rutherford’s model is similar to how scientists think about atoms today: a massive nucleus in the center, occupying a small fraction of the space, and a cloud of very light, negatively charged electrons that are dispersed throughout the atom. Within the nucleus, there are two types of particles that have very similar masses: neutrons and positively charged protons.
The nucleus of the most common element in the universe, hydrogen, consists of just a single proton. The number of protons in an atomic nucleus determines what kind of atom it is: one for hydrogen, two for helium, three for lithium, and so on; adding one more proton to the nucleus turns it into a different element. Almost all chemistry, including reactions like burning or wine turning into vinegar (oxidation), is determined by the equal number of protons and electrons. The players in chemistry are the electrons, which are shared, swapped, or moved around in chemical reactions. As Bill Bryson observed, “Protons give an atom its identity, electrons its personality.”5
Neutrons, which have no charge, aren’t involved in chemistry, which is why atoms are usually called by one name regardless of how many neutr
ons are in the nucleus. For most purposes, there is no distinction between the two types of nitrogen in the Earth’s atmosphere; both have seven protons, but one has seven neutrons while the other has eight neutrons. The name for atoms with the same number of protons but different numbers of neutrons is isotopes. Because both isotopes of nitrogen have the same number of electrons, their chemistry is almost exactly the same.
But for nuclear physics, what’s in the nucleus matters. So the difference between isotopes is important, and can be the difference between life and death—as you’ll see in a later chapter when we come to the story of Bikini Atoll and the Lucky Dragon. Fusion and fission are nuclear reactions because they change the number of protons and neutrons in the nucleus. Deuterium and tritium, the fuel for the star builders’ preferred form of fusion, are isotopes of hydrogen. They all have one proton, but deuterium and tritium have neutrons too, which makes them more massive. The names give a clue as to how they relate to the more common form of hydrogen that has a single proton in its nucleus—deuterium is approximately twice as massive as usual hydrogen, while tritium is three times as massive. There’s one neutron and one proton in deuterium; and two neutrons and one proton in tritium.
Even the broad structure of the atom that Rutherford discovered was revelatory to scientists of the day. Ernest Mach, after whom the Mach numberI is named, said in 1910 that “if belief in the reality of atoms is so crucial, then I renounce the physical way of thinking, I will not be a professional physicist, and I hand back my scientific reputation.”6 The new theory was a huge paradigm shift that excited strong feelings. Rutherford clearly enjoyed mashing theories just as much as potatoes.