The second thing that would strike a visitor was the air of quiet desperation that hung about the lab. The staff was trying to sell fusion to the public, and while the TFTR was setting temperature records almost daily, nobody seemed to be buying. Budgets were still dropping, and the taxpayers didn’t protest. The lab, quietly, tried to change that attitude. Along each wall of the laboratory’s lobby, colorful posters exhorted the taxpayer to back fusion research. “Why Fusion?” read one. “Do We Really Need To Spend This Much On Energy Research?” asked another. Rush Holt, a physicist and the spokesman for the TFTR project, promised great things for TFTR—6 watts out for every 10 put in, within spitting distance of breakeven—but most of all, he conjured a future with fusion energy. Without it, he said, humanity would be in trouble.
64
Where can we as a society get our energy? Fossil fuels pollute, cause global warming, and are running out. Renewable sources—solar, geothermal, wind—can’t provide nearly enough energy for an industrial society.
65
That leaves nuclear energy: fusion or fission. Holt argued that fission is messy: a fission reactor uses up its fuel rods and leaves behind a radioactive mess that nobody knows how to dispose of. Fusion, on the other hand, leaves no harmful by-products. It runs on deuterium and tritium, he said, and leaves only harmless helium behind. Clean fusion energy would be a much better choice.
This is the sales pitch of faithful magnetic fusion scientists everywhere. Fusion provides unlimited power—clean, safe energy without the harmful by-products of fission. But there is a dirty little secret. Fusion is not clean. Once again, it’s the fault of those darn neutrons.
Magnetic fields can contain charged particles, but they are invisible to neutral ones. Neutrons, remember, carry no charge and do not feel magnetic forces. They zoom right through a magnetic bottle and slam into the walls of the container beyond. Since a deuterium-deuterium fusion reaction produces lots of high-energy neutrons (one for every two fusions), the walls of a tokamak reactor are bombarded with zillions of the particles every moment it runs.
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Neutrons are nasty little critters. They are hard to stop: they whiz through ordinary matter rather easily. When they do stop—when they strike an atom in a hunk of matter—they do damage. They knock atoms about. They introduce impurities. A metal irradiated by neutrons becomes brittle and weak. That means the metal walls of the tokamak become susceptible to fracture before too long. Every few years, the entire reactor vessel, the entire metal donut surrounding the plasma, has to be replaced.
Unfortunately, neutrons also make materials radioactive. The neutrons hit the nuclei in a metal and sometimes stick, making the nucleus unstable. The longer a substance is exposed to neutrons, the “hotter” it gets with radioactivity. By the time a tokamak’s walls need to be replaced, they are quite hot indeed.
Though fusion scientists portray fusion energy as cleaner than fission, a fusion power plant would produce a larger volume of radioactive waste than a standard nuclear power plant. It would also be just as dangerous—at first. Much of the waste from a fusion reactor tends to “cool down” more quickly than the waste from a fission reactor, taking a mere hundred years or so until humans can approach it safely. But it means that humans will have to figure out where to store it in the meantime, as well as the rest of the waste that, like spent fission fuel, will remain untouchable for thousands of years. Fusion is a bit cleaner than fission, but it still presents a major waste problem.
Fusion scientists recognize this, of course. They are working on exotic alloys that are less affected by neutron bombardment, materials made of vanadium and silicon carbide. However, developing those materials is going to cost a lot of money, and they will still present a waste problem, albeit a reduced one.
It’s an open secret. Fusion isn’t clean, and it probably never will be.
CHAPTER 8
BUBBLE TROUBLE
Hegel observes somewhere that all great incidents and individuals of world history occur, as it were, twice. He forgot to add: the first time as tragedy, the second as farce.
—KARL MARX, THE 18TH BRUMAIRE OF LOUIS NAPOLEON
T
he mere mention of cold fusion made everyone bristle. The scientists, the press office, the editor of the magazine all objected to anyone’s using the term. But the phrase was soon echoing across the nation. It was on the front pages, in the evening television broadcasts, and plastered all over the press. Cold fusion rides again. History seemed to be repeating itself.
The controversy seemed familiar from the start. Scientists at Oak Ridge National Laboratory and Rensselaer Polytechnic Institute, both well-respected institutions, claimed that they had created fusion in a little beaker of acetone not much bigger than the original Pons and Fleischmann cell. In many ways, though, this situation was very different from cold fusion. Rather than announcing their results at a press conference, the scientists sent them to
Science
magazine, the most prestigious peer-reviewed journal in the United States, and their paper had been accepted. The scientists weren’t saying they had discovered dramatically new physics, as Pons and Fleischmann’s palladium-catalyzed fusion would have required. These bubble fusion reactions were supposedly happening at tens of millions of degrees, rather than at room temperature.
But like cold fusion, the bubble fusion researchers believed their work could lead to an unlimited source of energy. And like Pons and Fleischmann, the bubble fusion scientists quickly came under attack by some of the leading fusion physicists in the nation. Even before their paper had been published in
Science
, the bubble fusion scientists were labeled as incompetent. It got worse after publication. Increasingly isolated, they were forced toward the fringe, and before long they were fighting accusations of scientific misconduct and a fraud investigation that led all the way to Capitol Hill. History
had
repeated itself.
The bubble fusion imbroglio was a twisted reflection of the cold-fusion affair. The second time around, the tale would be a tragedy as well as a farce. Researchers, peer reviewers, editors, journalists, press officers, and all the other players in the drama were caught in a colossal web of mutual misunderstanding. It was a story of good intentions gone wrong, of paranoia and mistrust, and of hubris that led to the downfall of a scientist.
When the bubble fusion story broke in 2002, I was a reporter for
Science
, ground zero for the controversy.
Science
is famous because it is arguably the premier peer-reviewed scientific journal in the United States. For many scientists, a publication in it (or its British rival,
Nature
) would be considered a major coup, perhaps even the crowning achievement in an average scientific career. Researchers from around the world submit manuscripts to
Science
, and it is an enormous task to examine the submissions and select those worth publishing.
I had nothing to do with the peer-reviewed section of
Science.
I worked for the news pages at the front of the magazine. News reporters at
Science
are deliberately isolated from the peer-reviewed section. We weren’t told about manuscripts in the pipeline, or about the status of a paper undergoing peer review. We weren’t even allowed to know who the peer reviewers of a given manuscript were.
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So I was quite surprised when, on February 5, 2002, my editor, Robert Coontz, e-mailed me a paper entitled “Nuclear Emissions during Acoustic Cavitation.” It had already been through the peer-review process, but it wasn’t an ordinary manuscript. “Here’s a
Science
paper that’s likely to be
very
controversial,” Coontz wrote. “First task is to decide whether we want to cover it.” Within a few seconds, I knew it was going to be explosive.
The manuscript was couched in the typical cold, technical language of the scientific paper, but its authors, a team led by Rusi Taleyarkhan at the Oak Ridge National Laboratory, were making a claim that seemed eerily reminiscent of cold fusion. They claimed to have induced fusion reactions on a tabletop using a process that might lead to energy production. More important, they did it in an ingenious, and seemingly plausible, way. They did it with a technique linked to a mysterious phenomenon known as sonoluminescence.
As early as the 1930s, scientists had discovered a bizarre method to convert sound into light. If you take a tub of liquid and bombard it with sound waves in the correct manner, the tub begins to generate tiny little bubbles that glow with a faint blue light. This phenomenon is not perfectly understood, but scientists are pretty sure they know what is going on, at least in gross terms.
If you have ever belly flopped off a diving board, you know that a liquid like water doesn’t always behave quite like a fluid. Hit it hard enough and fast enough, faster than the water can flow out of your way, and it feels almost like concrete. It behaves more like a solid than like a liquid. This is more than a mere metaphor. Under certain circumstances—if you hit a liquid in the right way—it will “crack” just as a solid would. The liquid ruptures, creating tiny vacuum-filled bubbles that instantly fill with a tiny bit of evaporated liquid. This phenomenon is known as cavitation, and it occurs in a number of different places. Submarine propellers, for example, cause cavitation if they spin too fast. Sound waves rattling through a fluid can also create these bubbles.
Under the right conditions, the sound waves reverberating through the liquid also cause these bubbles to compress and expand, compress and expand. Each time the bubbles are squashed by the sound waves, they heat up. If the sound waves are just right, the bubble can collapse to roughly one-tenth its original size, heating up to tens of thousands of degrees and emitting a flash of light. This is sonoluminescence.
Taleyarkhan wondered what was happening at the center of those collapsing bubbles. What would happen if you replaced water with a deuterium-laden liquid? If those bubbles got squashed far enough and became hot enough, could they induce the little bit of deuterium vapor in the center of the bubble to fuse? Could they induce a fusion reaction in a beaker?
The first problem he encountered was that tens of thousands of degrees isn’t nearly enough to induce fusion, so ordinary sonoluminescence didn’t have any hope of getting deuterium nuclei to stick together. For fusion, Taleyarkhan needed to heat deuterium and to tens of
millions
of degrees, a thousand times hotter than what traditional sonoluminescence could achieve. The only way to get those temperatures was to compress the bubbles far more than had ever been done before, either by squashing them tighter or by starting with bigger bubbles. Taleyarkhan had figured out an innovative way to do the latter.
His research team started with a solution of deuterated acetone, the same molecule that’s in nail polish remover, except for the fact that its six hydrogen atoms have been replaced with deuteriums. Then they irradiated the liquid with energetic neutrons and exposed it to sound waves. The energetic neutrons poured their energy into the solution and birthed very large bubbles—tens or hundreds of times larger than the ordinary bubbles in sonoluminescence—and, according to Taleyarkhan and his colleagues, the sound waves compressed them by a factor of ten thousand. This was a much higher compression than had ever been observed before. Taleyarkhan’s calculations implied that this extreme compression led to a temperature in the range of millions of degrees. This, in turn, supposedly led to fusion.
To all appearances, Taleyarkhan and his colleagues did all the right things when they went looking for deuterium-deuterium fusion. The paper told of how the researchers looked for neutrons—and found them. Tritium? Found it. They also avoided many of Pons and Fleischmann’s mistakes. They ran the obvious control experiments, substituting ordinary acetone for the deuterated variety. The neutrons and tritium disappeared. Finally, the paper convinced a science editor and a group of peer reviewers who, presumably, were satisfied with its quality.
But I was skeptical. For one thing, I knew Taleyarkhan, and while I held him in reasonably high esteem, I didn’t think of him as a fusion expert. A few years earlier—in 1999, when I was a reporter for
New Scientist
magazine—I had written about one of his inventions. He had figured out a clever way to make a gun that would shoot bullets at different speeds. In theory, you would be able to turn a dial on a gun and set it to “stun” with low-velocity bullets or to “kill” with high-velocity ones. (It used an aluminum-based propellant that could do things ordinary gunpowder couldn’t.) Interesting stuff, but not the sort of thing a fusion expert would invent. Taleyarkhan was a nuclear engineer, and I associated him with steam explosions and propellants and reactor safety, not fusion physics. What really bothered me, though, were the neutrons.
The bubble fusion paper was going to live or die by the neutrons Taleyarkhan was claiming to see. Neutrons were what killed Pons and Fleischmann. Neutrons were what killed ZETA. Without a nice, clear demonstration of neutrons of the proper energy—2.45 MeV—streaming from the experimental cell, nobody would take Taleyarkhan seriously for a minute. So the first thing I looked at was the paper’s graph of neutrons. I was surprised.
Skeptical physicists would only be convinced by a detailed graph showing how many neutrons were detected at what sorts of energies. Taleyarkhan’s paper had a few graphs, but they were far from detailed. The main one only had four points—two for the deuterium experiment and two for the control experiment—telling how many neutrons were detected above and below 2.5 MeV. That wasn’t
nearly
enough, at least in my opinion. I expected a neutron spectrum to have tens of points, not two. Without that level of detail, I didn’t think that there was enough information to determine whether the experimenters were seeing something real.