by Sam Kean
Bismuth has helped scientists probe the deeper structure of radioactive matter as well. For decades, scientists couldn’t resolve conflicting calculations about whether certain elements would last until the end of time. So in 2003, physicists in France took pure bismuth, swaddled it in elaborate shields to block all possible outside interference, and wired detectors around it to try to determine its half-life, the amount of time it would take 50 percent of the sample to disintegrate. Half-life is a common measurement of radioactive elements. If a bucket of one hundred pounds of radioactive element X takes 3.14159 years to drop fifty pounds, then the half-life is 3.14159 years. After another 3.14159 years, you’d have twenty-five pounds. Nuclear theory predicted bismuth should have a half-life of twenty billion billion years, much longer than the age of the universe. (You could multiply the age of the universe by itself and get close to the same figure—and still have only a fifty-fifty shot of seeing any given bismuth atom disappear.) The French experiment was more or less a real-life Waiting for Godot. But amazingly, it worked. The French scientists collected enough bismuth and summoned enough patience to witness a number of decays. This result proved that instead of being the heaviest stable atom, bismuth will live only long enough to be the final element to go extinct.
The wild, Technicolor swirls of a hopper crystal form when the element bismuth cools into a staircase crystalline pattern. This crystal spans the width of an adult hand. (Ken Keraiff, Krystals Unlimited)
(A similarly Beckettesque experiment is running right now in Japan to determine whether all matter will eventually disintegrate. Some scientists calculate that protons, the building blocks of elements, are ever-so-slightly unstable, with a half-life of at least 100 billion trillion trillion years. Undaunted, hundreds of scientists set up a huge underground pool of ultra-pure, ultra-still water deep inside a mineshaft, and they surrounded it with rings of hair-trigger sensors, in case a proton does split on their watch. This is admittedly unlikely, but it’s a far more benevolent use of the Kamioka mines than previously.)
It’s time to confess the full truth about bismuth, though. It’s technically radioactive, yes, and its coordinates on the periodic table imply that element eighty-three should be awful for you. It shares a column with arsenic and antimony, and it crouches among the worst heavy-metal poisons. Yet bismuth is actually benign. It’s even medicinal: doctors prescribe it to soothe ulcers, and it’s the “bis” in hot-pink Pepto-Bismol. (When people got diarrhea from cadmium-tainted lemonade, the antidote was usually bismuth.) Overall, bismuth is probably the most misplaced element on the table. That statement might cause chagrin among chemists and physicists who want to find mathematical consistency in the table. Really, it’s further proof that the table is filled with rich, unpredictable stories if you know where to look.
In fact, instead of labeling bismuth a freakish anomaly, you might consider it a sort of “noble metal.” Just as peaceful noble gases cleave the periodic table between two sets of violent—but differently violent—elements, pacific bismuth marks the transition of poisoner’s corridor from the conventional retching-and-deep-pain poisons discussed above to the scorching radioactive poisons described below.
Lurking beyond bismuth is polonium, the poisoner’s poison of the nuclear age. Like thallium, it makes people’s hair fall out, as the world discovered in November 2006 when Alexander Litvinenko, an ex–KGB agent, was poisoned by polonium-laced sushi in a London restaurant. Past polonium (skipping over, for now, the ultra-rare element astatine) sits radon. As a noble gas, radon is colorless and odorless and reacts with nothing. But as a heavy element, it displaces air, sinks into the lungs, and discharges lethal radioactive particles that lead inevitably to lung cancer—just another way poisoner’s corridor can nip you.
Indeed, radioactivity dominates the bottom of the periodic table. It plays the same role the octet rule does for elements near the top: almost everything useful about heavy elements derives from how, and how quickly, they go radioactive. Probably the best way to illustrate this is through the story of a young American who, like Graham Frederick Young, grew obsessed with dangerous elements. But David Hahn wasn’t a sociopath. His disastrous adolescence sprang from a desire to help people. He wanted to solve the world’s energy crisis and break its addiction to oil so badly—as badly as only a teenager can want something—that this Detroit sixteen-year-old, as part of a clandestine Eagle Scout project gone berserk in the mid-1990s, erected a nuclear reactor in a potting shed in his mother’s backyard.*
David started off small, influenced by a book called The Golden Book of Chemistry Experiments, written in the same wincingly earnest tone as a 1950s reel-to-reel educational movie. He grew so excited about chemistry that his girlfriend’s mother forbade him to speak to guests at her parties because, in the intellectual equivalent of talking with his mouth full, he’d blurt out unappetizing facts about the chemicals in the food they were eating. But his interest wasn’t just theoretical. Like many prepubescent chemists, David quickly outgrew his box chemistry set, and he began playing with chemicals violent enough to blow his bedroom walls and carpet to hell. His mother soon banished him to the basement, then the backyard shed, which suited him fine. Unlike many budding scientists, though, David didn’t seem to get better at chemistry. Once, before a Boy Scout meeting, he dyed his skin orange when a fake tanning chemical he was working on burped and blew up in his face. And in a move only someone ignorant of chemistry would try, he accidentally exploded a container of purified potassium by tamping it with a screwdriver (a baaaad idea). An ophthalmologist was still digging plastic shards out of his eyes months later.
Even after that, the disasters continued, although, in his defense, David did take on increasingly complicated projects, like his reactor. To get started, he applied the little knowledge he’d gleaned about nuclear physics. This knowledge didn’t come from school (he was an indifferent, even a poor, student) but from the glowingly pro–nuclear energy pamphlets he wrote away for and from correspondence with government officials who believed sixteen-year-old “Professor Hahn’s” ruse about wanting to devise experiments for fictitious students.
Among other things, David learned about the three main nuclear processes—fusion, fission, and radioactive decay. Hydrogen fusion powers stars and is the most powerful and efficient process, but it plays little role in nuclear power on earth, since we can’t easily reproduce the temperatures and pressures needed to ignite fusion. David instead relied on uranium fission and the radioactivity of neutrons, which are by-products of fission. Heavier elements such as uranium have trouble keeping positive protons bound in their tiny nuclei, since identical charges repel, so they also pack in neutrons to serve as buffers. When a heavy atom fissions into two lighter atoms of roughly equal size, the lighter atoms require fewer neutron buffers, so they spit the excess neutrons out. Sometimes those neutrons are absorbed by nearby heavy atoms, which become unstable and spit out more neutrons in a chain reaction. In a bomb, you can just let that process happen. Reactors require more touch and control, since you want to string the fission out over a longer period. The main engineering obstacle David faced was that after the uranium atoms fission and release neutrons, the resulting lighter atoms are stable and cannot perpetuate the chain reaction. As a result, conventional reactors slowly die from lack of fuel.
Realizing this—and going obscenely far beyond the atomic energy merit badge he was originally seeking (really)—David decided to build a “breeder reactor,” which makes its own fuel through a clever combination of radioactive species. The reactor’s initial source of power would be pellets of uranium-233, which readily fissions. (The 233 means the uranium has 141 neutrons plus 92 protons; notice the excess of neutrons.) But the uranium would be surrounded with a jacket of a slightly lighter element, thorium-232. After the fission events, the thorium would absorb a neutron and become thorium-233. Unstable thorium-233 undergoes beta decay by spitting out an electron, and because charges always balance in nature, when it loses a
negative electron, thorium also converts a neutron to a positive proton. This addition of a proton shifts it to the next element on the table, protactinium-233. This is also unstable, so the protactinium spits out another electron and transforms into what you started with, uranium-233. Almost magically, you get more fuel just by combining elements that go radioactive in the right way.
David pursued this project on weekends, since he lived only part-time with his mom after his parents’ divorce. For safety’s sake, he acquired a dentist’s lead apron to protect his organs, and anytime he spent a few hours in the backyard shed, he discarded his clothes and shoes. (His mom and stepdad later admitted that they’d noticed him throwing away good clothes and thought it peculiar. They just assumed David was smarter than they were and knew what he was doing.)
Of all the work he did, probably the easiest part of the project was finding the thorium-232. Thorium compounds have extremely high melting points, so they glow extra-bright when heated. They’re too dangerous for household lightbulbs, but in industrial settings, especially mines, thorium lamps are common. Instead of wire filaments as wicks, thorium lamps use small mesh nets called mantles, and David ordered hundreds of replacement mantles from a wholesaler, no questions asked. Then, showing improvement in his chemistry, he melted down the mantles into thorium ash with sustained heat from a blowtorch. He treated the ash with $1,000 worth of lithium he had obtained by cutting open batteries with wire cutters. Heating the reactive lithium and ash over a Bunsen burner purified the thorium, giving David a fine jacket for his reactor core.
Unfortunately, or perhaps fortunately, however well David learned radioactive chemistry, the physics escaped him. David first needed uranium-235 to irradiate the thorium and turn it, the thorium, into uranium-233. So he mounted a Geiger counter (a device that registers radioactivity with a click-click-click-click) on the dashboard of his Pontiac and cruised rural Michigan, as if he’d just stumble onto a uranium hot spot in the woods. But ordinary uranium is mostly uranium-238, which is a weak source of radioactivity. (Figuring out how to enrich ore by separating uranium-235 and uranium-238, which are chemically identical, was in fact a major achievement of the Manhattan Project.) David eventually scored some uranium ore from a sketchy supplier in the Czech Republic, but again it was ordinary, unenriched uranium, not the volatile kind. Eventually abandoning this approach, Hahn built a “neutron gun” to irradiate his thorium and get the uranium-233 kindling that way, but the gun barely worked.
A few sensational media stories later implied that David almost succeeded in building a reactor in the shed. In truth, he wasn’t close. The legendary nuclear scientist Al Ghiorso once estimated that David started with at least a billion billion times too little fissionable material. David certainly gathered dangerous materials and, depending on his exposure, might well have shortened his life span. But that’s easy. There are many ways to poison yourself with radioactivity. There are very, very few ways to harness those elements, with proper timing and controls, to get something useful from them.
Still, the police took no chances when they uncovered David’s plan. They found him late one night poking around a parked car and assumed he was a punk stealing tires. After detaining and harassing him, they searched his Pontiac, which he kindly but stupidly warned them was full of radioactive materials. They also found vials of strange powder and hauled him in for questioning. David was savvy enough not to mention the “hot” equipment in the potting shed, most of which he’d already dismantled anyway, scared that he was making too much progress and might leave a crater. While federal agencies wrangled about who was responsible for David—no one had tried to illegally save the world with nuclear power before—the case dragged on for months. In the meantime, David’s mother, fearing her house would be condemned, slipped into the laboratory shed one night and hauled almost everything in there to the trash. Months later, officials finally stormed across the neighbors’ backyards in hazmat gear to ransack the shed. Even then, the leftover cans and tools showed a thousand times more radioactivity than background levels.
Because he had no malevolent intentions (and September 11 hadn’t happened yet), David was mostly let off the hook. He did argue with his parents about his future, however, and after graduating from high school, he enlisted in the Navy, itching to work on nuclear submarines. Given David’s history, the Navy probably had no choice, but instead of letting him work on reactors, it put him on KP and had him swab decks. Unfortunately for him, he never got the chance to work on science in a controlled, supervised setting, where his enthusiasm and nascent talent might, who knows, have done some good.
The denouement of the story of the radioactive Boy Scout is sad. After leaving the military, David drifted back to his suburban hometown and bummed around without much purpose. After a few quiet years, in 2007 police caught him tampering with (actually stealing) smoke detectors from his own apartment building. With David’s record, this was a significant offense, since smoke detectors run on a radioactive element, americium. Americium is a reliable source of alpha particles, which can be channeled into an electric current inside detectors. Smoke absorbs the alpha particles, which disrupts the current and sets off the shrill alarm. But David had used americium to make his crude neutron gun, since alpha particles knock neutrons loose from certain elements. Indeed, he’d already been caught once, when he was a Boy Scout, stealing smoke detectors at a summer camp and had been kicked off the grounds.
In 2007, when his mug shot was leaked to the media, David’s cherubic face was pockmarked with red sores, as if he had acute acne and had picked every pimple until it bled. But thirty-one-year-old men usually don’t come down with acne. The inescapable conclusion was that he’d been reliving his adolescence with more nuclear experiments. Once again, chemistry fooled David Hahn, who never realized that the periodic table is rife with deception. It was an awful reminder that even though the heavy elements along the bottom of the table aren’t poisonous in the conventional way, the way that elements in poisoner’s corridor are, they’re devious enough to ruin a life.
10
Take Two Elements, Call Me in the Morning
The periodic table is a mercurial thing, and most elements are more complicated than the straightforward rogues of poisoner’s corridor. Obscure elements do obscure things inside the body—often bad, but sometimes good. An element toxic in one circumstance can become a lifesaving drug in another, and elements that get metabolized in unexpected ways can provide new diagnostic tools in doctors’ clinics. The interplay of elements and drugs can even illuminate how life itself emerges from the unconscious chemical slag of the periodic table.
The reputations of a few elemental medicines extend back a surprisingly long time. Roman officers supposedly enjoyed better health than their grunts because they took their meals on silver platters. And however useless hard currency was in the wild, most pioneer families in early America invested in at least one good silver coin, which spent its Conestoga wagon ride across the wilderness hidden in a milk jug—not for safekeeping, but to keep the milk from spoiling. The noted gentleman astronomer Tycho Brahe, who lost the bridge of his nose in a drunken sword duel in a dimly lit banquet hall in 1564, was even said to have ordered a replacement nose of silver. The metal was fashionable and, more important, curtailed infections. The only drawback was that its obviously metallic color forced Brahe to carry jars of foundation with him, which he was always smoothing over his nasal prosthesis.
Curious archaeologists later dug up Brahe’s body and found a green crust on the front of his skull—meaning Brahe had probably worn not a silver but a cheaper, lighter copper nose.* (Or perhaps he switched noses, like earrings, depending on the status of his company.) Either way, copper or silver, the story makes sense. Though both were long dismissed as folk remedies, modern science confirms that those elements have antiseptic powers. Silver is too dear for everyday use, but copper ducts and tubing are standard in the guts of buildings now, as public safety measures. Copper’s ca
reer in public health began just after America’s bicentennial, in 1976, when a plague broke out in a hotel in Philadelphia. Never-before-seen bacteria crept into the moist ducts of the building’s air-conditioning system that July, proliferated, and coasted through the vents on a bed of cool air. Within days, hundreds of people at the hotel came down with the “flu,” and thirty-four died. The hotel had rented out its convention center that week to a veterans group, the American Legion, and though not every victim belonged, the bug became known as Legionnaires’ disease.
The laws pushed through in reaction to the outbreak mandated cleaner air and water systems, and copper has proved the simplest, cheapest way to improve infrastructure. If certain bacteria, fungi, or algae inch across something made of copper, they absorb copper atoms, which disrupt their metabolism (human cells are unaffected). The microbes choke and die after a few hours. This effect—the oligodynamic, or “self-sterilizing,” effect—makes metals more sterile than wood or plastic and explains why we have brass doorknobs and metal railings in public places. It also explains why most of the well-handled coins of the U.S. realm contain close to 90 percent copper or (like pennies) are copper-coated.* Copper tubing in air-conditioning ducts cleans out the nasty bugs that fester inside there, too.
