Armed with information from his friends in government and industry, David typed up a list of sources for fourteen radioactive isotopes. Americium-241, he learned from the Boy Scout atomic-energy booklet, could be found in smoke detectors; radium-226, in antique luminous dial clocks; uranium-238 and minute quantities of uranium-235, in a black ore called pitchblende; and thorium-232, in Coleman-style gas lanterns.
To obtain americium-241, David contacted smoke-detector companies and claimed that he needed a large number of the devices for a school project. One company agreed to sell him about a hundred broken detectors for a dollar apiece. (He also tried to “collect” detectors while at scout camp.) David wasn’t sure where the americium-241 was located, so he wrote to BRK Electronics in Aurora, Illinois. A customer-service representative named Beth Weber wrote back to say she’d be happy to help out with “your report.” She explained that each detector contains only a tiny amount of americium-241, which is sealed in a gold matrix “to make sure that corrosion does not break it down and release it.” Thanks to Weber’s tip, David extracted the americium components and then welded them together with a blowtorch.
As it decays, americium-241 emits alpha rays composed of protons and neutrons. David put the lump of americium inside a hollow block of lead with a tiny hole pricked in one side so that alpha rays would stream out. In front of the lead block he placed a sheet of aluminum. Aluminum atoms absorb alpha rays and in the process kick out neutrons. Since neutrons have no charge, and thus cannot be measured by a Geiger counter, David had no way of knowing whether the gun was working until he recalled that paraffin throws off protons when hit by neutrons. David aimed the apparatus at some paraffin, and his Geiger counter registered what he assumed was a proton stream. His neutron gun, crude but effective, was ready.
With neutron gun in hand, David was ready to irradiate. He could have concentrated on transforming previously non-radioactive elements, but in a decision that was both indicative of his personality and instrumental to his later attempt to build a breeder reactor, he wanted to use the gun on radioisotopes to increase the chances of making them fissionable. He thought that uranium-235, which is used in atomic weapons, would provide the “biggest reaction.” He scoured hundreds of miles of upper Michigan in his Pontiac looking for “hot rocks” with his Geiger counter, but all he could find was a quarter trunkload of pitchblende on the shores of Lake Huron. Deciding to pursue a more bureaucratic approach, he wrote to a Czechoslovakian firm that sells uranium to commercial and university buyers, whose name was provided, he told me, by the NRC. Claiming to be a professor buying materials for a nuclear-research laboratory, he obtained a few samples of a black ore—either pitchblende or uranium dioxide, both of which contain small amounts of uranium-235 and uranium-238.
David pulverized the ores with a hammer, thinking that he could then use nitric acid to isolate uranium. Unable to find a commercial source for nitric acid—probably because it is used in the manufacture of explosives and thus is tightly controlled—David made his own by heating saltpeter and sodium bisulfate, then bubbling the gas that was released through a container of water, producing nitric acid. He then mixed the acid with the powdered ore and boiled it, ending up with something that “looked like a dirty milk shake.” Next he poured the “milk shake” through a coffee filter, hoping that the uranium would pass through the filter. But David miscalculated uranium’s solubility, and whatever amount was present was trapped in the filter, making it difficult to purify further.
Frustrated at his inability to isolate sufficient supplies of uranium, David turned his attention to thorium-232, which when bombarded with neutrons produces uranium-233, a man-made fissionable element (and, although he might not have known it then, one that can be substituted for plutonium in breeder reactors). Discovered in 1828 and named after the Norse god Thor, thorium has a very high melting point, and is thus used in the manufacture of airplane engine parts that reach extremely high temperatures. David knew from his merit-badge pamphlet that the “mantle” used in commercial gas lanterns—the part that looks like a doll’s stocking and conducts the flame—is coated with a compound containing thorium-232. He bought thousands of lantern mantles from surplus stores and, using the blowtorch, reduced them into a pile of ash.
David still had to isolate the thorium-232 from the ash. Fortunately, he remembered reading in one of his dad’s chemistry books that lithium is prone to binding with oxygen—meaning, in this context, that it would rob thorium dioxide of its oxygen content and leave a cleaner form of thorium. David purchased $1,000 worth of lithium batteries and extracted the element by cutting the batteries in half with a pair of wire cutters. He placed the lithium and thorium dioxide together in a ball of aluminum foil and heated the ball with a Bunsen burner. Eureka! David’s method purified thorium to at least 9,000 times the level found in nature and 170 times the level that requires NRC licensing.
At this point, David could have used his americium neutron gun to transform thorium-232 into fissionable uranium-233. But the americium he had was not capable of producing enough neutrons, so he began preparing radium for an improved irradiating gun.
Radium was used in paint that rendered luminescent the faces of clocks and automobile and airplane instrument panels until the late 1960s, when it was discovered that many clock painters, who routinely licked their brushes to make a fine point, died of cancer. David began visiting junkyards and antiques stores in search of radium-coated dashboard panels or clocks. Once he found such an item, he’d chip paint from the instruments and collect it in pill vials. It was slow going until one day, driving through Clinton Township to visit his girlfriend, Heather, he noticed that his Geiger counter went wild as he passed Gloria’s Resale Boutique/Antique. The proprietor, Gloria Genette, still recalls the day when she was called at home by a store employee who said that a polite young man was anxious to buy an old table clock with a tinted green dial but wondered if she’d come down in price. She would. David bought the clock for $10. Inside he discovered a vial of radium paint left behind by a worker either accidentally or as a courtesy so that the clock’s owner could touch up the dial when it began to fade. David was so overjoyed that he dropped by the boutique later that night to leave a note for Gloria, telling her that if she received another “luminus [sic] clock” to contact him immediately. “I will pay any some [sic] of money to obtain one.”
To concentrate the radium, David secured a sample of barium sulfate from the X-ray ward at a local hospital (staff there handed over the substance because they remembered him from his merit-badge project) and heated it until it liquefied. After mixing the barium sulfate with the radium paint chips, he strained the brew through a coffee filter into a beaker that began to glow. This time, David had judged the solubility of the two substances correctly; the radium solution passed through to the beaker. He then dehydrated the solution into crystalline salts, which he could pack into the cavity of another lead block to build a new gun.
Whether David fully realized it or not, by handling purified radium he was truly putting himself in danger. Nevertheless, he now proceeded to acquire another neutron emitter to replace the aluminum used in his previous neutron gun. Faithful to Erb’s instructions, he secured a strip of beryllium (which is a much richer source of neutrons than aluminum) from the chemistry department at Macomb Community College—a friend who attended the school swiped it for him—and placed it in front of the lead block that held the radium. His cute little americium gun was now a more powerful radium gun. David began to bombard his thorium and uranium powders in the hopes of producing at least some fissionable atoms. He measured the results with his Geiger counter, but while the thorium seemed to grow more radioactive, the uranium remained a disappointment.
Once again, “Professor Hahn” sprang into action, writing his old friend Erb at the NRC to discuss the problem. The NRC had the answer. David’s neutrons were too “fast” for the uranium).
He would have to slow them down using a filter of water, deuterium, or tritium. Water would have sufficed, but David likes a challenge. Consulting his list of commercially available radioactive sources, he discovered that tritium, a radioactive material used to boost the power of nuclear weapons, is found in glow-in-the-dark gun and bow sights, which David promptly bought from sporting-goods stores and mail-order catalogues. He removed the tritium contained in a waxy substance inside the sights, and then, using a variety of pseudonyms, returned the sights to the store or manufacturer for repair—each time collecting another tiny quantity of tritium. When he had enough, David smeared the waxy substance over the beryllium strip and targeted the gun at uranium powder. He carefully monitored the results with his Geiger counter over several weeks, and it appeared that the powder was growing more radioactive by the day.
Now seventeen, David hit on the idea of building a model breeder reactor. He knew that without a critical pile of at least thirty pounds of enriched uranium he had no chance of initiating a sustained chain reaction, but he was determined to get as far as he could by trying to get his various radioisotopes to interact with one another. That way, he now says, “no matter what happened there would be something changing into something—some kind of action going on there.” His blueprint was a schematic of a checkerboard breeder reactor he’d seen in one of his father’s college textbooks. Ignoring any thought of safety, David took the highly radioactive radium and americium out of their respective lead casings and, after another round of filing and pulverizing, mixed those isotopes with beryllium and aluminum shavings, all of which he wrapped in aluminum foil. What were once the neutron sources for his guns became a makeshift “core” for his reactor. He surrounded this radioactive ball with a “blanket” composed of tiny foil-wrapped cubes of thorium ash and uranium powder, which were stacked in an alternating pattern with carbon cubes and tenuously held together with duct tape.
David monitored his “breeder reactor” at the Golf Manor laboratory with his Geiger counter. “It was radioactive as heck,” he says. “The level of radiation after a few weeks was far greater than it was at the time of assembly. I know I transformed some radioactive materials. Even though there was no critical pile, I know that some of the reactions that go on in a breeder reactor went on to a minute extent.”
Finally, David, whose safety precautions had thus far consisted of wearing a makeshift lead poncho and throwing away his clothes and changing his shoes following a session in the potting shed, began to realize that, sustained reaction or not, he could be putting himself and others in danger. (One tip-off was when the radiation was detectable through concrete.) Jim Miller, a nuclear-savvy high-school friend in whom David had confided, warned him that real reactors use control rods to regulate nuclear reactions. Miller recommended cobalt, which absorbs neutrons but does not itself become fissionable. “Reactors get hot, it’s just a fact,” Miller, a nervous, skinny twenty-two-year-old, said during an interview at a Burger King in Clinton Township where he worked as a cook. David purchased a set of cobalt drill bits at a local hardware store and inserted them between the thorium and uranium cubes. But the cobalt wasn’t sufficient. When his Geiger counter began picking up radiation five doors down from his mom’s house, David decided that he had “too much radioactive stuff in one place” and began to disassemble the reactor. He placed the thorium pellets in a shoebox that he hid in his mother’s house, left the radium and americium in the shed, and packed most of the rest of his equipment into the trunk of the Pontiac 6000.