Dr Hahn or: How I Learned to Stop Worrying and Love the Bomb.
One of the more unusual merit badges you used to be able to get as an Eagle Scout in America was the Atomic Energy badge. To get this badge, you had to be able to describe how fission happens and also build a working device that uses or detects a radiation source, such as an electroscope, Geiger counter or cloud chamber.
One such overeager Michigan Eagle Scout decided to take things a bit further and try to build his own breeder nuclear reactor. A breeder reactor is one where it ‘breeds’ more fissile fuel than it consumes — it could, in theory, extract all the energy from uranium or thorium. Compared to light water reactors, which only extract around 1% of the energy in uranium, they are very fuel efficient and remarkably powerful.
In the early 1990’s, David Hahn was fascinated by chemistry and the periodic table; he frequently conducted amateur experiments at home, even going as far as making nitroglycerine in his mid teens. He decided to try and collect a sample of every element known, even the extremely rare and radioactive ones.
All of this led David to want to build his own neutron gun, in order to generate his own uranium. Now, most people wouldn’t have the first clue about how to actually do this, but David was resourceful and armed with a small amount of knowledge about how radiation worked.
Smoke detectors are a decent source for radioactive material, specifically americium-241, an alpha-particle emitter. Alpha particles are two protons and two neutrons bound together into a particle identical to a helium nucleus. These are very safe, as even the thin plastic shell around the smoke detector is more than thick enough to shield from alpha particles, but David managed to buy about a hundred broken detectors cheaply.
Not knowing exactly where the americium-241 was located inside, he wrote to an electronics company in Illinois, posing as a high school teacher. The customer service representative there helped him with his enquiry and thanks to the information he got, he managed to extract the americium-241.
Now armed with an alpha emitter, he placed it inside a hollow block of lead with a small hole drilled into the side that would act as the gun barrel, allowing a thin stream of alpha particles to stream out. In front of this block, he placed a sheet of aluminium, the atoms of which would emit neutrons as the alpha particles slammed into them. Since neutrons have no charge, and therefore can’t be measured by a Geiger counter, David had no way of knowing whether the gun was working or not until he recalled that paraffin throws off protons when hit by neutrons. David aimed his makeshift neutron gun at some paraffin, and his Geiger counter registered what he assumed was a proton stream. His neutron gun was ready and waiting to use.
In order to use his gun to obtain uranium, he needed a source. Again, armed with his chemistry knowledge, he knew that the mantles on gas lanterns (the cloth pouch that fits over the flame) contained a compound that contains thorium-232. Thorium-232, when bombarded with neutrons, produces uranium-233, which can be used as fissionable fuel. He bought thousands of lantern mantles from surplus stores and proceeded to grind them into powder, before using a blowtorch to burn them to ash.
To isolate the thorium, he needed lithium. He bought close to $1000 worth of lithium batteries and extracted the lithium by cutting the batteries in half. He then mixed the lithium with the mantle ash, wrapped the whole thing in aluminium foil and heated it with a bunsen burner. The lithium purified the thorium from the ash, leaving him with thorium that was about 9000 times as pure as found in nature and 170 times the level that requires mandatory licensing from the Nuclear Regulatory Commission in the US.
Now he had his thorium, he turned his neutron gun on it to try and convert it into uranium. Depending on your point of view, fortunately or unfortunately, it just wasn’t powerful enough.
Undeterred, David devised a more powerful gun, using radium as the power source. He drove miles, seeking out junk shops that stocked old radium paint coated clocks. He’d chip the paint off and collect it. One day, his Geiger counter went wild outside a junk shop — inside was a clock in which a small tin of radium paint had been left behind. He snapped it up and took it home.
David secured a sample of barium sulphate from a local hospital X-ray ward at and heated it until it liquefied. He then mixed the paint and paint chips he had collected with the liquid and strained the brew through a coffee filter into a beaker that began to glow. He heated the mixture until it crystallised. At this point, he was standing near to a very potent source of radiation.
He packed the salts into another lead container, pricked a small hole in one side and now all he needed was a source of neutrons. Aluminium wasn’t up to the task, so he settled on beryllium; a friend who attended the nearby Macomb Community College stole a strip from the chemistry classroom there. He secured the strip in front of the hole and pointed it at the thorium ash in the hopes that it would begin to produce uranium.
Whilst the thorium ash became more and more radioactive, he was disappointed that no uranium was being created. Using the pseudonym “Professor Hahn”, he wrote to the NRC to enquire about it. Dutifully, they wrote back to tell him that his neutrons were too fast for uranium formation, he needed a way to slow them down.
In order to slow neutrons, David needed a neutron moderator — the most common of which are water, deuterium or tritium. He could have used water, as it was the easiest to obtain, but as we know by now, David liked a challenge. He learnt that glow in the dark gun sights have a tiny amount of tritium in them, so he bought them, removed the tritium and returned them saying that they needed repairing. He’d get the sight back, remove the tritium again and repeat the process. After collecting enough tritium, he smeared the beryllium with the waxy tritium and pointed the gun at the thorium once again.
David then decided he wanted to build a model breeder reactor. Although he knew that without a critical pile of at least 15 kg 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 radioactive materials to interact with one another.
His blueprint was a diagram of a breeder reactor he’d seen in one of his father’s college textbooks. David took the radium and americium out of their respective lead casings and, after another round of filing and mixing, mixed those materials with the 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.
After a couple of weeks, David noticed that the level of radioactivity was significantly higher than when he had begun, to the point when he finally figured out that he could be putting himself, and others, in serious danger.
When his Geiger counter began picking up radiation five doors down from his mother’s house, David realised that he had “too much radioactive stuff in one place” and began to break up the reactor. He placed the thorium in a shoebox that he hid in his mother’s house, left the radium and americium in his shed, and packed most of the rest of his equipment into the boot of his car.
Someone called the police to alert them to a suspicious character who had been apparently stealing tires from a car. When they arrived and found David, they discovered a toolbox shut with a padlock and sealed with duct tape. The car also contained over fifty foil wrapped cubes of powder, small disks and cylindrical metal objects, lantern mantles, mercury switches, a clock face, various ores, fireworks, vacuum tubes, and assorted chemicals and acids. The police were especially alarmed by the toolbox, which David warned them was radioactive and which they feared was an atomic bomb.
The police called in the Michigan State Police Bomb Squad to examine the car and the State Department of Public Health (DPH) to supply radiological assistance. They found David’s car contained radioactive materials, including concentrations of thorium ”not found in nature, at least not in Michigan”. That discovery automatically triggered the Federal Radiological Emergency Response Plan, and state officials soon were embroiled in tense phone consultations with the DOE, EPA, FBI, and NRC.
Almost a year after David had been searched by the police, the cleanup was completed. The cleanup necessitated thirty-nine sealed barrels, which were sent to Envirocare, a dump facility located in the middle of the Great Salt Lake Desert. There, the remains of David’s experiments were entombed along with tons of low-level radioactive debris from the government’s atomic-bomb factories, plutonium-production facilities, and contaminated industrial sites.
According to the official assessment, there was no noticeable damage to flora or fauna in the back yard in Golf Manor, but 40,000 nearby residents could have been put at risk during David’s experiments due to the dangers posed by the release of radioactive dust and radiation. A tin can found, for example, registered at 50,000 counts per minute; about 1,000 times higher than normal levels of background radiation. David’s mother, however, terrified that the government would seize her house, had almost completely the shed and threw away most of what was there, including his neutron gun, the radium, pellets of thorium that were far more radioactive than what the officials found, and several kg of radioactive powder. As David later said “They only got the garbage, and the garbage got all the good stuff.”
