Bitten by the Nuclear Dragon
This is a classic Damn Interesting article which originally appeared on 13 October 2005. We apologize for the re-run.
After World War 2, a few of the Manhattan Project scientists remained on duty at Los Alamos to further explore the behaviors and potential of nuclear technology. Among them was Dr. Louis Slotin, who in his own words was kept around because he was “one of the few people left here who are experienced bomb putter-togetherers.”
During his time there, Dr. Slotin’s duties were to perform criticality tests on fissile uranium and plutonium. The tests required him to bring two half-spheres of the radioactive materials into close proximity, and measure the beginnings of the fission reaction. This way, scientists could indirectly determine the critical mass of the material without actually starting a nuclear chain reaction. Slotin’s preferred method of keeping the two hemispheres separated was an ordinary screwdriver, because he had a strong distrust of automated safety systems.
Dr. Richard Feynman, a fellow Los Alamos scientist, had remarked that these criticality tests were “tickling the tail of a sleeping dragon,” because they brought the fissile materials so close to a dangerous critical mass. In fact, another physicist at Los Alamos, Harry K. Daghlian, had been injured by radiation exposure during a criticality test just nine months earlier, when he accidentally dropped a brick of tungsten carbide onto a plutonium mass. Tungsten carbide is a neutron reflector, which decreases the amount of nuclear material needed to go critical. In Daghlian’s case, it caused the plutonium mass to go supercritical, bathing him in radiation. He died less than a month later from radiation sickness.
Louis Slotin’s experiment of May 21, 1946 didn’t involve such neutron reflecting bricks, but it did utilize the same plutonium cores as Daghlian’s experiment, and it was similarly ill-fated. At the secret Omega Site Laboratory, as six observers looked on, Slotin was training a colleague who was meant to replace him, one Alvin C. Graves. As Slotin demonstrated the criticality test, the screwdriver he used to separate the two sphere halves slipped, and the hemispheres came into contact.
Immediately, all eight scientists in the room felt a wave of heat accompanied by a blue glow as the plutonium sphere vomited an invisible burst of gamma and neutron radiation into the room. As the lab’s Geiger counter clicked hysterically, Louis used his bare hand to push the upper plutonium hemisphere off and onto the floor, which terminated the supercritical reaction moments after it began.
Louis, having been closest to the event, soon complained of a painful burning sensation in his left hand, and a sour taste in his mouth. His colleagues rushed him outside and into a car bound for the hospital, but he had already begun vomiting, a sign of acute radiation poisoning. The other scientists who had been in the room didn’t experience any immediate symptoms, indicating that Louis’ reflex to separate the plutonium hemispheres had spared them from a similar level of exposure. All too familiar with the consequences of such a powerful dose of radiation, he said to his colleagues in the car, “You’ll be OK, but I think I’m done for.” After arriving at the Los Alamos hospital, Slotin said to Alvin Graves, “I’m sorry I got you into this. I’m afraid I have less than a 50 per cent chance of living. I hope you have better than that.”
He had a telegram sent to his parents in Winnipeg to inform them of the accident, and a few days later, he telephoned them with the assistance of a nurse who held the receiver for him. Major-General Leslie R. Groves, the administrator of the Manhattan Project, sent a U.S. Army DC-3 to pick up his parents, and they arrived just days before he died of radiation exposure, nine days after the incident. Within the next couple of years, two of the scientists who had been observing the experiment died with symptoms of radiation sickness.
Louis Slotin is generally regarded as a hero for his quick action, and his sacrifice was indeed selfless and heroic. The true tragedy, however, is that the entire accident could have been avoided with some simple safety precautions. A better method would have been to fix the upper plutonium hemisphere in an elevated position, with a levered mechanism to lift the lower hemisphere up towards it. In the event of a problem with such an assembly, the lower hemisphere would fall harmlessly down and away. He had also neglected to use two tiny safety spacers which had been developed after his colleague had been killed by radiation nine months earlier.
As he had awaited the inevitable, the Los Alamos authorities issued a special citation, which was read to him in the hospital:
More information and links (a few factual errors in some of the linked pages)
More information on critical mass can be found found in the DamnInteresting.com article: Nature’s Nuclear Reactors
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This type of thing baffles me. I suppose that many lessons are learned through mistakes such as these, but you would think that when it comes to experimenting with nuclear materials more precaution would be taken than a mere couple of screwdrivers and some steady hands.
I am sure there are countless fatal errors such as this that are all but unknown. Even outside of that it is already very apparent some of the ill-fated results of nuclear fallout and exposure to citizens in this country due to nuclear testing in the Nevada desert.
I always find this fascinating to learn of such things. A friend of mine who attended nuclear energy school for the US Navy often commented on case studies or accidents that they were precautioned about due to highly radioactive nuclear materials… in one story he shared an incident in which some nuclear material no bigger than a marble caused paint to peel off of a wall and curl all the way to the ceiling. In another the gov’t experimented and found that exposure of materials would turn glass a dark, almost black color when in near contact to similar materials.
I guess the disturbing thing is that people actually engaged in this and that there were such lessons learned. As I have read about the effects of radiation poisoning I realize that many of these symptoms are know as a direct results of people witnessing and being exposed to radioactive materials.