"Rufus" - the core to a 3rd nuclear bomb that was to be dropped on Japan. It was only 4 days away from being shipped out from the American nuclear program's base of operations at Los Alamos to be fitted in the shell of a "Fat Man"-style implosion bomb when the Emperor himself surrendered on August 15th, 1945.
About 13 and a half pounds of metallic material, mostly Plutonium, in a sphere that was 3.5 inches in diameter.
That's smaller than a baseball, but slightly larger than the cue ball in a billiards set. Either way, you could easily hold it in the palm of your hand.
That's all you need... to flatten a city and kill everyone in it.....
And though the body count wouldn't be anywhere near the estimated 200,000 that died in the nuclear bombings of Hiroshima and Nagasaki, Rufus would kill just enough people in its' short life that it would earn the nickname "The Demon Core"
With the bombing called off, the Los Alamos scientists had a unique opportunity to use the core, far too expensive to have produced just to tinker with, to test on.
Specifically, they were interested in just how close it could be brought to criticality (the point at which nuclear reaction can self-sustain) without actually going critical. As-built, the core was 5% below this limit as a safety feature. It's important to note, passing this threshold would not make the thing explode in a mushroom cloud, that's a phenomenon called Prompt
SUPERcriticality and can only be achieved by using lenses of explosive material to compact it into a much tighter space and do it so rapidly that it doesn't have a chance to stabilize itself by shedding radioactive byproducts and heat. Still, if the core did go critical, it would release an enormous amount of ionizing radiation, the same as if you were to stand directly next to a nuclear reactor and have someone turn it on, so, not a good idea....
No points for guessing what happened only a week after the bomb it was intended for was canceled.
On August 21st of that year, Physicist Harry Daghlian Jr was working on the core in a lab, alone and in violation of safety protocol. He had been stacking a series of tungsten carbide bricks around the core to act as neutron reflectors. The purpose of these blocks of dense and heat resistant material was to take neutrons that had escaped without impacting any of the other plutonium atoms and reflect them back into the core, thereby increasing the number of free neutrons flying around, upping the rate of fission, and inching \that much closer to critical.
As he worked, he accidentally dropped one of these bricks directly on top of the core. Though he swatted it away almost instantly, it was too late. A fatal dose of radiation had blasted Daghlian who would slip into a coma and die 25 days later of acute radiation poisoning. The pictures of his bare hand after he used it to pick up the brick off the critical core are
not for the squeamish.
Incredibly, this mishap didn't seem to dampen the other scientists from continuing to toy with Rufus. A new procedure was developed that was supposedly "safer". In this protocol, the core would be sandwiched between two hemispheres of reflective beryllium. The top one would be lowered until it rested on a set of shims that would keep it from closing completely, this tiny slit between the two providing room for just enough neutrons to leak out and prevent criticality.
Naturally, being so perilously close to disaster proved an irresistible compulsion for one scientist, Louis Slotin, to "Tickle the dragon's tail" , a term he used for removing the safety shims and holding the two hemispheres apart with only the tip of a flathead screwdriver. It was a trick he supposedly sometimes performed for no other reason than to amaze onlookers.
No less an authority than famed Italian nuclear physicist Enrico Fermi had warned him that if he kept it up, he'd be "Dead within a year".
It didn't even take that long.
On May 21st, 1946, Slotin was demonstrating the core and his "tickling" procedure to a group of new scientist that were slated to take over research when the inevitable happened. Slotin's hand slipped, the screwdriver pulled out, and the two reflectors came completely together.
Despite it being daytime and in a room with large windows, everyone present testified they saw a bright blue flash and felt the heat as the core went critical, again.
Like Daghlian, Slotin immediately stopped the reaction by pulling the upper reflector off, but it was already too late, and he knew it. He reportedly told physicist Alvin Graves, standing nearby "Well, that does it".
In all, seven men in the room were exposed to high levels of radiation, but only Slotin's dose would prove fatal. Having been standing directly over the core at the time of the incident, it was later estimated he'd received double the amount of radiation needed to kill him. Rushed to hospital immediately, Slotin's condition still deteriorated rapidly, and he died only nine days later. His doctors, describing his condition to the press, said Slotin was "Suffering a three dimensional sunburn". Several of the others present also had to be treated for acute radiation poisoning, and would survive, albeit with long-term effects on their health.
The second accident delayed the core's scheduled inclusion into the famous "Crossroads" nuclear test (the one where that cluster of obsolete warships get blown up) and the reputation of it was such that aside from earning it's macabre "Demon Core" nickname, it was thought best to quietly ship it back to be melted down and re-integrated into the military's stockpile of weapons material.
It also finally drilled into the heads of the scientific community that working hands-on with radioactive materials was too dangerous, and safety procedures changed again so that only remote controlled robots and mechanical arms, viewed by closed circuit TV as they worked, could be used to conduct further research on such things.
Which is really the most amazing thing about it all, two men, who surely knew the risks of what they were doing, especially after Daughlian's mistake, continued to be cavalier to the point of near-suicide around things they should, by all conventional wisdom, know how to avoid dying to.
