There were three atomic bombs originally destined for Japan. American pilots dropped the bomb code-named "Little Boy" over Hiroshima and the one called "Fat Man" over Nagasaki. The bombs carried cores containing uranium and plutonium, respectively, and immediately killed 200,000 people in the two Japanese cities.
The third core remained unexploded and was returned to physicists working at the Los Almos National Laboratory in New Mexico, reports Kyle Hill for Nerdist. There, scientists studied what would be dubbed "The Demon Core," in an attempt to figure out what caused the chain-reaction of atomic jostling that leads to an explosion.
Tests on the core would claim the lives of two people—Harry K. Daghlian, Jr., who had returned late at night to do one more test, and Louis Slotin, who would pick up where Daghlian had left off and die seven months after his colleague. Both accidents were accompanied by a "blast of blue light and a wave of heat," Hill writes. And days after their exposures, the men close to the core died of severe radiation poisoning.
Slotin’s accident was traced to his habit of using a screwdriver to lower the reflective half-sphere over the core, instead of using spacers that would keep the sphere from closing. That strategy worked for him many times, just not the last. When the screwdriver slipped, that blast of light betrayed what had happened, and Slotin quickly flipped the half-sphere off the core.
But it was too late. Slotin had been "exposed to almost 1,000 rads of radiation, far more that a lethal dose," wrote Martin Zeilig in 1995 for The Beaver, according to The Manhattan Project Heritage Preservation Association. A colleague standing three to four feet away was exposed to 90 to 100 rads. Two of the men in the room would die 19 years later of conditions known to be linked to radiation exposure.
The accident was dramatized in the 1989 movie "Fat Man and Little Boy."
Slotin’s accident put an end to the experiments, which Richard Feynman had likened to "tickling the tail of a sleeping dragon," and the demon core met its end in a detonation over the Bikini Atoll during atomic tests.