In 1946, physicist Louis Slotin was conducting a dangerous experiment at Los Alamos Laboratory using a plutonium sphere dubbed the "Demon Core."
The procedure, ominously nicknamed "tickling the dragon's tail," required him to keep two halves of a beryllium reflector slightly separated around the radioactive core.
Ignoring standard safety protocols, Slotin used only a flathead screwdriver to wedge the heavy halves apart.
On May 21, the screwdriver slipped. The upper hemisphere fell into place, instantly triggering a supercritical chain reaction. A blinding blue flash of ionized air filled the room, accompanied by a sudden wave of intense heat.
Reacting instantly, Slotin knocked the top hemisphere away, saving the lives of the seven other scientists present in the room.
However, he had already absorbed a highly concentrated, lethal dose of neutron radiation in a fraction of a second.
He immediately experienced a sour taste in his mouth, and his health rapidly declined. After suffering extreme blistering, intestinal paralysis, and total organ failure, Slotin died nine days later.
The core, which had killed another scientist just months prior, was eventually melted down.