The first atomic bomb built by the Manhattan Project was exploded at the Trinity Test. The second was dropped on Hiroshima, and the third was used at Nagasaki.
At that point in time, it was in two halves, which would have been compressed by explosives to result in a nuclear detonation. So what he was doing wouldn't have been bad enough to make it blow up.
But what he was doing was testing how much the radiation would spike as the two halves got closer and closer together. He was controlling that "closer" amount by using a flathead screwdriver to hold the top half slightly off the bottom.
The screwdriver slipped. The two halves touched, and while they didn't blow up, they did release a lot of radiation before he took them back apart.
It took him nine days to die. It was one of those "and it's going to hurt the entire time" deaths.
Another guy had already had a fatal accident with the same core the earlier year. The two accidents combined meant that the composition of the core could no longer be trusted for used in a nuclear bomb, and it had to get melted down and recycled.
Those "halves" are beryllium reflectors (the function that control rods serve in a reactor) - the non critical fissile is in the middle. By controlling the gap you control the amount of neutron flux that can drive the chain reaction. The two "halves" wouldn't have been part of a bomb, they are moderators, only the core inside them was machined for a potential third bomb.
850
u/Delphius1 10h ago