There are conflicting reports about what went wrong. An onlooker said Slotin’s approach on this occasion was “improvised”. Others said what he did was perfectly normal. In Schreiber’s official report, he said Slotin acted “too rapidly and without adequate consideration”, but that the others in the room “by their silence, agreed to the procedure”.
The screwdriver slipped and the upper reflector enclosed the core. The screwdriver slipped and the upper reflector enclosed the core.
“I turned because of some noise or sudden movement,” wrote Schreiber. “I saw a blue flash… and felt a heat wave simultaneously.” It seems the screwdriver had slipped and the plutonium had gone “prompt critical” as the reflector dropped down over it. It happened, as Schreiber wrote, in “a few tenths of a second.” Slotin flipped the upper reflector to the floor, but his reaction was already too late. In the moments after the accident, the room was silent.