Harry K. Daghlian, Jr., a scientist working on the Manhattan Project at the Los Alamos Laboratory in New Mexico, became the first person in history to die in a nuclear criticality event. While preparing a bomb for the Operation Crossroads series of nuclear tests, Daghlian accidentally dropped a tungsten-carbide brick onto a plutonium-gallium alloy bomb-core, causing it to go supercritical. Daghlian received an estimated 510 REM of neutron radiation and quickly developed severe radiation poisoning. He died in a coma 25 days after the initial incident.
Submission by Logan Agle. Thank you.