Harry Daghlian's Criticality Accident

Date: August 21, 1945 • Location: Washington, United States

American physicist Harry Daghlian accidentally dropped a tungsten carbide brick onto a plutonium bomb core, exposing himself to neutron radiation and later becoming the first Manhattan Project fatality due to a criticality accident.

Haroutune Krikor Daghlian Jr. was an American physicist involved in the Manhattan Project, which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico and died 25 days later from the resultant radiation poisoning.