List of Military Nuclear Accidents - 1940s

1940s

• June 23, 1942 – Leipzig, Germany (then Nazi Germany) – Steam explosion and reactor fire*
  • Shortly after the Leipzig L-IV atomic pile — worked on by Werner Heisenberg and Robert Doepel — demonstrated Germany's first signs of neutron propagation, the device was checked for a possible heavy water leak. During the inspection, air leaked in, igniting the uranium powder inside. The burning uranium boiled the water jacket, generating enough steam pressure to blow the reactor apart. Burning uranium powder scattered throughout the lab causing a larger fire at the facility.

• August 21, 1945 – Los Alamos National Laboratory, Los Alamos, New Mexico, USA – Accidental criticality
  • Harry K. Daghlian, Jr. dropped a tungsten carbide brick onto a plutonium core, inadvertently creating a critical mass at the Los Alamos Omega site. He quickly removed the brick, but was fatally irradiated, dying September 15.
• May 21, 1946 – Los Alamos National Laboratory, Los Alamos, New Mexico, USA – Accidental criticality
  • While demonstrating his technique to visiting scientists at Los Alamos, Canadian physicist Louis Slotin manually assembled a critical mass of plutonium. A momentary slip of a screwdriver caused a prompt critical reaction. Slotin died on May 30 from massive radiation poisoning, with an estimated dose of 1,000 rads (rad), or 10 grays (Gy). Seven observers, who received doses as high as 166 rads, survived, yet three died within a few decades from conditions believed to be radiation-related.

In the above incidents, both Daghlian (August 21, 1945 case) and Slotin (May 21, 1946 case), were working with the same bomb core which became known as the "demon core".