Criticality and Radiation Accidents

The nuclear weapons industry, like any other large industrial enterprise, is subject to the normal range of accidents from vehicle wrecks to falls from a height. These accidents are by far the most common that happen. There is one class of accident that is unique to the nuclear industry: criticality accidents, where an amount of fissile material accidentally comes together into a supercritical amount. There is a sudden release of energy and deadly radiation.

Criticality Accidents -- The Dragon Bites

The "Dragon Experiment" was the first attempt to create a temporarily critical mass of fissionable material by sliding a slug of Uranium-235 hydride through a larger mass of the same substance. These manual experiments continued with the hemispheres of plutonium used in the Trinity test bomb, the Fatman, and the bombs used at Operation Crossroads in 1946. There were numerous "criticality accidents" with run-away output of energy and radiation. Within a year of the Trinity test, these accidents would claim the lives of two members of the team that assembled the plutonium core at Trinity: Harry Daghlian and Louis Slotin.

Louis Slotin Accident Diagram

Illustration of Louis Slotin Accident

Photo of Godiva Reactor replica.

Photo of Godiva Reactor replica.

The Atomic Energy Commission, under its mandate from Congress, reported all criticality and radiation accidents in the following documents. The use of understatement is astounding, as when the "Table of Criticality Accidents" lists the accidents involving Harry Daghlian and Louis Slotin, but neglects to include that fact that fatalities were involved. Also note that these reports only relate to direct Atomic Energy Commission installations and do not reports accidents in commercial nuclear power plants nor any accidents that occurred within the military.

Table of Criticality Accidents, 1945-1970

A summary table of criticality accidents under the U.S. Atomic Energy Commission.

Summary Descriptions of Criticality Accidents, 1945-1970

A short paragraph describes the circumstances of the accident.

Radiation Exposures exceeding 15 REM whole-body exposure, 1945-1970

A short summary paragraph for each radiation incident. Some criticality incidents are also reported.