A Brief History of Nuclear Accidents Worldwide

Serious accidents at nuclear power plants have been uncommon—but their stories teach us the importance of nuclear safety.

SL-1

Idaho Falls, Idaho, USA, January 3, 1961

The withdrawal of a single control rod caused a catastrophic power surge and steam explosion at the SL-1 boiling water reactor that killed all the workers on duty at the time.

How did it happen?
On January 3, 1961, workers were in the process of reattaching to their drive mechanisms control rods they had disconnected earlier that day to enable test equipment to be inserted in the reactor core. They lifted the central control rod 20 inches, instead of the four inches that was required. This error caused the reactor to go critical and its power to surge 6,000 times higher than its normal level in less than a second. As a result, nuclear fuel vaporized and a steam bubble was created. The steam bubble expanded so quickly that it pushed water above it against the reactor vessel, which caused it to jump out of its support structure. It hit an overhead crane and then returned to the reactor vessel. In the process, all of the water and some of the fuel was released from the reactor vessel. All three workers on duty received lethal doses of radiation, in addition to trauma from the explosion.

Serious accidents at nuclear power plants have been uncommon—but their stories teach us the importance of nuclear safety.