The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the central control rod, responsible for absorbing neutrons in the reactor core. The event is the only known fatal reactor accident in the United States. The accident released about 80 curies (3.0 TBq) of Iodine-131, which was not considered significant due to its location in a remote desert of Idaho. About 1,100 curies (41 TBq) of fission products were released into the atmosphere.
The facility, at the National Reactor Testing Station about 40 miles (64 km) west of Idaho Falls, Idaho, was part of the Army Nuclear Power Program and was known as the Argonne Low Power Reactor (ALPR) during its design and build phase. It was intended to give electrical power and heat for small, remote military facilities, such as radar sites near the Arctic Circle, and those in the DEW Line.
The Distant Early Warning (DEW) Line, was a system of radar stations in the far northern Arctic region of Canada, with more stations along the North Coast and Aleutian Islands of Alaska, in addition to the Faroe Islands, Greenland, and Iceland. It was set up to detect incoming Soviet bombers during the Cold War, and give early warning of any sea-and-land invasion.
The bodies of all three were buried in lead-lined caskets sealed with concrete and placed in metal vaults with a concrete cover. Some highly radioactive body parts were buried in the Idaho desert as radioactive waste. Army Specialist Richard Leroy McKinley is buried in section 31 of Arlington National Cemetery.
Further information about the SL-1 reactor accident can be found at http://en.wikipedia.org/wiki/Sl-1