It was built in the 1940s as part of the "Manhattan Project" to develop the first atomic weapon during World War II.

CNN: Federal funds aim to clean up nuclear wasteland

Perhaps the most spectacular failure of the United States was in misjudging how soon the former Soviet Union ended America's nuclear monopoly in August 1949 by testing its own atomic weapon.

CENTERFORSECURITYPOLICY: Questionable intelligence on Iran

The Obama administration has staunchly opposed allowing countries seeking nuclear-cooperation with the U.S. to engage in enrichment or reprocessing, because either path could be used to create the fissile material required to create an atomic weapon.

WSJ: Seoul Seeks Ability to Make Nuclear Fuel

U.S. and United Nations officials have documented what they describe as serious limitations in Iran's ability to quickly and efficiently produce the enriched uranium required to either fuel a nuclear power reactor or to build an atomic weapon.

WSJ: North Korea Nuclear Find Raises Fears It Will Share With Iran

It weighed about 10 tonnes when it entered the Earth's atmosphere and broke apart 30-50km (20-30 miles) above ground, according to Russia's Academy of Sciences, releasing several kilotons of energy - the equivalent of a small atomic weapon.

BBC: Russia sends clean-up team to meteorite-hit Urals

India and Pakistan declared themselves nuclear weapon states when they tested atomic bombs in 1998.

NPR: Nuclear Weapons Gain Importance for Regional Powers