Contacts: Daryl Kimball, Executive Director, (202) 463-8270 x107
Updated: February 2019
Since the first nuclear test explosion on July 16, 1945, at least eight nations have detonated 2,056 nuclear test explosions at dozens of test sites from Lop Nor in China, to the atolls of the Pacific, to Nevada, to Algeria where France conducted its first nuclear device, to western Australia where the U.K. exploded nuclear weapons, the South Atlantic, to Semipalatinsk in Kazakhstan, across Russia, and elsewhere.
Most of the test sites are in the lands of indigenous peoples and far from the capitals of the testing governments. A large number of the early tests—528—were detonated in the atmosphere, which spread radioactive materials through the atmosphere. Many underground nuclear blasts have also vented radioactive material into the atmosphere and left radioactive contamination in the soil.
Through nuclear test explosions, the testing nations have been able to proof-test new warhead designs and create increasingly sophisticated nuclear weapons. In 1996, negotiations on a global Comprehensive Test Ban Treaty (CTBT) were concluded and the treaty was opened for signature on September 24, 1996. The CTBT, which prohibits "any nuclear weapon test explosion or any other nuclear explosion" and established a international test monitoring and verification system, has not yet entered into force.
1. In accordance with the definition of a nuclear test contained in the Threshold Test Ban Treaty and to allow accurate comparison with other countries' figures, India's three simultaneous nuclear explosions on May 11 are counted as only one nuclear test, as are the two explosions on May 13. Likewise, Pakistan's five simultaneous explosions on May 28 are counted as a single test.
2. In the article "Radionuclide Evidence for Low-Yield Nuclear Testing in North Korea in April/May 2010," Lars-Erik De Geer argued that the xexon and barium isotope concentrations in air currents from North Korea in April and May of 2010 were consistent with two low-yield nuclear tests. However, this theory was largely debunked when the Earth Institute at Columbia University measured seismology records and determined that no well-coupled explosion larger than one ton could have occurred during that timeframe. According to the report, such a low yield explosion would have been incapable of advancing the North Korean's technical understanding of a nuclear weapon explosion.