Contacts: Daryl Kimball, Executive Director, (202) 463-8270 x107

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, including Lop Nor in China, the atolls of the Pacific, Nevada, Algeria where France conducted its first nuclear device, western Australia where the U.K. exploded nuclear weapons, the South Atlantic, 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. The 1963 Limited Test Ban Treaty brought about the end of most, but not all, nuclear test explosions in the atmosphere. However, many underground nuclear blasts have also vented radioactive material into the atmosphere and left radioactive contamination in the soil.

Type of Test United States USSR/ Russia United Kingdom France China India Pakistan North Korea Total Atmospheric 215 219 21 50 23 0 0 0 528 Underground 815 496 24 160 22 3 2 6 1,528 Total 1,0301 (Note: does not include atomic bombings of Hiroshima and Nagasaki.) 715 45 210 45 3 2 6 2,056



Through nuclear test explosions, the nuclear testing nations have been able to proof-test new warhead designs and create increasingly sophisticated nuclear weapons. The overwhelming majority of the nuclear weapon test detonations were for "weapons development" and "weapons effects" purposes.

Following Russian and U.S. nuclear testing moratoria, multilateral negotiations on a global Comprehensive Test Ban Treaty (CTBT) began in 1994 and were concluded in 1996. 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 an international test monitoring and verification system, has not yet entered into force.