
Fifty years ago, on July 3, the Soviet Union and the US signed the Treaty on the Limitation of Underground Nuclear Weapon Tests. The subsequent Comprehensive Nuclear-Test-Ban Treaty (CTBT) in 1996 never came into force. Eight of the 44 countries that had nuclear potential and technology at the time – Egypt, India, Iran, Israel, China, North Korea, Pakistan, and the US – either did not sign it or failed to ratify it. Russia renounced the treaty in 2023 — but said this does not mean that it intends to conduct nuclear tests.
Since the first US nuclear test on July 16, 1945, more than 2,000 blasts have been conducted by at least eight nations, according to the Arms Control Association.
- The US leads in number of tests (1032). Like the USSR (715), France (210), UK (45) and China (45), it carried out most tests before the NPT in 1968.
- India and Pakistan conducted tests in 1998 but then adopted unilateral moratoriums.
- The Russian Federation has never tested nuclear weapons. The USSR conducted its last underground nuclear explosion in 1990 at the Novaya Zemlya test site.
- The UK’s last test of a reported 11-kiloton Trident nuclear warhead in Nevada, codenamed ‘Julin Bristol,’ was conducted in 1991.
- The last US nuclear test ‘Shot Divider’ took place in 1992 in Nevada.
- France conducted its last blast at the Moruroa and Fangataufa Atoll test site in the South Pacific in 1996.
- China conducted its last nuclear test in 1996.
- The DPRK broke its test moratorium in 2006, 2009, 2013, 2016 and 2017. On September 3 2017, it tested a hydrogen bomb with a yield of over 100 kilotons of TNT.
Underground explosions make up about 75% of all tests. The UN has warned that some countries may still conduct nuclear tests in secret. The US suspended underground tests in 1992 but began ‘subcritical’ tests five years later. An experiment at the Nevada site on October 18, 2023, used chemical high explosives. Another ‘subcritical’ experiment was held on May 14, 2024. The US claims those tests do not produce a self-sustaining chain reaction, and comply with the zero-yield standard of the Comprehensive Nuclear-Test-Ban Treaty.
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