Since the first nuclear test explosion on 16 July 1945, at least eight states have conducted a total of at least 2,050 nuclear test explosions at dozens of test sites around the world. After North Korea's last test detonation in 2017, concern was expressed at heightened seismic activity following the test and the risk of radiation escape. Pyongyang announced a moratorium on nuclear testing in April 2018 (and destroyed the Punggye-ri test site in May 2018) but declared an end to this moratorium on 31 December 2019.
India and Pakistan both exploded nuclear devices in 1998. The United Kingdom undertook its last explosive test in 1991. France completed its last nuclear explosive test in 1996 and completely dismantled its nuclear testing site in the Pacific. The United States conducted its last explosive tests in 1992, but in November 2017 the US government decided to shorten its testing readiness timeline from between 24 and 36 months to between 6 to 10 months ‘for a simple test’. Information disclosed by The Washington Post in May 2020 reported discussions by senior US national security officials about the option of a demonstration nuclear blast as a political signal to Russia and China.
China’s last explosive nuclear test was in July 1996, only a few months prior to the adoption of the CTBT by the UN General Assembly. The Soviet Union/Russia undertook its last known explosive test in 1990. In late May 2019, a senior US official accused China and Russia of potentially having conducted low-yield explosive testing of nuclear weapons but did not adduce any evidence in support of this assertion. Other authorities within the US Government, however, contested the official’s allegations, as did China and Russia. Furthermore Lassina Zerbo, head of the CTBTO, said that the ‘international monitoring system has been operating as normal and has not detected any unusual event’.
In September 1979, a flash over the Indian Ocean detected by a US satellite (Vela) was suspected of being a South African nuclear test, conducted in collaboration with Israel. This was never confirmed officially by either of these states.
For information on the effects of nuclear testing please refer to the sections on the obligation to assist victims and the obligation to remediate affected territory.