26 November 1991 - Last UK nuclear test
On 26 November 1991, the last British nuclear test, code-named Julin Bristol, took place at the Nevada Test Site (renamed Nevada National Security Site in 2010) in the United States. The explosion had a yield below 20 kilotons and was part of the development of the most recent generation of UK nuclear warheads, designed for the submarine-based Trident missiles. In contrast to previous versions, the latest warhead featured a novelty － the dial-a-yield function which allowed the operator to specify the yield, with ranges from a sub-kiloton to 100 kilotons.
The United Kingdom started its nuclear testing programme in 1952 with the ‘Hurricane’ test, conducted in Australia with the permission of the Australian government. A few years later, the United Kingdom relocated its nuclear testing programme to remote atolls in the central Pacific Ocean, where it demonstrated its ability to develop thermonuclear weapons in the ‘Grapple’ testing series.
This led to the conclusion of the 1958 UK-US Mutual Defense Agreement. From then on, both countries cooperated closely in their nuclear weapons programmes, the UK participating in many of the U.S. nuclear tests conducted at the Nevada Test Site. At 45, the number of nuclear tests directly attributed to the United Kingdom (only) is therefore relatively low.
Nuclear testing at Nevada had started in 1951 and amounted to 928 of a total of 1,032 U.S. nuclear tests. Some of the mushroom clouds were visible at distances of up to 160 kilometres, even becoming a tourist attraction in Las Vegas. The last test conducted at Nevada was the ‘Divider’ test on 23 September 1992.
Today, the test site is highly contaminated with radioactivity. Radionuclides and radioactive noble gases which were transported up to thousands of miles away from the test site exposed populations in different parts of the United States to varying levels of radiation; settlements in the vicinity, or downwind, of the test site received the highest doses. The U.S. government had issued assurances in the 1950s that the tests were harmless; see for example the 1955 brochure Atomic Test Effects in the Nevada Test Site Region. An increase in leukaemia in people living downwind of the Nevada Test Site is documented in the 1982 publication Killing Our Own: The Disaster of America’s Experience with Atomic Radiation (PDF).
Five years after the Julin Bristol nuclear test, the United Kingdom signed the Comprehensive Nuclear-Test-Ban Treaty on 24 September 1996, the day it opened for signature. Together with France, it was the first nuclear weapon possessor State to ratify the Treaty two years later on 6 April 1998.
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