"South Africa was isolated from interactions and activities with most of the developed countries for many years because of its nuclear weapons development program and the practice of apartheid. This isolation was especially true in the areas of nuclear energy and its applications. South Africa developed a complete nuclear fuel cycle, including advanced waste management techniques. South Africa operates two nuclear power reactors (built by the French, but based on a Westinghouse design) at Koeberg near Cape Town.
South Africa also acquired the technology to build nuclear weapons. South Africa developed at least six nuclear warheads, which it later acknowledged, along with a variety of missiles and other conventional weapons. These projects were undertaken with some cooperation from Israel -- another technologically advanced, militarily powerful, nuclear-capable nation surrounded by hostile neighbors.
Beginning in 1975 two test shafts over 250 meters deep for conducting nuclear tests were drilled at the Vastrap military base in the Kalahari Desert. A Soviet surveillance satellite detected these test preparationss in August 1977, and the Soviets notified the US of their discovery. South Africa was forced to cancel the tests in the face of diplomatic pressure from America, the Soviet Union, and France.
A flash over the Indian Ocean detected by an American satellite in September 1979 was suspected of being a nuclear test, possibly conducted by either Israel or South Africa, alone or in combination. the Carter administration assembled a panel of scientists from academia to review the data. After their review, the panel concluded that, lacking independent collaborative data to support a nuclear origin of the signals, the original interpretation of the satellite data could not be justified. The panel said the flash could have been caused by a combination of natural events, specifically a micrometeorite impact on the detector sunshade, followed by small particles ejected as a result of the impact.
The international fear of nuclear proliferation made South Africa the focus of intense concern during the 1980s. Cape Town academic Renfrew Christie was jailed for passing details of South Africa's nuclear power program to the African National Congress [ANC] in 1980."--Federation of American Scientists,
http://fas.org/nuke/guide/rsa/nuke/index.html