The Republic of South Africa is the first and only nation to have successfully developed nuclear weapons, and then voluntarily relinquished that capability. The decision to completely destroy weapons related technology and information was to keep nuclear weapons out of the hands of the black-led government.
In a 24 March 1993 speech, President de Klerk not only revealed that South Africa had produced nuclear weapons, but that the arsenal had been destroyed before 10 July 1991, when South Africa joined the Nuclear Nonproliferation Treaty (NPT). Not only have the weapons themselves been destroyed, and the fissile material recast into non-weapon ingots, but all design and production information has been destroyed as well. Of course, it is very easy to get this information today.
A secret project was begun by the Atomic Energy Board (AEB) in the early 1960s to develop a unique uranium enrichment technology. Initially the project was housed in a small warehouse in Pretoria, but was later moved to Pelindaba. The technology was nozzle or vortex enrichment, achieves separation by generating a near-sonic speed vortex of a mixture of uranium hexafluoride and hydrogen gases in a narrow stationary tube. The centrifugal forces caused by the high speed rotation concentrate heavier U-238 at the periphery and lighter U-235 at the axis, so that axial and peripheral out take tubes can extract isotopically enriched and depleted materials respectively, a process analogous to that produced by the spinning rotor of a gas centrifuge.
The strategic implications of Soviet involvement in Africa - either direct or by proxy - weighed heavily on South Africa's leaders and was a chief motivation for the later actual manufacture of nuclear weapons to provide a hedge against Soviet-sponsored aggression. The strategy then was to use these weapons as leverage with Western powers - demonstrating their existence, and then threatening to resort to nuclear attack if assistance was not provided, should outside assistance prove necessary.