The Republic of South Africa is the first and (thus far) only nation to have successfully developed nuclear weapons, and then voluntarily relinquished that capability.
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 NPT. Indeed - it appears that 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.
South Africa has had a significant involvement in the nuclear age since its beginning by virtue of its large uranium reserves and its mining-oriented economy. South Africa has an estimated recoverable uranium resources of 354,000 tonnes, 11% of the world total. Since the beginning of uranium production South Africa has produced a total of 153,460 tonnes of uranium through the end of 2000. South Africa began exporting significant amounts of uranium towards the end of World War II, providing part of the supply to the Manhattan Project, but the volume was small until the early 50s. South Africa had become a major world producer by 1959. In 1981 South Africa had 14 operating uranium mines and produced 14% of the world's uranium production, falling to five mines and 8 percent of world production in 1991. Although four mines are operating today (Vaal Reefs, Palabora, Hartebeestfontein, and Western Areas) their uranium production is a by-product of gold mining and at least one of them (Western Areas) has halted uranium extraction for economic reasons. In 2000 South Africa's production was 878 tonnes, only 2.5% of world production. But 80% of this production (711 tonnes) was from a single mine - the Vaal Reefs mine in the Witwatersrand Basin. This is enough to make this one mine the 10th largest in the world.
The Atomic Energy Board (AEB) was established in 1948 by an Act of Parliament to conduct general nuclear research and development. The United States agreed to supply South Africa with a nuclear research reactor (SAFARI-I), train additional scientists and reactor technicians, and provide fuel for the reactor under an agreement reached in 1957. These arrangements provided South Africa with a firm foundation to conduct its civilian nuclear research and development (R&D) program [Horton99]. To that end the Nuclear National Research Centre (also called the Pelindaba Nuclear Research Center, and now the Pelindaba Nuclear Institute) was established at Pelindaba, 30 km west of Pretoria, in 1961. Although initially devoted to peaceful nuclear research, a secret project was begun by the 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.
This technology, called 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. Considerable trial-and-error experimentation was required and laboratory scale enrichment was achieved by the end of 1967.
The underlying reason for this program was a mixture of military and commercial strategic considerations. The military potential of acquiring a means for producing nuclear weapons was clear, but also of concern was South Africa's dependence on foreign supplies of enriched uranium which the government viewed as a critical material for the South African economy, even though at that time South Africa had no nuclear power plants.
During the 1960s international opposition and resistance to the governing National Party's apartheid policies grew swiftly. Stringent discrimination against black South Africans was nothing new of course, but since its election victory in 1948 the National Party had systematically codified these practices, increasing their rigor and placing the full weight of the national government behind their implementation, even as a growing interest and emphasis on civil rights swept the rest of the non-communist world. In 1961 South Africa withdrew from the Commonwealth. South Africa's national course was clearly set toward increasing isolation.
The aerodynamic vortex enrichment process was inherently energy intensive compared to competing commercial enrichment technologies (gas diffusion and gas centrifuge at that time) and had no chance of being commercially competitive since energy is a dominant cost of even the most efficient of these processes. But the South African government was intent on securing a source of enriched uranium without sparing the expense. Since South Africa already was a uranium exporting nation, it needed only a method enrichment to be independent from the outside world for nuclear fuel.
A large research reactor, SAFARI-I, supplied by the US began operating in 1965 at Pelindaba. SAFARI-I is a light-water tank type reactor, with a design power of 20 MW (thermal) running on 4.5 kg of 90% enriched uranium, which was supplied by the US until 1981.
The indigenously built Pelinduna Critical Facility went critical in 1967. It used 606 kilograms of 2 percent enriched uranium and 5.4 metric tons of heavy water supplied by the US. Because it was not competitive with light-water reactors and was draining resources from the enrichment program, both the criticality facility and this reactor type were abandoned in 1969. Before the enriched uranium was returned to the United States in 1971, the slightly irradiated fuel produced at Pelinduna was sent to Britain for reprocessing [Albright 1994a].
The decision to proceed with the construction of an industrial scale pilot plant was made in 1969. The existence of this technology became public on 20 July 1970 when Prime Minister John Vorster informed Parliament about its existence. The Uranium Enrichment Corporation (UCOR) was formed to construct the pilot plant at a site adjacent to Pelindaba called Valindaba.
The program had grown to large to remain secret, but it continued to be camouflaged by the cover of commercial application, although the primary function of this pilot plant, known as the Pilot Enrichment Plant or "Y Plant" (shades of the "Y-12" enrichment plant at Oak Ridge!) was always to be for the production of highly enriched uranium for weapons. Construction of the plant began in late 1970, with the first stages of the cascade being commissioned by the end of 1974 [Albright et al 1997; pg. 379-380].
The program of weapons development began with research on nuclear explosive design started in 1971 when Minister of Mines Carl De Wet approved preliminary investigations into the feasibility of producing nuclear explosives. As in the early Indian nuclear weapon program, this work was conducted secretly but under the rubric of "peaceful nuclear explosives". Initially the work was confined to literature searches, but later added theoretical investigations on the physics and design of both implosion and gun-type nuclear devices. According to JW de Villiers, chairman of the AEC, who is widely believed to have headed the nuclear explosive program in the 1970s. He said that only three engineers were involved in the ballistics research and theoretical implosion work. [Stumpf 1995], [Albright 1994a].
Because the AEB lacked adequate facilities for explosives-related work at Pelindaba, a small team of AEB personnel worked under tight security during 1972-73 at a propulsion laboratory at the Somchem establishment in Cape Province. Until the early 1990s, Somchem was an Armscor facility involved in the development and manufacture of explosives and propellants and, later rocket launchers. Somchem is now a division of Denel Limited. At Somchem, AEB personnel worked on the mechanical and pyrotechnic subsystems for a gun-type device. The team designed a scale model that, with a projectile constructed of non-nuclear material was tested at Somchem in May 1974[Albright 1994a].
A report supporting feasibility was completed in 1974. Based on this assessment Prime Minister Vorster issued a secret decision to proceed with actual development of nuclear explosives, including the development of a testing site for an underground testing the Kalahari Desert [Stumpf 1995].
Despite Stumpf's emphasis on industrial applications at this point in the nuclear program it should be pointed out that the low yield, low efficiency devices South Africa developed, using very costly fissile material due to the inefficient production process, possessed not even theoretical cost advantages over conventional explosives. In addition extreme secrecy was the rule,a trait typical of military not civilian-oriented programs. In his March 1993 speech revealing the programs existence FW de Klerk himself implied that the decision to "develop a limited nuclear deterrent capability" was made as early as 1974. This is very reminiscent of the early Indian nuclear weapons program, where the highly secret program was also internally described by the euphemism "PNE" (peaceful nuclear explosive), though in recent years participants have acknowledged that it was always intended as a weapon. The South Africans were fully as aware as the Indians that there was no practical difference between a "PNE" and a weapon. Thus other strategic motivations very likely influenced this decision, regardless of the internal justification.
Whatever the original rationale, the withdrawal of Portugal from its colonies in 1975, followed by large scale intervention in central and southern Africa by the Cuban military (eventually reaching 50,000 troops) certainly set the focus of the program on non-civil application. 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.
Conversely the later decision to abandon its nuclear arsenal was motivated by the end of Cold War inspired intervention in Africa, and the prospect of reintegrating with the world if and when apartheid was abandoned. The decision to completely destroy weapons related technology and information may have been made in part to keep nuclear weapons out of the hands any future black-led government.