Valindaba

The Valindaba site, also known as Pelindaba East or Y-plant, was an experimental uranium enrichment plant, located 35 km west of Pretoria, Gauteng province, South Africa. Valindaba is a Zulu word that means "about this we do not speak at all". The plant's name is consistent with South African government's policy of official secrecy that concealed the plant's role in nuclear weapons production.
History.
Y-Plant was completed in 1975 by the Uranium Enrichment Corporation of South Africa (UCOR) and started producing HEU in 1978. During the 1970s, it was speculated that Valindaba may have supported the production of nuclear weapons.
It was shut down for almost two years following an accident in 1979, but was back in production by 1981 and since that time produced all the fuel required by SAFARI-1.
Y-Plant ceased production on 1 February 1991 and was dismantled the same year.
In 1992, it was revealed that the plant had enriched uranium for the production of nuclear weapons.
The plant used the Helikon vortex separation process, a process developed in South Africa, to accumulate the uranium 235 isotope.