In the mid- to late-1970s the nuclear weapon research, development, and production activities were housed in a valley in the southwestern section of the Pelindaba site. These facilities were correctly identified by U.S. intelligence in the late-1970s. The main facilities were the following:
Building 5000 - This facility contained a pulse reactor for the experimental verification of theoretical computer models. In 1979, the reactor was used as a fast critical assembly in an experiment often referred to as "tickling the tail of the dragon" that proved the design of the gun-type device. The reactor was never used as a pulse reactor and the facility was shut down in the early 1980s.
Building 5100 - This building contained the control room for Building 5000, offices, research and development laboratories and machining facilities for uranium metal. After the nuclear weapons program was transferred to ARMSCOR in 1979, the building continued to house the program's small theoretical group until 1989.
Building 5200 - This building housed a critical facility to verify separately the multiplication factors of the two parts of a nuclear explosive device, providing confidence that the gun-type design would work. The first nuclear explosive device was also assembled in this building.
Building 5300 - This building was designed exclusively as a laboratory for high explosives. In the early stage of the South African nuclear weapons program, small quantities of high explosives were pressed and machined into shapes at this facility.