This annotated chronology is based on the data sources that follow each entry. Public sources often provide conflicting information on classified military programs. In some cases we are unable to resolve these discrepancies, in others we have deliberately refrained from doing so to highlight the potential influence of false or misleading information as it appeared over time. In many cases, we are unable to independently verify claims. Hence in reviewing this chronology, readers should take into account the credibility of the sources employed here.

Inclusion in this chronology does not necessarily indicate that a particular development is of direct or indirect proliferation significance. Some entries provide international or domestic context for technological development and national policymaking. Moreover, some entries may refer to developments with positive consequences for nonproliferation.

1970s
The Atomic Energy Corporation of South Africa (AEC) constructs the "Building 5000" complex at Pelindaba "with high explosive, criticality, and weapons-manufacturing capability."
—David Albright, "Slow But Steady," Bulletin of the Atomic Scientists, July-August 1993, p. 5.

1970s
South Africa begins research on uranium enrichment using ultracentrifuges.
—D.M. Kemp et al., "Uranium Enrichment Technologies in South Africa," Atomic Energy Corporation of South Africa Ltd., paper presented at the International Symposium on Isotope Separation and Chemical Exchange Uranium Enrichment, 29 October 1990, Tokyo, Japan; cited in David Albright, Frans Berkhout, and William Walker, Plutonium and Highly Enriched Uranium 1996: World Inventories, Capabilities and Policies (Oxford University Press, 1997), p. 383.

20 July 1970
Prime Minister John Vorster informs Parliament of the government's 1969 decision to construct a pilot uranium enrichment facility based on an indigenous technique involving jet-nozzle enrichment and a sophisticated cascade process. The project seeks to demonstrate the validity of the design on an industrial scale.
—Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today, p. 25 (December 1995/January 1996), p. 3; Seymour Hersh, The Samson Option: Israel's Nuclear Arsenal and American Foreign Policy (New York: Random House, 1989), p. 266.

23 July 1970
The UN Security Council adopts Resolution 282 calling on member states to revoke all licenses and military patents granted to the South African government or to South African companies for the manufacture of arms and ammunition, aircraft and naval craft, or other military vehicles. It also prohibits investment or technical assistance for the manufacture of these items.
—Timothy U. Mozia, "Chronology of Arms Embargoes against South Africa," in Effective Sanctions on South Africa: The Cutting Edge of Economic Intervention, ed. George W. Shepherd, Jr. (New York: Greenwood Press, 1991), pp. 97-98.

November 1970
South Africa establishes the Uranium Enrichment Corporation (UCOR) to oversee the uranium enrichment program and the construction of the new enrichment pilot plant.
—Waldo Stumpf, "South Africa: Nuclear Technology and Non-Proliferation," Security Dialogue 4 (1993): 458.

1971
Before South Africa returns the enriched uranium from the abandoned critical assembly at Pelindaba to the United States, it sends the slightly irradiated fuel to the United Kingdom for reprocessing.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 4, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

1971
Uranium Enrichment Corporation (UCOR) is assigned responsibility for overseeing the uranium enrichment program, and construction of a pilot-scale uranium enrichment plant—the "Y-plant"—is initiated.
—Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996): 3.

March 1971
Inspired by the Plowshares Peaceful Nuclear Explosion (PNE) Program promoted by the US government and Lawrence Livermore National Laboratory, South African Minister of Mines Carl de Wet approves research on PNEs, which are expected to be useful to the mining industry. The AEC is put in charge of the research. The AEC is said to have "a good technological base with respect to electronics and metallurgy because of its uranium enrichment program," but it has "no expertise in internal ballistics." The AEC acquires information on nuclear weapons construction from open sources, including volumes of declassified data from the Manhattan Project. According to Armaments Corporation (Armscor) officials. South African Minister of Mining Carl de Wet authorizes the AEB to conduct research on constructing the first nuclear explosive device.
—Mark Hibbs, "South Africa's Secret Nuclear Program: The Dismantling," NuclearFuel, 24 May 1993, p. 10; Michael Barletta, "Pernicious Ideas in World Politics: Peaceful Nuclear Explosives," paper presented to the Annual Meeting of the American Political Science Association, San Francisco, CA, 30 August 2001, <http://cns.miis.edu/cns/staff/mbarlett/apsa2001.pdf>; Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to Deterrent," NuclearFuel, 10 May 1993, p. 3.

1972-1975
South Africa provides Israel with depleted uranium and natural uranium rods.
—US Central Intelligence Agency, Directorate of Intelligence, New Information on South Africa's Nuclear Program and South African-Israeli Nuclear and Military Cooperation, 30 March 1983, top secret report partially declassified and released 27 April 1997, <http://www.foia.ucia.gov>.

1972
Lacking adequate facilities at Pelindaba, a small team of AEB staff begins working on mechanical and pyrotechnic subsystems for a gun-type nuclear explosive device at a propulsion laboratory at Somchem, in Cape Province.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 6, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

1973
South Africa begins research on the separation of lithium isotopes for use in boosted-fission nuclear explosive devices.
—Adolf Von Baeckmann, Gary Dillon, and Demetrius Perricos, "Nuclear Verification in South Africa," IAEA Bulletin, January 1995, p. 6, <http://www.iaea.or.at/worldatom/Periodicals/Bulletin/Bull371/
baeckmann.html>; David Albright, "South Africa and the Affordable Bomb," Bulletin of the Atomic Scientists, July 1994, p. 10.

1973
According to a 1983 US intelligence report, "[deleted passage] indicates that South Africa formally launch(es) a weapons program in 1973," and scientists are instructed to develop gun-assembly, implosion, and thermonuclear weapon designs. The report also concludes that research on both a gun-type device, using two modified naval guns, and on the firing system of an implosion device was conducted at the Somerset West explosives installation in South Africa.
—US Central Intelligence Agency, Directorate of Intelligence, "New Information on South Africa's Nuclear Program and South African-Israeli Nuclear and Military Cooperation," 30 March 1983, secret report partially declassified and released on 27 April 1997, <http://www.foia.ucia.gov>.

6 October 1973
Syria and Egypt attack Israel, beginning the October 1973 War. The war results in all but three black African states (Malawi, Lesotho, and Swaziland) breaking off relations with Israel, eliminating much of the need for Israel to keep its growing relationship with South Africa secret.
—James Adams, The Unnatural Alliance (London: Quartet Books, 1984), pp. 23, 35-36; "Arab-Israeli Wars," Encyclopedia Britannica Online, undated, <http://search.eb.com/bol/topic?eu=8252&sctn=1>.

1974
Israeli Prime Minister Shimon Peres and South African President John Vorster hold a secret meeting in Geneva. The two reportedly sign an agreement for strategic cooperation between the two countries. The agreement is a mutual defense pact according to which "the two countries would assist each other in wartime by supplying spare parts and ammunition from emergency stocks. Each country agreed that its territory would be used to store all types of weapons for the other country." According to Dieter Gerhardt, a senior commander in the South African Navy who for many years spied for the Soviet Union, under a later clause in the agreement called "Chalet," Israel agreed to arm eight Jericho II missiles with "special warheads" for South Africa.
—"Treasons of Conscience," Weekly Mail & Guardian, 11 August 2000, <http://www.sn.apc.org/wmail>.

1974
South African and other international sources provide different estimates on the initiation of the nuclear weapons program. According to F.W. de Klerk, president of South Africa from 1989-1994, the decision to "develop a limited nuclear deterrent capability" is made "as early as 1974."

International Atomic Energy Agency (IAEA) safeguards officials charged with verifying South Africa's past nuclear activities likewise report that the prime minister approves a "limited program for development of nuclear weapons as a deterrent" in 1974.

However, according to Waldo Stumpf, head of the Atomic Energy Corporation (AEC), the government officially does not change the objective of its nuclear explosive program from peaceful purposes to developing a nuclear deterrent capability until 1977.

Alternatively, Armaments Corporation (Armscor) officials maintain that in October 1978, Prime Minister P.W. Botha decides to shift the emphasis of the nuclear program from peaceful nuclear explosives to developing nuclear weapons, just one month after taking office.
—"De Klerk Tells World South Africa Built and Dismantled Six Nuclear Weapons," NuclearFuel, 29 (March 1993): 7; Adolf Von Baeckmann, Gary Dillon, and Demetrius Perricos, "Nuclear Verification in South Africa," IAEA Bulletin, January 1995, p. 4. <http://www.iaea.or.at/worldatom/Periodicals/Bulletin/Bull371/ baeckmann.html>; Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996): pp. 5-8; Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to a Deterrent," Nuclear Fuel 10 (May 1993): 4; David Albright, "A Curious Conversion," Bulletin of the Atomic Scientists, June 1993, <http://bullatomsci.org/issues/1993/j93/j93reports.html>.

1974
In a report to Prime Minister John Vorster, the AEB concludes that it can build a nuclear explosive device. Vorster approves the development of PNE's and construction of an underground nuclear test site.
— Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996): 4; David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 6.

1974
West Germany's Steinkohlen Elektrizitaia AG (STEAG), a government-controlled firm charged with commercialization of the Becker jet nozzle uranium enrichment process, states in a press release that it has signed a contract with UCOR "to carry out a joint comparative economic feasibility study" of the process developed in South Africa. The feasibility study will be used to consider the construction of a commercial enrichment facility in South Africa.
—J.D.L Moore, "The Development of South Africa's Nuclear Capability," in South Africa and Nuclear Proliferation (New York: St. Martin's Press, 1987), p. 89; U.S., Embassy in South Africa, "Vorster Comments on SA Uranium Enrichment Project," May 1974, classified memorandum declassified and released 22 December 1985.

1974
The United States enriches uranium ore for fuel fabrication in France to supply South Africa's Koeberg nuclear power station. ESKOM, the South African electric utility, operates a two-unit site at Koeberg Nuclear Power Station near Capetown. Each unit is a three-loop Framatome Pressurized Water Reactor rated at 920MWe. Unit 1 started up in 1984 and Unit 2 in 1985.
—"Pressure on SA to Sign Nuclear Pact," The Star, 14 April 1982, p. 21; "Nuclear Power Plants - South Africa," The Vitual Nuclear Tourist, <http://www.nucleartourist.com/>.

1974
A pilot uranium enrichment plant, referred to as the Y-plant by the South African government, begins operation. According to Waldo Stumpf, head of the Atomic Energy Corporation, the first stages at the lower end of the cascade at the Y-plant were commissioned at the end of 1974, but the full cascade was not operational until March 1977. Other reports state that the plant came on line in 1975 and was not safeguarded. On 7 April 1975, Prime Minister Vorster announces in the South African House of Assembly that the pilot enrichment plant had commenced operations on 5 April 1975. [Note: Conflicting statements have been made about the location of the Y-plant; some sources say that the plant is located at the Pelindaba site; others say it is at the Valindaba site, one-quarter of a mile away. The confusion has been compounded by the fact that South Africa changed the name of Valindaba to "East Pelindaba."]
—Mark Hibbs, "IAEA Believes South Africa Produced More Than 200 kg of High Enriched Uranium," NuclearFuel, 28 September 1992, p. 2; Leonard S. Spector, The Undeclared Bomb: The Spread of Nuclear Weapons 1987-1988 (Cambridge, Massachusetts: Ballinger Publishing Company, 1988), p. 303; Waldo Stumpf, "South Africa: Nuclear Technology and Non-Proliferation," Security Dialogue 4 (1993): p. 458; U.S. Embassy in South Africa, "South African Uranium Enrichment," April 1975. classified memo, partially declassified and released 19 August 1987.

1974
Construction begins on a bore hole at the test site in the Kalahari Desert.
—Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to a Deterrent," Nuclear Fuel, 10 May 1993, p. 3.

May 1974
The AEB team at Somchem tests a scale model of a gun-type device using non-nuclear material as a projectile.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 6.

22 May 1974
South Africa and the United States sign amendments to their cooperation agreement on the civil uses of nuclear energy. The amendments extend the 1957 agreement, which would have expired in 1977, until 2007, and will allow South Africa to import increased quantities of enriched uranium fuel for two nuclear power reactors. The amendments also allow South Africa to import relatively small quantities of U235 for fuelling research and testing reactors, as well as plutonium for fueling purposes. According to a Department of State memorandum, the US government believes that continuing a nuclear relationship with South Africa is important in order to maintain nuclear safeguards in the country and to avoid alienating South African actors who oppose communism. The memorandum notes that "South Africa contains 27 percent of the free world's supply of uranium."
—US Department of State, "Signing of Amendment to U.S./S.A. Atomic Energy Agreement," memorandum, 21 May 1974, unclassified memo released 19 August 1987.

October 1974
The Director of Central Intelligence issues a Special National Intelligence Estimate (SNIE) in which the prospective capabilities and motivations for a number of countries seeking nuclear weapons are addressed. The SNIE states that South Africa's decision to pursue nuclear weapons will be based on its "growing feeling of isolation and helplessness, perceptions of major military threat, and desires for regional prestige" although the estimate does not foresee a serious military threat from any of its African neighbors during the 1970s.
—US Central Intelligence Agency, Directorate of Intelligence, "Prospects for Further Proliferation of Nuclear Weapons," 2 October 1974, classified interagency intelligence memorandum, partially declassified and released, Digital National Security Archive, <http://nsarchive.chadwyck.com/>.

1975
The South African government, believing that it faces a "total onslaught" from the Soviet Union, urges scientists working on the nuclear weapon program at the Pelindaba plant to redouble their efforts toward conducting the first test detonation before the end of the year.
—David Watts, "Foreign Scientists Helped to Develop 'Apartheid Bomb'," Times (London), 26 March 1993.

1975
Safari-1 operates using approximately 105kg HEU enriched to 45 percent supplied by the United States.
—Mark Hibbs, "South Africa's Secret Nuclear Program: The Dismantling," Nuclear Fuel, 24 May 1993, p. 12.

1975
South Africa, which had been producing uranium hexafluoride (UF6) on a laboratory scale since the early 1970s, commissions a small UF6 production plant at Pelindaba. The plant, which has a capacity to produce 200t UF6 per year, is to become fully operational in 1978.
—J.D.L Moore, "The Development of South Africa's Nuclear Capability," in South African and Nuclear Proliferation (New York: St. Martin's Press, 1987), p. 94.

October 1975
The International Herald Tribune reports that South Africa negotiated a contract to supply Iran with enriched uranium in exchange for Iranian investment in a commercial enrichment facility in South Africa. The agreement was cancelled when Iran's nuclear power program was suspended, following the Islamic revolution in 1978-79.
—J.D.L Moore, "The Development of South Africa's Nuclear Capability," in South African and Nuclear Proliferation (New York: St Martin's Press, 1987), p. 91.

1976
One nuclear explosive test shaft is completed at the Vastrap testing range in the Kalahari Desert.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 7, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

1976
The AEB team at Somchem tests a full-scale model of a gun-type device, using natural uranium as the projectile. [Note: Natural and depleted uranium have the same physical and chemical properties as HEU, and can be used to test the design and function of an HEU-based nuclear explosive assembly, although they can not produce nuclear explosions.]
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 6, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

1976
The Ford administration suspends shipments of nuclear fuel for the Safari isotope production reactor. The first nuclear weapons site at Vastrap is completed.
—Waldo Stumpf, "South Africa's Limited Nuclear Deterrent Programme and the Dismantling thereof Prior to South Africa's Accession to the Nuclear Non-Proliferation Treaty," press conference, Washington, DC, 23 July 1993; Leonard S. Spector, The Undeclared Bomb: The Spread Of Nuclear Weapons 1987-88 (Cambridge: Massachusetts: Ballinger Publishing Company, 1988), p. 432.

1976
According to Deiter Gerhardt, Soviet officials ask for US cooperation in stopping the South African nuclear weapons program. One of the options mentioned by the Soviets is a preemptive strike on the Y Plant. US officials reject this option.
—Davis Albright, "South Africa and the Affordable Bomb," Bulletin of the Atomic Scientists, July/August 1994, <http://www.bullatomsci.org/issues/1994/a94/a94Albright.html>.

1976
According to a 1984 CIA report, the South African Air Force (SAAF) employs Buccaneer S MK 50 bombers to practice nuclear delivery techniques. The Buccaneers drop conventional bombs to destroy a decommissioned World War II salvage ship off the coast of Cape Town. The bombers release the conventional bombs three to five miles away from the target, and "then pulled up sharply and veered away." The SAAF describes the exercise as using "computerized technique to deliver nuclear bombs and escape the effect of the resulting explosions."
—US Central Intelligence Agency, Directorate of Intelligence, Trends in South Africa's Nuclear Security Policies and Programs, 4 October 1984, top secret report partially declassified and released 27 April 1997, <http://www.foia.ucia.gov>, p. 17.

March 1976
West Germany's STEAG cancels its contract with UCOR because the two firms cannot agree on conditions for investment or supply of natural uranium feed for a commercial enrichment plant.
—J.D.L Moore, "The Development of South Africa's Nuclear Capability," in South African and Nuclear Proliferation (New York: St Martin's Press, 1987), p. 89.

April 1976
In an uncorroborated report, James Adams claims that South Africa and Israel signed a technical cooperation agreement during the visit of South African Prime Minister John Vorster to Israel. Under the terms of the accord, Israel provides South Africa with nuclear information and sends technicians and scientists to assist in nuclear research, including development of atomic weapons. Israeli scientists travel to South Africa to provide advice on establishment of Safari-2, a nuclear research reactor.
—Davar (Tel Aviv), 13 April 1984, pp. 1-2; cited in "Cooperation with South Africa on Nuclear Pursuits Alleged," Worldwide Report, 7 June 1984, pp. 30-31.

5 August 1976
The South African Energy Supply Commission (Eskom) and the French Framatome-Framateg consortium sign a contract to construct the Koeberg nuclear power station. According to the contract, the French consortium is to "supply capital works, nuclear fuel and services for Koeberg Units 1 and 2." [Note: Although Framatome-Framateg is commonly used in referring to this French consortium, Newby Fraser calls it Framatome-Alsthome-Spie Batignolles-Framateg.]
—A.R. Newby-Fraser, Chain Reaction: Twenty Years of Nuclear Research and Development (Pretoria: Atomic Energy Board, 1979), pp. 131-132.

15 October 1976
The governments of South Africa and France formalize the Koeberg negotiations by signing a bilateral agreement.
—A.R. Newby-Fraser, Chain Reaction: Twenty Years of Nuclear Research and Development (Pretoria: Atomic Energy Board, 1979), p. 132.

1977
A second nuclear explosive test shaft is completed at the Vastrap testing range.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 7, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

1977
The AEB completes manufacture of South Africa's first full-scale nuclear explosive device based on a gun-type design. The device does not contain a highly enriched uranium (HEU) core, however, because the Y-plant has not yet produced a sufficient quantity of HEU. The device is loaded with a depleted uranium core in preparation for a "cold" test planned for August 1977 at the Kalahari test site. The AEB plans to conduct a "true" test using a HEU pit in 1978. The device with the depleted uranium pit is later "dismantled and scrapped."
—Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996), p. 5; Mark Hibbs, "South Africa's Secret Nuclear Program: The Dismantling," Nuclear Fuel, 24 May 1993, p. 9; Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 10; Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to a Deterrent," Nuclear Fuel, 10 May 1993, p. 4.

1977
Vorster assembles senior officials to discuss the future of the nuclear program and directs them to draft an outline for South Africa's future "nuclear course."
—Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 9.

1977
South Africa breaks off negotiations with the International Atomic Energy Agency (IAEA) regarding safeguards for a semi-commercial enrichment plant at Valindaba.
—Ann MacLachan, "The IAEA and South Africa Have Resumed Negotiations on Safeguards," Nucleonics Week, 16 August 1984, p. 9; Leonard S. Spector, The Undeclared Bomb: The Spread of Nuclear Weapons 1987-1988 (Cambridge: Massachusetts: Ballinger Publishing Company, 1988), p. 303.

1977
The World Conference for Action against Apartheid urges states and firms to cease all assistance and cooperation enabling South Africa to acquire nuclear technology.
—Neta C. Crawford and Audie Klotz, eds., How Sanctions Work: Lessons from South Africa (New York: St. Martin's Press, 1999), p. 284.

1977
South Africa trades 50 metric tons of yellowcake for 30 grams of Israeli tritium. The material is code-named "Teeblare" (Afrikaans for "tea leaves") and is shipped secretly to South Africa in small "capsules each containing 2.5 grams."
—David Albright, "Slow but Steady," Bulletin of the Atomic Scientists, July-August 1993, p. 6.

1977
As a result of the suspension of US nuclear fuel shipments, Safari-1 is down-rated to 5 megawatts (MW) and operated only five days per week.
—Mark Hibbs, "South Africa's Secret Nuclear Program: The Dismantling," Nuclear Fuel, 24 May 1993, p. 12.

June 1977
The IAEA removes South Africa from its Board of Governors.
—Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 9.

Mid-1977
The AEC's design and engineering team finishes its work on the first gun-type device after experiencing timing and projectile-velocity problems. South Africa obtained tungsten from Rhodesia, Zaire, and Zambia in the 1970s. By this point AEC has gained "expertise in internal ballistics...as well as experience related to igniters and propellants." These developments confirm that South Africa has opted for a gun-type device rather than an implosion bomb.
—Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to a Deterrent," Nuclear Fuel, 10 May 1993, p. 4; Mark Hibbs, "South Africa's Secret Nuclear Program: The Dismantling," Nuclear Fuel, 24 May 1993, p. 10; Waldo Stumpf, "South Africa's Limited Nuclear Deterrent Programme and Dismantling thereof Prior to South Africa's Accession to the Nuclear Non-Proliferation Treaty," press conference, Washington, DC, 23 July 1993.

Mid-1977
The AEB transfers the nuclear weapons program from Somchem to the weapons research and development facilities that it built at Pelindaba.
—David Albright, "South Africa's Secret Nuclear Weapons," ISIS Report, May 1994, p. 7, <htpp://www.isis-online.org/publications/southafrica/ir-594.html>.

30 July 1977
A Soviet surveillance satellite discovers the nuclear test site in the Kalahari desert.
—Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities, (Washington, D.C.: Woodrow Wilson Center, 1995), p. 10.

6 August 1977
A second Soviet satellite completes four more passes over the test site. The Soviet Union immediately informs the United States. that South Africa is making preparations for a nuclear test. Under international pressure, South Africa subsequently covers the test shafts with concrete slabs and abandons the site.

The Soviet Union begins to intensify its allegations that the United States is helping South Africa acquire nuclear weapons technology. At the same time, behind-the-scenes cooperation between the Soviets and Americans is underway to pressure South Africa into foregoing planned tests of a nuclear device in the Kalahari Desert.
—Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 10; U.S. Mission UN, "News Coverage," 29 August 1977, unclassified memorandum released, Digital National Security Archive, <http://nsarchive.chadwyck.com/>; US Department of State, "Your Meeting with Gromyko: South African Nuclear Issues," 21 September 1977, secret memorandum partially declassified and released, Digital National Security Archive, <http://nsarchive.chadwyck.com/>; US Mission to the UN, "Non-proliferation Issues at the 32nd UNGA: South Africa Nuclear Issues," 6 October 1977, confidential memorandum partially declassified and released, <http://nsarchive.chadwyck.com/>.

October 1977
A delegation of African states calls for a UN Security Council resolution pressing tougher sanctions on South Africa, including a ban on nuclear cooperation. The US government states it will veto any such resolution and proposes a compromise that consists of a temporary arms embargo. The United States asserts that any break in nuclear cooperation will be counterproductive and that maintaining a nuclear relationship is necessary in order to exert pressure on South Africa to sign the NPT.
—U.S. Department of State, "Milton R. Benjamin Article in Washington Post," 31 October 1977, unclassified memorandum, Digital National Security Archive, <http://nsarchive.chadwyck.com/>.

December 1977
The Y-plant commences operation.
—Leonard S. Spector and Jacqueline R. Smith, Nuclear Ambitions: The Spread of Nuclear Weapons 1989-1990 (San Francisco: Westview Press, 1990), p. 288.

30 January 1978
The first small quantity of HEU is withdrawn from the Y-plant. For the next 19 months, the Y-plant produces HEU enriched to approximately 80 percent U235. The nominal capacity of the plant is believed to be between 10,000 and 20,000 separative work units (SWUs) per annum.
—Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996): p. 4; Waldo Stumpf, "South Africa: Nuclear Technology and Non-Proliferation," Security Dialogue 4 (1993): p. 458; David Albright and Mark Hibbs, "South Africa: The ANC and the Atom Bomb," Bulletin of the Atomic Scientists, April 1993, p. 34; Mark Hibbs, "Pretoria Replicated Hiroshima Bomb in 7 Years, then Froze Design," Nucleonics Week, 6 May 1993, p. 16.

1978
As a result of success of the Y-plant, a second and smaller nuclear device is built by the AEC for loading with a uranium core, in order to conduct a "rapidly deployed, fully instrumented test at the Kalahari site, if required."
—Mark Hibbs, "South Africa's Secret Nuclear Program: From a PNE to Deterrent," Nuclear Fuel, 10 May 1993, p. 4.

April 1978
Prime Minister Vorster formally approves a draft document prepared by senior officials outlining South Africa's future nuclear course as defense minister, P.W. Botha approves adoption of a three-phase nuclear deterrent strategy. In phase one, the government will neither acknowledge nor deny its nuclear capability. If South African territory were threatened, the government would move to phase two and consider privately revealing its nuclear capability to certain international powers, such as the United States, to catalyze international intervention. If aid were not forthcoming, the government would move to phase three and consider demonstrating its nuclear capability in public, perhaps by conducting an underground nuclear test.
—Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 9; Waldo Stumpf, "South Africa's Nuclear Weapons Program: From Deterrence to Dismantlement," Arms Control Today 25 (December 1995/January 1996): 5.

October 1978
Botha creates an "Action Committee" to recommend plans for production of nuclear devices.
— Mitchell Reiss, "South Africa: Castles in the Air," in Bridled Ambition: Why Countries Constrain Their Nuclear Capabilities (Washington, DC: Woodrow Wilson Center, 1995), p. 9.

December 1978
The Y-plant produces its first load of HEU, with an enrichment level at 80 percent. Although the HEU is suboptimal, the first device is fitted with this HEU. Later, the material is removed, recycled, and the enrichment level upgraded.
—Waldo Stumpf, "South Africa's Limited Nuclear Deterrent Programme and the Dismantling thereof Prior to South Africa's Accession to the Nuclear Non-Proliferation Treaty," press conference, Washington, DC, 23 July 1993.

	Updated November 2003