CNS Research Story

South Korea's Nuclear Experiments

The closed TRIGA Mark-II research reactor in Seoul.

South Korean scientists produced small amounts of plutonium with the TRIGA Mark-III research reactor in the early 1980s.

By Daniel A. Pinkston[1]

November 9, 2004

South Korea's experiments to extract plutonium in 1982 and to enrich uranium in 2000 do not indicate a present and dedicated effort to develop nuclear weapons. However, the experiments could have broad implications given South Korea's past nuclear weapons development program and the ongoing efforts to thwart North Korea's nuclear ambitions. South Korea has an extensive nuclear energy infrastructure, and South Korean officials have long expressed an interest in establishing an independent fuel cycle capability. South Korean officials have claimed these experiments were the result of "scientific curiosity" or part of plans to localize the production of nuclear fuel.[2] However, these experiments do have applications for weapons development, and there are still questions about past activities that appear to have more direct weapons applications. This report provides information on the nuclear experiments and the linkages to South Korea's desire to establish an independent fuel cycle capability. This desire has had serious implications because South Korea had a nuclear weapons program in the past, and suspicions could derail nonproliferation efforts targeted at North Korea and elsewhere.

South Korea's Uranium Enrichment Experiments

On August 17, 2004, South Korea's Ministry of Science and Technology (MOST) reported to the International Atomic Energy Agency (IAEA) that South Korea had conducted experiments to enrich uranium. The report was part of South Korea's commitments under the Additional Protocol (INFCIRC/540), which had become effective when ratified by the South Korean National Assembly on February 19, 2004.[3] The information about the uranium experiments was later leaked to the press when South Korean officials urged IAEA Director-General Mohammed ElBaradei not to report the issue to the IAEA Board of Governors in September and then threatened to undermine ElBaradei's efforts for election to a third term if the information were disclosed. South Korean officials also asked the U.S. government to keep the information secret in bilateral discussions held on August 19. U.S. officials asked for full and transparent disclosure, but South Korea continued its efforts to contain the information throughout late August.[4]

Once it was clear the information would be leaked and reported to the IAEA Board of Governors, South Korean officials requested that disclosure be limited to uranium enrichment experiments in 2000, even though South Korea had also carried out experiments to extract plutonium and had produced uranium metal in the 1980s. However, Director-General ElBaradei did mention South Korea's production of uranium metal and the uranium and plutonium experiments in his statement to the Board of Governors on September 13.[5]

The Laboratory for Quantum Optics at the Korea Atomic Energy Research Institute (KAERI) conducted experiments to enrich uranium three times during January and February 2000. The experiments were conducted using atomic vapor laser isotope separation (AVLIS) and yielded about 0.2 grams of uranium enriched to an average of 10 percent in the three experiments. The peak level of enrichment in the experiments was 77 percent.[6] Korean scientists separated the U235 from uranium nitrate salt with equipment that had been used to separate stable isotopes such as gallium, samarium, thallium, and ytterbium.[7] KAERI developed the laser equipment for the uranium enrichment experiments in the second half of the 1990s,[8] but South Korea has been interested in laser isotope separation since at least the early 1980s.[9]

South Korea has received foreign assistance in laser technology from the United States and Russia. In particular, KAERI has received assistance from the General Physics Institute in Moscow in the field of AVLIS.[10] The techniques used in collaboration with the General Physics Institute to enrich ytterbium could be used to enrich uranium according to an American laser enrichment expert.[11] This technique could not be used to produce bomb quantities of U235, but experiments on the properties of U235 would be necessary prior to ramping up a program to produce large quantities of U235 for weapons.

South Korea probably disclosed the experiments to the IAEA in August 2004 because officials realized they would be discovered through monitoring and verification measures under the Additional Protocol. Even though the experiments were conducted prior to South Korea's ratification of the Additional Protocol, the experiments are still a technical violation of Seoul's nuclear Non-Proliferation Treaty safeguards (INFCIRC/236) commitments that have been in effect since 1975, as well as a violation of the 1992 North and South Korean "Joint Declaration on the Denuclearization of the Korean Peninsula." Furthermore, the South Korean government's initial explanations included a number of inconsistencies that increased suspicions surrounding Seoul's nuclear ambitions or raised questions about the control and oversight of South Korea's nuclear facilities and materials.

History of South Korea's Nuclear Program

South Korea's peaceful nuclear program dates from the late 1950s, when South Korea began to establish the infrastructure to sustain a nuclear development program.[12] South Korea began to operate its first research reactor in November 1962 and its first power reactor in April 1978.[13] By the mid 1970s, South Korea was actively pursuing the development of nuclear weapons.[14] Presidents Park Chung Hee, Chun Du Hwan, and Roh Tae Woo later pledged to forgo the development of nuclear weapons, but there are reports that all three governments seriously considered a nuclear weapon option while expanding the nuclear power program.[15] Many South Koreans believe the country should maintain a "virtual nuclear weapons program" in case the security situation suddenly deteriorates and Seoul can no longer rely upon the American nuclear umbrella.

On September 8, 1972, President Park Chung Hee reportedly received a report entitled "Atomic Fuel Development Plan" that included plans to develop nuclear weapons. Park is said to have decided to pursue a plutonium bomb, and in 1973 South Korea sought to acquire a reprocessing facility from France and a research reactor and heavy water reactor from Canada to produce bomb-grade plutonium.[16] However, under extreme U.S. pressure the reprocessing and research reactor deals were cancelled and President Park agreed to abandon the nuclear weapons program in exchange for security assurances from Washington.[17]

Despite U.S. security assurances and Park's assassination in October 1979, South Korean nuclear activities continued. KAERI contracted with the Youngnam Chemical Corporation to import phosphate compounds with a high-level of uranium in the early 1980s. KAERI specifically selected phosphate rock with a high uranium content for extraction and conversion. Between 1981 and 1984, yellow cake (U3O8) was converted to uranium oxide (UO2). The UO2 was used to produce fuel rods for the Wŏlsŏng-1 Nuclear Power Reactor in 1985.[18]

In 1982, South Korea converted UO2 into UF4 at an undeclared facility, and the UF4 was then used to produce about 154kg of uranium metal between May 1982 and November 1984. Scientists used about 3.5kg of this uranium metal in the laser isotope separation experiments in 2000.[19] Questions remain whether South Korea produced any UF6, the feedstock for gaseous centrifuge enrichment, but the processes for producing the two compounds are very similar.[20]

The plutonium experiments of the early 1980s were also part of South Korea's long desire to possess nuclear facilities and the right to maintain a complete nuclear fuel cycle. However, the knowledge and experience gained through the plutonium extraction experiments could also be applied to weapons development. The plutonium experiments were carried out on 2.5kg of depleted uranium (DU) that was fabricated into five test fuel rods and irradiated in the now closed TRIGA-III research reactor in Seoul. The DU had been imported from West Germany in May 1978, and the test fuel rods were loaded into the reactor in the second half of 1981. The plutonium was extracted in a hotcell during April and May 1982, but the hotcell was dismantled when the reactor was closed down and KAERI moved to Taejŏn.[21]

South Korea notified the IAEA in September 1983 that unapproved fuel rods had been used in the TRIGA-III reactor, but it was several years before the IAEA discovered traces of plutonium at the TRIGA-III reactor site and notified South Korea in 1998. The IAEA carried out an investigation of the environmental sample results and once again notified South Korea of the plutonium discovery in 2003.[22] South Korea is now cooperating with the IAEA to account for these past activities.[23]

Proliferation Implications of South Korea's Nuclear Program

Initially, in September 2004, the South Korean government claimed that the uranium enrichment experiments were "isolated, laboratory-scale scientific experiments conducted at the initiative of a small number of scientists."[24] Japan's Mainichi Shimbun caused a stir when it reported in an interview with former President Kim Young Sam that the experiments were for "nuclear development," that there was no way the South Korean president could be unaware of such experiments, and that South Korean scientists are not free to conduct experiments as they please. President Kim later said the Mainichi Shimbun was misleading and that he had only said he was unaware of any such experiments during his tenure in office.[25]

There are still conflicting reports about oversight and control of South Korea's nuclear materials and personnel. KAERI Director Chang In Sun has said the plutonium experiments in the early 1980s were chemical experiments as part of an effort to develop an indigenous capability to produce nuclear fuel.[26] However, it appears that the KAERI director approved the uranium enrichment experiments in 2000, but he did not report them to the Minister of Science and Technology or the president. This possible breakdown in oversight and accountability raises concerns in the wake of the recently discovered nuclear trafficking network directed by A.Q. Khan of Pakistan.

On August 1, 2004, the Segye Ilbo published a report and photographs of a KAERI conceptual study for a reprocessing pilot plant. The 1974 document, disclosed by Dr. Kim Ch'ŏl, included plans provided by the French firm Saint Gobain Techniques Nouvelles. Kim, the former scientist in charge of South Korea's plan to build a plutonium reprocessing facility, said that after the nuclear development program was closed down due to U.S. pressure, the personnel were scattered and the related documents were either destroyed or disappeared.[27]

There have been no reports of disciplinary actions against individual scientists or administrators for the uranium separation or plutonium extraction experiments. KAREI Director Chang In Sun approved the uranium experiments but according to rumors he will be appointed to another term. However, South Korean government implemented an institutional change on October 25 when the Technology Center for Nuclear Control (TCNC) was transferred from KAERI's jurisdiction to the Korea Institute of Nuclear Safety (KINS).[28] TCNC was originally established to conduct bilateral inspections under the "Joint Declaration on the Denuclearization of the Korean Peninsula" of 1992. The Center will now be responsible for "material control and accounting of nuclear materials, inspection interface with the IAEA, export controls and Korean representation in the Nuclear Suppliers Group (NSG), as well as nuclear security and physical protection."[29]

The IAEA Board of Governors will meet in late November to consider whether the South Korean experiments should be reported to the UN Security Council. South Korean diplomats have lobbied strongly to prevent this action.[30] The South Korean government also started a media blitz in September to emphasize the country's "four-point non-nuclear policy."[31] However, North Korea could exploit the experiments as a pretext for declining to participate in the Six-Party Talks to resolve the North Korean nuclear crisis. In early September, Han Song Ryol, North Korea's deputy ambassador to the United Nations, said that the South Korean experiments could trigger a nuclear arms race in Northeast Asia, and that the U.S. was applying a double standard to the two Koreas.[32]


Korean division and the legacies of the Korean War and the Cold War exacerbate the security dilemma in Northeast Asia. South Korea's dependence on nuclear power creates a legitimate economic incentive to establish a domestic fuel cycle capability to eliminate dependence on nuclear fuel imports and to deal with the country's spent fuel storage problem. Many South Koreans resent that Japan has been permitted to enrich uranium and reprocess spent fuel. Koreans believe this is a double standard and that Japan's militaristic past should bring restrictions upon Tokyo instead of Seoul. However, South Korea's past bomb program and the security dynamics on the peninsula mean that the U.S. will not support a complete South Korean fuel cycle.

South Korea's plutonium extraction and uranium enrichment experiments were not part of a robust program to develop nuclear weapons, but they provided data and experience that could be applied to a bomb program or to a peaceful nuclear fuel cycle that could later be part of a "virtual bomb program" under certain contingencies. The South Korean government is correct that the experiments were insignificant in terms of bomb production. In sum, the Koreans were sloppy and got caught. However, the experiments do not help alleviate suspicions in Pyongyang or the region and they make it more difficult for diplomats working to achieve a non-nuclear Korean peninsula. The experiments and how the issue is resolved also have implications for the nuclear nonproliferation regime deals with Iran and other states considering their nuclear options.

Despite the possible oversight problems, the good news is that there has been no apparent diversion of significant nuclear materials or technology to the South Korean military or other consumers. The South Korean government is cooperating with the IAEA and Seoul has implemented institutional reforms to prevent a similar problem in the future. However, the experiments are another indication of the potential problems we face if diplomacy fails to end North Korea's nuclear ambitions. There are several legal and political constraints preventing Seoul and Tokyo from going nuclear--but no real technical obstacles. South Korea could probably live with a limited and ambiguous North Korean nuclear capability, but no South Korean president could resist the nuclear option if Seoul believes Tokyo is moving forward with its own nuclear weapons program to match Pyongyang's.

[1] The author would like to thank Sarah Diehl for helpful comments, and Dave Kim, Lee Jin Sung and Mun Il Hun for research assistance.
[2] Comments by the Spokesman of the Ministry of Foreign Affairs and Trade," September 12, 2004, <>; "Chang In Sun Sojang 'Plutonium Ch'uch'ulsanghwang' Par'ŏn Ŭimi," Hankryoreh Shinmun, September 10, 2004.
[3] South Korea signed the Additional Protocol in June 1999 after coming under intense U.S. pressure in the 1990s.
[4] "ROK Claimed IAEA Knew of U Work, Pressed for No IAEA Board Report," Nucleonics Week, Vol. 45 No. 39, 23 September 23, 2004, p. 1; Mark Hibbs, "'We Played this Badly,' Koreans Say about IAEA Report Response," Nucleonics Week, Vol. 45, No. 40, September 30, 2004, pp. 7-8.
[5] Mohamed ElBaradei, "Introductory Statement to the Board of Governors," September 13, 2004, <>.
[6] Mark Hibbs, "77% U-235 Was Peak Enrichment Reported to IAEA by South Korea," NuclearFuel, Vol. 29, No. 30, September 27, 2004, pp. 7-8.
[7] "South Korea's KAERI Quantum Optics Lab Used Dye Lasers to Separate U-235," Nucleonics Week, Vol. 45 No. 37, September 9, 2004, p. 1.
[8] Ibid.
[9] Mark Gorwitz, "The South Korean Laser Isotope Separation Experience," ISIS Online, October 5, 2004, <>; Yu Yong Won, "Han'gug'ŭn Hangmujang Nŭngnyŏg'ŭl Kajyŏya Handa," Wolgan Chosun, October 1991, pp. 222-237.
[10] Ibid.
[11] "South Korea's KAERI Quantum Optics Lab Used Dye Lasers to Separate U-235," Nucleonics Week, Vol. 45 No. 37, September 9, 2004, p. 1.
[12] Ha Yŏng Sŏn, Hanbandoŭi Haengmugiwa Segyejilsŏ (Seoul: Nanam, 1991).
[13] Korea Atomic Energy Research Institute High-flux Advanced Neutron Application Reactor, "Timeline," <>; Korea Hydro & Nuclear Power (KHNP), "Nuclear Power Status," <>.
[14] Ha Yŏng Sŏn, Hanbandoŭi Haengmugiwa Segyejilsŏ (Seoul: Nanam, 1991); Young Sun Ha, "Nuclearization of Small States and World Order: The Case of Korea," Asian Survey, Vol. 18, No. 11 (November 1978); Michael J. Siler, "US Nuclear Nonproliferation Policy in the Northeast Asian Region During the Cold War: The South Korean Case," East Asia: An International Quarterly, Vol. 16 (Autumn 1998), pp. 41-79; "ROK Professor Avails Documents Attesting to Nuclear Development Plans in 1970s," Chosun Ilbo, August 4, 2004, in FBIS Document ID: KPP20040803000060.
[15] Yu Yong Won, "Han'gug'ŭn Hangmujang Nŭngnyŏg'ŭl Kajyŏya Handa," Wolgan Chosun (October 1991), pp. 222-237.
[16] O Tong Yong, "[T'ŭkchong] Park Chong Hee'ŭ W onjap'okt'an Kaebal Pimil Kyehoiksŏ Wŏnmun Pal'gul," Wolgan Chosun, August 10, 2003, <>; Ch'ae Hŭi Ch'ang, Park Pyŏng Chin, Chu Ch'un Ryŏl, Kim Hyŏng Ku, and Lee U Sŭng, "Park Chŏndaet'ongnyŏng Kŭkpich'ujin Haek Kaebalsaŏp Sŏlgyedo Palgyŏndoaetta," Segye Ilbo, August 1, 2004.
[17] Ibid.; William H. Gleysteen, Jr., Massive Entanglement, Marginal Influence (Washington, DC: Brookings Institution Press, 1999), pp. 14-15.
[18] Confidential documents and interviews; Mark Hibbs, "KAERI Report Documents Production of 200 Kilograms UF4, DU Imports," Nucleonics Week, Vol. 45, No. 44, October 28, 2004, pp. 15-16.
[19] Ibid.
[20] Mark Hibbs, "Conversion to U Metal by ROK Raises Questions on UF4, UF6," Nuclear Fuel, Vol. 29, No. 21, October 11, 2004, pp. 18-19.
[21] Confidential documents and interviews; Mark Hibbs, "KAERI Report Documents Production of 200 Kilograms UF4, DU Imports," Nucleonics Week, Vol. 45, No. 44, October 28, 2004, pp. 15-16.
[22] Ibid.
[23] Between the time of the disclosure of the experiments in August and early November 2004, the IAEA dispatched three teams of inspectors to investigate the experiments.
[24] "Comments by the Spokesman of the Ministry of Foreign Affairs and Trade," September 12, 2004, <>.
[25] Pak Chung Ŏn, "Il Mainich'i Podo...YS 'Kŭrŏnmal Hanjŏk Ŏptta," Hankryoreh Shinmun, September 23, 2004.
[26] "Chang In Sun Sojang 'Plutonium Ch'uch'ulsanghwang' Par'ŏn Ŭimi," Hankryoreh Shinmun, September 10, 2004.
[27] "Pak Chŏndaet'ongnyŏng Kŭkpich'ujin Haek Kaebalsaŏp Sŏlgyedo Palgyŏndoaetta," Segye Ilbo, August 1, 2004; "Urido Maŭm Mŏgŭmyŏn 2~3 Nyŏndui Haekpoyu Kanŭng," Segye Ilbo, August 1, 2004.
[28] Mark Hibbs, "Korean Safety Agency to Take over Nuclear Materials Accounting Center," Nuclear Fuel, Vol. 29, No. 23, November 8, 2004, pp. 3-5.
[29] Ibid., p. 4.
[30] Mark Hibbs and Daniel Horner, "South Korea Calls Fuel-cycle Testing a 'Technical Violation'," Nucleonics Week, Vol. 45, No. 42, October 14, 2004, pp. 15-17.
[31] "National Security Council Statement on the Peaceful Use of Nuclear Energy," Korea Update, Vol. 15, No. 17, September 21, 2004; "Chŏngbu 'Haengmugi Kaebal-Poyuŭisa Ŏptta'," Hankryoreh Shinmun, September 18, 2004.
[32] Yonhap News Agency, September 8, 2004, in "DPRK's UN Envoy Warns 'Additional Measures Will Follow' Regarding ROK's Uranium Tests," FBIS Document ID: KPP20040908000137; James Brooke, "North Korea Says Seoul's Nuclear Experiments Stoke Arms Race," New York Times, September 9, 2004.

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Author(s): Daniel A. Pinkston
Related Resources: Nuclear, East Asia, Research Story
Date Created: November 9, 2004
Date Updated: -NA-
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