In 1981, South Korean engineers produced five test fuel rods using depleted uranium. The fuel rods were placed in a research reactor and irradiated between July and December 1981. The spent fuel rods were removed and scientists conducted experiments in hot-cells to extract 0.3 grams of plutonium. [2] The South Korean Ministry of Science and Technology (MOST) claimed that this experiment was conducted by "a small group of scientists to analyze the chemical characteristics of plutonium."[3] These experiments were not revealed to the public until the summer of 2004, after South Korea had ratified the Additional Protocol. Under this modified safeguards agreement with the IAEA, South Korean nuclear facilities were subject to more detailed inspections.[4] In the summer of 2004, South Korea also reported that its scientists had conducted laser isotope separation experiments to enrich about 0.2 grams of uranium. Both the plutonium extraction and uranium enrichment experiments were in violation of Seoul's safeguards commitments, but the government cooperated with the IAEA to account for these violations and to ensure there were no future violations.[5] During the June 2008 IAEA Board of Governors meeting, a "broader conclusion" was drawn that all nuclear material in South Korea had been placed under safeguards and remained in peaceful nuclear activities. [6]

In November 1991, President Roh Tae Woo (노태우) declared that South Korea would not "manufacture, possess, store, deploy, or use nuclear weapons."[7] Two months later, North and South Korea signed the Joint Declaration on the Denuclearization of the Korean Peninsula. In this agreement, Seoul and Pyongyang agreed not "to test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons," and not to "possess nuclear reprocessing and uranium enrichment facilities." However, both sides failed to implement the agreement's provisions relating to a bilateral inspection regime. Although North Korea has clearly violated the Joint Declaration, particularly in light of its two nuclear weapons tests (in 2006 and 2009), South Korea has never officially renounced its obligations under the declaration and has called on the North to abide by the agreement. Seoul has been a participant in the Six-Party Talks, aimed at ending the nuclear crisis on the Korean Peninsula, since their inception in 2003.

South Korea has a total of 21 nuclear power reactors in operation—ranking fifth in the world in number of reactors. Nuclear energy currently provides almost 31 percent of its total electricity.[8] Furthermore, the Ministry of Science and Technology (MOST) has five reactors under construction and six more ordered or planned by 2021.[9] South Korea has also recently become a major player as a nuclear exporter, with Korean companies winning a number of lucrative contracts in 2010. These include a US$20 billion contract to construct four reactors in the UAE, and a $173 million contract to construct a nuclear research reactor in Jordan.[10]

Despite South Korea's extensive nuclear energy infrastructure and technological base, South Korea does not possess any independent means of enrichment or reprocessing. While its legal validity remains ambiguous, South Korea is politically constrained by the 1992 Joint Declaration with North Korea. However, South Korean officials have expressed a keen interest in establishing a closed nuclear fuel cycle. In light of the projected expansion of nuclear power in South Korea and the problem of mounting spent fuel, the Korea Atomic Energy Research Institute (KAERI) has been conducting research on dry pyroprocessing technology.[11] While South Korean officials argue that pyroprocessing is different from reprocessing, outside experts, including many in the U.S. government disagree. Since much of South Korea's nuclear fuel is U.S.-origin, South Korea cannot undertake any reprocessing (or pyroprocessing) without the consent of the U.S. government.

Sources:
[1] Ha Yeong-seon, 한반도의 핵무기와 세계질서 [Nuclear Weapons on the Korean Peninsula and World Order] (Seoul: Nanam, 1991).
[2] Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, 9 November 2004, http://cns.miis.edu.
[3] Anthony Faiola and Dafna Linzer, "S. Korea Admits Extracting Plutonium," Washington Post, 10 September 2004, www.washingtonpost.com.
[4] Anthony Faiola and Dafna Linzer, "S. Korea Admits Extracting Plutonium," Washington Post, 10 September 2004, www.washingtonpost.com.
[5] Mohamed El-Baradei, "Introductory Statement to the Board of Governors," IAEA Website, 13 September 2004, www.iaea.org.
[6] "IAEA Confirms S. Korea's Nuclear Activity Peaceful," Yonhap, 3 June 2008, in www.lexisnexis.com.
[7] Roh Tae Woo, "President Roh Tae Woo's Declaration of Non-Nuclear Korean Peninsula Peace Initiatives," 8 November 1991, available at www.fas.org.
[8] "Nuclear Power in South Korea," World Nuclear Association, February 2012, http://world-nuclear.org.
[9] "Nuclear Power in South Korea," World Nuclear Association, February 2012, http://world-nuclear.org.
[10] "Korean consortium for Jordan's first reactor," World Nuclear News, 7 December 2009, and "UAE picks Korea as nuclear partner," World Nuclear News, 29 December 2009, www.world-nuclear-news.org.
[11] "Fuel Cycle Process Development Division," KAERI, http://ehome.kaeri.re.kr.