Last Updated: December, 2015
South Korea first became interested in nuclear technology in the 1950s but did not begin construction of its first power reactor until 1970.  Changes in the international security environment influenced South Korea's decision to begin a nuclear weapons program in the early 1970s. Under significant pressure from the United States, Seoul abandoned the program and signed the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in April 1975. Section 123 of the 1954 US Atomic Energy Act prohibits indigenous uranium enrichment, reprocessing used fuel, and restricts raw material imports.
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.  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."  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 International Atomic Energy Agency (IAEA), South Korean nuclear facilities were subject to more detailed inspections.  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.  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. 
In November 1991, President Roh Tae Woo (노태우) declared that South Korea would not "manufacture, possess, store, deploy, or use nuclear weapons."  Two months later, North Korea 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 violated the Joint Declaration, particularly in light of its three nuclear weapons tests (in 2006, 2009, and 2013), 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 24 nuclear power reactors in operation and four under construction—ranking fifth in the world in number of reactors. As of 2015, nuclear energy provides approximately one third of its total electricity.  Korea plans to complete 11 new nuclear power plants by 2024. The South Korean government previously planned for 41 percent of the nation’s energy supplies to come from nuclear power by 2030, but policies released in January 2014 revised that number to 29 percent of total power supply by 2035.  A joint research project by the Korea Atomic Energy Research Institute (KAERI) and National Fusion Research Institute (NFRI) is currently underway to develop the 4th generation of nuclear power plants (Gen IV) which will incorporate Sodium-cooled Fast Reactor (SFR) and Very High Temperature gas-cooled Reactor (VHTR). The goal is to commercialize these technologies by 2030. 
South Korea is an exporter of nuclear power technology. In January 2010, the Ministry of Knowledge Economy announced that it plans to export 80 nuclear power reactors by 2030 which is worth $400 billion. Thus far, South Korea has agreed to a USD $20 billion contract to construct four reactors in the United Arab Emirates, a $173 million contract to construct a nuclear research reactor in Jordan, and a nuclear cooperation agreement to build several reactors in Saudi Arabia worth $2 billion.  South Korea’s nuclear industry has also shown keen interest in penetrating into Chinese market which holds significance since China has been known to transfer its nuclear technologies and equipment to Pakistan, which is not a member of the NPT.  South Korean nuclear reactors have also faced safety and security issues with forged safety certificates for replacement parts. 
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 and the 1972 bilateral pact with the U.S. on nuclear cooperation. However, South Korean officials have expressed a keen interest in establishing a closed nuclear fuel cycle toward its goal of overtaking 20 percent of the global nuclear reactor market.  Additionally, South Korea’s own reliance on nuclear power is projected to grow, and the problem of mounting spent nuclear fuel is a pressing one.  As a country that has one of the highest population density in the world, South Korea’s problem of spent nuclear fuel storage stems from both securing the physical space and the strong domestic opposition from the Koreans who do not want the interim storage site in their neighborhood. Despite objections, low and intermediate-level waste (LILW) is stored at each reactor site with a total of about 60,000 drums of 200 liters.  A central disposal facility for low to medium level waste at Gyeongju was completed in June 2014. A recent report from an independent advisory body indicates that South Korea will begin to run out of interim storage space for waste materials beginning in 2016. 
Concerns about South Korea's interest in a form of nuclear fuel recycling called pyroprocessing, and in uranium enrichment technology hampered the renewal of the U.S.-South Korea nuclear cooperation agreement. The agreement, originally set to expire in 2014, was extended until 2016 to allow Washington and Seoul to come to some agreement about South Korea's interest in enrichment and reprocessing technology.  In April 2015, South Korea and the U.S. reached a deal, replacing the 1972 agreement, to lift the ban on reprocessing of spent nuclear fuel, as well as uranium enrichment, and reaffirmed the research on pyroprocessing technology.  The South Korean Cabinet approved the agreement in June. 
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Get the Facts on South Korea
- Operates 23 nuclear power reactors which provide 35% of its electricity
- Completed destruction of its chemical weapons stockpile in July 2008
- Owns a well-developed biotechnology infrastructure, but no evidence suggests the pursuit of a biological weapons program