In the late 1950s, the DPRK started research on nuclear technology. The former Soviet Union helped the DPRK to set up the "Yongbyon Atomic Energy Research Institute" in 1965 and trained some nuclear technicians. At that time, the DPRK imported the first 800-kilowatt nuclear reactor from the former Soviet Union, and nuclear technology research took shape. Yongbyon became the center of the DPRK's nuclear industry, where enriched uranium can be refined for the production of nuclear weapons, and thus became a place of special interest for the U.S. and the International Atomic Energy Agency (IAEA).
Worried about North Korea's development of nuclear weapons, the U.S. and North Korea signed an Agreed Framework on the North Korean nuclear issue in Geneva in October 1994, promising to provide two light-water reactors in exchange for a freeze on North Korea's nuclear facilities. Since then, 8,000 spent fuel rods from the 5-megawatt reactor at Yongbyon have been removed and sealed.
By the end of the 20th century, the DPRK had successively built six nuclear research centers, two nuclear reactors of a research nature and a nuclear power test reactor, and had already proved as much as 4 million tons of mineable uranium reserves throughout the country, with six uranium mines ready to be mined.
The DPRK has built three uranium dioxide conversion plants, a natural uranium fuel assembly manufacturing plant and a nuclear waste storage site, basically completing a nuclear fuel cycle system from uranium mining to nuclear waste disposal, and possessing the capability to research and manufacture nuclear weapons.
In 1989, the DPRK admitted that a graphite-cooled research reactor with an electrical power of 5 megawatts built at Yongbyon had to reprocess its nuclear waste because of the breakage of the zirconium layer on the outer surface of the uranium fuel rods, and that it had obtained 130 grams of plutonium as a result. In October 1994, fearing that the DPRK was developing nuclear weapons, the United States and the DPRK signed a Geneva Nuclear Agreed Framework on the DPRK nuclear issue in Geneva. Under the agreement, the DPRK agreed not to refuel a 5-megawatt nuclear reactor, to halt construction of two graphite deceleration reactors, to seal off the nuclear fuel reprocessing plant, and ultimately to dismantle these nuclear facilities. Under the terms of the agreement, the United States will be responsible for building either one 2,000-megawatt or two 1,000-megawatt light water reactors for the DPRK by the end of 2003. Until the light water reactors are built, the U.S. will provide 500,000 tons of heavy oil per year to the DPRK as energy compensation. Since then, 8,000 spent fuel rods from the 5 MW reactor at Yongbyon have been removed and sealed. International Atomic Energy Agency personnel have also installed monitoring devices at nuclear facilities such as the 5-megawatt reactor at Yongbyon.
After the second North Korean nuclear crisis erupted in late 2002, the U.S. stopped supplying heavy fuel oil to the DPRK. on Dec. 12, 2002, the DPRK, accusing the U.S. of failing to honor its commitments, announced the restart of the frozen Yongbyon nuclear facility. It dismantled monitoring equipment installed by the International Atomic Energy Agency (IAEA) at its nuclear facilities and expelled IAEA personnel.
In order to bring about a peaceful resolution of the DPRK nuclear issue, the Chinese government actively mediated and facilitated the tripartite talks on the DPRK nuclear issue in April 2003 with the participation of the DPRK, China and the United States. In August of the same year, China also facilitated the six-party talks on the DPRK nuclear issue with the participation of China, the DPRK, South Korea, the United States, Japan and Russia. So far, five rounds of the six-party talks have been held. In 2007, the DPRK suspended the operation of its 5-megawatt graphite decelerator reactor in accordance with the agreement reached at the six-party talks on the DPRK nuclear issue in October of the same year. According to the document, on the morning of June 27, 2008, the DPRK blew up the cooling tower of the Yongbyon nuclear reactor in accordance with the agreement of the Six-Party Talks. In November 2010, the DPRK allowed Haeckel, a former director of the U.S. Los Alamos National Laboratory and an expert in nuclear physics, access to the Yongbyon nuclear facility. Haeckel claimed to have confirmed that "hundreds of centrifuges" had been secretly installed at the North Korean uranium enrichment facility. The DPRK said 2,000 centrifuges were in operation at the time.
Satellite images from Nov. 3, 2011, show that a new nuclear reactor building at Yongbyon, North Korea, is nearly complete, with the outer wall of the reactor already in place.
On May 17, 2012, a study by the Korea-U.S. Institute at the Johns Hopkins University School of Advanced International Studies (SAIS) reported that North Korea appeared to have restarted construction of a light-water reactor at its Yongbyon nuclear facility. The report said that this may be the first nuclear test by North Korea to engage in highly enriched uranium enrichment activities .