Construction of the 5 MWe experimental reactor began in 1980, and the reactor first went
critical in 1986. The 5 MWe experimental reactor operated intermittently until 1994 when it was shut down in accordance with the
U.S.-North Korea Agreed Framework. Following the breakdown of the Agreed Framework in 2002, operation restarted in February 2003, creating
plutonium within its fuel load at a rate of about 6 kg per year. The reactor fuel was replaced between April and June 2005. The
spent nuclear fuel has been reprocessed with an estimated yield of about 24 to 42 kg of plutonium metal, Nyongbyon is also the site of a 50
MWe Magnox prototype power reactor, but construction was halted in 1994 about a year from completion in accord with the Agreed Framework, and by 2004 the structures and pipework had deteriorated badly. This construction was being dismantled in 2010. In return for this
North Korea will receive emergency energy assistance from the other five parties in the form of 50,000 tons of heavy fuel oil.
International Atomic Energy Agency (IAEA) inspectors arrived at the site on 28 June to discuss verification and monitoring arrangements for the shutdown. This had been delayed from April due to a dispute with the United States over
Banco Delta Asia. On 3 June an anonymous South Korean government official indicated that the shutdown may start following the first oil shipment later in the month. On 14 July,
Sean McCormack stated that North Korea had told the US that the reactor had been shut down. He added that the US welcomed the news, and was awaiting verification from the IAEA team. The next day, IAEA chief
Mohamed ElBaradei announced the UN's confirmation that the reactor had been shut down. On 18 July 2007, the IAEA confirmed that all five nuclear facilities at Nyongbyon had been shut down. In his Introductory Statement to the IAEA Board of Governors on 2008-03-03, the Director General stated that he could not provide an update on the disabling of the facilities, as it was not undertaken by the IAEA. All fuel rods from the 5 MWe Experimental Nuclear Power Plant and nuclear material generated by the disabling of the Nuclear Fuel Fabrication Plant were under IAEA containment and surveillance.
2008 cooling tower demolition On 27 June 2008 North Korea destroyed the most visible symbol of its nuclear weapons program – the
cooling tower at its main atomic reactor in the complex. The implosion was witnessed by a number of international journalists and diplomats. The demolition of the -tall cooling tower, which carried off waste heat to the atmosphere, is a response to U.S. concessions after the North delivered a declaration of its nuclear programs to be dismantled. The United States paid the US$2.5 million demolition fee.
Possible reactivation During 2008 tensions resurfaced between North Korea and the U.S. due to disagreements over the
six-party talks disarmament process. On 8 October 2008,
IAEA inspectors were forbidden by the North Korean government to conduct further inspections of the site. However two days later the U.S. removed North Korea from the U.S.
State Sponsors of Terrorism list and the Nyongbyon deactivation process resumed.
2009 resumption of reprocessing According to the state-run North Korean news agency KCNA website, the DPRK resumed the reprocessing of spent fuel to recover plutonium on 25 April 2009 in response to the UN's condemnation of its recent
rocket launch. This material supplemented that used for nuclear weapons testing.
Light water reactor In 2009, North Korea announced its intention to build an indigenous experimental
light water reactor (LWR) and the uranium enrichment technology to provide its nuclear fuel. In 2010, a 2,000
gas centrifuge uranium enrichment plant to produce
low enriched uranium (LEU) fuel began operating, and construction started on the experimental 25 to 30 MWe LWR, with a target operation date for the reactor of 2012. In November 2011, satellite imagery indicated that the LWR construction was progressing rapidly, with the concrete structures largely completed. The LWR is being built on the site of the demolished cooling tower of the experimental Magnox reactor. Following the building of this experimental LWR, North Korea intends to build larger LWRs for electricity generation. but the reactor was not externally complete until 2016. In 2017, several activities were noted involving construction, a dam was built to provide sufficient amount of water for cooling system, a switchyard and connections to transmission line were made along with facilities presumably used for maintenance and repair. Activity that suggests components were being transferred to the building were noted too. In 2018, it was believed that the preliminary testing of the reactor had started and that the reactor would begin to operate 2018 or 2019. The reactor is linked to the power grid, with an expected output is 25 to 30 megawatts, enough to supply electricity for about 50,000 inhabitants. As of May 2024, intermittent cooling water flows indicate pre-operational tests are probably being conducted. According to the IAEA, the reactor ran intermittently for nearly two years up to August 2025, running 70% of the time from August 2024 to August 2025 though unlikely at full power. It is estimated the reactor at full power could produce around 20 kilograms of plutonium per year, though it is not clear whether the fuel will be reprocessed. The
Institute for Science and International Security (ISIS) assessed that operation of reactor was resumed in November 2025.
Suspension of uranium enrichment In February 2012, North Korea announced that it would suspend uranium enrichment at Nyongbyon, and not conduct any further tests of nuclear weapons while productive negotiations involving the United States continue. Additionally, North Korea would allow IAEA inspectors to monitor operations at Nyongbyon. The U.S. reaffirmed that it does not have hostile intent toward the DPRK, and is prepared to improve bilateral relationships. Nuclear enrichment was presumably resumed following the collapse of the Leap Day Deal.
2013 planned restart of operation In March 2013, North Korea announced that they would be restarting operation of the 5 MWe experimental reactor. In order to do so, the disabled secondary cooling system will have to be restored. On 15 September 2015, North Korea announced that the Yongbyon nuclear site is in full operation, including the 5 MWe experimental reactor. Infra-red imagery analysis covering from September 2016 to June 2017 showed that the 5 MWe experimental reactor had either not been operated, or operated at a low-level. The Radiochemical Laboratory had operated intermittently.
2018 Pyongyang Agreement During the
September 2018 inter-Korean summit, North Korean leader Kim Jong-Un and South Korean leader Moon Jae-In signed the "Pyongyang Joint Declaration of September 2018" The agreement states, among other things, that the North Korean government will only dismantle Nyongbyon if the US would engage in correlative action. As of January 2019, Nyongbyon's main facilities did not appear to be operating. However, in August 2021, the
International Atomic Energy Agency reported that
North Korea appeared to have restarted the 5 MW reactor. ==Organization==