Yongbyon 5MWe Reactor

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Last Updated: July 19, 2018
Other Name: 5MWe실험용원자로; Experimental Nuclear Power Station-1; Experimental Nuclear Power Plant No. 1(시험원자력발전소 1호기); Yongbyon No. 1 Machine (영변1호기); the Second Reactor, Reactor No. 2 (제2호원자로); February Enterprise (2월기업소); Reactor 1; 5MWe pilot plant; Calder Hall Clone
Location: Bungang-jigu (분강지구), Yongbyon-gun (영변군), Pyeonganbuk-do (평안북도), North Korea
Subordinate To: Nuclear Physics Research Institute (핵물리연구소), Yongbyon Nuclear Research Center (영변원자력연구센터), General Department of Atomic Energy (원자력총국), Cabinet (내각)
Size: 5MWe, about 20-25MWth
Facility Status: Under Construction for Restart


The Yongbyon 5MWe reactor is a graphite-moderated and gas-cooled reactor with a thermal power range of 20-25MW. Construction of the reactor began in 1979 and was completed by 1986. It was modeled after the U.K.’s Calder Hall reactor. [1] This type of reactor had several advantages for North Korea: it is fueled by natural uranium, which is abundant in North Korea; it is cooled by a carbon-dioxide gas rather than difficult to acquire heavy water; and it is moderated by graphite, plentiful in North Korea.

Although North Korea told the International Atomic Energy Agency (IAEA) the reactor would be used for electricity generation, experts were skeptical and suspected a possible military purpose as the reactor’s design can easily produce weapons-grade plutonium. [2] These suspicions were confirmed when North Korea announced its nuclear weapons in 2005 and conducted its first test in 2006. [3]

U.S. satellite imagery and analysis indicates the reactor likely shut-down in 1989, 1990, and 1991. [4] Only the 1989 shutdown is believed to have been long enough to enable unloading of all or much of the fuel in the reactor core. North Korea later reported to the IAEA that it reprocessed about 90 grams of plutonium from damaged spent fuel rods that were removed from the reactor in 1989, but made no reference to the reactor being shut down in 1990 or 1991. [5]

The IAEA inspection of the 5MWe reactor and other nuclear facilities in the Yongbyon Nuclear Research Center commenced following the ratification of its safeguards agreement in April 1992. [6] During these inspections, the IAEA discovered discrepancies in North Korea's initial declaration, which led the IAEA to request special ad hoc inspections. North Korea balked at this request and announced its intention to withdraw from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). [7] However, following talks with Washington, Pyongyang suspended its withdrawal from the NPT in June 1993, just days before it would have gone into effect. [8]

In May and June of 1994, North Korean technicians, without the supervision of IAEA inspectors, once again discharged up to 60 percent of the reactor's spent fuel rods and placed them in a cooling pond. [9] This action nearly led to a military confrontation with the United States, before former President Jimmy Carter's trip to Pyongyang defused the crisis. Carter's trip encouraged North Korean leader Kim Il Sung to continue negotiating on the Agreed Framework, which concluded successfully in October 1994. Under the terms of the agreement, spent fuel rods unloaded in 1994 were canned and stored in Yongbyon until they could be shipped to a third country. [10]

In October 2002, the United States confronted North Korea about a suspected uranium enrichment program, leading to the breakdown of the Agreed Framework. [11] Subsequently, Pyongyang indicated in December that it intended to restart the 5MWe reactor and withdraw from the NPT. [12] U.S. officials later confirmed the reactor was restarted in February 2003. [13] North Korea indicated that 8,000 spent fuel rods that were in storage since 1994 were processed, and that another 8,000 spent fuel rods were discharged and processed in 2005. [14]

As part of the 2007 round of Six-Party Talks, agreements were made to disable the reactor and remove the fuel. In 2008, the cooling tower was demolished as part of the agreement. In April 2009, North Korea threatened to restore the reactor in response to the U.N. Security Council's condemnation of the North Korean missile test earlier in the month. However, satellite imagery from August 2009 indicated that no construction had begun on either the reactor site or the cooling tower. [15] In a November 2010 visit by U.S. experts to the facility, the reactor still appeared to be inactive. They were told that it is in stand-by status with regular maintenance. [16]

On 2 April 2013, North Korea announced plans to restart the Yongbyon 5MWe Reactor for plutonium production as part of a nationwide restart of all its nuclear facilities. [17] Commercial satellite imagery of the site from late March 2013 shows that work has begun to connect the reactor’s secondary cooling system to the pump house of the adjacent experimental light water reactor. [18] This is an essential step to restoring the reactor to an operational status, and suggests that it may indeed be restarted. By September 2013, satellite imagery indicated that North Korea restarted the 5 MWe reactor, presumably for the production of weapons grade plutonium. [19] Satellite imagery showed white steam rising from a building nearby containing steam turbines used for generating electricity. [20] Following an exchange of artillery fire between North Korea and South Korea in late August 2015, North Korea announced that the facility was “fully operational” and that it was improving its weapons in both “quality and quantity.” [21]

April 2016 satellite imagery confirmed increased activity such as construction of an additional access road and construction of a new storage facilities for possibly intended for reprocessing purposes. [22] However, the same images indicated that the reactor had been shut off, possibly to unload spent fuel rods for reprocessing purposes. Commercial satellite imagery from 18 January 2017 indicated that North Korea completed the unloading process and was planning to restart the reactor in order to produce more plutonium. [23] Imagery from 22 January however showed a clear water plume emanating from a cooling outlet indicating it had most likely been switched back on. [24]

[1] International Atomic Energy Agency, “IAEA and DPRK: Fact Sheet on DPRK Nuclear Safeguards," www.iaea.org.
[2] David Albright and Kevin O'Neill, eds., Solving the North Korean Nuclear Puzzle (Washington, D.C.: Institute For Science and International Security, 2000).
[3] “DPRK FM on Its Stand to Suspend Its Participation in Six-party Talks for Indefinite Period," Korean Central News Agency, 11 February 2005, www.kcna.co.jp; "DPRK Successfully Conducts Underground Nuclear Test," Korean Central News Agency, 10 October 2006, www.kcna.co.jp; "Magnitude 4.3 — North Korea," USGS, 9 October 2006, http://earthquake.usgs.gov.
[4] David Albright and Kevin O'Neill, eds., Solving the North Korean Nuclear Puzzle, (Washington, D.C.: Institute For Science and International Security, 2000).
[5] David Albright and Kevin O'Neill, eds., Solving the North Korean Nuclear Puzzle, (Washington, D.C.: Institute For Science and International Security, 2000).
[6] International Atomic Energy Agency, “Agreement of 30 January 1992 between the Government of the Democratic People's Republic of Korea and the International Atomic Energy Agency for the Application of Safeguards in Connection with the Treaty on the Non-Proliferation of Nuclear Weapons," Information Circular, INFCIRC/403, May 1992, www.iaea.org.
[7] International Atomic Energy Agency, “IAEA and DPRK: Fact Sheet on DPRK Nuclear Safeguards," www.iaea.org; "Letter from Kim Yong-nam, DPRK Minister of Foreign Affairs," Reuters, 12 March 1993.
[8] “China welcomes North Korea's NPT decision," Agence France Presse, 12 June 1993, via: www.lexisnexis.com.
[9] "북한 핵연료봉 60% 빼내 “[North Korea Discharged 60% of Nuclear Fuel Rods]" Yonhap News Agency, 31 May 1994, www.yonhap news.co.kr.
[10] “Agreed Framework between the United States of America and the Democratic People's Republic of Korea," 21 October 1994, via: www.nti.org.
[11] Richard Boucher, "Press Statement: North Korean Nuclear Program," U.S. Department of State, 16 October 2002, www.state.gov; James A. Kelly, "U.S.-East Asia Policy: Three Aspects," Remarks at the Woodrow Wilson Center, Washington, DC, 11 December 2002, www.state.gov.
[12] “Statement of DPRK Government on its withdrawal from NPT," Korean Central News Agency, 11 January 2003, www.kcna.co.jp.
[13] "Chronology of U.S.-North Korean Nuclear and Missile Diplomacy," Arms Control Association, www.armscontrol.org.
[14] “KCNA Report on Nuclear Activities in DPRK," Korean Central News Agency, 3 October 2003, www.kcna.co.jp; “Spent Fuel Rods Unloaded from Pilot Nuclear Plant,” Korean Central News Agency, 11 May 2005, www.kcna.co.jp; “DPRK Completes Reprocessing of Spent Fuel Rods," Korean Central News Agency, 3 November 2009, www.kcna.co.jp.
[15] "No Reconstruction at the Yongbyon Reactor Site," ISIS Imagery Brief, 4 September 2009, http://isis-online.org.
[16] Siegfried Hecker, "A Return Trip to North Korea's Yongbyon Nuclear Complex," Center for International Security and Cooperation, Stanford University, 20 November 2010, http://iis-db.stanford.edu.
[17] “DPRK to Adjust Uses of Existing Nuclear Facilities," KCNA, 2 April 2013, www.kcna.co.jp.
[18] Nick Hansen and Jeffrey Lewis, “Satellite Images Show New Construction at North Korea’s Plutonium Production Reactor; Rapid Restart?” 38 North, 3 April 2013, www.38north.org.
[19] Nick Hansen and Jeffrey Lewis, “North Korea Restarting Its 5 MW Reactor," 38 North, 11 September 2013, www.38north.org; Nick Hansen, “More Evidence That North Korea Has Restarted Its 5 MWe Reactor," 38 North, 2 October 2013, www.38north.org.
[20] “North Korea Restarting its 5 MW Reactor,” 38 North, 11 September 2013, www.38North.org
[21] “North Korea Yongbyon Nuclear Site ‘in operation’”. BBC News, 15 September 2015, www.bbc.com
[22] “More Evidence of Possible Reprocessing Campaign at Yongbyon; Progress at Experimental Light Water Reactor;” 38 North, 15 April 2016, www.38North.org
[23] David Brunnstrom. “North Korea appears to have restarted plutonium reactor: think tank,” 27 January 2017, www.reuters.com.
[24] “North Korea has restarted reactor to make plutonium, fresh images suggest,” 27 January 2017, www.theguardian.com.

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