Fact Sheet

North Korea Nuclear Overview

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North Korea Nuclear Overview

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This page is part of the North Korea Country Profile.

North Korea (aka the Democratic People’s Republic of Korea or DPRK) is the only country to have withdrawn from the Treaty on the Nonproliferation of Nuclear Weapons (NPT) to pursue a nuclear weapons program, and possesses an increasingly sophisticated nuclear arsenal. The DPRK remains outside of the Comprehensive Nuclear Test-Ban Treaty (CTBT), and has repeatedly violated the international norm against nuclear testing by conducting tests in 2006, 2009, 2013, two tests in 2016, and a test in 2017. North Korea claimed its sixth nuclear test, in September 2017, was of a thermonuclear device. 1 The United Nations Security Council has passed numerous resolutions condemning North Korea’s nuclear activities, and has imposed increasingly harsh sanctions on the North Korean military and economy.

International efforts to negotiate an end to North Korea’s nuclear program, which had been stalled since the discontinuation of the Six Party Talks in 2009, were rekindled in early 2018. A diplomatic thaw on the Korean Peninsula led to direct talks between the heads of state of the two Koreas, Kim Jong-un and Moon Jae-in, on 27 April 2018, followed by the 12 June 2018 summit between North Korean leader Kim Jong-un and U.S. President Donald Trump in Singapore. Although North Korea affirmed its commitment to the denuclearization of the Korean Peninsula at both summits, there has been little tangible progress towards denuclearization.

Click to take a virtual tour of North Korea’s nuclear test tunnels at Punggye-ri.


1950s to 1960s: Early Developments

North Korea began its nuclear program in the early 1950s. In December 1952, the government established the Atomic Energy Research Institute and the Academy of Sciences, but nuclear work only began to progress when North Korea established cooperative agreements with the Soviet Union. 2 Pyongyang signed the founding charter of the Soviet Union’s Joint Institute for Nuclear Research in February 1956, and began to send scientists and technicians to the USSR for training shortly thereafter. In 1959, North Korea and the Soviet Union signed an agreement on the peaceful use of nuclear energy that included a provision for Soviet help to establish a nuclear research complex in Yongbyon, North Pyongan Province. 3

In the early 1960s, the Soviet Union provided extensive technical assistance to North Korea in constructing the Yongbyon Nuclear Research Center, which included the installation of a Soviet IRT-2000 nuclear research reactor and associated facilities. North Korea used this small research reactor to produce radioisotopes and to train personnel. 4 Although the cabinet and the Academy of Sciences were given operational and administrative oversight of the nuclear facilities, then-North Korean leader Kim Il Sung retained ultimate control of the nuclear program and all decisions associated with weapons development.

Although bolstered by early assistance from Moscow, and to some extent Beijing, North Korea’s nuclear program developed largely without significant foreign assistance. Reportedly, Kim Il Sung asked Beijing to share its nuclear weapons technology following China‘s first nuclear test in October 1964, but Chinese leader Mao Zedong refused. 5 Shortly thereafter, North Korean relations with China began to deteriorate.

1970s to 1993: Indigenous Development under the Radar of the International Community

In the late 1960s, North Korea expanded its educational and research institutions to support a nuclear program for both civilian and military applications. By the early 1970s, North Korean engineers were using indigenous technology to expand the IRT-2000 research reactor, and Pyongyang had begun to acquire plutonium reprocessing technology from the Soviet Union. 6 In July 1977, North Korea signed a trilateral safeguards agreement with the IAEA and the USSR that brought the IRT-2000 research reactor and a critical assembly in Yongbyon under IAEA safeguards. The Soviets were included in the agreement because they supplied the reactor’s fuel. 7

The early 1980s was a period of significant indigenous expansion, when North Korea constructed uranium milling facilities, a fuel rod fabrication complex, and a 5MW(e) nuclear reactor, as well as research and development institutions. Simultaneously, North Korea began experimenting with the high explosives tests required for building the triggering mechanism of a nuclear bomb. By the mid-1980s, the country had begun constructing a 50MW(e) nuclear reactor in Yongbyon, while also expanding its uranium processing facilities. 8

The DPRK also explored the acquisition of light water reactor (LWR) technology in the early to mid-1980s. This period coincided with the expansion of North Korea’s indigenously designed reactor program, which was based on gas-graphite-moderated reactors similar in design to the Calder Hall reactors first built in the United Kingdom in the 1950s. North Korea agreed to sign the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as a non-nuclear weapon state in December 1985 in exchange for Soviet assistance constructing four LWRs. 9

In September 1991, U.S. President George H. W. Bush announced that the United States would withdraw its nuclear weapons from South Korea, and on 18 December 1991, President Roh Tae Woo declared that South Korea was free of nuclear weapons. 10 North Korea and South Korea then signed the Joint Declaration on the Denuclearization of the Korean Peninsula, whereby both sides promised they would “not test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons.” The agreement additionally bound the two sides to forgo the possession of “nuclear reprocessing and uranium enrichment facilities.” The agreement also provided for a bilateral inspections regime, but the two sides failed to agree on its implementation. 11

The 1994 Crisis and the Agreed Framework

North Korea signed an IAEA safeguards agreement on 30 January 1992, and the Supreme People’s Assembly ratified the agreement on 9 April 1992. Under the terms of the agreement, North Korea provided an initial declaration of its nuclear facilities and materials, and provided access for IAEA inspectors to verify the completeness and correctness of its declaration. 12 Six rounds of inspections began in May 1992 and concluded in February 1993. Pyongyang’s initial declaration included a small plutonium sample (less than 100 grams), which North Korean officials said was reprocessed from damaged spent fuel rods that were removed from the 5MW(e) reactor in Yongbyon-kun. However, IAEA analysis indicated that Korean technicians had reprocessed plutonium on three occasions—in 1989, 1990, and 1991. 13 When the Agency requested access to two suspected nuclear waste sites, North Korea declared them to be military sites and therefore off-limits. 14

After the IAEA was denied access to North Korea’s suspected waste sites in early 1993, the Agency asked the United Nations Security Council (UNSC) to authorize special ad hoc inspections. In reaction, North Korea announced its intention to withdraw from the NPT on 12 March 1993. 15 Under the terms of the treaty, a state’s withdrawal does not take effect until 90 days after it has given notice. Following intense bilateral negotiations with the United States, North Korea announced it was suspending its withdrawal from the NPT one day before the withdrawal was to take effect. Pyongyang agreed to suspend its withdrawal while talks continued with Washington, but claimed to have a special status in regard to its nuclear safeguards commitments. Under this special status, North Korea agreed to allow the continuity of safeguards on its present activities, but refused to allow inspections that could verify past nuclear activities. 16

As talks with the United States over North Korea’s return to the NPT dragged on, North Korea continued to operate its 5MW(e) reactor in Yongbyon. On 14 May 1994, Korean technicians began removing the reactor’s spent fuel rods without the supervision of IAEA inspectors. 17 This action worsened the crisis because the random placement of the spent fuel rods in a temporary storage pond compromised the IAEA’s capacity to reconstruct the operational history of the reactor, which could have been used in efforts to account for the discrepancies in Pyongyang’s reported plutonium reprocessing. 18 U.S. President Bill Clinton’s administration announced that it would ask the UNSC to impose economic sanctions; Pyongyang responded that it would consider economic sanctions “an act of war.” 19

The crisis was defused in June 1994 when former U.S. President Jimmy Carter traveled to Pyongyang to meet with Kim Il Sung. Carter announced from Pyongyang that Kim had accepted the broad outline of a deal that was later finalized as the Agreed Framework in October 1994. 20 Under the agreement, North Korea agreed to freeze work at its gas-graphite moderated reactors and related facilities, and to allow the IAEA to monitor that freeze. Pyongyang was also required to “consistently take steps to implement the North-South Joint Declaration on the Denuclearization of the Korean Peninsula,” and to remain a party to the NPT. In exchange, the United States agreed to lead an international consortium to construct two light water power reactors, and to provide 500,000 tons of heavy fuel oil per year until the first reactor came online with a target date of 2003. Furthermore, the United States was to provide “formal assurances against the threat or use of nuclear weapons by the U.S.” 21

2001 to 2003: Collapse of the Agreed Framework and Withdrawal from the NPT

While the Agreed Framework froze North Korea’s plutonium program for almost a decade, neither party was completely satisfied with either the compromise reached or its implementation. The United States was dissatisfied with the postponement of safeguards inspections to verify the DPRK’s past activities, and North Korea was dissatisfied with the delayed construction of the light water power reactors.

In 2001, the new George W. Bush administration initiated a North Korean policy review, which it completed in early June. The review concluded that the United States should seek “improved implementation of the Agreed Framework, verifiable constraints on North Korea’s missile program, a ban on missile exports, and a less threatening North Korean conventional military posture.” 22 From Washington’s perspective, “improved implementation of the Agreed Framework” meant an acceleration of safeguards inspections, even though the agreement did not require Pyongyang to submit to full safeguards inspections to verify its past activities until a significant portion of the reactor construction was completed, but before the delivery of critical reactor components.

The international community also became concerned that North Korea might have an illicit highly enriched uranium (HEU) program. In summer 2002, U.S. intelligence reportedly discovered evidence of HEU technology and/or materials transfers from Pakistan to North Korea in exchange for ballistic missile technology. 23 (Later, in early 2004, it was revealed that Pakistani nuclear scientist Dr. A. Q. Khan had sold gas-centrifuge technology to North Korea, Libya and Iran.) 24 Around this time, North Korea began construction of the covert uranium enrichment facility at Kangson in the outskirts of Pyongyang. Although U.S. intelligence was reportedly aware of the site, its existence was only revealed to the public in July 2018 through the efforts of open-source analysts. 25

In October 2002, bilateral talks between the United States and North Korea finally resumed when U.S. Assistant Secretary of State for East Asia and Pacific Affairs James Kelly visited Pyongyang. 26 During the visit, Kelly informed First Vice Foreign Minister Kang Sok Chu and Vice Foreign Minister Kim Kye Kwan that Washington was aware of a secret North Korean program to produce HEU. The U.S. State Department stated that North Korean officials admitted to having such a program during a second day of meetings with Kelly, but North Korea later argued that it had only admitted to having a “plan to produce nuclear weapons,” which Pyongyang claimed was part of its right to self-defense. 27

The United States responded in December 2002 by suspending heavy oil shipments, and North Korea retaliated by lifting the freeze on its nuclear facilities, expelling IAEA inspectors monitoring that freeze, and announcing its withdrawal from the NPT on 10 January 2003. 28 Initially, North Korea claimed it had no intention of producing nuclear weapons, and that the lifting of the nuclear freeze was necessary to generating electricity.

2003 to 2006: New Crises, and the Beginning and End of the Six-Party Process

In early 2003, U.S. intelligence detected activities around the Radiochemisty Laboratory, a reprocessing facility in Yongbyon, which indicated that North Korea was probably reprocessing the 8,000 spent fuel rods that had been in a temporary storage pond. 29 In September 2003, a North Korean Foreign Ministry spokesman said that North Korea had completed the reprocessing of this spent fuel—this would have given North Korea enough plutonium for approximately four to six nuclear devices. 30 In January 2004, a delegation of invited U.S. experts confirmed that the canisters in the temporary storage pond were empty. 31

In April 2003, a multilateral dialogue began in Beijing with the aim of ending Pyongyang’s nuclear weapons program. Initially trilateral in format (China, North Korea and the United States), the process expanded to a six-party format with the inclusion of Japan, Russia and South Korea. The first round began in August 2003. Six months later, in February 2004, the second round of talks was held, and a third round followed in June 2004. However, tensions between the parties—particularly the United States and North Korea—caused the talks to stall for more than a year, restarting in July 2005.

While the six-party process stagnated, North Korea shut down its 5MW(e) reactor in April 2005 and removed the spent fuel. 32 The reactor had been operating since February 2003, meaning that it could have produced enough plutonium for between one and three nuclear devices in its spent fuel. However, it would take a few months for North Korean engineers to extract the plutonium from the spent fuel rods. In July 2005, satellite imagery indicated that the reactor had begun operations once again. 33

On 19 September 2005, the fourth round of Six-Party Talks concluded and the six parties signed a Statement of Principles, whereby North Korea would abandon its nuclear programs and return to the NPT and the IAEA safeguards regime at “an early date.” The United States stated that it had no intention of attacking North Korea with nuclear or conventional weapons, and Washington affirmed that it had no nuclear weapons deployed in South Korea. The parties also agreed that the 1992 Joint Declaration on the Denuclearization of the Korean Peninsula, which prohibited uranium enrichment or plutonium reprocessing, should be observed and implemented. 34

Although hailed as a breakthrough by some participants, the viability of the Statement of Principles was immediately brought into question by North Korean and U.S. actions. The parties disagreed over the implications of the Statement of Principles for light water reactor transfers to North Korea. While Pyongyang argued that the six-party statement permitted LWR transfers, Washington countered that this was not guaranteed under the statement and could only occur after North Korea had dismantled its existing nuclear program. Shortly after signing the agreement in Beijing, the U.S. Treasury Department announced that U.S. financial institutions were barred from having correspondent accounts with Banco Delta Asia (BDA), a Macao-based bank, which it accused of assisting North Korea in illicit transactions. 35 North Korea asserted that unless the so-called “sanctions” were lifted, Pyongyang would not carry out its part of the September 2005 agreement. 36 Due to these and other disagreements, the Six-Party Talks stalemated, and the Statement of Principles remained dormant for more than 18 months.

2006 to 2011: A Nuclear Test, Failed Negotiations, and Another Nuclear Test

The nuclear crisis on the Korean Peninsula continued to deteriorate throughout 2006, reaching a low point in October when North Korea conducted its first nuclear test at 10:35AM (local time) at the Punggye-ri test site 37 The Korean Central News Agency (KCNA) announced that the test was conducted at a “stirring time when all the people of the country are making a great leap forward in the building of a great prosperous powerful socialist nation.” 38 The North Korean nuclear test did not, however, produce a significant yield. The yield from this test appeared to be less than 1 kiloton. North Korea was reportedly expecting at least a 4 kiloton yield, possibly indicating that the North Korean plutonium program still had a number of technical hurdles to overcome before it would have a nuclear warhead. 39

Immediately following the test, UNSC Resolution 1718 imposed sanctions on North Korea. 40 After intense diplomatic activities by the Chinese government and others involved in the Six-Party process, the parties met again in December 2006 following a hiatus of more than a year. However, these talks ended without any sign of progress. 41 In what appeared to be a breakthrough in the negotiations, the six parties in February 2007 agreed on the Initial Actions for the Implementation of the Joint Statement, whereby North Korea agreed to abandon all of its nuclear weapons and existing nuclear programs, and to return to the NPT and the IAEA safeguards regime in exchange for a package of incentives that included the provision of energy assistance to North Korea by the other parties. 42 The agreement also established a 60-day deadline during which North Korea was to shut down and seal its main nuclear facilities at Yongbyon-kun under IAEA supervision. Additionally, the United States agreed to release the approximately $25 million in North Korean assets held at the Macao-based Banco Delta Asia (BDA). 43 However, the BDA part of the agreement again became a sticking point; much of the international financial community, concerned about the possible legal ramifications of dealing with a bank that was technically still under U.S. sanctions, refused to take part in the transfer of the funds. The issue was eventually resolved when a Russian bank agreed to transfer the funds in June 2007. 44

After the February 2007 agreement, North Korea extended invitations to IAEA officials, opening the door to reestablishing its relationship with the Agency. In July 2007, North Korea began shutting down and sealing it main nuclear facilities at Yongbyon-kun under IAEA supervision. 45 Further progress was made in the Six-Party Talks when the parties adopted the Second Action Plan, calling on North Korea to disable its main nuclear facilities and submit a complete and correct declaration of all its nuclear programs by 31 December 2007. 46 While disablement activities on North Korea’s three key plutonium production facilities at Yongbyon-kun (the 5MW(e) experimental reactor, the Radiochemistry Laboratory and the Fuel Fabrication Plant) progressed, North Korea failed to meet the 31 December deadline to submit its declaration. 47 Sharp disagreements over North Korea’s past illicit procurement efforts and controversies surrounding suspected North Korean nuclear cooperation with Syria proved to be the key sticking points.

Almost six months past the deadline, on 26 June 2008, North Korea submitted its much-awaited declaration. 48 While the contents of North Korea’s declaration have not been disclosed to the public, various media reports claimed that the declaration failed to address both North Korea’s alleged uranium enrichment program and suspicions of its nuclear cooperation with countries such as Syria. 49 Despite problems with the declarations, the Bush administration notified the U.S. Congress that it planned to remove North Korea from the U.S. list of state sponsors of terrorism, and also issued a proclamation lifting some sanctions under the Trading with the Enemy Act. 50 Following the U.S. government’s actions, North Korea demolished the cooling tower at the Yongbyon 5MW(e) reactor, an event broadcast by international media. 51

Delays with the U.S. removal of North Korea from the state sponsors of terrorism list contributed to North Korean delays in meeting its own commitments, and eventually Pyongyang announced in late August 2008 that it had restored the nuclear facilities in Yongbyon-kun, and barred international inspectors from accessing the site. 52 On 11 October 2008, the United States finally dropped North Korea from the terrorism list after reaching a deal in which North Korea agreed to resume the disabling of its nuclear facilities, and to allow inspectors access to the nuclear sites. 53 The six parties then resumed negotiations to map out a verification plan in Beijing in December 2008. These negotiations focused on ways to verify the disablement of North Korea’s nuclear program, including taking nuclear samples. However, the negotiations failed to reach an agreement on a verification protocol, and the issue remains stalled. 54

After a dispute over rocket launches in March 2009, North Korea kicked out IAEA and U.S. inspectors and began to rebuild the Yongbyon 5MW(e) reactor for the purpose of reprocessing plutonium from its spent fuel rods, in contravention of its previous promises at the Six-Party Talks. On 25 May 2009, North Korea conducted its second nuclear test. KCNA announced that Pyongyang had carried out the nuclear test, and that it “was safely conducted on a new higher level in terms of its explosive power and technology of its control.” 55 Initial estimates from the U.S. government showed the test causing seismic activity equivalent to an earthquake of magnitude of 4.7 on the Richter Scale, and was located close to the site of the first nuclear test in 2006. 56 The test was estimated to be about 4 kilotons. 57 The United Nations Security Council released Resolution 1874; in response Pyongyang announced that “the processing of uranium enrichment will be commenced.” North Korea further indicated that it did not intend to return to the Six-Party Talks, and asserted that it would not be bound by agreements made earlier through this forum. 58

Tensions continued to rise in 2010 and 2011. North Korean leader Kim Jong Il visited China three times within one year, each time indicating he was willing to proceed with denuclearization efforts; however, North Korea also engaged in several military confrontations with the South. 59 In March 2010, North Korea torpedoed a South Korean ship killing 46 sailors, and in November of the same year it shelled Yeonpyeong Island, killing four South Koreans, including two civilians. 60 Additionally, in March 2010, North Korea announced the construction of a light-water reactor (LWR) at Yongbyon. 61 U.S. nuclear expert Siegfried Hecker confirmed that construction for a 25-30MW(e) experimental LWR had commenced during his November 2010 visit. In November 2011 analysts estimated that the experimental LWR might be externally completed within the next year, but operations were unlikely to begin for another two to three years as machinery and equipment would need to be loaded and installed. 62 Additionally, Hecker reported that North Korea had completed the construction of a uranium enrichment facility at Yongbyon with 2,000 P-2 centrifuges in six cascades. 63 Although satellite imagery showed that activity had been halted since late April 2014, subsequent imagery from September 2015 showed new activity, likely indicating increased uranium production. 64

On 15 March 2011, Pyongyang announced its willingness to return to the Six-Party Talks without preconditions, and agreed to discuss its uranium enrichment program. 65 After the death of Kim Jong Il and ascension of Kim Jong Un to power in December 2011, the U.S. and North Korea held a series of bilateral talks. These talks culminated in the “Leap Day Agreement” of 29 February 2012, a moratorium on North Korean nuclear testing, uranium enrichment and long-range missile tests in exchange for food aid. 66 However, the U.S. withdrew its offer of food aid after North Korea attempted to launch a satellite into orbit using an Unha rocket on 12 April 2012. The U.S. considered the space launch to be a violation of the agreement. North Korea successfully launched an additional Unha rocket in December 2012, leading the UN Security Council to follow up with Resolution 2087 demanding North Korea end its nuclear and missile programs. 67

2012-2016: Working on Miniaturization and a Thermonuclear Bomb

On 12 February 2013, North Korea conducted a third nuclear test at the Punggye-ri Nuclear Test Facility. 68 The USGS reported a 5.1 magnitude seismic shock in the vicinity of the test site. 69 North Korea claimed to have successfully tested a “lighter, miniaturized atomic bomb.” 70

In April 2013, North Korean state media announced that Pyongyang was restarting its 5MW graphite-moderated reactor and uranium enrichment plant at Yongbyon. 71 Though the original cooling tower was demolished in 2008, satellite analysis confirmed activity consistent with connecting cooling pipes from the 5MW reactor to the adjacent river. 72 By August 2013, satellite imagery confirmed steam venting from the reactor’s turbine and generator building. 73 Meanwhile, the external work on the adjacent experimental light water reactor appears to have concluded based on January 2014 satellite imagery; however, the reactor is likely not yet fully operational. 74

In March 2014, KCNA announced the DPRK’s intention to conduct a “new form” of nuclear testing, and September 2015 commercial satellite imagery indicated increased activity at the Punggye-ri nuclear test site. 75

In December 2015, according to state-run Rodong Sinmun, Kim Jong Un claimed that North Korea possessed thermonuclear capabilities during his visit to the Pyongchon Revolutionary Site. This claim was met with wide skepticism from the international community. 76 On 6 January 2016 North Korea announced it had successfully tested a thermonuclear device at the Punggye-ri Nuclear Test Site. 77 The test registered as a 5.1 magnitude earthquake according to the USGS; given that the magnitude was similar to the 2013 test, most experts believe that North Korea tested a fission device similar in yield to the 2013 test instead of a thermonuclear device as it had claimed. 78 79 Some have also speculated that North Korea actually tested a miniaturized version of the 2013 device instead of a boosted fission device. 80 No conclusive radionuclide readings have been provided. The test was met with widespread international criticism and led to further sanctions being imposed by the United Nations in March 2016. On 9 March 2016, North Korea released photographs depicting Kim Jong Un examining what the DPRK claims is a miniaturized nuclear implosion device in front of several partially assembled KN-08 mod 1 and mod 2 missiles. 81 Six days later, on 15 March 2016, North Korea announced its intention to conduct another nuclear test. 82 North Korea later announced in August what U.S. experts had long suspected, that it had restarted reprocessing spent fuel rods, creating more plutonium for its nuclear weapons program. 83

On 9 September 2016, North Korea carried out its fifth nuclear test to coincide with the 68th anniversary of the founding of North Korea. 84 The U.S. Geological Survey registered the test as a 5.3 magnitude earthquake. 85 Shortly afterwards, North Korea released a defiant statement warning its “enemies” that it now has the capability to produce a warhead small enough to fit onto the end of a missile and can retaliate against any attack. 86 Experts remain unsure about the exact yield of the explosion. The yield appears to be larger than all previous tests carried out by the regime, with most estimates placing the yield between 10 and 20 kilotons. 87 The test drew sharp international condemnation; in a statement issued by the White House, President Obama condemned the test and stated that the regime’s actions have only added to the instability of the region. 88 Even China, North Korea’s only major ally, condemned the test and called on North Korea to refrain from provocative acts. 89 At an emergency meeting following the 9 September test, the UN Security Council unanimously adopted Resolution 2321 on 30 November 2016. 90

Recent Developments and Current Status

In a speech marking the beginning of 2017, Kim Jong-un emphasized the advancement of North Korea’s missile and nuclear program in his outlined goals for North Korea. 91 In contrast to his 2016 address, Kim made explicit mention of nuclear tests, noting the (allegedly) successful hydrogen bomb test of September 2016, as well as claiming that North Korea was entering the “final stage of preparation for the test launch of an intercontinental ballistic missile (ICBM).” 92

2017 saw significant developments in the North Korean nuclear and ballistic missile programs, as well as blustery rhetoric between North Korea and U.S. President Donald Trump. On 3 July 2017, North Korea tested the Hwasong-14 ballistic missile, which the United States later confirmed to be an ICBM. 93 On 8 August 2017, a leaked U.S. Defense Intelligence Agency report found that North Korea had produced miniaturized nuclear warheads capable of fitting on an ICBM. 94 On the same day, in response to North Korean criticism of the United States, President Trump told reporters that if North Korea made further nuclear threats against the United States “they will be met with fire and fury like the world has never seen.” 95

On 3 September 2017, North Korea conducted its sixth nuclear test at Punggye-ri. 96 According to initial U.S. intelligence assessments, the test released 140 kilotons of TNT equivalent, making it larger in explosive yield than the previous five tests combined. 97 Other analysts, using satellite imagery and seismic data, estimated an even higher explosive yield, perhaps as much as 250 kilotons. 98 North Korea claimed that the test was of a thermonuclear warhead, and immediately before the test released photographs of Kim Jong-un inspecting a “peanut-shaped” nuclear device resembling a Teller-Ulam design hydrogen bomb. 99 U.S. intelligence officials classified the test as an “advanced nuclear device.” 100 Following the successful test-flight of the Hwasong-15 ICBM in November 2017, North Korea announced that it had “finally realized the great historic cause of completing the state nuclear force.” 101

Subsequent months saw a diplomatic thaw between North and South Korea, as newly-elected South Korean president Moon Jae-in pursued a policy of openness toward the North and athletes from the two Koreas marched under a unified flag at the 2018 Pyeongchang Winter Olympic Games. On 27 April, the two leaders held a summit meeting in the demilitarized zone, the first such meeting since 2007. In a joint statement released after the summit, they “confirmed the common goal of realizing, through complete denuclearization, a nuclear-free Korean peninsula.” 102 Additionally, North Korea sought to ease nuclear tensions by declaring a halt to all nuclear and ICBM tests, and pledging to close a nuclear test site. 103 On 24 May 2018, North Korea closed the Punggye-ri nuclear test site, destroying underground tunnels and surface facilities in front of an audience that included Western journalists. 104

Softening relations between North and South Korea also helped facilitate an opening for diplomacy with the United States, which culminated in the 12 June 2018 summit meeting between Kim Jong-un and President Donald Trump in Singapore, marking the first face-to-face meeting between the leaders of North Korea and the United States in history. The summit resulted in a joint declaration and claims of success from both parties, as Trump and Kim agreed to “establish new US-DPRK relations,” “build a lasting stable peace regime on the Korean peninsula,” including Kim’s agreement to “work towards complete denuclearization on the Korean peninsula.” 105 Trump also mentioned his desire to end US-South Korean military exercises and eventually remove troops from South Korea in a post-summit news conference. 106

The summit has not yielded substantive plans for denuclearization, and, despite President Trump’s claim on 13 June 2018 that “there is no longer a nuclear threat from North Korea,” the country still possesses a considerable nuclear arsenal and long-range ballistic missile systems. The July 2018 revelation of the existence of a covert uranium enrichment site at Kangson suggests that North Korea is still concealing nuclear sites from the international community, which complicates any nuclear deal making. 107 Experts have cautioned against interpreting North Korean statements, which are supportive of denuclearization in principle, as Pyongyang being prepared to relinquish its nuclear weapons. Leading North Korea expert Jeffrey Lewis argues that Kim’s statements instead suggest a willingness to “engage in a process, headed toward an ambiguous goal.” 108

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Treaty on the Non-Proliferation of Nuclear Weapons (NPT)
The NPT: Signed in 1968, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the most widely adhered-to international security agreement. The “three pillars” of the NPT are nuclear disarmament, nonproliferation, and peaceful uses of nuclear energy. Article VI of the NPT commits states possessing nuclear weapons to negotiate in good faith toward halting the arms race and the complete elimination of nuclear weapons. The Treaty stipulates that non-nuclear-weapon states will not seek to acquire nuclear weapons, and will accept International Atomic Energy Agency safeguards on their nuclear activities, while nuclear weapon states commit not to transfer nuclear weapons to other states. All states have a right to the peaceful use of nuclear energy, and should assist one another in its development. The NPT provides for conferences of member states to review treaty implementation at five-year intervals. Initially of a 25-year duration, the NPT was extended indefinitely in 1995. For additional information, see the NPT.
Nuclear weapon
Nuclear weapon: A device that releases nuclear energy in an explosive manner as the result of nuclear chain reactions involving fission, or fission and fusion, of atomic nuclei. Such weapons are also sometimes referred to as atomic bombs (a fission-based weapon); or boosted fission weapons (a fission-based weapon deriving a slightly higher yield from a small fusion reaction); or hydrogen bombs/thermonuclear weapons (a weapon deriving a significant portion of its energy from fusion reactions).
Comprehensive Nuclear-Test-Ban Treaty (CTBT)
The CTBT: Opened for signature in 1996 at the UN General Assembly, the CTBT prohibits all nuclear testing if it enters into force. The treaty establishes the Comprehensive Test Ban Treaty Organization (CTBTO) to ensure the implementation of its provisions and verify compliance through a global monitoring system upon entry into force. Pending the treaty’s entry into force, the Preparatory Commission of the CTBTO is charged with establishing the International Monitoring System (IMS) and promoting treaty ratifications. CTBT entry into force is contingent on ratification by 44 Annex II states. For additional information, see the CTBT.
Thermonuclear weapon
Thermonuclear weapon: A nuclear weapon in which the fusion of light nuclei, such as deuterium and tritium, leads to a significantly higher explosive yield than in a regular fission weapon. Thermonuclear weapons are sometimes referred to as staged weapons, because the initial fission reaction (the first stage) creates the condition under which the thermonuclear reaction can occur (the second stage). Also archaically referred to as a hydrogen bomb.
United Nations Security Council
United Nations Security Council: Under the United Nations Charter, the Security Council has primary responsibility for maintaining international peace and security. The Council consists of fifteen members, five of which—China, France, Russia, the United Kingdom, and the United States—are permanent members. The other ten members are elected by the General Assembly for two-year terms. The five permanent members possess veto powers. For additional information, see the UNSC.
Punitive measures, for example economic in nature, implemented in response to a state's violation of its international obligations.
Nuclear energy
Nuclear energy: The energy liberated by a nuclear reaction (fission or fusion), or by radioactive decay.
Uranium is a metal with the atomic number 92. See entries for enriched uranium, low enriched uranium, and highly enriched uranium.
Light-water reactor
Light-water reactor: A term used to describe reactors using ordinary water, where the hydrogen is hydrogen-1, as a coolant and moderator, including boiling water reactors (BWRs) and pressurized water reactors (PWRs), the most common types used in the United States.
Non-nuclear weapon state (NNWS)
Non-nuclear weapon state (NNWS): Under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), NNWS are states that had not detonated a nuclear device prior to 1 January 1967, and who agree in joining the NPT to refrain from pursuing nuclear weapons (that is, all state parties to the NPT other than the United States, the Soviet Union/Russia, the United Kingdom, France, and China).
The positioning of military forces – conventional and/or nuclear – in conjunction with military planning.
Reprocessing: The chemical treatment of spent nuclear fuel to separate the remaining usable plutonium and uranium for re-fabrication into fuel, or alternatively, to extract the plutonium for use in nuclear weapons.
Enriched uranium
Enriched uranium: Uranium with an increased concentration of the isotope U-235, relative to natural uranium. Natural uranium contains 0.7 percent U-235, whereas nuclear weapons typically require uranium enriched to very high levels (see the definitions for “highly enriched uranium” and “weapons-grade”). Nuclear power plant fuel typically uses uranium enriched to 3 to 5 percent U-235, material that is not sufficiently enriched to be used for nuclear weapons.
Bilateral: Negotiations, arrangements, agreements, or treaties that affect or are between two parties—and generally two countries.
International Atomic Energy Agency (IAEA)
IAEA: Founded in 1957 and based in Vienna, Austria, the IAEA is an autonomous international organization in the United Nations system. The Agency’s mandate is the promotion of peaceful uses of nuclear energy, technical assistance in this area, and verification that nuclear materials and technology stay in peaceful use. Article III of the Nuclear Non-Proliferation Treaty (NPT) requires non-nuclear weapon states party to the NPT to accept safeguards administered by the IAEA. The IAEA consists of three principal organs: the General Conference (of member states); the Board of Governors; and the Secretariat. For additional information, see the IAEA.
Ratification: The implementation of the formal process established by a country to legally bind its government to a treaty, such as approval by a parliament. In the United States, treaty ratification requires approval by the president after he or she has received the advice and consent of two-thirds of the Senate. Following ratification, a country submits the requisite legal instrument to the treaty’s depository governments Procedures to ratify a treaty follow its signature.

See entries for Entry into force and Signature.
Spent nuclear fuel
Spent nuclear fuel: Irradiated nuclear fuel. Once irradiated, nuclear fuel is highly radioactive and extremely physically hot, necessitating special remote handling. Fuel is considered “self protecting” if it is sufficiently radioactive that those who might seek to divert it would not be able to handle it directly without suffering acute radiation exposure.
Safeguards: A system of accounting, containment, surveillance, and inspections aimed at verifying that states are in compliance with their treaty obligations concerning the supply, manufacture, and use of civil nuclear materials. The term frequently refers to the safeguards systems maintained by the International Atomic Energy Agency (IAEA) in all nuclear facilities in non-nuclear weapon state parties to the NPT. IAEA safeguards aim to detect the diversion of a significant quantity of nuclear material in a timely manner. However, the term can also refer to, for example, a bilateral agreement between a supplier state and an importer state on the use of a certain nuclear technology.

See entries for Full-scope safeguards, information-driven safeguards, Information Circular 66, and Information Circular 153.
Agreed Framework
Agreed Framework: The 1994 agreement between the United States and North Korea (Democratic People's Republic of Korea, DPRK) to "freeze" the DPRK’s nuclear program. The agreement outlined a 10-year program during which the United States, South Korea, and Japan would construct two new light-water-moderated nuclear reactors in the DPRK in exchange for the shutting down of all of the DPRK’s existing nuclear facilities. In addition, the DPRK agreed to remain a party to the NPT and to accept IAEA full-scope safeguards. The multilateral Korean Peninsula Energy Development Organization (KEDO) would oversee implementation of the agreement.

See glossary entries for Joint Declaration on the Denuclearization of the Korean Peninsula, Korean Peninsula Energy Development Organization; for additional information, see the Joint Declaration and KEDO.
Ballistic missile
A delivery vehicle powered by a liquid or solid fueled rocket that primarily travels in a ballistic (free-fall) trajectory.  The flight of a ballistic missile includes three phases: 1) boost phase, where the rocket generates thrust to launch the missile into flight; 2) midcourse phase, where the missile coasts in an arc under the influence of gravity; and 3) terminal phase, in which the missile descends towards its target.  Ballistic missiles can be characterized by three key parameters - range, payload, and Circular Error Probable (CEP), or targeting precision.  Ballistic missiles are primarily intended for use against ground targets.
Enriched uranium
Enriched uranium: Uranium with an increased concentration of the isotope U-235, relative to natural uranium. Natural uranium contains 0.7 percent U-235, whereas nuclear weapons typically require uranium enriched to very high levels (see the definitions for “highly enriched uranium” and “weapons-grade”). Nuclear power plant fuel typically uses uranium enriched to 3 to 5 percent U-235, material that is not sufficiently enriched to be used for nuclear weapons.
Multilateral: Negotiations, agreements or treaties that are concluded among three or more parties, countries, etc.
Dismantlement: Taking apart a weapon, facility, or other item so that it is no longer functional.
Kiloton: A term used to quantify the energy of a nuclear explosion that is equivalent to the explosion of 1,000 tons of trinitrotoluene (TNT) conventional explosive.
The splitting of the nucleus of a heavy atom into two lighter nuclei (called fission fragments). It is accompanied by the release of neutrons, gamma rays, and fission fragments with large amounts of kinetic energy.  It is usually triggered by absorption of a neutron, but in some cases may be induced by protons, gamma rays or other particles
Hydrogen bomb
Hydrogen bomb: See entries for Nuclear weapon and Thermonuclear weapon
Intercontinental ballistic missile (ICBM)
Intercontinental ballistic missile (ICBM): A ballistic missile with a range greater than 5,500 km. See entry for ballistic missile.


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  2. 북한개요 2009 [North Korea Introduction 2009] (Seoul: Korea Institute for National Unification, 2009), p.322.
  3. Park Yong Chae, "관심쏠린 원전기술 / 北발전설비 상당부분 국산화 [Focus on Nuclear Technology/ The North Produces Most Electricity Themselves]," Kyunghyang Shinmun, 21 June 1994, p. 5.
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  10. Don Oberdorfer, "U.S. Decides to Withdraw A-Weapons from S. Korea; North Korea to Be Pressed to Halt Program," Washington Post, 19 October 1991, pp. A1 and A19.
  11. "Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula," Inventory of International Nonproliferation Organizations and Regimes, James Martin Center for Nonproliferation Studies, www.nti.org.
  12. "Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula," Inventory of International Nonproliferation Organizations and Regimes, James Martin Center for Nonproliferation Studies, www.nti.org.
  13. Mark Hibbs, "Isotopics Show Three North Korean Reprocessing Campaigns Since 1975," Nuclear Fuel, 1 March 1993, pp. 8-9.
  14. Don Oberdorfer, The Two Koreas: A Contemporary History (Reading, MA: Addison-Wesley, 1997), p. 279; "March Letter and Memorandum from the UN Permanent Representative of the DPRK to the President of the UN Security Council," United Nations Security Council Document, 17 March 1993, pp. 1-10.
  15. Don Oberdorfer, The Two Koreas: A Contemporary History (Reading, MA: Addison-Wesley, 1997), p. 280; Gamini Seneviratne, "IAEA Struggling to Stand Firm and Find Face-Saver for North Korea," Nucleonics Week, 18 March 1993, p. 10; "Letter from Kim Yong-nam, DPRK Minister of Foreign Affairs," 12 March 1993; David E. Sanger, "West Knew of North Korea Nuclear Development," The New York Times, 13 March 1993, p. 3.
  16. R. Jeffrey Smith, "N. Korea Won't Quit Nuclear Ban Treaty; Inspection of Two Key Sites Still Rejected," Washington Post, 12 June 1993, p. A1; Don Oberdorfer, Two Koreas: A Contemporary History (Reading, Massachusetts: Addison-Wesley Reading, 1997), pp. 285-286; J. T. Nguyen, "North Korea Postpones Decision to Abandon Nuclear Treaty," United Press International, 11 June 1993; John Wright, "North Korea Remains in Nuclear Non-Proliferation Treaty," Associated Press, 12 June 1993.
  17. Eric Schmitt, "U.S. Delays Taking Steps Over A-Plant," The New York Times, 16 May 1994, pp. A1 and A3; David E. Sanger, "North Koreans Say Nuclear Fuel Rods Are Being Removed," The New York Times, 15 May 1994.
  18. David E. Sanger, "North Korea Foils Efforts to Halt Its Nuclear Plans," The New York Times, 29 May 1994; Paul Lewis, "UN Told North Korea's Nuclear Record Can't Be Retrieved," The New York Times, 4 June 1994, p. A3.
  19. Terence Hunt, "U.S. to Seek UN Sanctions against North Korea," Associated Press, 2 June 1994; Michael R. Gordon, "White House Asks Global Sanctions on North Koreans," The New York Times, 3 June 1994; Korean Central Broadcasting Agency (Pyongyang), 3 June 1994, in "Vice Foreign Minister's Statement on U.S.-Orchestrated Pressure on Nuclear Issue," BBC Summary of World Broadcasts, 6 June 1994, in Lexis-Nexis, http://web.lexis-nexis.com.
  20. "Kim Promises Not to Expel IAEA Inspectors," Agence France-Presse, 16 June 1994; David E. Sanger, "Carter Optimistic after North Korea Talks," The New York Times, p. A10; Kate Webb, "Carter Goes into Second and Crucial Round of Talks with Kim Il Sung," Agence France-Presse, 17 June 1994.
  21. "Agreed Framework between the United States of America and the Democratic People's Republic of Korea," 21 October 1994, via www.kedo.org; David E. Sanger, "Clinton Approves a Plan to Give Aid to North Koreans," The New York Times, 19 October 1994, p. A1; "Secret Annex to U.S.-North Korea Agreement," Deutsche Presse-Agentur, 20 October 1994; Michael R. Gordon, "U.S.-North Korea Accord Has a 10-Year Timetable," The New York Times, 21 October 1994, p. A8; Alan Riding, "U.S. and North Korea Sign Pact to End Nuclear Dispute," The New York Times, 22 October 1994, p. A5; "N. Korea's Pledge on Graphite-Moderated Reactors Cited," Japan Economic Newswire, 14 January 1999; Takashi Uemura, "N. Korea's Concession Revealed," Asahi News Service, 10 May 1999.
  22. Alex Wagner, "Bush Outlines Resuming Talks with North Korea," Arms Control Today, July/August 2001, pp. 23 and 25; Michael Knapik, "U.S. to Pursue Better Execution of U.S.-North Korea Agreed Framework," Nucleonics Week, Vol. 42, No 24, 14 June 2001.
  23. Stephen Fidler and Edward Luce, "U.S. Fears North Korea Could Gain Nuclear Capability through Pakistan," Financial Times, 1 June 2001, p. 1; "Pakistan Denies Export of Nuclear Technology," Japan Economic Newswire, 5 June 2001.
  24. "'Father of Pakistan's Nuclear Bomb Removed," Deutsche Presse Agentur, 31 January 2004; "Founder of Pakistan's Nuke Program Sacked as Advisor," Kyodo News Service, 31 January 2004; John Lancaster and Kamran Khan, "Pakistanis Say Nuclear Scientists Aided Iran," The Washington Post, 24 January 2004.
  25. Ankit Panda, “Exclusive: Revealing Kangson, North Korea’s First Covert Uranium Enrichment Site,” The Diplomat, 13 July 2018, www.thediplomat.com.
  26. "U.S. Special Envoy Leaves Pyongyang," Xinhua News Agency, 5 October 2002.
  27. Press Statement, Richard Boucher, Spokesman, "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; "Spokesman for DPRK FM on DPRK Visit of Special Envoy of U.S. President," KCNA, 7 October 2002, www.kcna.co.jp; "미국 대통령 특사는 심히 압력적이고 오만하게 나왔다. / 조선외무성 대변인 [U.S. Presidential Envoy was Arrogant and Pressured Us. / Representatives of DPRK's Ministry of Foreign Affair]," KCNA, 7 October 2002, www.kcna.co.jp.
  28. Carol Giacomo, "U.S. Says N. Korean Fuel Oil Deliveries Should End," Reuters, 13 November 2002, www.reuters.com; P.S. Suryanarayana, "IAEA Inspectors Leave N. Korea," The Hindu, 1 January 2003; "Statement of DPRK Government on Its Withdrawal from NPT," KCNA, 10 January 2003, www.kcna.co.jp.
  29. "Crisis on the Korean Peninsula: Implications for U.S. Policy in Northeast Asia," Speech by William Perry, Brookings Institution, 24 January 2003.
  30. David E. Sanger, "North Korea Says It Has Made Fuel from Atom Bombs,” The New York Times, 15 July 2003, www.nytimes.com; Jong-Heon Lee, "Analysis: N. Korea's Nuke Game Going Further," United Press International, 2 October 2003.
  31. Senate Committee on Foreign Relations Hearing on "Visit to the Yongbyon Nuclear Scientific Research Center in North Korea," Siegfried S. Hecker, Senior Fellow, Los Alamos National Laboratory, 21 January 2004, Committee Hearings 108th Congress Second Session — 2004, U.S. Senate Committee on Foreign Relations, http://foreign.senate.gov; Barbara Slavin, "Scientist Describes N. Korea Nuclear Evidence," USA Today, 22 January 2004.
  32. "N.K. Plans to Unload Fuel Rods from Reactor This Month," Yonhap News Agency, 16 April 2005; "N. Korea Moves to Bolster Nuclear Arsenal," Korea Times, 18 April 2005.
  33. "Report: North Korea Restarted Nuclear Reactor Before International Nuclear Talks," Associated Press Worldstream, 21 August 2005.
  34. "North Korea Agrees to Abandon Nuclear Weapons Program," U.S. Fed News, 19 September 2005, in LexisNexis, www.lexisnexis.com.
  35. U.S. Department of the Treasury, “Treasury Finalizes Rule against Banco Delta Asia BDA Cut off from U.S. Financial System,” 14 March 2007, www.treasury.gov.
  36. "Nuclear Talks Suspended Indefinitely: Korea," Agence France-Presse, 11 December 2005.
  37. "Magnitude 4.3 — North Korea," USGS, 9 October 2006, http://earthquake.usgs.gov.
  38. "DPRK Successfully Conducts Underground Nuclear Test," KCNA, 10 October 2006, www.kcna.co.jp.
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  40. Warren Hoge, "Security Council Supports Sanctions on North Korea," The New York Times, 15 October 2006, www.nytimes.com; Philip Sherwell, "UN Vote Slaps Sanctions on North Korea," Sunday Telegraph, 15 October 2006.
  41. "Nuclear Talks with N. Korea End in Failure; Six-Party Process Thrown into Doubt," Washington Post, 23 December 2006, www.washingtonpost.com.
  42. Audra Ang, "North Korea Agrees to Nuclear Disarmament," Associated Press, 13 February 2005.
  43. Audra Ang, "North Korea Agrees to Nuclear Disarmament," Associated Press, 13 February 2005; Christopher Bodeen, "U.S., North Korea Resolve Macau Bank Dispute as Six-Party Talks Begin," Associated Press, 19 March 2007.
  44. "Foreign Ministry Spokesman on Solution to Issue of Frozen Funds," KCNA, 25 June 2007, www.kcna.co.jp; "North Korea Says its Banking Row with Washington Resolved," Associated Press, 25 June 2007.
  45. Jae-Soon Chang, "UN Inspectors Verify All N. Korea Nuclear Facilities Closed Beyond Reactor," Associated Press, 18 July 2007.
  46. "Deadline For Disabling N.K. Nukes Set At Year-End," Korea Herald, 4 October 2007.
  47. Choe Sang Hun and Steven Lee Myers, "North Korea Says It Met Nuclear Disclosure Deadline in Previous Declaration," The New York Times, 5 January 2008; Blaine Harden, "All Nuclear Efforts Disclosed, N. Korea Says; U.S. Calls Pyongyang's Declaration Incomplete but Says Negotiations Will Continue," The Washington Post, 5 January 2008; Paul Richter, "N. Korea Says It Has Met Nuclear Criteria; U.S. Officials Say a Full List of Activities Has Not Been Produced," Los Angeles Times, 5 January 2008.
  48. "USA Hails North Korea Nuclear List - Yonhap," in BBC Monitoring, 26 June 2008.
  49. Glenn Kessler, "U.S. Ready to Ease Sanctions on N. Korea; Pyongyang Would Have to Acknowledge Evidence About Nuclear Activities," Washington Post, 11 April 2008.
  50. Norimitsu Onishi and Edward Wong, "U.S. to Remove North Koreans from Terror List; Nuclear Declaration is Rewarded as Disarmament Effort Advances," International Herald Tribune, 27 June 2008.
  51. "N. Korea Destroys Reactor Cooling Tower," Korea Times, 27 June 2008.
  52. Choe Sang-Hun, "North Korea Says It Stopped Disabling Nuclear Complex," The New York Times, 27 August 2008.
  53. Glenn Kessler, "U.S. Drops North Korea from Terrorism List," The Washington Post, 12 October 2008.
  54. Jin Dae-Woong, "Nuke Envoys Fail to Narrow Gaps over Verification Pact," The Korea Herald, 9 December 2008.
  55. "KCNA Report on One More Successful Underground Nuclear Test," KCNA, 25 May 2009, www.kcna.co.jp.
  56. "Magnitude 4.7 — North Korea," USGS, 25 May 2009, http://earthquake.usgs.gov.
  57. "Next Phase in the Analysis of the Announced DPRK Nuclear Test," CTBTO, 27 May 2009, www.ctbto.org.
  58. "North Korea To Push Ahead With Uranium Enrichment," Asia Pulse, 15 June 2009.
  59. "Kim Vows to Work on Return to N. Korea Nuclear Talks: Xinhua," Agence France-Presse, 7 May 2010; "DPRK Top Leader Kim Jong-il Hopes for Early Resumption of Six-Party Talks," Xinhua, 30 August 2010, http://news.xinhuanet.com; Haksoon Paik, “Kim Jong Il’s Visit to China: Implications for East Asia and the United States,” 38 North, 5 June 2011, http://38north.org.
  60. Victor Cha, "The Sinking of the Cheonan," Center for Strategic and International Studies, 22 April 2010, http://csis.org; Hyung-jin Kim and Kwang-tae Kim, "North Korean Shelling Killed 4, Gutted Homes," Associated Press, 24 November 2010; Seo Yoonjung and Keith B. Richburg, “Two Civilians Killed in North Korean Artillery Attack” Washington Post, 24 November 2010, www.washingtonpost.com.
  61. "KCNA on Despicable Inside Story about Megaphone War," KCNA, 29 March 2010, www.kcna.co.jp; "N. Korea to Build Light Water Reactor Soon: State Media," Agence France-Presse, 29 March 2010.
  62. “North Korea Makes Significant Progress in Building New Experimental Light Water Reactor (ELWR),” 38 North, 14 November 2011, www.38north.org.
  63. Siegfried S. 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.
  64. "Light Water Reactor Construction Progressing at Yongbyon Nuclear Site," ISIS Report, March 5, 2012, http://isis-online.org; Jack Liu, "North Korea's Punggye-ri Nuclear Test Site: All Quiet for the Moment," 38 North, August 11, 2014, http://38north.org; Jeffrey Lewis, “Recent Imagery Suggests Increased Uranium Production in North Korea,” 38 North, 12 August 2015, www.38north.org.
  65. "North Korea 'Ready to Discuss Nuclear Enrichment'," BBC, 15 March 2011, www.bbc.com.
  66. Steven Lee Myers and Choe Sang-hun, “North Koreans Agree to Freeze Nuclear Work; U.S. to Give Aid,” New York Times, 29 February 2012, www.nytimes.com.
  67. Evan Ramstad and Laura Meckler, "North Korean Launch Fails," The Wall Street Journal, 13 April 2012, http://online.wsj.com.
  68. David E. Sanger and Choe Sang-hun, "North Korea Confirms It Conducted 3rd Nuclear Test," New York Times, 12 February 2013, www.nytimes.com.
  69. "M5.1 - 23km ENE of Sungjibaegam, North Korea," U.S. Geological Survey, 12 February 2013, http://earthquake.usgs.gov.
  70. "제3차 지하핵시험을 성공적으로 진행 [Third Underground Nuclear Test Conducted Successfully]," KCNA, 12 February 2013, www.kcna.kp.
  71. “DPRK to Adjust Uses of Existing Nuclear Facilities,” KCNA, 2 April 2013, www.kcna.co.jp.
  72. Nick Hansen and Jeffrey Lewis, “Satellite Images Show New Construction at North Korea’s Plutonium Production Reactor; Rapid Restart?" 38 North, 3 April 2013, http://38north.org; David Albright and Serena Kelleher-Vergantini, “Monitoring Activity at Yongbyon Nuclear Site,” ISIS Reports, 23 April 2014, http://isis-online.org.
  73. Nick Hansen and Jeffrey Lewis, “Update on Yongbyon,” 38 North, 11 September 2013, http://38north.org.
  74. Joseph S. Bermudez Jr., Mike Eley, Jack Liu and Frank V. Pabian, “North Korea’s Yongbyon Facility: Probable Production of Additional Plutonium for Nuclear Weapons,” 38 North, 14 July 2017, http://38north.org.
  75. Kelsey Davenport, "N. Korea Warns of New Nuclear Test," Arms Control Association, May 2014, www.armscontrol.org; Jeffrey Lewis, "North Korean Nukes 2.0?" 38 North, 4 April 2014, http://38north.org; Jack Liu and Joseph S. Bermudez Jr., “New Activity at North Korea’s Punggye-ri Nuclear Test Site,” 38 North, 24 September 2014, http://38north.org.
  76. "Kim Jong Un Visits Reconstructed Pyongchon Revolutionary Site," Rodong Sinmun, 10 December 2015, rodong.rep.kp.
  77. David E Sanger and Choe Sang-Hun, “North Korea Says It Has Detonated Its First Hydrogen Bomb,” The New York Times, 5 January 2016, www.nytimes.com.
  78. Justin McCurry and Michael Safi, “North Korea claims successful hydrogen bomb test in ‘self-defense against US,’” The Guardian, 6 January 2016, www.theguardian.com; “North Korea nuclear H-Bomb claims met by skepticism,” BBC News, 6 January 2016, www.bbc.com/news.
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  80. Rick Gladstone and David E. Sanger, “New Sanctions on North Korea Pass in Unified U.N. Vote,” The New York Times, 7 March 2016, www.nytimes.com.
  81. Dave Schmerler, "N. Korea counters doubts with 'miniaturized' bomb photo," NK News, 10 March 2015, www.nknews.org.
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  83. Elaine Lies, "North Korea says it has resumed plutonium production: Kyodo," Reuters, 17 August 2016, www.reuters.com.
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  88. Anna Fifield, "North Korea conducts fifth nuclear test, claims it has made warheads with ‘higher strike power,'" The Washington Post, 9 September 2016, www.washingtonpost.com.
  89. Jesse Byrnes, "US, China condemn North Korea nuclear test," The Hill, 9 September 2016, www.thehill.com.
  90. Kelsey Davenport, “UN Security Council Resolutions on North Korea,” Arms Control Association, August 2017, www.armscontrol.org.
  91. “Kim Jong Un’s 2017 New Year’s Address,” The National Committee on North Korea, 1 January 2017, www.ncnk.org.
  92. Kent Boydston, “Kim Jogn-un’s 2017 New Year’s Address,” Peterson Institute for International Economics, 4 January 2017, www.piie.com; Richard C. Bush, “4 things to know about the Trump-Xi meeting,” Brookings Institute, 8 April 2017, www.brookings.edu.
  93. Choe Sang-Hun, “U.S. Confirms North Korea Fired Intercontinental Ballistic Missile,” New York Times, 4 July 2017, www.nytimes.com.
  94. Joby Warrick, Ellen Nakashima and Anna Fifield, “North Korea now making missile-ready nuclear weapons, U.S. analysts say,” The Washington Post, August 8, 2017, www.washingtonpost.com.
  95. Peter Baker and Choe Sang-Hun, “Trump Threatens ‘Fire and Fury’ Against North Korea if It Endangers U.S.,” The New York Times, 8 August 2017, www.nytimes.com.
  96. “M 6.3 Explosion – 22km ENE of Sungjibaegam, North Korea,” U.S. Geological Survey, 9 September 2017, www.earthquake.usgs.gov.
  97. Tom O’Connor, “North Korea’s Latest Nuclear Bomb is Stronger Than All Its Previous Tests Combined, Newsweek, 5 September 2017, www.newsweeek.com.
  98. Joseph S. Bermudez Jr., Mike Eley, Jack Liu and Frank V. Pabian, “North Korea’s Punggye-ri Nuclear Test Site: Satellite Imagery Shows Post-Test Effects and New Activity in Alternate Tunnel Portal Areas,” 38 North, 12 September 2017, www.38north.org.
  99. Reuters, “U.S. Intel Official: No Doubt North Korea Tested Advanced Device,” 3 September 2017, www.reuters.com.
  100. Damin Jung, "Kim Jong Un inspects thermonuclear weapon to be loaded in ICBM warheard," NK News, 3 September 2017, www.nknews.org.
  101. Christine Kim, Phil Stewart, “North Korea Says ‘Breakthrough’ Puts U.S. Mainland Within Range of Nuclear Weapons, Reuters, 28 November 2017, www.reuters.com.
  102. “READ: Full declaration of North and South Korean summit,” CNN, 27 April 2018, www.cnn.com.
  103. Leo Byrne, “Kim Jong Un says no further nuclear, ICBM tests needed,” NKnews.org, 20 April 2018, www.nknews.org.
  104. Geoff Brumfiel and Elise Hu, “North Korea Demolishes Its Nuclear Test Site in a ‘Huge Explosion,’” NPR, 24 May 2018, www.npr.org.
  105. Kelsey Davenport, “Chronology of U.S.-North Korean Nuclear and Missile Diplomacy,” Fact Sheets & Briefs, Arms Control Association, July 2018, www.armscontrol.org; Joshua Berlinger, “Singapore summit: Asia reacts to the Trump-Kim meeting,” CNN, 12 June 2018, wwww.cnn.com; Dominique Mosbergen and Nick Visser, “Trump and Kim Sign Joint Agreement As Historic Singapore Summit Closes,” Huffington Post, 12 June 2018, www.huffingtonpost.com.
  106. “President Trump News Conference on U.S.-North Korea Summit,” C-SPAN, 12 June 2018, www.cspan.org.
  107. Ankit Panda, “Exclusive: Revealing Kangson, North Korea’s First Covert Uranium Enrichment Site,” The Diplomat, 13 July 2018, www.thediplomat.com.
  108. Jeffrey Lewis, “The Word that Could Help the World Avoid Nuclear War,” The New York Times, 4 April 2018, www.nytimes.com.


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