North Korea has conducted two nuclear weapon tests. The first came on 9 October 2006, North Korea, at 10:35AM (local time) at Mount Mant'ap near P'unggye-ri, Kilchu-kun, North Hamgyong Province. The Korean Central News Agency 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." The North Korean nuclear test did not, however, produce a significant yield—some estimates gauge it to have been as low as 1kiloton. 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 nuclear program still had a number of technical hurdles to overcome before it had a usable warhead. In reaction to the test, the UN Security Council passed Resolution 1718 placing sanctions on North Korea.

After the October 2006 test, North Korea became reengaged in the Six-Party Talks process aimed at ending Pyongyang's nuclear program. In 2007, North Korea agreed to disable its nuclear facilities and give a complete accounting of all its nuclear programs. In June 2008 North Korea submitted a declaration of its nuclear activities and destroyed the cooling tower in its Yongbyon reactor; in response Washington moved toward lifting some sanctions on Pyongyang and removing the regime from the list of states sponsor of terrorism on 11 October 2008. However the six parties stalemated over U.S. and North Korean disagreement on a verification plan for the DPRK disablement.

On 25 May 2009, North Korea conducted its second nuclear test. North Korea's Korean Central News Agency (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." Initial estimates from the U.S. government showed the test causing seismic activity equivalent to a magnitude of 4.7 on the Richter Scale and located close to the site of the first nuclear test in 2006. Early estimates pointed to a possible yield for the test of between 4 and 8 kilotons; while this is stronger than the first test, some analysts still questions the viability of Pyongyang's nuclear warhead design.

Background

North Korea first became embroiled with nuclear politics during the Korean War. Although nuclear weapons were never used, U.S. political leaders and military commanders threatened their use to end the Korean War on terms favorable to the United States. In 1958, the United States deployed nuclear weapons to South Korea for the first time, and the weapons remained there until 1991. North Korean government statements and media reports often cite a "nuclear threat from the United States," and continue to claim that the United States has about 1,000 nuclear weapons deployed in South Korea.

There are different schools of thought on the motivations behind Pyongyang's nuclear weapons program. Those who believe North Korea is a revisionist state that is dissatisfied with its place in the current international structure argue that Pyongyang's nuclear aspirations are motivated by a need to create a serious external threat. This school of thought has ample evidence to support its claims: North Korea's initiation of the Korean War, acts of terrorism, forward-deployed military forces, a constitution that states that the DPRK is the sole legitimate government for all of Korea, and Korean Workers' Party bylaws calling for a "completion of the revolution in the south."

On the other hand, some analysts believe North Korea is a state satisfied with the status quo and that it seeks peaceful coexistence with South Korea and the international community. Proponents of this school of thought often argue that Pyongyang's nuclear motivations are defensive in nature and designed to deter external threats to North Korea. Evidence to support this argument includes the 1972 North-South Joint Communiqué; the 1991 Agreement on Reconciliation, Nonaggression, and Exchanges and Cooperation between North and South Korea (the so-called "Basic Agreement"); the 1991 Joint Declaration on the Denuclearization of the Korean Peninsula; the 2000 summit meeting between the leaders of North and South Korea; the Agreed Framework with the United States; and reunification proposals that would recognize "two systems" for the North and South.

Regardless of North Korean motivations, Pyongyang's record of exporting ballistic missiles and missile production technology have raised concerns that North Korea may also be willing to sell nuclear materials, technology, or even complete nuclear weapons to state or non-state actors.

Early Program

In the early 1950s, North Korea began establishing the institutional base to train personnel for its nuclear development program. The Atomic Energy Research Institute was established along with the Academy of Sciences in December 1952, but the nuclear program did not begin to take-off until North Korea established cooperative agreements with the Soviet Union. 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-kun, North Pyongan Province.

In the early 1960s, the Soviet Union provided extensive technical assistance while North Korea constructed the Yongbyon Nuclear Research Center, which included the installation of a Soviet IRT-2000 Nuclear Research Reactor and other facilities. The small research reactor has been used to produce radioisotopes and to train personnel. The cabinet and the Academy of Sciences were given operational and administrative oversight of the nuclear facilities, but ultimate control of the program and decisions over weapons development belonged to then-North Korean leader Kim Il Sung. The program appeared to begin as a peaceful one, but the 1962 Cuban Missile Crisis may have prompted North Korea to initiate a dedicated nuclear weapons program.

Indigenous Development

Although the beginnings of the development of North Korea's nuclear weapons program were bolstered by relevant assistance from Moscow, and to some extent Beijing, North Korea's program developed largely without significant foreign assistance. This was in part due to suspicions that the North Korean leadership had about the long-term reliability of the Soviet Union and China. While Kim Il Sung appreciated Soviet and Chinese support during the Korean War (1950-1953), he had expected more help, particularly from the Soviets, and he was dissatisfied that the war ended in a stalemate. In 1961, Pyongyang signed "treaties of friendship, cooperation, and mutual assistance" with both Moscow and Beijing, but Kim ultimately questioned the credibility of these alliances. Kim was particularly doubtful of Moscow's alliance commitment after Khrushchev backed down during the Cuban Missile Crisis. Soon after the missile crisis was over, the Korean Workers' Party Central Committee adopted policies to strengthen the military and to implement import-substitution programs to reduce dependency on arms imports. There are also reports that 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. Shortly thereafter, North Korean relations with China began to deteriorate.

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 began to acquire plutonium reprocessing technology from the Soviet Union. 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-kun under IAEA safeguards. The Soviets were included in the agreement since they supplied the reactor fuel.

The early 1980s was a period of significant indigenous expansion, which included uranium milling facilities, a fuel rod fabrication complex, and a 5MW(e) nuclear reactor, as well as research and development institutions. The early 1980s also marked the beginning of high explosives test that are required for the triggering mechanism in a nuclear bomb. By the mid-1980s, Pyongyang began construction on a 50MW(e) nuclear power reactor in Yongbyon-kun, while expanding its uranium processing facilities. Some of technology and equipment acquired during this period had dual-use applications for a uranium enrichment program that was not revealed until the late 1990s.

North Korea's energy concerns make nuclear energy a legitimate rationale for nuclear power, and Pyongyang 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. In the early 1980s, Pyongyang was also exploring the acquisition of light water power reactors, and agreed to sign the NPT in December 1985 in exchange for Soviet assistance in the construction of four LWRs.

In September 1991, President George 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. North and South Korea then signed the "Joint Declaration on the Denuclearization of the Korean Peninsula," whereby both sides promised to "not test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons." The agreement also 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.

North Korea finally signed an IAEA safeguards agreement on 30 January 1992, and the Supreme People's Assembly ratified the agreement on 9 April. Under the terms of the agreement, North Korea provided an "initial declaration" of its nuclear facilities and materials, provided access for IAEA inspectors to verify the completeness and correctness of the initial declaration. 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 reprocessed plutonium on three occasions - 1989, 1990, and 1991. When the Agency requested access to two suspect nuclear waste sites, North Korea declared them to be military sites and therefore off-limits.

1994 Crisis and the Agreed Framework

After the IAEA was denied access to North Korea's suspect 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. Under the terms of the treaty, withdrawal is not effective until 90 days after giving 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 become effective. 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.

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-kun. By the spring of 1994, the reactor core was burned up, and the spent fuel rods had to be discharged. On 14 May 1994, Korean technicians began removing the spent fuel rods without the supervision of IAEA inspectors. This action worsened the emerging 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. The administration of U.S. President Bill Clinton announced that it would ask the UNSC to impose economic sanctions; Pyongyang declared that it would consider economic sanctions "an act of war."

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. Under the agreement, North Korea agreed to freeze its gas-graphite moderated reactors and related facilities, and 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 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 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 US."

Collapse of the Agreed Framework

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 Pyongyang's past activities, and North Korea was dissatisfied with the delayed construction of the light water power reactors.

After coming to office in 2001, the new Bush administration initiated a North Korea policy review that was 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." 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.

There were also concerns about North Korea's suspected highly enriched uranium (HEU) program, which is a different path to produce fissile material for nuclear weapons. In the summer of 2002, U.S. intelligence reportedly discovered evidence about transfers of HEU technology and/or materials from Pakistan in exchange for ballistic missiles. 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. Compared to plutonium-production facilities, the type of HEU production facilities that North Korea was suspected of developing would be difficult to detect.

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. 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 highly-enriched uranium (HEU). The U.S. State Department claimed 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 only admitted to having a "plan to produce nuclear weapons," which Pyongyang claimed was part of its right to self-defense.

The United States responded in December 2002 by suspending heavy oil shipments, and North Korea then 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. Initially, North Korea claimed it had no intention of producing nuclear weapons, and that the lifting of the nuclear freeze was necessary to generate needed electricity.

New Crisis and the Six-Party Process

In the spring of 2003, U.S. intelligence detected activities around the Radiochemisty Laboratory, a reprocessing facility in Yongbyon-kun, that indicate North Korea was probably reprocessing the 8,000 spent fuel rods that had been in a temporary storage pond. In September 2003, a North Korean Foreign Ministry spokesman said that North Korea had completed the reprocessing of this spent fuel, which would give North Korea enough plutonium for about four to six nuclear bombs. In January 2004, a delegation of invited U.S. experts confirmed that the canisters in the temporary storage pond were empty.

In April 2003, a multilateral dialogue began in Beijing with the aim of ending North Korea'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 of the six-party talks began in August 2003. According to reports, North Korean diplomats stated at the talks that Pyongyang had "no choice but to declare its possession of nuclear weapons" and "conduct a nuclear weapons test." The North Korean delegation, however, reiterated that Pyongyang would be willing to dismantle its nuclear programs if the United States "changed its hostile policies, stopped obstructing North Korea's economic growth, and aided the energy needs of North Korea." Six months later, in February 2004, the second round of talks were held and a third round were held June 2004. However, tensions between the parties - particularly the United States and North Korea - meant the talks stalled for over a year, only 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. The reactor had been operating since February 2003, so it could have produced enough plutonium for 1 to 3 bombs. However, it would take a few months for North Korean engineers to extract the plutonium from the spent fuel rods. In September 2005, satellite imagery indicated that the reactor had begun operations once again.

"Statement of Principles" and Breakdown in Talks

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 IAEA safeguards at "an early date." The United States agreed that it has no intention of attacking North Korea with nuclear or conventional weapons, and Washington affirmed that it has no nuclear weapons deployed in South Korea. The parties also agreed that the 1992 Joint Declaration on the Denuclearization of the Korean Peninsula, which prohibits uranium enrichment or plutonium reprocessing, should be observed and implemented.

Although hailed as a breakthrough by some participants, the viability of the "Statement of Principles" were immediately brought into questions by North Korean and U.S. actions. One particularly sticking point was the extent to which different parties interpreted the agreement's provision of light water reactors to North Korea. While Pyongyang argued that the six-party statement had allowed for LWRs, Washington countered that this was not guaranteed under the statement and would only come after North Korea had dismantled its current nuclear program. Shortly after the agreement was signed in Beijing, the U.S. government announced that it was sanctioning Banco Delta Asia (BDA), a Macao based bank, for assisting North Korea with illegal activities including counterfeiting U.S. currency. North Korea demanded that the sanctions be lifted or Pyongyang would not carry-out its part of the September 2005 agreement. Due to these, and other disagreements, the six-party talks stalemated and the "Statement of Principles" remained dormant for over 18 months.

2006 Nuclear Tests and Resumption of Talks

The nuclear crisis on the Korean peninsula continued to deteriorate throughout 2006, reaching a low point in October when North Korea conducted a nuclear test. Immediately following the test, the UNSC imposed sanctions on North Korea. After intense diplomatic activities by the Chinese government and others involved in the six-party process, the parties met again in December 2006 after a hiatus of more than a year. However, these talks end without any sign of progress.

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 its nuclear weapons and existing nuclear programs, and return to the NPT and IAEA safeguards, in exchange for a package of incentives that included the provision of energy assistance to North Korea by the other parties. The agreement also established a 60-day deadline during which North Korea was to shut down and seal its main nuclear facilities at Yongbyon under IAEA supervision. In addition, the United States agreed to release the approximately $25 million in North Korean assets held at the Macao-based Banco Delta Asia. However, the BDA part of the February deal again became a sticking point; much of the the international financial community, concerned about possible legal ramification 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.

After the February 2007 agreement, the North Koreans extended invitations to IAEA officials opening the door to re-establishing its relationship with the Agency since expelling IAEA inspectors in December 2002. In March 2007, an IAEA delegation headed by Mohamed ElBaradei visited Pyongyang and met with North Korean officials to discuss the denuclearization process. In July 2007, North Korea began shutting down and sealing it main nuclear facilities at Yongbyon under IAEA supervision.

Further progress was made in the six-party talks when the parties adopt the second "action plan" that called on North Korea to disable its main nuclear facilities and submit a complete and correct declaration of all its nuclear programs by December 31, 2007. While disablement activities on North Korea's three key plutonium production facilities at Yongbyon—the 5MW(e) experimental reactor, the Radiochemical Laboratory and the Fuel Fabrication Plant—progressed, North Korea failed to meet the December 31 deadline to submit its declaration. Sharp disagreements over North Korea's past procurement efforts that support the development of a uranium enrichment capability and controversies surrounding suspected North Korean nuclear cooperation with Syria proved to be the key sticking points.

Almost six months past the deadline, on June 26, 2008, North Korea submitted its much-awaited declaration. 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 its alleged uranium enrichment program or suspicions of its nuclear proliferation to other countries, such as Syria. Despite problems with the declarations, the Bush administration notified U.S. Congress that it was removing 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. Following the U.S. government's action, North Korea demolished the cooling tower at the Yongbyon reactor which was broadcasted by the international media. However, North Korea announced in late August 2008 that they restored the nuclear facilities in Yongbyon and barred international inspectors from accessing the site. Pyongyang also criticizing the United States for delaying the removal ofNorth Korea from the list of state sponsors of terror.

On 11 October 2008, the United States 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 allow inspectors access to the nuclear sites. 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 disabling 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

	Updated June 2009