BEIJING, July 14 (Xinhua) -- Located 130 km north of Pyongyang, the capital of the Democratic People's Republic of Korea (DPRK), Yongbyon is the DPRK's leading nuclear research center, boasting the country's only functioning 5-megawatt reactor.

    According to the International Atomic Energy Agency (IAEA), Pyongyang started nuclear research as early as the late 1950s. In the mid-1960s, Yongbyon's capabilities were kick-started with the help of the former Soviet Union. The DPRK also trained a number of nuclear specialists then.

    A Soviet-imported 800-kilowatt reactor was then set up at Yongbyon, enabling the DPRK's nuclear research capacity to take its initial shape. Yongbyon has hence become the DPRK's major site of nuclear industry.

    The Yongbyon graphite-moderated reactor was built and went into operation in 1987. It is capable of extracting from spent nuclear fuel rods plutonium -- an essential raw material for making nuclear weapons.

    The DPRK's nuclear issue escalated in the early 1990s. The U.S. government considered that the Yongbyon nuclear reactor was capable of processing plutonium enough to make two or three atomic bombs. Worrying that the DPRK would develop nuclear weapons, the United States signed with the DPRK an agreement in October 1994 to suspend the nuclear facility in exchange for two relatively proliferation-resistant light-water reactors.

    Then, Pyongyang said it had frozen 8,000 fuel rods of the Yongbyon reactor until September 12, 2002, when it announced it would re-start the operation after accusing the United States of failing on its commitments.

    China has been playing an active role in defusing the Pyongyang nuclear tensions by bringing officials from China, the DPRK, the Republic of Korea, the United States, Japan and Russia to the negotiating table for the Six-Party talks.

    On February 13, 2007, the six-party talks produced a joint statement on the crucial step toward the denuclearization of the Korean Peninsula.

    According to the document, the DPRK will shut down and seal the Yongbyon nuclear facility, including the reprocessing facility, and invite back IAEA personnel to monitor and verify its actions.