North Korea may have restarted nuclear reactor at Yongbyon: sources

South Korean conservative activists hold placards showing portraits of North Korean leader Kim Jong-Un during an anti-Pyongyang rally in Seoul on June 24, 2013.</p>

South Korean conservative activists hold placards showing portraits of North Korean leader Kim Jong-Un during an anti-Pyongyang rally in Seoul on June 24, 2013.

North Korea may have restarted a reactor at its Yongbyon nuclear complex, which is believed to have once produced weapons-grade plutonium and had been shut down under a 2007 six-party agreement, several diplomatic sources said Wednesday.

The satellite image analysis showed white smoke, believed to be steam originated from the heat of the reactor, spewing intermittently from the 5-megawatt graphite-moderated reactor in late August, the sources said.

It is still unclear, however, whether North Korea has already started full-fledged operation of the reactor or is still conducting test runs.

If the reactor has gone back online, North Korea would be able to produce an extra 6 kilograms of plutonium a year, an amount sufficient to produce a nuclear weapon, by reprocessing spent nuclear materials from the fuel rods in the reactor after a certain period of operation, according to the sources.

The sources said countries such as Japan and the United States are now analyzing the data to determine whether the plant is fully operational, as there remains a possibility that North Korea is still testing the cooling function without loading fuel rods.

The latest revelation came at a time when US special representative for North Korea policy Glyn Davies is on a five-day tour of three member countries of the six-party talks — South Korea, China and Japan — to discuss with local officials how to tackle North Korea's nuclear development program.

If the reactor has indeed been rebooted, it reaffirms Pyongyang has no intention of abandoning its nuclear program. It also suggests it may be using it as a diplomatic card to have Washington respond to its call for a dialogue.

North Korea has repeatedly defied international calls for denuclearization, and it still remains uncertain whether the stalled six-party talks aimed at addressing the reclusive state's nuclear ambitions can be resumed. The six-party framework also involves Russia, in addition to the United States.

As part of a "new strategic line" to promote economic and nuclear development, a spokesman of North Korea's General Bureau of Atomic Energy said in April that the country will restart all nuclear facilities at the Yongbyon complex.

In a symbolic gesture of its commitment to the six-party process, North Korea blew up in June 2008 the cooling tower of the Yongbyon reactor, which had been operational since 1986.

The graphite-moderated reactor is believed to have been linked to the cooling system of an adjacent light-water reactor facility under construction.

The sources said in addition to drilling activities for linking the moderated reactor, pumps have also been spotted feeding water from a river nearby since around July.

The International Atomic Energy Agency said in its report in late August that North Korea could resume operations of the nuclear reactor without a new cooling tower.

In the report, the agency, citing evidence that the ground had been dug up between March and June, said North Korea could be building a new facility to replace the cooling tower.

North Korea's past missile launches and nuclear tests have alarmed neighboring countries such as South Korea and Japan, and the rest of the world. The country last conducted a nuclear test in February.