The Democratic People's Republic of Korea appeared to be restarting its 5-megawatt plutonium-producing reactor in the Yongbyon nuclear complex, which houses nuclear facilities such as centrifuges for uranium enrichment.

"New commercial satellite imagery of North Korea's Yongbyon nuclear facility indicates that Pyongyang is probably restarting its 5 megawatt gas-graphite plutonium production reactor," the US-Korea Institute at Johns Hopkins School of Advanced International Studies said in a Wednesday report posted on its website "38 North".

According to satellite images secured by the SAIS, white steam rose from a building near the reactor hall that was housing the reactor's steam turbines and electric generators.

The reactor generates electricity by using the heat from nuclear reaction in the core to create steam that spins the turbines, so white steam being vented indicates that the reactor is in or nearing operation, according to the report.

The report said the DPRK seemed not to use the cooling tower in the past, noting that Pyongyang could instead connect the reactor to a newly built pump house near the experimental light-water reactor at the site. A copy of the Yongbyon reactor in Syria constructed by the DPRK used a pump house instead of a cooling tower.

The DPRK agreed in 1994 with the United States to shut down the reactor under the Geneva Agreed Framework, but it was restarted in 2002 when the agreement collapsed. The reactor had been disabled since October 2007 under an agreement at the Six-Party Talks, leading to the televised demolition of the cooling tower in June 2008.

Amid escalating tensions on the Korean Peninsula following the DPRK's third nuclear test in February, Pyongyang announced its intention in early April to restart the reactor.

"Work has progressed rapidly over spring and summer to bring the facility back into operation," the institute said, estimating that the five-megawatt reactor can produce six kilograms of plutonium a year.

Republic of Korea Foreign Ministry spokesman Cho Tai-young declined to confirm the report but said Seoul was closely monitoring and tracing information related to the DPRK.

Russia said on Thursday that the DPRK was apparently conducting work on a nuclear reactor, warning that the aging facility was in such a "nightmarish state" it could cause a disaster.

"It is obvious that some works are being conducted, and for a long time at that. According to some signs, steps were indeed being taken to relaunch it," the Interfax News Agency quoted a diplomatic source as saying.

The source said Russia did not have definite information Pyongyang had restarted the reactor at Yongbyon, but warned of dire consequences if that happened.

"We do not have any information that the reactor has been relaunched," the source said.

Xinhua-AFP