SEOUL - 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 (DPRK)'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 (SAIS) said in a Sept 11 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 gas-graphite 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 the 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 like 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 the 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.

Regarding the report, Foreign Ministry spokesman Cho Tai-young declined to confirm it, but Cho said that Seoul was closely monitoring and tracing information related to the DPRK.