Recent satellite images have shown "suspicious" activity at North Korea's main nuclear site at Yongbyon, which could mean reprocessing is underway to produce more plutonium for atomic bombs, a report published by a U.S. research institute said on Monday.
The report on the 38 North website said that in the past five weeks, exhaust plumes had been detected on two or three occasions from the thermal plant at Yongbyon's Radiochemical Laboratory, the site's main reprocessing installation to produce plutonium.
"Exhaust plumes have rarely been seen there and none have been observed on any examined imagery this past winter. The plumes suggest that the operators of the reprocessing facility are heating their buildings, perhaps indicating that some significant activity is being undertaken, or will be in the near future," the report said.