WASHINGTON (Yonhap News) ― North Korea has made progress in building a light water reactor in its nuclear complex, a U.S. think tank said Wednesday, amid concerns that that might serve as another way of making nuclear weapons for the reclusive communist state. Citing commercial satellite imagery taken March 8, the Institute for Science and International Security said on its website that North Korea made “progress in the construction of what North Korea has stated will be a light water reactor.” The nonprofit, nonpartisan institution dedicated to nuclear nonproliferation said, “A cylinder can be seen in the image and it measures approximately 21 meters across.” “At this diameter, the cylinder would be too large for a light water reactor containment vessel,” it said. “It could, however, be part of the containment structure for a light water reactor. There is new excavation next to the cylinder as well. There is also a new clearing with a crane and what could be construction materials in an adjacent area northwest of the cylinder. It is unclear if this is a construction support or staging area or if a structure will be built there.” North Korea showed the new reactor and a nearby uranium enrichment plant to Siegfried Hecker, a professor at Stanford University, in November, saying the uranium enrichment is for fueling the light-water reactor for power generation. Hecker, former director of Los Alamos National Laboratory, has said he was shown the 100-megawatt experimental light-water reactor “in the early stages of construction.” He also said at the time that he saw hundreds of centrifuges in three rows in a nearby uranium enrichment plant and was told by North Koreans that the plant has 2,000 centrifuges. Unlike graphite, heavy-water reactors that produce weapons-grade plutonium, light-water reactors are seen as less conducive to nuclear weapons production. The scientist, however, has said, “The uranium enrichment facilities could be readily converted to produce highly enriched uranium bomb fuel.” He also said that North Korea might have more uranium enrichment plants than the one it revealed. “Parallel facilities could exist elsewhere.”