North Korea's Reactor Reboot Has Begun: Report Construction can be seen in satellite photos: Think tank By Matt Cantor, Newser User Posted Apr 4, 2013 5:02 AM CDT Updated Apr 4, 2013 7:55 AM CDT 42 comments Comments In this Feb. 14, 2008 file photo released by US researchers, the empty inner structure of a cooling tower at the Nyongbyon Nuclear Center in Nyongbyon, also known as Yongbyon, North Korea, is shown. (AP Photo/S.S. Hecker, File) (Newser) – Looks like North Korea may be making good on at least one of its threats: After saying it would restart its Yongbyon nuclear reactor, it has apparently launched construction on the site, according to a US think tank. The construction appears visible in a March 27 satellite image of Yongbyon, say experts at Johns Hopkins University, per AFP. The work may be to replace cooling mechanisms that North Korea destroyed under a Bush administration agreement. When working, the reactor can produce 13 pounds of plutonium annually. In another possible sign of action, the government has moved a missile to the east coast, the South's defense head says. Though its range is "considerable," it's not enough to reach the US and may have been moved for training purposes. The weapon is reportedly a Musudan, with a 1,900 mile range; Guam is some 2,200 miles away, the New York Times notes. Meanwhile, the North continues to make threats regarding the Kaesong industrial zone, Reuters reports. Northern officials said that if Southern media "bad-mouthing" continues, "we will be taking the stern measure of pulling out all of our workers"—some 53,000 people, the Times notes. That would amount to a closure of the park, which diplomats in the South consider a "red line," the Wall Street Journal reports. South Korean workers at Kaesong, however, are largely holding their ground, Reuters notes. Only 222 out of 828 who stayed at the site overnight said they planned to go home today. But the North has been denying access to those attempting to cross the border from the South to enter the park, the Times reports. Reports that Pyongyang was requiring Southern workers to exit Kaesong by April 10, however, have been inaccurate, the South says, per the Journal. Instead, the North had simply sought information on planned border crossings by staffers at South Korean businesses; Pyongyang wanted to know how many employees would be heading back to Seoul by that date.