image4North Korea may be attempting to restart its main nuclear bomb fuel reactor after a five-month shutdown, a U.S. research institute said Thursday. If true, the finding, which is based on recent commercial satellite imagery, will be an added worry for the United States and the North’s neighbours at a time of increasing animosity over recent U.S. sanctions against the North and Pyongyang’s fury about a U.N. push to punish its alleged human rights abuses. Activity at the 5-megawatt Nyongbyon reactor is closely watched because North Korea is thought to have a handful of crude nuclear bombs, part of its efforts to build an arsenal of nuclear tipped missiles that could one day hit America’s mainland. Nyongbyon, which has produced plutonium used for past nuclear test explosions, restarted in 2013 after being shuttered under a 2007 disarmament agreement. It has been offline since August. More