Fukushima Daiichi Nuclear Plant Japan's largest ongoing threat is at this nuclear power plant. There have been explosions at four of its six reactors and all four have released some radioactive mate rial. 15 Nov 2009 12 March 2011 North of Sendai This area, which includes Minamisanriku and the Onagawa nuclear plant, was closest to the epicenter of the quake. In Minamisanriku alone, more than 10,000 people are missing.