Japan has failed to mention 640 kilograms of unused plutonium in its reports to the International Atomic Energy Agency (IAEA) in 2012 and 2013. An official in Japan’s Atomic Energy Commission said on Saturday that the 640 kg was part of the plutonium-uranium mixed oxide fuel, known as MOX, that was placed in an offline reactor at the time and was considered as being used. The MOX fuel was loaded...