** FILE ** In this March 20, 2011, aerial file photo taken by a small unmanned drone and released by AIR PHOTO SERVICE, the crippled Fukushima Dai-ichi nuclear power plant is seen in Okumamachi, Fukushima prefecture, northeastern Japan. From top to bottom: Unit 1, Unit 2, Unit 3 and Unit 4. (AP Photo/AIR PHOTO SERVICE, File)