Care managers tend elderly people in March 2012 in Minamisoma, Japan. The home's residents were evacuated eight days after the Fukushima Dai-ichi nuclear power station was crippled by the March 11, 2011 tsunami. Koji Sasahara/AP hide caption

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Smoke rises from Unit No. 3 of the stricken Fukushima Dai-ichi nuclear plant after the March 11, 2011 earthquake and tsunami. Anonymous/AP hide caption

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This photo, taken by a remote-controlled endoscope and released by Tokyo Electric Power Co., shows structures assumed to be small size piping or cable conduit inside the beaker-shaped containment vessel of No. 2 reactor at the damaged Fukushima Dai-ichi nuclear power plant. Tepco/AP hide caption

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Workers in protective suits and masks wait to enter the emergency operation center at the crippled Fukushima Dai-ichi nuclear power station on Nov. 12, 2011. David Guttenfelder /AFP/Getty Images hide caption

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Japan's Parliamentary Secretary for the Cabinet Office Yasuhiro Sonoda drinks a glass of decontaminated water taken from puddles inside the buildings housing reactors 5 and 6 at the Fukushima No. 1 plant.

Jiji Press/AFP/Getty Images hide caption

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The tsunami flows over sea walls towards TEPCO's Fukushima Daiichi nuclear power plant on March 11, 2011. This photo was taken by Tokyo Electric Power Company. TEPCO/AFP/Getty Images hide caption

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A levee protects a home surrounded by floodwater from the Yazoo River near Vicksburg, Mississippi on May 18, 2011. Scott Olson/Getty Images hide caption

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An aerial view of Chubu Electric Power's Hamaoka nuclear power plant in February 2005. STR/AFP/Getty Images hide caption

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