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
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
This file handout picture shows workers spraying water to cool down the spent nuclear fuel in the fourth reactor building at TEPCO's Fukushima Daiichi nuclear power plant. TEPCO/via AFP/Getty Images hide caption
This handout picture, taken by Tokyo Electric Power Co (TEPCO) shows radioactive water on the floor inside the building of a water treatment facility at TEPCO's Fukushima Daiichi nuclear plant. TEPCO/AFP/Getty Images hide caption
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 captionThe 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
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
An aerial view of Chubu Electric Power's Hamaoka nuclear power plant in February 2005. STR/AFP/Getty Images hide caption
April 29: An image from video taken by Tokyo Electric Power Co. as robots explored the nuclear reactor building of Unit 1 at the Fukushima Dai-Ichi plant. TEPCO/AFP/Getty Images hide caption