**FILE** Smoke rises March 15, 2011, from the badly damaged Unit 3 reactor (left), next to the Unit 4 reactor covered by an outer wall at the Fukushima Dai-ichi nuclear complex in Okuma, Japan. The emergency command center at Japan's stricken nuclear plant shook violently when hydrogen exploded at Unit 3 and the plant chief reacted by shouting, "This is serious, this is serious," reveal videos of the crisis as it happened. (Associated Press/Tokyo Electric Power Co., File)