An in-house investigation by Tokyo Electric Power Co. has found that the crisis at the Fukushima No. 1 nuclear plant was triggered by tsunami that flooded key structures after the March 11 earthquake, causing equipment inside to fail, sources said.
In an interim report of its investigation into the world's worst nuclear crisis in 25 years, Tepco says it plans to take thorough measures to prevent buildings and important equipment from being exposed to water, the sources said Monday.
While vowing to take steps to avoid accidents that would result in further reactor core damage, Tepco says in the report that it also plans to have measures in place to prevent hydrogen explosions and massive releases of radioactive substances into the environment.