Nuclear firm was warned of tsunami risks
THE company that runs Japan's stricken nuclear power station carried out an extensive underwater survey that should have identified the plant's vulnerability to a tsunami after an earthquake hit one of its plants four years ago.
The Tokyo Electric Power Company (Tepco) carried out geological and sonic surveys around the Fukushima plant to assess the station's resistance to earthquakes and phenomena such as tsunamis.
The survey was carried out as part of a review of power plant safety after a 6.6 earthquake struck the Niigata region in north-west Japan in July 2007, causing a leak of radioactive water from the Kashiwazaki-Kariwa plant.
Nuclear safety specialists said that, despite the surveys, it appeared officials at Fukushima Daiichi had not considered the scenario that a tsunami might hit the power plant at a time when they would need to use backup generators to provide power to the reactor cooling systems.
Fuel tanks for the generators, positioned at ground level just yards from the sea, were among the first parts of the facility to be destroyed by the tsunami last week.
Officials from Tepco said the plant was designed to be resistant to an 18ft wave but was struck by a wall of water more than 22ft high.
Hidehiko Nishiyama of Japan's Nuclear and Industrial Safety Agency said backup power systems had been improperly protected. "I cannot say if it was a human error, but we should examine the case closely," he said.
Dr John Large, an independent nuclear safety expert, said: "The buildings will have been built to withstand a tsunami, but it appears the backup generators were not."
Tatsuya Ito, a politician, also claimed Tepco had been repeatedly warned about the danger posed by a tsunami.
He said a 2002 report by the Japan Society of Civil Engineers described the dangers posed by a tsunami of about 20ft. The report used data from a tsunami that struck Miyagi prefecture in 1960 after a 9.5 magnitude earthquake off the coast of Chile.
Tepco has faced mounting criticism over its level of preparedness, and has been condemned by the Japanese government over the amount of information it was releasing about the incident.
Reports from the families of staff risking their lives at the power plant also provide a glimpse of the chaos that ensued after the tsunami hit. One employee said staff had even attempted to jump-start emergency cooling systems using car batteries and small diesel generators after back-up systems failed.