The operator of a damaged Japanese nuclear power plant said Friday in its first official report that a larger-than-expected tsunami was the direct cause of the nation's worst-ever nuclear disaster.
The Fukushima Daiichi Nuclear Power Station has been leaking radioactive material since it was crippled by the March 11 earthquake and ensuing tsunami, DPA reported.
The 13-metre-high tsunami was higher than Tokyo Electric Power Co, which runs the plant, had factored in, it said in an interim report on an investigation into the nuclear disaster.
"As a result, we were not able to take measures to counter the accident at the Fukushima Daiichi Nuclear Power Station and could not prevent reactor cores from sustaining damage," the report said.
The report also said that key facilities at the plant did not lose their functions as a direct result of the magnitude-9 quake, but the flooding caused by the devastating tsunami caused a "simultaneous loss of multiple safety functions."
The loss of power and the failure of cooling functions led to the meltdowns in reactors 1 through 3. A series of fires and explosions triggered the massive release of radioactive substances into the environment. Some 87,000 local residents have been forced to leave the area.
Vice president Masao Yamazaki said the utility had been taking "the best possible measures at the time" to secure the safety of the power plants, Kyodo News reported.
Yamazaki, however, also conceded the view was different from that of an advisory panel set up in the utility. The panel concluded that the utility's safety measures were "insufficient," which was also a factor in the disaster, Kyodo reported.
Tokyo Electric plans to compile a final report by mid-2012, while a third party panel, which is looking into the causes of the nuclear disaster, will also issue an interim report later this month.