Fukushima No. 1 tsunami risk ignored

Tokyo Electric Power Co.'s nuclear facility management department did not heed the risk of a massive tsunami striking near the Fukushima No. 1 power plant after it was projected in an in-house study in 2008, and ruled out an immediate need to bolster defenses against the sea, Tepco sources said.

Despite a projection for tsunami as high as 10.2 meters, officials in the section at Tepco headquarters insisted that the risk was unrealistic, the sources said Sunday. The power station was ravaged by tsunami as high as about 15 meters on March 11 that knocked out the reactor cooling systems, leading to three meltdowns. The waves easily overran the plant's sea wall.

The power plant was designed based on Tepco's assumption that the biggest tsunami expected in the area would be 5.7 meters high. The 2008 study estimated tsunami 15.7 meters high could inundate the facility.

Company sources now figure Tepco could have prepared to cope with the March tsunami if it heeded the 2008 projection.

The section supervising the nuclear facilities was set up in 2007, and had been headed until June last year by Masao Yoshida, chief of the Fukushima No. 1 plant.