Tepco has so far refused to admit its precautions fell short.

In the days after March 11, Tepco said both the Fukushima No. 1 and No. 2 nuclear plants were designed to resist a 5.5-meter wave based on standards set by the Japan Society for Civil Engineers.

The utility said it simply didn't anticipate the 10-meter-plus March 11 tsunami.

"Japan's nuclear power plants are designed to withstand any earthquake imaginable and not to release radioactive materials to the surrounding area even if its facilities are damaged," Tepco still says on its website, even though the March 11 tsunami has proven otherwise.