TEPCO, the operator of the crippled Fukushima nuclear plant, had tried to fill the containment vessel of the No. 1 reactor with water, but it decided to abandon the plan after it discovered that a meltdown had occurred at the reactor.

Masanori Naito, director in charge of safety analysis at the Institute of Applied Energy, said, "TEPCO could have conducted similar analysis at an early stage and assumed the meltdown had occurred. TEPCO should have prepared other cooling methods besides the method of filling the reactor with water."

[link to mdn.mainichi.jp]