Goshi Hosono, the minister in charge of the nuclear crisis, said improving the ability of water decontamination facilities at the Fukushima No. 1 power plant is a "major challenge" toward achieving cold shutdown of the crippled reactors.

He made the remarks at a news conference Wednesday to announce the latest version of the road map for containing the crisis, which left unchanged the broad time frame to stabilize the reactors by January at the latest.

Hosono also highlighted the need for "planned training and deployment" of experts on radiation dose management.