But conditions have stabilized in recent days, giving the utility, widely known as Tepco, the confidence to unveil its schedule for shutting the reactors.

The first part of the plan would take about three months and include installing a cooling system to lower the temperature in the reactors and spent fuel pools, as well as reducing radiation in the surrounding area, said Tsunehisa Katsumata, the chairman of Tokyo Electric.

The second part, which would take up to six more months, would include more pumping of water, the introduction of a heat removal system and reducing the amount of contaminated water. The wreckage from the three damaged buildings would then be removed and the buildings covered.