Tokyo Electric Power Co. President Masataka Shimizu was highly criticized for keeping a low profile during the early days of the nuclear crisis. Shimizu stepped down Friday but vowed that the utility will continue to do everything it can to bring the Fukushima Dai-ichi plant under control.
Three reactors at the plant were threatened when the plant's cooling systems were destroyed in the March 11 disasters.
The quake and tsunami, which left 24,000 people dead or missing, damaged farms, ports and hundreds of suppliers.
Leaking radiation has prompted the evacuation of thousands of residents, and the perilous struggle to contain the reactors is expected to continue into next year.
Meantime, TEPCO released dramatic new photos of the tsunami that damaged the nuclear power plant.
A photo taken from the fourth floor of the radiation waste treatment facility shows huge waves pouring into the plant.
Another photo shows the waves about to breach the seawall protecting the facility.
The water washed up to a nearby road, inundating some of the plant's buildings and left several cars bobbing in the water.
The Associated Press contributed to this report.