NHK has learned that Tokyo Electric Power Company, or TEPCO, has drafted a plan for disposing of radioactive wastewater stored at the troubled Fukushima Daiichi nuclear power plant.
Water used to cool molten nuclear fuel from the 2011 accident is treated to remove most radioactive material. But tritium and other substances remain in the water, a huge amount of which is stored in about 1,000 large tanks.
A government panel last month compiled a report that says releasing diluted radioactive wastewater into the sea or air are realistic options.
TEPCO's plan for doing so would involve diluting the wastewater with seawater, aiming for a tritium level of one-fortieth that allowed by national regulation.
The firm would gradually release the diluted water over about 30 years, taking into consideration the amount of similar water released at other nuclear plants.
TEPCO would also test treating the wastewater again to further remove other radioactive materials.
The utility is to explain the plan to local officials and residents in Fukushima Prefecture. People in the local fishery and tourism industries oppose releasing the water into the ocean.