The operator of the damaged Fukushima Daiichi nuclear power plant says it will start the fourth round of releasing treated and diluted water from the plant into the sea on Wednesday.

Tokyo Electric Power Company announced the plan on Monday.

The utility intends to discharge about 7,800 tons of treated water over a period of 17 days for the final round of the release during the current fiscal year that ends in March.

A total of about 31,200 tons of treated water is expected to be released in the year as originally planned from the plant in Fukushima Prefecture, which suffered a triple meltdown in the 2011 earthquake and tsunami.

The company says the past three rounds experienced no major trouble. It says analyses of water samples taken in the sea near the plant have shown the concentration of tritium far below the level the utility has set for suspending the release.

However, during the water treating process at the plant, two workers were temporarily hospitalized in October after being directly exposed to liquid containing radioactive substances.

On February 7, untreated water was found to be leaking from a filtering device.

The company says it will carry out the coming release with the utmost care.

Water used to cool molten fuel at Fukushima Daiichi has been mixing with rain and groundwater.

The accumulated water is being treated to remove most radioactive substances but still contains tritium. The treated water is stored in more than 1,000 tanks.

Before releasing the treated water into the sea, the plant's operator dilutes it to reduce tritium levels to about one-seventh of the World Health Organization's guidance level for drinking water.

The utility began discharging the treated water into the ocean in accordance with government policy in August last year.