FUKUSHIMA: Tokyo Electric Power Company Holdings Inc. on Thursday started releasing treated water containing tritium into the ocean from its disaster-stricken Fukushima No. 1 nuclear power plant.

The water discharge, which started around 1 p.m., represents a major turning point for the reconstruction of Fukushima Prefecture, home to the plant, the site of the March 2011 triple meltdown, over 12 years after the nuclear disaster.

The Japanese government and TEPCO aim to accelerate decommissioning work at the plant by reducing the number of tanks storing treated water.

Water used to cool the melted nuclear fuel at the plant is purified by the advanced liquid processing system (ALPS) to remove radioactive materials. But the treated water still contains tritium, a radioactive substance and a type of hydrogen.

TEPCO dilutes treated water with seawater to reduce the concentration of tritium to less than one-40th of Japanese safety standards, or 1,500 becquerels per liter, and discharge it into the Pacific Ocean from a point about 1 kilometer off the plant.

On Tuesday night, TEPCO started preparations to dilute about 1 ton of treated water with some 1,200 tons of seawater. As the concentration of tritium in the diluted water was confirmed to have fallen way below the standards, TEPCO decided to start the water discharge as planned. Just before the release, TEPCO announced that the concentration was between 43 becquerels and 63 becquerels.   

In fiscal 2023 through next March, TEPCO plans to release 31,200 tons of treated water.

At a press conference held ahead of the water release, Junichi Matsumoto of TEPCO, who is in charge of handling the treated water, said that “safety is the top priority for the treated water release into the ocean.” “We will deal with the water release with a greater sense of tension,” he added.

There are over 1,000 treated water storage tanks on the premises of the plant. The tanks were to reach their full capacity in February 2024 at the earliest unless TEPCO starts discharging the water into the sea, according to TEPCO.

The space to be vacated as a result of the water discharge will be used as a site to move out and store the melted nuclear fuel. The decommissioning work will continue for about 30 years.

In April 2021, the government decided to start releasing the treated water into the sea in two years.

The government on Tuesday decided to begin the water release on Thursday as it judged that the water release plan won a certain level of understanding in Japan and abroad, thanks partly to a comprehensive report by the International Atomic Energy Agency concluding that the plan was consistent with relevant international safety standards.

JIJI Press