Following a decision on August 22 by the Inter-Ministerial Council for Contaminated Water Issues and Decommissioning at Fukushima Daiichi, TEPCO began preparing for the release. In accordance with the government’s basic policy on release of the water into the sea―that the release would begin with small volumes accompanied by checks of the surrounding environment, to minimize reputational damage caused by unfounded fears and rumors―TEPCO planned the releases in two stages for the time being.

The first stage would consist of confirming the tritium concentration in the diluted ALPS-treated water. The second stage, then, would consist of discharging the water while verifying the soundness of the facilities and operational procedures. On August 22, in anticipation of the first stage, a very small amount of ALPS-treated water (about 1m3) was diluted in seawater (about 1,200m3), directed into a vertical release shaft and left to stand.

On August 24, the diluted water was sampled and the concentration of tritium measured, and it was confirmed that the water had been diluted as intended. An analysis value below the level of 1,500Bq/l, one-fortieth the regulatory limit of 60,000Bq/l, was ascertained. Based on the weather and water conditions that morning, TEPCO moved to the second stage in the afternoon.

According to the FY23 plan, there will be four releases within the year of about 7,800m3 each. The total tritium will represent about 5 trillion Bq; the control value for operations prior to the accident in 2011 was 22 trillion Bq annually. The first (current) release is expected to be at a rate of about 460m3 per day, over some 17 days.

For the disclosure of data, TEPCO has established a portal site, called the Treated Water Portal Site, describing conditions at each facility. It can be found as follows:

On August 23, TEPCO established two project teams—the Project Team for Integrated ALPS-Treated Water Measures and the Team for ALPS-Treated Water Effects—to bolster its overall system for implementing the ALPS-treated water release, and to oversee the various horizontal sections involved. Both teams are under the direct control of TEPCO President KOBAYAKAWA Tomoaki, who will visit the work site frequently to oversee the situation.

JAIF President ARAI Shiro released a message, stating, “The start of offshore release represents a major step forward in the decommissioning of Fukushima Daiichi.”