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TEPCO Implements Measures to Limit Concentration of Radioactive Materials in Water Set for Sea Release

The Yomiuri Shimbun

13:58 JST, June 28, 2023

Tokyo Electric Power Company Holdings Inc. has completed the construction of facilities for the offshore discharge of treated water from the stricken Fukushima No. 1 nuclear power plant, the utility firm announced Tuesday.

The treated water contains tritium, which is difficult to remove, even with an advanced liquid processing system.

TEPCO will dilute the treated water on site by mixing it with a large amount of seawater to reduce the concentration to less than 1,500 becquerels per liter — about one-fortieth of the national safety standard.

The treated water will be diluted more than 100 times. Multiple measures are in place to ensure that water with a concentration exceeding the standard is not discharged into the sea.

TEPCO has installed emergency isolation valves at two locations that will automatically operate within 10 seconds of detecting an abnormality in the event of an equipment malfunction that interferes with the seawater dilution process.

A seawall has also been constructed around the isolation valves as an emergency measure.

One of the valves is powered by air pressure and can operate even during power outages.

The facility has three seawater pumps. Even if two of the pumps break down, the target concentration can still be achieved.

Radioactive materials in the treated water will be measured before the dilution process, and tritium levels will also be checked before the water is released into the sea.

If tritium concentration exceeds 700 becquerels per liter within three kilometers of the plant, the discharge will be stopped immediately.

Hiroshi Miyano, former visiting professor of nuclear reactor systems at Hosei University, said, “In terms of equipment, the measures are sufficient. Going forward, it will be important to carefully explain both domestically and internationally that the International Atomic Energy Agency (IAEA) and other organizations have confirmed the safety of the plant.”