Photo/Illutration Tanks used to measure the concentration of radioactive substances at the Fukushima No.1 nuclear power plant (Tatsuya Shimada)

The second round of releasing treated radioactive water from the crippled Fukushima No. 1 nuclear power plant into the sea will begin Oct. 5, the plant’s operator announced on Sept. 28.

Similar to the first round that started on Aug. 24 and ended on Sept. 11, around 7,800 tons of treated water stored in tanks will be discharged into the ocean over 17 days after being diluted with seawater.

Ahead of the second release, plant operator Tokyo Electric Power Co., a private analytical agency and the Japan Atomic Energy Agency each measured the treated water before dilution.

Most radioactive substances in the water can be removed via treatment processes.

All results from the three organizations showed the concentration of 29 kinds of radioactive materials, including cesium, were below the legal standards set in the plan approved by the Nuclear Regulation Authority.

But the processes cannot remove tritium, a radionuclide inseparable from water.

Around one ton of water stored in tanks will be diluted with about 1,200 tons of seawater on Oct. 3 and transferred to other tanks to measure the tritium levels, according to TEPCO.

If the concentration is confirmed to be below 1,500 becquerels per liter, the utility will begin releasing the water into the sea on Oct. 5, TEPCO said.

Officials have measured tritium levels in seawater and in fish taken from around the plant, with no abnormalities detected since the discharge started in late August.

TEPCO increased the frequency of measuring the tritium concentrations in seawater within 3 kilometers of the plant from once a week to every day since the first discharge.

On Aug. 31, one sample detected 10 becquerels of tritium per liter, the highest level, at about 200 meters from the underwater discharge point, which is 1 kilometer offshore from the plant. None of the other samples reached that level.

It is also far below 700 becquerels per liter, the level set for the utility to suspend the release.

The Fisheries Agency also measured tritium levels in 50 samples of fish, such as fluke and red sea bream, taken from areas several kilometers north and south of the discharge point until Sept. 25.

The levels from all samples were less than 10 becquerels per kilogram.

(This article was written by Keitaro Fukuchi and Ryo Sasaki.)

Related News