TOKYO -- Water from the Fukushima Daiichi Nuclear Power Station is set to be released into the ocean before results showing the concentration of radioactive tritium are available, plant operator Tokyo Electric Power Company (TEPCO) Holding Inc. has announced.
TEPCO said the release of the water -- which is diluted with seawater -- is necessary because it requires a half to a full day for the test results to come back, and there is no place to store the water for that time.
The treated water stored in tanks on the Fukushima Daiichi plant grounds contains 64 radioactive substances. Seventy percent of the wastewater produced at the plant has concentration levels of radioactive substances besides tritium that exceed national government standards for release into the sea. The radioactive substances in the water are therefore reduced to levels meeting the standards using equipment including Advanced Liquid Processing System (ALPS), a multi-nuclide removal system.
However, it is technologically difficult to remove tritium. Therefore, the contaminated water will be mixed with seawater drawn from pumps and diluted by at least 100 times, so that the tritium concentration is below 1,500 becquerels per liter. The diluted water will be released into the sea, and radioactive substance concentration level measurements will be conducted regularly by taking samples at the release point.
But because of the half to full-day wait for the test results, if the water is not released until they come back, TEPCO would have to prepare another storage site to keep the water in the meantime.
TEPCO will also measure the tritium concentration levels before the contaminated water is diluted with seawater. Based on these results, the company will calculate the amount of seawater to be mixed with the water and manage the amount to be pumped in. TEPCO has adopted the stance that given this procedure, the treated water's radioactive concentration level will be below 1,500 becquerels per liter, and there are no issues.
However, under the proposed system, even if radioactive concentration levels were to exceed 1,500 becquerels in measurements conducted prior to the water's release into the sea, the water would continue to be discharged until the results were out.
Reiko Hachisuka, head of the Okuma Town Society of Commerce and Industry in Okuma, Fukushima Prefecture, and a member of the Nuclear Regulation Authority (NRA)'s Fukushima Daiichi decommissioning panel, said, "If possible, I'd like them to release the water after checking their concentration levels."
Kiyoshi Takasaka, an advisor on nuclear countermeasures to the Fukushima Prefectural Government, commented, "I can understand the plan set out by TEPCO to a certain extent. I'd like them to monitor the amount of seawater used in dilution at all times and ensure that there is no malfunction in the seawater pumps."
TEPCO will shortly submit its plan to the NRA outlining the process and the designs of equipment used to release the treated water for review before the plan is implemented, in about two years.
NRA Chairman Toyoshi Fuketa indicated that he wants to have the company file an application by mid-August.
(Japanese original by Ei Okada, Science & Environment News Department)