Photo/Illutration Water storage tanks are dismantled at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant on Feb. 21 in Futaba, Fukushima Prefecture. (Asahi Shimbun file photo)

Around 100,000 tons of treated water have been released from the Fukushima No. 1 nuclear power plant since the operation started two years ago on Aug. 24, but roughly 1.28 million tons remain.

About 70 percent of the remaining water stored in tanks on the plant’s premises contains concentrations of radioactive substances that are above safety standards. This water will require another purification round known as “secondary treatment.”

If this work is significantly delayed, the release of all water might not be completed by 2051, the goal for finishing the plant’s decommissioning process.

Tokyo Electric Power Co. (TEPCO), the plant’s operator, continuously circulates water to cool the nuclear fuel that melted inside reactor buildings in the 2011 disaster.

However, rainwater and groundwater keep flowing into the damaged buildings and mixing with the cooling water, raising the volume of contaminated water.

TEPCO treats the contaminated water using equipment called the Advanced Liquid Processing System (ALPS), which is designed to remove radioactive substances other than tritium.

The treated water is then stored in huge tanks, which now exceed 1,000 in number and are spread across the plant site.

To make room for the decommissioning work at the Fukushima plant, TEPCO began releasing treated water into the ocean in August 2023.

Before discharge, the water is diluted with seawater more than a hundred times. Officials have checked to make sure the concentration of tritium is less than one-40th of the Japanese government’s standard for release.

By Aug. 3 this year, roughly 102,000 tons of treated water had been released.

But since the release period started, the volume of stored water at the plant decreased by only 58,000 tons because rainwater and groundwater have kept flowing into the damaged reactor buildings and becoming contaminated.

Every day, about 80 tons of new contaminated water is generated at the plant.

At the current water-release pace, it will take an estimated 40 years to empty all the tanks.

Even so, TEPCO has insisted that all contaminated water will be treated and discharged by the decommissioning target year of 2051.

“While not exceeding the annual release limit of 22 trillion becquerels, we may increase either the frequency or the amount (of water) released at a time,” a TEPCO representative said.

Since February, TEPCO has dismantled 11 tanks that were emptied by the water release.

Its plan is to discharge about 400,000 tons of treated water by around fiscal 2030, which will allow the company to dismantle more tanks and free up between 50,000 and 110,000 square meters of space needed for decommissioning work.

However, as of the end of June, TEPCO reported that about 870,000 tons of the stored water still had radioactive substance levels above safety standards, requiring secondary treatment using the ALPS purification system.

The process requires installing piping and other equipment. If the secondary treatment takes too long, the dismantling of tanks will be delayed, which could affect the schedule for removing the melted nuclear fuel debris.

When TEPCO began releasing the treated water in August 2023, China immediately suspended all imports of Japanese seafood.

In May this year, Japan and China reached an agreement to lift the blanket ban, but import restrictions remain for marine products from 10 prefectures, including Fukushima and Tokyo.

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