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The Japanese government announced on April 13 that it would begin dumping the contaminated water into the ocean. (Yonhap News)

Masahisa Sato, a senior member of Japan’s ruling Liberal Democratic Party and head of the party’s foreign affairs division, tweeted, “South Korea will become a laughingstock when people learn that its nuclear reactors emit more tritium than Japan’s.”

Sato was responding to an order given on April 14 by South Korean President Moon Jae-in for officials to look into filing a claim with the International Tribune for the Law of the Sea against Japan’s decision to release contaminated water from its Fukushima nuclear power plant into the ocean. In the tweet, Sato ridiculed Moon’s order as “sheer bluster.”

In a press conference the previous day, Deputy Prime Minister of Japan and Minister of Finance Taro Aso said that if Japan released the contaminated water into the ocean, it would only be doing what China and South Korea are already doing.

When the Japanese media announced the government’s decision to release the contaminated water into the ocean, they noted that South Korea’s Wolseong Nuclear Power Plant releases 23 trillion becquerels (Bq) of tritium into the ocean, which is greater than the 22 trillion Bq that Japan is planning to release each year. It seems clear where Japanese politicians got their arrogant attitude toward countries that object to Japan’s decision to release the water.

The amount of tritium released from the Wolseong plant varies each year, but 23 trillion Bq was indeed released in 2016.

According to a 2016 report by Korea Hydro and Nuclear Power that assessed radioactivity in the environment, 22.9 trillion Bq of tritium was released in liquid form from the Wolseong plant. When the 1.25 million tons of contaminated water is divided by the 30-year schedule during which Japan plans to release it, the annual amount of tritium is indeed a little over 22 trillion Bq.

There’s one key difference, however. The Wolseong plant will be decommissioned and stop releasing tritium before Japan has finished releasing those 1.25 million tons of contaminated water, but water will continue being contaminated at the site of the Fukushima accident even after the Wolseong plant has been decommissioned. At this very moment, an average of 140 tons of water is contaminated at Fukushima every day.

One gets the impression that Japan’s continued emphasis on tritium in the debate over the contaminated water at Fukushima is designed to distract the public from the really important issues. I’m talking about strontium-90, which is known to build up in the bone marrow and cause blood cancer, and carbon-14, whose half-life is 466 times longer than tritium and whose bioconcentration factor in fish is 50,000 times greater.

In fact, it’s odd that Japan would offer to compare the water being discharged from a nuclear plant in normal operations – that is, Wolseong – with the contaminated water produced in a horrific accident that even melted down the nuclear fuel rods at Fukushima.

It’s true that ordinary nuclear fission at a reactor produces the same radioactive materials produced in the Fukushima accident. But barring an accident, the vast majority of those materials are blocked by the nuclear fuel rods, the fuel cladding, and the containment vessel, with only a tiny amount escaping into the environment.

At Fukushima, however, those various containment measures all failed, allowing the radioactive materials to seep into the groundwater. That’s why contaminated water is still being produced today.

It may be useful here to compare carbon-14 and strontium-90. France’s Institute for Radiological Protection and Nuclear Safety explains that carbon-14 is an interesting material in radiobiology because it enters cellular DNA. That can cause damage to the DNA and molecular division, potentially destroying the cell or causing genetic mutations.

The Advanced Liquid Processing System (ALPS) that Japan uses to treat the contaminated water at Fukushima isn’t capable of removing carbon-14. Japan holds that the water can still be released because the carbon-14 concentration is within the safety limits.

According to figures released in December 2020 by the Tokyo Electric Power Company, the average concentration of carbon-14 in the 1.25 million tons of contaminated water at Fukushima is 42.981Bq/L. Even the highest reported level of 215Bq/L is far below the safety standard of 2,000Bq/L.

But the problem isn’t concentration but total volume. Applying the average level, the total volume of carbon-14 in the contaminated water at Fukushima is estimated to be around 53.7 billion Bq. The 2016 figures for the Wolseong plant – which Japan used for its tritium comparison – show that the plant released 417 million Bq of carbon-14 in that year. Japan’s contaminated water is 120 times greater, which means that Japan would be annually releasing four times more carbon-14 over the next 30 years than the Wolseong plant does.

Strontium-90 presents a more serious problem. The contaminated water stored at Fukushima contains an average of 3,355.342 Bq/L of strontium-90, with a maximum reported level of 433,000 Bq.

The average concentration is a hundred times the safety limit of 30Bq/L. The total amount of strontium-90 is estimated to be over 4 trillion Bq.

Japan plans to run the contaminated water through its ALPS equipment again, to bring all the radioactive materials – other than tritium – under the safety limits. Environmental groups and experts doubt that Japan can keep that promise using its current ALPS equipment.

Even if Japan manages to keep its promise despite these predictions, that doesn’t mean the problem is solved. There would still be about 37.5 billion Bq of strontium-90 level in the contaminated water at the safety levels.

Under Japan’s plan, 1.25 billion Bq of strontium-90 will enter the ocean each year for the next 30 years. That’s 5,400 times the 228,000Bq of strontium-90 released from the Wolseong plant in 2016.

By Kim Jeong-su, senior staff writer

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