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Radioactive cesium-137 released from Fukushima 1.5 times Tepco estimate: study

Kyodo

The total amount of radioactive cesium-137 released into the atmosphere and seawater from the crippled Fukushima No. 1 nuclear power plant is estimated at between 17,500 and 20,500 terabecquerels, a study by a Japanese research team showed Friday.

The team’s finding on the cumulative amount of cesium-137 is nearly 1.5 times more than the estimate by plant operator Tokyo Electric Power Co. of less than 13,600 terabecquerels.

The team announced its findings on cesium-137 during an academic session of the European Geosciences Union in Vienna on geoscience processes related to the Fukushima nuclear disaster.

Michio Aoyama, a professor at Fukushima University’s Institute of Environmental Radioactivity who is part of the team, told Kyodo News that TEPCO “underestimates” the amount of cesium-137 that was released into the atmosphere and later fell into the sea.

Scientists are trying to detect the levels of radioactive cesium due to its potential, long-term risks to the land and sea. Cesium-137, which has a half-life of around 30 years, can cause cancer.

The total amount of cesium-137 differs based on researchers’ estimates but Aoyama has expressed confidence about the data his team gathered and analyzed, saying theirs is the “most probable” figure as it is based on actual measured data.

The study estimates that 14,000 to 17,000 terabecquerels of cesium-137 were released into the atmosphere, while about 3,500 terabecquerels directly flowed into the ocean. A terabequerel is equal to 1 trillion bequerels.

In the 1986 Chernobyl nuclear disaster, 85,000 terabecquerels of cesium-137 were released.

But in the case of the Fukushima nuclear disaster, Aoyama said the release of radioactive cesium-137 has a “big impact on the ocean,” since the Fukushima nuclear complex is near the coast.

The study also found that 12,000 to 15,000 terabecquerels of the cesium-137 released into the atmosphere fell into the sea, while the remaining amount fell into the soil. Of the amount that fell on land, up to 400 terabecquerels fell on North America, while Europe was hardly affected.