The total amount of radioactive substances released into the sea as a result of the crisis at the Fukushima No. 1 nuclear power plant is believed to have been three times the initial estimate by the plant's operator, according to the Japan Atomic Energy Agency.
A team led by senior researcher Takuya Kobayashi estimated the actual quantity at 15,000 terabecquerels, including substances in polluted water and substances released into the air that eventually fell into the sea. Tera means one trillion.
The figure is more than triple the estimate by Tokyo Electric Power Co. Also, the new estimate does not include cesium-134, meaning the actual total could be even larger.
The research team will announce its findings at a conference of the Atomic Energy Society of Japan scheduled to start in Kitakyushu on Sept. 19.
TEPCO's calculation was based on the premise that polluted water containing high levels of radioactive substances was only released into the sea from April 1 to 6.
TEPCO estimated a total of 4,700 terabecquerels of radioactive substances--iodine-131, cesium-134 and cesium-137--leaked into the sea during that period.
Based on the density of radioactive materials near the nuclear plant's water-intake facility, Kobayashi's team calculated backward to the March 21 to April 30 period. Radioactive substances were first detected in the sea on March 21.
The team simulated the proliferation of the substances in the ocean based on its new estimate and confirmed that the results matched data from the sea near the nuclear plant.