Radioactive water from the damaged Fukushima No. 1 nuclear power plant has reached the international date line, about 4,000 kilometers east of Japan in the Pacific Ocean, according to estimates.
Radioactive water from the damaged Fukushima No. 1 nuclear power plant has reached the international date line, about 4,000 kilometers east of Japan in the Pacific Ocean, according to estimates.
The concentration of radioactive cesium-137 will be 0.1-0.01 becquerel per liter by the end of November, 10 to 100 times higher than before the accident started, according to estimates by the Japan Agency for Marine-Earth Science and Technology.
The concentration will be at one-2,000th to one-20,000th of the government safety standard for potable water, but monitoring will be necessary for any impact on fish and shellfish.
A team of researchers led by Yukio Masumoto estimated the flow based on radiation levels measured in waters around the Fukushima No. 1 plant, taking convection and other factors into account.
Radioactive water that leaked from the plant first moved along the coast and then gradually moved offshore.
The researchers estimated that it reached the international date line in four to five months after spreading amid complex flows between the Oyashio and Kuroshio currents.
The dispersion will not change much even on the assumption that airborne radioactive materials have fallen to the ocean.
A science ministry survey has found radiation levels of several becquerels in waters around the Fukushima No. 1 plant.