Fukushima Daiichi nuclear disaster for caesium-137, which is about 11% of Chernobyl emissions. Earlier estimations were 150 PBq and 12 PBq. In 2011, scientists working for the Japan Atomic Energy Agency, Kyoto University and other institutes, recalculated the amount of radioactive material released into the ocean: between late March through April they found a total of 15 PBq for the combined amount of iodine-131 and caesium-137, more than triple the 4.72 PBq estimated by TEPCO. The company had calculated only the direct releases into the sea. The new calculations incorporated the portion of airborne radioactive substances that entered the ocean as rain. In the
Radiation effects from the Fukushima Daiichi nuclear disaster be the most relevant isotope as far as doses was concerned and indicated the possibility "to follow this nuclide over long distances for several years." The organization also said it could take months or years for the isotope to reach "other shores of the Pacific". The survey by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) reveals that radioactive caesium released from Fukushima I Nuclear Power Plant reached the ocean 2000 kilometers from the plant and 5000 meters deep one month after the accident. It is considered that airborne caesium particles fell on the ocean surface, and sank as