Atmospheric transport and deposition of Fukushima-derived radionuclides

Hirao, Shigekazu*; Satou, Yukihiko   

The environmental impacts of radioactive materials released into the atmosphere from the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP) as a result of the tsunami caused by the 2011 Tohoku Earthquake are both wide-ranging and long-lasting. Inherent radioactive particles were released into the atmosphere in the early stages of the FDNPP accident. The particles were mainly composed of silica but also contained iron and zinc, and above all, caesium could be detected by elemental analysis using SEM-EDS. The particles reached the Tokyo metropolitan area on March 15 and were deposited on the ground surface, mainly in the Nakadori area of Fukushima Prefecture. At least three types of these particles have been identified, and they were generated by all the reactors that suffered core meltdowns. It has been shown that the particles released from Unit 1 may have melted due to caesium adhering to the insulation, but the formation process of the particles from the other reactors has not yet been clarified. Fortunately, several studies have verified that the effects of inhaling these particles are minimal. More than a decade after the accident, this presentation provides an overview of the current understanding of the early environmental impacts via the atmosphere and the related findings regarding the release of radionuclides into the atmosphere.