Suh, K.-S.; Kim, S., and Min, B.-I., 2017. Atmospheric dispersion and sea surface deposition of radionuclides by the Fukushima nuclear accident. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 85–88. Coconut Creek (Florida), ISSN 0749-0208.A large amount of radioactive material was released to the atmosphere and to the sea by the Fukushima nuclear accident in 2011. Most of the radioactive materials released into the air were moved to the Pacific Ocean due to the westerly jet stream, and some of them dispersed on land in Japan and were deposited in the area northwest of the Fukushima Daiichi power plant. A lot of radionuclides transported to the Pacific Ocean were deposited on the sea surface by a dry/wet deposition process, seawater and seabed sediments along the coastline of Fukushima Prefecture were contaminated. All of this deposition occurred in the early phase of the accident from March 11 to March 25 before the direct discharge into the sea on March 26. In this study, a three-dimensional atmospheric dispersion model has been used to evaluate the characteristics of the dispersion and deposition of radioactive materials released into the atmosphere, especially 137Cs with its long half-life is considered. It is inferred that the measurements of 137Cs in seawater of the Pacific Ocean in 2011 originated from atmospheric deposition, because 137Cs directly released into the sea could not have reached the central part of the Pacific Ocean at that time.