Abstract
We examined long-term influence of 137Cs leaked in the ocean during the accident of the Fukushima Daiichi Nuclear Power Plant occurred after the East Japan earthquake disaster on March 11, 2011. We calculated the currents off Sanriku using a box model and predicted the diffusion extent of 137Cs in seawater and bottom sediment using the OECD/NEA model.We applied annual averaged water temperature and salinity data to a quarter degree grid box model and were able to show the flow of Kuroshio, Oyashio and Tsugaru warm currents.Using this flow field, we performed a long term diffusion calculation. As a result, the distribution of 137Cs in seawater showed extensions to the northeast and the southwards. Results from the bottom model showed that the distribution of 137Cs was limited to the west of 142°E, and this distribution tendency was in agreement with the monitoring data.
