Radioactive cesium migration and its origin released due to the 1F accident

We have continuously measured radioactive cesium (¹³⁷Cs) in groundwater in two wells to understand the migration behavior of radioactive materials released by the Fukushima Dai-ichi NPP accident. As a result, an upward trend of the ¹³⁷Cs concentration in recent years has been observed. In order to estimate the source of the ^137Cs, groundwater flow analysis and particle tracking analysis have been performed based on existing information. The results of the analysis have showed that the different sources of ¹³⁷Cs for the two wells. Furthermore, as a result of groundwater flow analysis on a larger have shown that the groundwater had recharged from the Abukuma Mountains discharge at a specific point in the plain. At these points, there is concern that the concentration of ¹³⁷Cs will increase in the future, so continuous monitoring is indispensable. (author)