Estimation of radionuclide migration considering sorption to suspended particles and soil near spring water points in a coastal zone

Sawaguchi, Takuma ; Miwa, Kazuji*; Shimada, Taro ; Takeda, Seiji 

In the previous dose assessment for the radioactive waste disposal, the dissolved radionuclides leaking from the repository were assumed to flow directly into the living environment (ocean, lake, river, etc.) through natural barriers. However, based on the knowledge after the Fukushima Daiichi Nuclear Power Plant accident, it was considered that radionuclides via groundwater could sorb and desorb with soil near spring water points, and that radiocesium was mainly transferred as sorbed to suspended particles in the living environment. In this study, in order to contribute to the dose assessment for intermediate-depth disposal, we analytically understood the influence on the migration in the living environment with or without consideration of the nuclide sorption on the seabed soil during spring water inflow into a coastal zone. In addition, the effects were also evaluated for the presence or absence of the nuclide sorption/desorption on suspended particles and the particle sedimentation. As a result, the radioactivity concentrations in seabed soil and seawater immediately above the seabed were higher in the estimate that considered the sorption/desorption and the sedimentation than in the estimate that did not. These results indicate that it is important to consider the radionuclide sorption on the seabed soil and the migration of radionuclides sorbed on suspended particles in the estimation of radionuclide migration in the living environment because these phenomena could cause the increase of radionuclide concentrations in the interface layer and the seabed soil and the higher exposure due to benthic fish and shellfish ingestion, etc.