Simulation study on 3H behavior in the Fukushima coastal region: Comparison of influences of discharges from the Fukushima Daiichi and rivers

Abstract

The release of tritium (³H) to the ocean is planned on the coastal environment in the Fukushima coastal region from Spring or Summer of 2023. Before its release, we evaluate the effect of ³H discharges from the port of Fukushima Daiichi and rivers in the Fukushima coastal region using a three-dimensional hydrodynamic model (3D-Sea-SPEC). The simulation results showed that discharges from the port of Fukushima Daiichi dominantly affected the ³H concentrations in monitoring points within approximately 1 km. Moreover, the results indicate that the effect of riverine ³H discharge was limited around the river mouth under base flow conditions. However, its impact on the Fukushima coastal regions under storm flow conditions was found, and the ³H concentrations in seawater in the Fukushima coastal region were formed around 0.1 Bq/L (mean ³H concentrations in seawater in the Fukushima coastal region) in the near shore.

Keywords: (3)H concentrations in seawater; (3)H derived from Fukushima Daiichi; Fukushima Daiichi Nuclear Power Plant accident; Riverine (3)H input; Three-dimensional hydrodynamic model.