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

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.

Automated summary

The planned release of tritium (3H) into the ocean in the Fukushima coastal region is expected to take place in Spring or Summer of 2023. Prior to the release, the impact of 3H discharges from both the port of Fukushima Daiichi and rivers in the region was evaluated using a three-dimensional hydrodynamic model (3D-Sea-SPEC). The simulation results showed that the discharges from the port of Fukushima Daiichi had the dominant effect on 3H concentrations within a range of approximately 1 km. Additionally, under storm flow conditions, the riverine 3H discharge was found to have an impact on the Fukushima coastal regions, resulting in an average seawater 3H concentration of approximately 0.1 Bq/L near the shore.