Short-term emergency assessment system of the marine environmental radioactivity

Kawamura, Hideyuki  ; Kamidaira, Yuki   ; Kobayashi, Takuya 

The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of the Marine Environmental Radioactivity (STEAMER). STEAMER is in daily test operation to predict the oceanic dispersion of radionuclides that are released into the ocean from nuclear facilities. The predictability of oceanic dispersion simulations is validated in this study. Oceanic dispersion simulations are performed for a hypothetical release of Cs-137 from the Fukushima Daiichi Nuclear Power Plant using oceanographic forecast and reanalysis data. Comparison between forecast and reanalysis simulations enables us to estimate the predictability quantitatively. Ensemble forecast simulations are also performed to improve the predictability. Moreover, a Regional Ocean Modeling System is applied to simulate ocean circulations accurately in the coastal and offshore areas. As a result, submesoscale eddies and tidal currents affect the oceanic dispersion of Cs-137.