Long-term simulation of Cs in the Irish Sea by using ocean environment assessment system

Kobayashi, Takuya ; Otosaka, Shigeyoshi  ; Togawa, Orihiko ; Hayashi, Keisuke

An ocean environment assessment system that forecasts the detailed migration processes of radionuclides in the ocean has been developed. This system consists of an ocean current model and a particle random-walk model. The ocean current model is the modified Princeton Ocean Model (POM). The POM calculates tidal currents by giving tide levels at the open boundary. The particle random-walk model, SEA-GEARN, calculates the radionuclides migration in the ocean. Radionuclides that exist in the ocean are modeled in three phases, such as dissolved in seawater, adsorbed with suspended solids and adsorbed with active bottom sediment. As model validation, the system has been applied to the Irish Sea to simulate the long-term dispersion of Cs actually released from the BNFL spent nuclear fuel reprocessing plant at Sellafield in UK. The calculation well reproduces the main characteristic of migration of dissolved surface Cs concentration in the Irish Sea.