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

海洋環境評価システムを用いたアイリッシュ海におけるCsの長期拡散シミュレーション

小林 卓也 ; 乙坂 重嘉  ; 外川 織彦 ; 林 圭佐

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

海洋中における放射性物質の移行過程を詳細に予測する海洋環境評価システムの検証として、英国BNFL再処理工場から放出されたCsの長期拡散シミュレーションを実施した。検証のためIAEA-MELが開発した海洋放射能データベース(MARIS)から抽出したアイリッシュ海における溶存態Cs表層濃度分布と計算結果を比較した結果、アイリッシュ海における表層濃度分布を比較的良好に再現することを確認した。

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.