An Overview of marine modelling activities in IAEA MODARIA Program; Lessons learnt from the Baltic Sea and Fukushima scenarios

IAEA MODARIAプログラムにおける海洋放射能拡散モデルの概要; バルティック海と東京電力福島原子力発電所事故シナリオからの知見

Periez, R.*; Bezhenar, R.*; Brovchenko, I.*; Duffa, C.*; Iosjpe, M.*; Jung, K.-T.*; 小林 卓也 ; Lamego, F.*; Maderich, V.*; Min, B.-I.*; Nies, H.*; Osvath, I.*; Outola, I.*; Psaltaki, M.*; Suh, K.-S.*; de With, G.*

Periez, R.*; Bezhenar, R.*; Brovchenko, I.*; Duffa, C.*; Iosjpe, M.*; Jung, K.-T.*; Kobayashi, Takuya; Lamego, F.*; Maderich, V.*; Min, B.-I.*; Nies, H.*; Osvath, I.*; Outola, I.*; Psaltaki, M.*; Suh, K.-S.*; de With, G.*

IAEAのMODARIAプログラムの枠組みの中で、海洋拡散モデルの詳細な相互比較を、チェルノブイリ原子力発電所事故に伴うバルティック海及び東京電力福島第一原子力発電所事故に伴う福島沖海域における放射性物質の海洋汚染について、Cs-137を対象として実施した。複数の海洋拡散モデルとしてBOXモデルや3次元力学モデル等の多様なモデルを用いた。バルティック海におけるモデル比較では極めて良好な一致を示したものの、福島沖海域における比較では各研究機関が所有する海況場を入力として計算した結果に大きな相違が確認されたが、海況場を統一することで良好な一致を得た。発表では、緊急時対応としてシステムを運用する際の課題に焦点を当てて報告する。

State-of-the art dispersion models were applied to simulate Cs dispersion from Chernobyl nuclear power plant disaster fallout in the Baltic Sea and from Fukushima Daiichi Nuclear Plant releases in the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models and between models and experimental data (from HELCOM database) was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted.