Mirjana Ćujić

Inter-comparison of dynamic models for radionuclide transfer to marine biota in a Fukushima accident scenario.

We report an inter-comparison of eight models designed to predict the radiological exposure of radionuclides in marine biota. The models were required to simulate dynamically the uptake and turnover of radionuclides by marine organisms. Model predictions of radionuclide uptake and turnover using kinetic calculations based on biological half-life (TB1/2) and/or more complex metabolic modelling approaches were used to predict activity concentrations and, consequently, dose rates of (90)Sr, (131)I and (137)Cs to fish, crustaceans, macroalgae and molluscs under circumstances where the water concentrations are changing with time. For comparison, the ERICA Tool, a model commonly used in environmental assessment, and which uses equilibrium concentration ratios, was also used. As input to the models we used hydrodynamic forecasts of water and sediment activity concentrations using a simulated scenario reflecting the Fukushima accident releases. Although model variability is important, the intercomparison gives logical results, in that the dynamic models predict consistently a pattern of delayed rise of activity concentration in biota and slow decline instead of the instantaneous equilibrium with the activity concentration in seawater predicted by the ERICA Tool. The differences between ERICA and the dynamic models increase the shorter the TB1/2 becomes; however, there is significant variability between models, underpinned by parameter and methodological differences between them. The need to validate the dynamic models used in this intercomparison has been highlighted, particularly in regards to optimisation of the model biokinetic parameters.

Review of Remediation Approaches Implemented in Radioactively Contaminated Areas

The chapter aims to summarize different remediation approaches of radionuclide pollutants in water and soil media carried out after decommissioning of nuclear installations worldwide. The attention was focused on different methods of remediation, e.g. natural attenuation, bioremediation, excavating and removing contaminated soil and in situ treatments. The results of radiological assessments of the influence of nuclear cycle facilities in the environment using different modelling approach of the radionuclides transport through the environmental medium are adopted as a useful tool in decision making process applied in remediation of contaminated areas. The current trend in development strategy to support the environmental decision systems for optimization of remediation actions is to use databases on environmental and managerial parameters and radioecological models for the prediction of the effectiveness of remediation measures.