MODELING INSITU MUSSEL RU-106 CONCENTRATION DYNAMICS DUE TO FLUCTUATING SEAWATER RADIONUCLIDE CONCENTRATIONS

A 'laboratory' model of radionuclide transfer between marine organisms and seawater was extended with a view to using it in situ. The model was applied to results of experiments performed in situ on the French shores of the English Channel. Therefore 2 first experiments on the transfer of 106-ruthenium between Mytilus edulis and its environment were carried out to establish parameters. The results of these experiments confirmed that the model could predict the time-course of concentrations in the organisms, in the accumulation experiment as well as during the elimination phase in which comparison of the results with other work allowed some of the proposed hypotheses to be validated. Once the transfer model had been characterized, it was applied to results obtained in an independent test experiment. The accuracy of the model fitting to the data was not entirely satisfactory but the discrepancy between the estimates and observations was much smaller than that obtained using the standard 'concentration factor' method. The results obtained in the 2 experiments were compared and factors were considered that might be responsible for the differences observed between real and calculated concentrations. Previous work led to the conclusion that the main factor still to be represented in the model was seasonal change in the metabolism of the mussels and more precisely the mussels' weight fluctuations. Although the formulation of the model has yet to be perfected, results obtained indicate that it could constitute a satisfactory tool for describing concentrations of radioactivity in an organism in situ.