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(45-04) Importance of particle classes for radionuclide transfers in rivers: Application to an irrigation canal. El Ganaoui, Ouafae1, Boyer, Patrick*,1, Eyrolle, Frédérique2, Anselmet, Fabien3, Amielh, Muriel3, Morello, Marcel4, 1 IPSN/DPRE/SERLAB/LMODE, St Paul Lez Durance, France2 IPSN/DPRE/SERNAT/LERCM, St Paul Lez Durance, France3 I R P H E, UMR CNRS 6594 - Universités d'Aix-Marseille I et II, Marseille, France4 IPSN/DPRE/SERLAB/LRE, St Paul Lez Durance, France ABSTRACT- The interactions of radionuclides with naturally occurring particles depend upon the radionuclide itself, the nature of compounds and the physico-chemical conditions. When a radionuclide is adsorbed, its transfer will be, for a large part, linked to the behaviour of its supporting particle. Such a transfer is characterized by the sedimentary dynamic, which involves deposition, erosion, and transport fluxes. These fluxes depend on both the occurring particles and the hydraulic conditions. Within aquatic systems particles are distributed on a large range of different natures and forms for which it is well known that the interaction with the radionuclides concerns mainly the cohesive class (diameter < 64 micrometers). However, even in this cohesive domain, the radionuclide distribution and the behaviour are not homogeneous (settling velocities, critical erosion shear stress...). Consequently, when deposition or erosion processes occur, these heterogeneities play an important role on the spatial and the temporal radionuclide distribution both in the suspended matter and the bottom sediment. This paper present an application to an irrigation canal of a radioecological model coupled to a hydraulic and a multi-class sedimentary sub models. It describes the experimental methods used to identify and characterize the particle classes. 137Cs activities measured in the bottom sediment evince a continuous increase along the canal. In part, this may be explained by the natural particle size sorting as the percentage of the finest particles (the more caesium reactive) increases in the bottom sediment along the canal. Key words: surface water modelling, artificial radionuclides, sedimentary dynamics |
