Long-term Environmental Behaviour of Radionuclides

T his document provides an overview on the recent advances in Europe concerning the long-term environmental behaviour of radionuclides. It describes and illustrates the most significant scientific achievements gathered through three European projects, PEACE, LANDSCAPE and EPORA, which have been co-funded by the European Commission (DGXII) under the Nuclear Fission Safety Programme. The improvement of radiation protection issues requires an accurate understanding of the radionuclide contaminants behaviour within ecosystems. The three projects have therefore been focused on the soil-plant system of agricultural lands and semi-natural forest ecosystems based on both, experimental approaches in controlled conditions and in the field. A particular emphasis is devoted to unravelling intra-compartments loads and inter-compartments movements of 137Cs, 90Sr and 239+240Pu, addressing also for the first time the potential influence of non-radioactive additional pollutants (heavy metals). The variety of conditions encountered in Europe is emcompassed through a wide selection of experimental sites ranging from Mediterranean up to Boreal ecosystems. Experimental data acquisition and mechanistic modelling are synergistically developed in order to promote access to improved assessment predictions in an accidental situation. The knowledge generated first includes the redistribution of radionuclides in the soilplant system with emphasis on vertical migration in soils and root uptake by plants. It provides next recent advances into the mechanistic modelling of these features. From the new data gathered through three years of investigations, essential conclusions on contamination discharge via run-off water are drawn, and insights discussed with respect to counter-measure, and spatial variations. Preliminary conclusions are finally derived in the perspective of dose assessment, and areas deserving further research identified.