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Soil-radionuclides interaction and subsequent impact on the contamination of plant food products based on a simulated accidental source.



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François Bréchignac, Yves Thiry, Nadia Waegeneers, Ramon Vallejo, Teresa Sauras, Jaume Casadesus, Graeme Shaw, Joanna Marchant, Sverker Forsberg, Chantal Madoz-Escande, Claude Colle, Marc André Gonze. In Proceedings of the SPERA 2000 Conference, Nouméa, New Caledonia, 19-23 June 2000, published in Enviromnental changes and Radioactive tracers, Fernandez J.M. & Fichez R., eds., 2002, IRD Editions, Paris, 532 p. (ISBN: 2-7099-1493-X) pp. 397-419


The Chernobyl accident, which resulted in a substantial release of radioactive materials in the atmosphere, demonstrated that large environmental areas may be contaminated by fall-out deposition of radioactivity. In particular, contamination by 137Cs and 90Sr of agro-ecosystems where food production is taking place is most liable to contribute to population radiation dose (Strand et al., 1996). Nuclear safety analysis shows that the possibility, although very small, of an accident occurring on a pressurized water reactor (PWR) cannot be completely ruled out. In such a situation, decision making and management of the contaminated agricultural surfaces largely depends on our ability to predict how, and to which extent, the initial contamination may cause foodstuffs to be polluted. Furthermore, the efficiency of the prediction models relies on our level of understanding of the mechanisms governing the transfer of radionuclides in the soil-plant system. Gaining an understanding of these mechanisms from in situ observations of environmental areas contaminated by past events is difficult due to the lack of knowledge and control on both, the contamination itself, arising from a critical situation, and the natural environment, which is highly variable, temporally and spatially. Such conditions prevent a clear identification of the most relevant parameters influencing the radionuclides transfer and thereby the prediction goal from being achieved. This is why IRSN developed a unique research facility capable of generating, in closed and controlled environmental conditions, a mini-accident with release of radioactive aerosols onto small-scale, but realistic, samples of crops. These crops are grown on undisturbed soil monoliths, featuring several soil types from various European countries, managed in advanced lysimeters, and placed in greenhouses where various climatic conditions can be reproduced artificially under computer control. The PEACE Programme, gathering a European scientific collaboration around this facility, has been designed to tackle the consequences of an accidental release of 137Cs and 90Sr on the soil-plant system of agricultural lands. The research conducted has focused on the interaction of radionuclides with soils with a view to improve our understanding of the mechanisms governing their transfer to plants via the roots, and their modelling for prediction.