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La Recherchev2

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Peace programme for evaluating the impact of accidents contaminating the environment.


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Brechignac, F.; Vallejo, R.; Sauras, T.; Casadesus, J.; Thiry, Y.; Waegeneers, N.; Forsberg, S.; Shaw, G.; Madoz-Escande, C.; Gonze, M.A. RAPPORT INIS-FR-2000-263, 207p.

Résumé

The Chernobyl accident, which led to 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 Cs and Sr of agro-ecosystems where food production is taking place is most susceptible to contribute to population radiation dose. Nuclear safety analysis shows that, although very small, the probability of an accident occurring on a pressurized water reactor (PWR) cannot be completely set aside. In such a situation, decision making and management of the contaminated agricultural surfaces largely depend on our ability to predict how, and to which extent, the initial contamination may lead to polluted foodstuffs. 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. Unraveling these mechanisms from in situ observations of environmental areas contaminated by past events is difficult due to the lack of control on both, the contamination itself, which happened in 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. In particular, current transfer factors introduced in prediction models suffer from unresolved and poorly documented variabilities. 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 on small-scale, but realistic, samples of crops. These crops are conducted on undisturbed soil monoliths, featuring several soil types from various European countries, managed in lysimeters with advanced water movement control, and placed in greenhouses where three typical climates can be reproduced artificially, and yearly repeated, by means of computer control.