A generic model for assessing the effects of countermeasures to reduce the radionuclide contamination levels in abiotic components of fresh water systems and complex catchments

This paper describes a generic model for predicting the migration of 137Cs and 90Sr through complex catchments and the effects of countermeasures to reduce the contamination levels. The model provides assessments of radionuclide behaviour in water systems comprised of rivers, lakes and reservoirs. It makes use of aggregate, “collective” parameters which summarise the overall effects of competing migration processes occurring in fresh water bodies. The model accounts for the radionuclide fluxes from the water column to the sediment and vice-versa, for the radionuclide migration from the catchment and for the transport of contaminated matter through the water body. It has been applied to several European fresh water systems contaminated by 90Sr and 137Cs due to nuclear weapon tests in the atmosphere of past decades and to the Chernobyl accident. The model can predict the effects of the following countermeasures: (a) Sediment removal; (b) Diversion of water from sub-catchments; and (c) Decontamination of subcatchments. The results of the sensitivity and uncertainty analyses are described. Some examples of countermeasure applications are described and discussed.