DIFFUSIONAL MODELING OF RADIOCESIUM FIXATION BY SOILS

A diffusional model of radiocaesium fixation in soils and bottom sedim ents was developed. According to this model fixation is a result of ra diocaesium cations diffusing into the surface layer of soil or sedimen t particles. Good agreement between predicted and experimental time de pendences of Cs-137 fixation rate in soils indicates that the proposed model seems adequately to reflect the actual mechanism of radiocaesiu m fixation and can be used for prediction of this radionuclide's long- term behaviour in natural soil-water systems. Its major advantage is a small number of parameters which have a clear physical meaning and ca n, in principle, be determined in an independent experiment or assesse d theoretically.