Radioactive nuclides leaching

Therefore, the problem of effective remediation of soils of radioactive nuclides is very relevant. Most technologies of soil decontamination that are currently developed are based on flushing soils with various chemicals and include processes of chemical leaching and selective extraction of radioactive nuclides (Prozorov et flZ., 2000 Shevtsova, 2003). The electrokinetic technique is a new and perspective method of soil remediation, whose main advantage consists in its applicability to decontaminating soils with low filtration ability directly at the site of its local pollution (e.g. in a rock mass) (Pamukcu and Wittle, 1992 Acar et al, 1993, 2001 Janosy and Piot, 1998 Korolev, 2001, 2006 Korolev, Barkhatova, and Shevtsova, 2007). 

The most efficient electrokinetic removal of radioactive nuclides from polluted ground can be achieved in combination with electrochemical leaching, that is, with... 

Radioactive disequilibria may be caused by different solubilities of mother and daughter nuclide, by different probabilities of escape or by different leaching rates due to recoil effects. Examples of different solubilities are U/Th and U/Pa. The probability of escape may be very high in radioactive equilibria with Rn. Recoil effects due to a decay lead to displacement and local lattice defects and may cause higher leaching rates. For instance, a change in the ratio caused by... 

At equilibrium, the activity ratio between any two members of a decay series is 1.00. However, at and near the Earth s surface, disequilibrium of the various nuclides of the uranium series is found to occur. The disequilibrium is especially pronounced in groundwaters (Cherdyntsev, 1971 Osmond and Cowart, 1976). The fractionation of the nuclides can occur as a result of chemical differences between elements, the fractionation of isotopes of a given element may occur because of preferential leaching of one (because of its radiogenic origin), or by the direct action of recoil during radioactive decay (Osmond and Cowart, 1976). 

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