Problems of Protection of Urban Areas from Radionuclides Strontium-90 and Caesium-137 after Technological Disasters

The methods of decontamination of radionuclides from soils are considered. The literature focuses on fixing radionuclides in soils and creating geochemical barriers that it is prevent the spread of pollution. The main disadvantage of these methods is excluding the possibility of building a territory. It is needed to clean up the area to the sanitary and hygienic requirements for further use and then it is desirable to fix the residual activity. The conducted analysis of forms of radionuclides fixation in soils and mechanics of this fixation, therewith revealed that Cs-137 fixed more strongly on mineral components of soil, than Sr-90, which is mainly in the acid-soluble and exchangeable form, and, as a consequence, passes into the liquid phase during soil deactivation more easily. Contaminated soil deactivation in the urbanized territory is possible by washing it by ferric chloride solution at a concentration 0.02–0.05 M and with an equimolar addition of an ammonium chloride. Therewith, most efficient methods, which use in-situ conditions, are heap and convection leaching technologies with treatment degree, which is not less than 80%. At the same time, the most efficient methods which use in-situ conditions are heap and the convection leaching. The hardware-technological scheme of a convection leaching is presented. It is worth to note that ammonium salts additions slightly rise coefficient of treatment from Sr-90. Because ammonium salts are inexpensive, their additions allow to obtain significant economic benefits due to decreasing ferric chloride consumption, which is more valuable, and waste water volume reduction.