Increase in the 200 - 500 times the migratory ability of 90Sr in underground waters occurs in a highly alkaline environment at pH > 9.5 in a reducing or transitional environment. The nature of the spatial distribution of the increase in 90Sr suggests that this process is triggered not by the leakage of block water, but by changes in the aquatic environment. Determination of 90Sr migration forms in a highly alkaline environment using thermodynamic modeling shows an increase of 12 to 16 % of the fraction 90Sr in the form of a neutral SrCO3 molecule. At the same time, the proportion of 90Sr in the form of free ion decreases from 95 – 97 %, which is typical for a neutral or slightly alkaline, to 81 – 84 %. In the article with the help of thermodynamic modeling, the possibility of increasing the concentration of 90Sr in 500 times in underground water samples from observation wells is analyzed view of the growth of the fraction of its migration form in the form of SrCO3 in a highly alkaline environment. The possibility of increasing the groundwater pH > 9.5 in the process of inflow into the aquifer of infiltration water, which was in contact with concrete or communications enriched with products of leaching of concrete (Са2+ and ОН-), is shown with the help of thermodynamic simulations. Concentration of strontium in the composition of complex compound SrOH+ increases 57 times. There was an assumption that the main factor of desorption process is high concentration of hydroxide OH-. This process prevents sorption of radioactive strontium by soils in the highly alkaline environment. Increased migratory ability is caused by complex compound SrOH+.
Keywords: ChNPP industrial site, underground waters, strong-limestone environment, pH > 9.5, increased migration 90Sr, thermodynamic modeling, SrOH+.
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