Factors influencing the increased 90Sr radioisotope migration in highly alkaline groundwater at Chornobyl NPP site.

This paper analyses the formation of high Sr2+ concentration in strong alkaline (pH = 9.5-12.5) groundwater using data of the 27 years of observations around the destroyed Chernobyl NPP Unit 4. It appears that the formation of strong alkaline groundwater in different monitoring wells is consistent with the distribution of 90Sr, pH and main ions. The reason for the increase in 90Sr concentrations is the process of its migration from the sources of contamination - leaks of highly active water localized in certain premises inside the «Shelter ¼ object. These computational experiments showed that for the groundwater in pH range 9.5-12.4, the concentration of strontium in the form of SrOH + increases and in the form of Sr2+ - decreases. In addition, the fraction of 90Sr in the form of a soluble neutral complex compound SrCO30, which is not sorbed, reaches 14-35%. Increased fractions of 90Sr in forms of SrOH+ and SrCO3 are factors which reduce the isotope ability to be sorbed by soils and therefore increase its migration ability. In strongly alkaline groundwater a sharp increase in 90Sr volumetric activity may also be caused by ionic strength (IS) increase above 5 mmol/L. Thus, the factors that influence the increase in 90Sr volumetric activity in strongly alkaline groundwater are the formation of its complex compounds and an increase in ionic strength (IS), which reduces the thickness of the double electric layer and, as a result, reduces the sorption capacity of soils.

Isotope composition of groundwater and surface waters in the area of the Dombrovsky quarry of Kalush-Golinsk deposit of potassium salts.

Enrichment of heavy isotopes of hydrogen (D, 3H) and oxygen (18О) is observed in water samples collected from open brine storage of Kalush-Golinsky deposit. The brine storage facilities were formed during the operation of the Kalush-Golynsky deposit of potassium salts and after its decommissioning. Enrichment of isotopes is also observed in groundwater samples, collected from wells located along with downstream groundwater from brine storage facilities. The analysis of levels of influence of possible sources of chemical pollution of groundwater (waters of the Dombrovsky quarry, tailings and sludge storage, salt dumps, saline soils) and correlation relationships between isotopes and groundwater mineralization have been determined by statistical processing of geochemical data.