Radionuclide Sequential Extraction from Reservoir R-17 Bottom Sediments of the Mayak Production Association

Abstract

The extraction parameters and speciation of ¹³⁷Cs and ²⁴¹Am in bottom sediments of reservoir R-17 of the Mayak Production Assocation were studied. The extraction was performed with four solutions with different pH values (water simulating in its composition the groundwater from the investigated area, 0.1 M Na₂CO₃, acetate buffer solution, and 1 × 10⁻³ M HNO₃). With the first solution, the degree of extraction of ¹³⁷Cs and ⁹⁰Sr becomes constant in 24 h. The desorption percentage did not depend on pH. The ¹³⁷Cs distribution coefficients were calculated. The lowest values were observed in the buffer solution (27) and sodium carbonate solution (21), and the highest values, in water (9250). As shown by sequential extraction, the major fraction of cesium (90%) occurs in the insoluble form. Incorporation into the crystal lattice of clay minerals was found to be the main sorption mechanism. The ²⁴¹Am sorption mainly occurs by the mechanism of complexation with carbonates.