ALBERT

Description: Distribution coefficients for strontium and cesium, as one component of a hydrogeological site investigation, were determined by the batch method on 12 samples of glacial till and 7 samples of sand from the radioactive waste operations site 2 of the Bruce Nuclear Power Development. The tests were performed using two types of equilibrating solutions traced with radioisotopes; one was a solution with cation concentrations equal to the concentrations obtained in 1:1 solid–solution extracts and the other was natural groundwater obtained from piezometers at or near the depths from which the soil samples were obtained. The measured Kd values were relatively uniform within an individual hydrogeological unit, and differences between units were related to the chemical properties of both the solid and solution phases. The Kd values for both Sr and Cs obtained in the tests performed using the synthetic solutions differed from those obtained in tests using natural groundwater. The differences appeared to be related to the major chemistry of the test solutions and indicated that, to obtain Kd values that were most representative of the in situ conditions, natural groundwater should be used in the batch procedure.The measured Kd values, when used in the linear retardation equation, indicated that in the till materials, 90Sr would migrate at a rate no greater than 0.2 cm∙year−1 and 137Cs would migrate at a rate no greater than 0.001 cm∙year−1. Based on the relatively high Kd value for Cs in the sand (300 mL∙g−1), 137Cs migration through the sand unit would be of little environmental concern. On the other hand, the relatively low Kd for Sr (2 mL∙g−1) indicates that attention should be paid to the pathway role of the sand layer in any assessment of the isolation capability of the site.