ARCHAEOLOGICAL GLASSES – A MODEL FOR THE STABILITY EVALUATION OF THE VITRIFIED RADIOACTIVE WASTE

Abstract

This article presents the possibility of usage of the archaeological glasses to predict the behavior of radionuclides incorporated into the glass matrix, under the conditions of the underground storage during prolonged contact with the groundwater. Archaeological glasses, whose age is more than two thousand years old, selected from the cultural horizon of the archaeological reserve "Olvia" were examined. A gel layer was formed on the surface of the glass prolonged contact with the soil, on the outer surface of which layered aluminosilicates are formed. The formation of a protective layer of the glass occurs by the mechanism of the incongruent dissolution. It has been experimentally established that alkaline and alkaline earth cations (Na, Ca), partially silicon and iron, are intensively removed into the soil during leaching from the glass, with the practical immobility of aluminum. Simulation of glass fracture was performed in Soxhlet extractors under conditions of continuous exposure to hot water (t = 75–80 °C) saturated with carbon dioxide for 6 months. The change in the rate of components removal from the glass is connected with an increase in the thickness of the "locking" gel layer, the thickness of which increases over time. Cyclic changes in the dissolution rate of the glass are connected with the partial destruction of the gel layer due to the increase in thickness of the gel layer and, accordingly, a decrease in the adhesion of the gel to the glass. The results of the aluminosilicate (archaeological) glasses fracture study and their comparison with the results of the borosilicate glasses fracture study indicate that archaeological glasses can be a model for the predicting of the behavior in natural conditions of the glass matrices intended for radioactive waste volume reduction for centuries.