Characterization of Radioactive Wastes Incorporated in a Cement Matrix

Abstract

The incorporation of radioactive material in cement mixtures is a commonly used procedure for conditioning various kinds of low and medium active waste streams. The resulting solid products are non-combustible, sufficiently radiation resistant, and exhibit reasonable mechanical strength as well as chemical and thermal stability. In order to learn more about the underlying mechanisms responsible for the fixation of the radioelements, phase characterization studies have been performed. Main interest was focussed on the question of whether cesium and strontium show mineralization and thus improve their leachability resistance. It could be shown that both elements appear to be just more or less uniformly distributed in the gelatinous filled pore spaces. Improvement of Cs and Sr leach rates is mostly due to sorption phenomena on selected additives, but more important, it depends essentially on the degree of porosity of the cementitious products.