RADIOPROTECTIVE CEMENT FOR LONG-TERM STORAGE OF NUCLEAR WASTE

Abstract

To enhance the service safety of the geological repositories which are intended for a highly long-term storage of nuclear waste, we proposed coating the walls of repositories with a hermetically sealed radiation-resistant material. To this end, the compounds of a fourcomponent system CaO–BaO–Fe2O3–SiO2 were suggested. Based on these compounds, we developed the technology for the production of special polyfunctional corrosion-resistant cements that can be used for the production of extra strong radiation-protective and corrosion–resistant plugging cements. The thermodynamic analysis revealed probable phase equilibriums and enabled the tetrahedration of the system at the synthesis temperature of 12000Ñ, which allowed minimizing the volume of required thermodynamic calculations. The processes of hydration of calcium-barium ferrosilicate cement were investigated. It was established that barium hydrosilicates and calcium and barium hydroferrites of a different basicity are the main hydration products; this provides high strength properties of the cement stone. The obtained materials are cements with a high strength (the compressive strength of 58.9 MPa), enhanced protective and corrosion-resistant properties (the calculated mass absorption coefficient and sulfate-resistance factor being equal to 247 cm2/g and 1.31, respectively). The protective concretes with different fillers, which were fabricated based on the developed cements, have a high strength (ultimate compressive strength of 58.4 MPa), a low level of softening in the temperature range of 20–12000Ñ (from 15 to 19%). They can be used at the service temperature of up to 12000Ñ.