Persistence of lutetium disilicate

RE2Si2O7 is one of the final products of the chemical interaction of radioactive cation simulators and the silicates used in the engineered barrier of deep geological repositories. The aim of this paper is to study the chemical and structural behaviour of Lu2Si2O7 (Lu as actinide tripositive state simulator) in several different chemical systems. The conditions expected at the repositories are simulated in the laboratory with solutions of different compositions and pH. Both the solid products and remnant solutions were analyzed using techniques that give information on the short- and long-range structural order. The results show good stability of Lu2Si2O7, under the studied conditions, and, therefore, encapsulation of the radioactive actinide cations as a disilicate phase could be considered a viable method to ensure the long-term safety of the repositories.