Home – Home – Jornals – Chemistry for Sustainable Development 2021 number 3

The matrix material based on NdAlO₃ was obtained by means of self-propagating high-temperature synthesis of the NiAl intermetallic compound by diluting the mixture of Ni and Al components with Nd₂O₃-Al₂O₃ oxides. Nd₂O₃ was used as a simulator of actinoids in high-level radioactive wastes. The influence of the batch parameters of the initial components on the synthesis process was studied and optimal conditions for preparation were determined: the density of the system should not exceed 5.2 g/cm³ and the content of the included radioactive waste simulator should not exceed 40 mass %. The composition of the final product and its properties were studied using a complex of physicochemical methods. According to the data of XRD analysis, the maximum possible formation of the NdAlO₃ phase is observed for the sample containing 40 mass % Nd₂O₃-Al₂O₃, with the density of 5.15 g/cm³, obtained by pressing at a pressure of 30 MPa. The studies of the material characteristics have shown the simulator maximum leaching rate 2.66 · 10^-9 g/(cm² · day) . The limits of matrix characteristics variations were determined through the simulation of the storage of matrix material in geological formations by irradiation with neutron fluxes in a research reactor. For instance, a decrease in hydrolytic stability was 10-13 % and a decrease in compressive strength was 7 % on average. The general regularities of structural changes in the matrix material under the influence of ionizing radiation fluxes were considered. Insignificant destruction of the crystal structure was observed due to the appearance of various defects. The limiting value of the changes in sample volume was 4.3 %. However, the characteristics of the samples meet all the requirements to materials intended for the immobilization of radioactive waste.