Thermophysical Properties and Bulk Ion Irradiation Investigations in Ceramics with Potential Nuclear Applications

Abstract

The growing stockpiles of plutonium and minor actinides have become a worldwide issue. Methods of actinide management include developing materials for nuclear waste forms and inert-matrix fuels (IMF) for actinide burning. The work described here has included thermal property assessment of potential IMF materials produced via a novel synthesis method, and radiation-damage studies of a range of ABO4 compounds with potential as nuclear waste forms. In the first study, a smaller particle size (submicron) and improved homogeneity of MgO-Nd2Zr2O7 IMF mixtures were achieved via a novel aqueous solution method. Thermal diffusivity, heat capacity, thermal expansion and thermal conductivity measurements found that the smaller particles did not significantly reduce the resulting material’s thermal properties when compared to samples prepared by more traditional synthetic methods. Importantly, the homogeneity produced is a key factor that could significant effect the performance of the IMF at elevated temperature in reactor. Study 2 and study 3 were focused on the effects of Au ion-beam irradiation on the structural properties of ABO4 compounds. It was found that CaWO4 (scheelite) and YVO4 (zircon) both with tetragonal structures, displayed less damage than LaVO4 (fergusonite), LaNbO4 (fergusonite) and YNbO4 (monazite) with monoclinic structures. The results suggest that the radiation tolerance was better with higher atomic number in group II and CaWO4 showed evidence of a slow recovery from its damaged structure, even at room temperature. Further, thermal annealing experiments were undertaken to investigate recovery of the material from the damage.