Investigation of physico-mechanical properties of ceramic oxide kernels for nuclear applications

In the present work, two different classes of oxide kernels were investigated: unirradiated thoria, urania and (Th,U)O2 fuel kernels and low-density Al2O3 kernels for the incorporation of minor actinides. The physical mechanism of oxide kernel failure under uniaxial compression was investigated. A new method for determining the physico-mechanical properties of kernels has been developed and the parameters PS and δ, characterising the level of stress required for destruction of the material structure and the brittleness of the investigated materials, respectively, were evaluated and discussed. It was shown that the value of PS is analogous to traditional characteristics of material such as microhardness Hv. The `quantisationʹ effect was revealed in the kernel crushing strength and deformation distributions. The physico-mechanical properties of ceramic kernels (average particle size, microstructure, phase state, density, PS and δ) were investigated and comparative analysis of different kernel types was performed. Additionally, the impact of annealing time on the properties of low-density Al2O3 kernels was examined.