The paper presents the effects of the mechanochemical activation of ThO2-UO3 and ThO2-CeO2 mixtures in air and (for ThO2-UO3) in suspension in H2O or CHCl3. Planetary ball mill (Pulverisette 5, Fritch) with stainless steel triboreactors and milling balls from the same materials are used. Milling for 5 h of the ThO2-UO3 mixture does not affect significantly the crystal structure of the ThO2 but leads to amorphization of UO3, sharp decrease of its crystallites size and increase of the ionic character of the U-O bond. Storage of the activated product (2 months at room temperature) or heating (3 h, 165 oC) leads to partial relaxation of the UO3 crystal structure. The X-ray diffraction data does not give proves for formation of ThO2-UO3 solid solution.
Formation of solid solution Ce0.6Th0.4O2 accompanied with some amount of amorphisized ThO2, is established as a result of co-milling at the same conditions of the mixture ThO2 – CeO2 with a mole ratio 1. XRD-determined lattice parameter (5.4804(9) Å) and crystallites size (14 nm) of the obtained solid solution are in satisfactory agreement with literature data for the same product obtained via wet chemistry route.