Abstract

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 Ce_0.6Th_0.4O₂ 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.