Perovskite Ceramics from Mechanically Activated Batches for Immobilization of Rare Earth– Actinide Fraction of HLW

Abstract

ABSTRACTThe effects of different methods of grinding or mechanical milling of precursor mixtures were determined for the structure and properties of perovskite ceramics with the formulation Ca1-xGdxTi1-xAlxO3 (0 ≤x ≤ 1). The ceramics were prepared by coldpressing finely ground precursor mixtures at 100-300 MPa to form pellets that were then sintered at 1300-1500oC. Ceramic samples prepared from precursor material batches treated in a ball or planetary mill or ground in a mortar contained unreacted oxides and had low mechanical integrity and chemical durability. The ceramics produced from precursor material treated by high performance mechanical milling using a high speed rotating vortex layer of ferromagnetic bodies were composed of a major perovskite-structured phase (90-95%) with a Ca-Ti-Gd-Al-O composition and a minor pyrochlore-structured phase with a composition close to that of gadolinium titanate; these ceramics had the highest bending strength (200-340 MPa) and density (~90% of theoretical) and the lowest leach rates for uranium, plutonium, and americium among all the samples studied.