The effect of synthesis conditions on the phase composition, structure, and chemical durability of uranium-bearing murataite ceramics

摘要

The samples of U-bearing ceramics with a composition (wt%) 5 Al2O3, 10 CaO, 55 TiO2, 10 MnO, 5 Fe2O3, 5 ZrO2, 10 UO2 were produced by melting of oxide mixtures in a Pt ampoule, glassy carbon crucibles in a resistive furnace, and cold crucible inductive melting (CCIM). In total 85-95 vol% of the samples produced were composed of murataite polytypes with 5- (5C), 8- (8C), and 3- (3C) fold elementary fluorite unit cell forming respectively core, medium part and rim of the murataite grains. Crichtonite, rutile, and Mn/Fe titanate (pyrophanite/ilmenite) were found to be minor phases. The latter was primarily present in the ceramics produced by melting in glassy carbon crucibles. Cold crucible melted ceramics contained the traces of vitreous phase due to melt contamination with a cold crucible putty material. Average U leach rates from the ceramics measured by SPFT procedure were found to be 10(-3) gm(-2) d(-1) and lower.