Titanate ceramics for immobilisation of uranium-rich radioactive wastes arising from 99Mo production

Uranium-rich liquid wastes arising from UO2 targets which have been neutron-irradiated to generate medical radioisotopes such as Tc-99m require immobilisation. A pyrochlore-rich hot isostatically pressed titanate ceramic can accommodate at least 40 wt% of such waste expressed on an oxide basis. In this paper, the baseline waste form composition (containing 40 Wt% UO2) was adjusted in two ways: (a) varying the UO2 loading with constant precursor oxide materials, (b) varying the precursor composition with constant waste loading of UO2. This resulted in the samples having a similar phase assemblage but the amounts of each phase varied. The oxidation states of U in selected samples were determined using diffuse reflection spectroscopy (DRS) and electron energy loss spectroscopy (EELS). Leaching studies showed that there was no significant difference in the normalised elemental release rates and the normalised release rates are comparable with those from synroc-C. This demonstrates that waste forms based on titanate ceramics are robust and flexible for the immobilisation of U-rich waste streams from radioisotope processing. (C) 2009 Elsevier B.V. All rights reserved.