Effects of uranium oxide high-level waste on the structure of iron phosphate211 glasses

摘要

Because of their unusually good chemical durability, iron phosphate glasses are a211u001enatural candidate for a nuclear waste disposal glass. We have studied the effects 211u001eof UO(sub 2) high-level waste on the structure of iron phosphate glasses with 211u001eboth neutron and high-energy x-ray diffraction using the GLAD instrument of the 211u001eIntense Pulsed Neutron Source and the 1-BM bending magnet beamline of the 211u001eAdvanced Photon Source, respectively. The results of neutron scattering, which is 211u001emostly sensitive to correlations involving light atoms i.e. O-O, Fe-O and P-O, 211u001esuggest the main structural features of the base glass are largely unaffected by 211u001ethe addition of UO(sub 2). The nearest-neighbor P-O, Fe-O and O-O peaks remain at 211u001ethe same position in real space and their intensities scale approximately with 211u001econcentration. These findings are consistent with the earlier results of Raman 211u001escattering and EXAFS on the Fe-K edge wherein both cases the spectra remain 211u001esimilar to the base glass. High-energy x-ray scattering which is sensitive to 211u001ecorrelations involving the heavier atoms and thus complements the neutron 211u001emeasurements, is also consistent with uranium occupying interstitial sites in the 211u001erelatively undisturbed base glass structure. However, important questions remain 211u001eas to the precise local structure and oxidation state of uranium in these 211u001eglasses.