Crystal chemistry of uranium (V) and plutonium (IV) in a titanate ceramic for disposition of surplus fissile material

Uranium luminescence in La2Zr2O7: effect of concentration and annealing temperature

“…As evident from the figures, there was no shifting of the peaks or appearance of additional peaks in the diffraction patterns, indicating that up to 8 mol% of uranium doping, no phase separation occurs. This is line with the results obtained by Fortner et al, who was observed that up to 20 wt% of natural uranium can be accommodated in a titanate-based pyrochlore without phase separation (13).…”

Exploring Actinide Materials Through Synchrotron Radiation Techniques

“…Therefore, the pyrochlore was regarded as a suitable conditioning matrix . Fortner et al reported XANES and EXAFS spectra of the Pu L III and U L III edges in titanate pyrochlore ceramic, which were the type proposed to serve as a matrix for the immobilization of fissile materials. The results showed that Pu(IV) occurs in the calcium site within pyrochlore/zirconolite as expected.…”

“…The titanate ceramic that has served as a matrix for the immobilization of surplus fissile materials and the chemical information of actinides in the ceramic was of great concern. Fortner et al investigated a ceramic sample containing approximately 10 wt% fissile plutonium and 20 wt% natural uranium. XANES spectra confirmed that the oxidation state of uranium was +5 and the uranium atoms might occupy the octahedral sites in pyrochlore.…”

A New Generation of Adsorbent Materials for Entrapping and Immobilizing Highly Mobile Radionuclides

“…More recent development of this technology allows us to avoid using Ag or other heavy metals for iodine immobilization and subsequent vitrification (see Section 5 of this chapter). Existing waste forms tend to incorporate radionuclides into rigid crystal structures (e.g., Xu and Wang, 2000;Fortner et al, 2002;Ewing, 2006;Grambow, 2006), and the waste loading of those materials is generally limited by various structural factors such as the size and charge of a target radionuclide. Unlike the existing waste forms, the new waste forms we developed incorporate radionuclides as nano-scale inclusions in a host matrix and thus effectively relax the constraint of crystal structure on waste loadings.…”