Technetium-99 is a major fission product of uranium-235 and is found in radioactive waste from nuclear fuel and, in certain jurisdictions, from the production of plutonium. Technetium is unique amongst the transition metals in that no stable isotope exists. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi 2Tc 2O 7-d. The oxide is found to be oxygen deficient with a stoichiometry of Pb 2Tc 2O 7-d. The structure of lead-technetium pyrochlore has been refined in space group F d 3 ¯ m with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. 6Department of Nuclear System Safety Engineering, Nagaoka University of Technology, Nagaoka, Japan.

5Australian Synchrotron, Australian Nuclear Science and Technology Organisation, Clayton, VIC, Australia.4Nuclear Materials, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, Australia.3Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, Australia.2Nuclear Fuel Cycle, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, Australia.1School of Chemistry, The University of Sydney, Sydney, NSW, Australia.Wallwork 5, Zhaoming Zhang 2, Hanliang Zhu 2 and Gordon J. Carter 2, Linda Losurdo 1, Matilde Saura-Muzquiz 1, Kevin J.

Double bonds crystalmaker