PNNL

Abstract

Technetium (99Tc) is a problematic fission product for the long-term disposal of nuclear waste due to its long half-life, high fission yield, and to the environmental mobility of pertechnetate, the stable Tc species in aerobic environments. One approach to preventing 99Tc contamination is using durable waste forms based on environmentally stable natural analogs such as hematite (-Fe2O3) or magnesioferrite (MgFe2O4). The incorporation of Tc into hematite, magnesioferrite, and magnetite (Fe3O4) by means of simple, aqueous chemistry is presented starting from TcO4- in 5 M nitric acid. A combination of X-ray diffraction and X-ray absorption fine structure spectroscopy reveals that Tc(IV) replaces Fe(III) within the iron oxide structures. Following incorporation, Tc doped samples were suspended in deionized water under aerobic conditions, and the release rate of Tc under these conditions was determined. The results of this work show that Tc leaches more quickly from Fe3O4 than from -Fe2O3 or MgFe2O4.