Solid solubilities of Pu, U, Gd and Hf in candidate ceramic nuclear wasteforms

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dc.contributor.authorVance, ERen_AU
dc.contributor.authorCarter, MLen_AU
dc.contributor.authorLumpkin, GRen_AU
dc.contributor.authorDay, RAen_AU
dc.contributor.authorBegg, BDen_AU
dc.date.accessioned2023-01-13T00:55:39Zen_AU
dc.date.available2023-01-13T00:55:39Zen_AU
dc.date.issued2001-04-02en_AU
dc.date.statistics2022-10-18en_AU
dc.description.abstractThe goal of this research project was to determine the solid solubility of Pu, U, Gd, and Hf in candidate ceramics for immobilization of high-level nuclear waste. The experimental approach was to saturate each phase by adding more than the solid solubility limit of the given cation, using a nominated substitution scheme, and then analyzing the candidate phase that formed to evaluate the solid solubility limit under firing conditions. Confirmation that the solid solution limit had been reached insofar as other phases rich in the cation of interest was also required. The candidate phases were monazite, titanite, zirconolite, perovskite, apatite, pyrochlore, and brannerite. The valences of Pu and U were typically deduced from the firing atmosphere, and charge balancing in the candidate phase composition as evaluated from electron microscopy, although in some cases it was measured directly by x-ray absorption and diffuse reflectance spectroscopies (for U). Tetravalent Pu and U have restricted (< 0.1 formula units) solid solubility in apatite, titanite, and perovskite. Trivalent Pu has a larger solubility in apatite and perovskite than Pu4+. U3+ appears to be a credible species in reduced perovskite with a solubility of {approximately} 0.25 f.u. as opposed to {approximately} 0.05 f.u. for U4+. Pu4+ is a viable species in monazite and is promoted at lower firing temperatures ({approximately} 800 C) in an air atmosphere. Hf solubility is restricted in apatite, monazite (< 0.1 f.u.), but is {approximately} 0.2 and 0.5 f.u. in brannerite and titanite, respectively. Gd solubility is extended in all phases except for titanite ({approximately} 0.3 f.u.). U5+ was identified by DRS observations of absorption bands in the visible/near infrared photon energy ranges in brannerite and zirconolite, and U4+ in zirconolite was similarly identified.en_AU
dc.identifier.citationVance, E. R., Carter, M. L., Lumpkin, G. R., Day, R. A., & Begg, B. D. (2001). Solid solubilities of Pu, U, Gd and Hf in candidate ceramic nuclear wasteforms. Australian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia.en_AU
dc.identifier.placeofpublicationLucas Heights, New South Walesen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14334en_AU
dc.language.isoenen_AU
dc.publisherAustralian Nuclear Science and Technology Organisationen_AU
dc.relation.ispartofseriesProject Number 60387;DOE/ER/45676en_AU
dc.subjectCeramicsen_AU
dc.subjectGadoliniumen_AU
dc.subjectRadioactive wastesen_AU
dc.subjectPlutoniumen_AU
dc.subjectSolubilityen_AU
dc.subjectUraniumen_AU
dc.subjectWaste formsen_AU
dc.subjectHafniumen_AU
dc.titleSolid solubilities of Pu, U, Gd and Hf in candidate ceramic nuclear wasteformsen_AU
dc.typeExternal Reporten_AU
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