A preliminary validation study of PuO 2 incorporation into zirconolite glass-ceramics
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.109
A preliminary validation study of PuO2 incorporation into zirconolite glass-ceramics Stephanie M. Thornber1, Martin C. Stennett1, Eric R. Vance2, Dorji T. Chavara2, Ian Watson2, Miodrag Jovanovic2, Joel Davis2, Daniel Gregg2 and Neil C. Hyatt1 1 Immobilisation Science Laboratory, Materials Science and Engineering Dept., The University of Sheffield, Mapping Street, Sheffield, S1 3JD, UK 2 Australian Nuclear Science and Technology Organisation, Kirrawee DC, Locked Bag 2001, NSW 2232, Australia
Abstract:
Zirconolite glass-ceramics are being developed as potential wasteforms for the disposition of Pu wastes in the UK. Previous studies utilised a variety of surrogates whilst this work uses both cold-press and sinter and hot isostatic press methods to validate the wasteform with PuO2. A cold press and sinter sample was fabricated as part of a validation study for plutonium incorporation in hot isostatically pressed (HIPed) wasteforms. The results confirmed the cold-press and sinter, achieved successful waste incorporation and a microstructure and phase assemblage that was in agreement with those expected of a HIPed equivalent. A HIP sample was fabricated of the same composition and characterised by SEM and XRD. Results were in agreement with the sintered sample and achieved complete waste incorporation into the glass-ceramic wasteform. These samples have demonstrated successful incorporation of PuO2 into glass-ceramic HIPed wasteforms proposed for processing Pu-based waste-streams in the UK.
Corresponding author: [email protected]
Introduction Hot isostatic pressing (HIPing) is a leading thermal treatment option for treating Pu-based wastes in the UK [1,2]. Pu-residues are a category of higher activity wastes requiring consolidation into long-term stable wasteforms. These wastes are highly variable in their physical form, from powders and sludges, to MOx fuel pellets and fuel pins [3]. They also fluctuate compositionally and have varying degrees of impurities present. As a result, a flexible process and wasteform matrix are required to accommodate the complexity and variability of these wastes in order to produce high quality wasteforms suitable for long-term storage and eventual geological disposal. In addition to the Pu-residue wastes, the UK civil separated PuO2 stockpile contains some material unsuitable for fuel fabrication and requires an immobilisation route [4]. In comparison to the complexity of Pu-residues, this material is relatively pure and has a
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fine particle size. It is envisaged that a consolidation route suitable for treating the Pu-residues inventory could also be applied to the fraction of PuO2 stockpile material considered to be waste, or potentially, the whole stockpile in the future [5].
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