The effect of pre-treatment parameters on the quality of glass-ceramic wasteforms for plutonium immobilisation, consolidated by hot isostatic pressing

• Published in: Journal of nuclear materials Vol. 485; no. C; pp. 253 - 261
• Main Authors: Thornber, Stephanie M., Heath, Paul G., Da Costa, Gabriel P., Stennett, Martin C., Hyatt, Neil C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2017; Elsevier BV; Elsevier
• Subjects: Cans; Ceramics; Consolidation; Electron microscopy; Frit; Glass ceramics; High temperature; Hip; Hot isostatic press; Hot isostatic pressing; Immobilization; Microstructure; Plutonium; Plutonium residues; Powder; Pretreatment; Reagents; Roasting; Scanning electron microscopy; Stainless steel; Studies; Temperature effects; Volatiles; X ray analysis; X-ray diffraction; Glass-ceramics; Plutonium residues; Hot isostatic press
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2016.12.028

Glass-ceramics with high glass fractions (70 wt%) were fabricated in stainless steel canisters by hot isostatic pressing (HIP), at laboratory scale. High (600 °C) and low (300 °C) temperature pre-treatments were investigated to reduce the canister evacuation time and to understand the effect on the phase assemblage and microstructure of the hot isostatically pressed product. Characterisation of the HIPed materials was performed using scanning electron microscopy (SEM), coupled with energy dispersive X-ray analysis (EDX) and powder X-ray diffraction (XRD). This analysis showed the microstructure and phase assemblage was independent of the variation in pre-treatment parameters. It was demonstrated that a high temperature pre-treatment of batch reagents, prior to the HIP cycle, is beneficial when using oxide precursors, in order to remove volatiles and achieve high quality dense materials. Sample throughput can be increased significantly by utilising a high temperature ex-situ calcination prior to the HIP cycle. Investigation of glass-ceramic wasteform processing utilising a glass frit precursor, produced a phase assemblage and microstructure comparable to that obtained using oxide precursors. The use of a glass frit precursor should allow optimised throughput of waste packages in a production facility, avoiding the need for a calcination pre-treatment required to remove volatiles from oxide precursors. [Display omitted] •Optimisation of pre-treatment parameters for HIP glass-ceramics was investigated.•Entrained porosity was minimised by ex-situ bake-out of oxide precursors at 600 °C.•Phase assemblage and microstructure proved independent of bake-out parameters.•Use of glass-frit precursor further improved process s throughput and simplification.