Flash sintering of stoichiometric and hyper-stoichiometric urania

Journal Article · Thu Mar 29 00:00:00 EDT 2018 · Journal of Nuclear Materials

DOI: https://doi.org/10.1016/j.jnucmat.2018.03.049 · OSTI ID:1431082

Valdez, James Anthony ^[1]; Byler, Darrin David  ^[1]; Kardoulaki, Erofili ^[1]; Francis, John stanley Curtis ^[2]; Mcclellan, Kenneth James  ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Lupine Laboratories, Boulder CO (United States)

Flash sintering (FS), a novel fabrication technique belonging to the family of field assisted sintering (FAS) techniques, has been utilized in this study to fabricate uranium dioxide (UO₂) pellets. Stoichiometric (UO_2.00) and hyper-stoichiometric (UO_2.16) pellets were flash sintered at 600 °C within a few (2–3) minutes. This is in sharp contrast to conventional sintering where temperatures hundreds of degrees higher are necessary and the sintering time extends to hours. Relating this in terms of the homologous temperature ratio (T_H) for both conditions shows that in the case of flash sintering at 600 °C, T_H = 0.3 versus T_H = 0.6 for conventional sintering at 1600 °C. The highest density achieved for a UO_2.00 pellet was 81% theoretical density (TD) when flash sintered at 600 °C for 184 s at a field of 188 V/cm and a current density of 442 mA/mm². For the UO_2.16 pellet, the highest achieved density was 92% TD when flash sintered at 600 °C for 140 s at a field of 188 V/cm and a current density of 632 mA/mm². X-ray diffraction (XRD) characterization of the sintered pellets showed the final sintered material to be single cubic fluorite phase. Scanning electron microscopy (SEM) of longitudinal sections revealed non-uniform microstructures with regions of high density where the grain size ranged from 1 to 15 μm. Comparisons between conventionally and flash sintered pellets that achieved equivalent shrinkage strains were also conducted. Lastly, in all cases, the flash sintered pellets achieved similar densification to the conventionally sintered pellets at much lower furnace temperatures and shorter times.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1431082
• Report Number(s): LA-UR-18-20238
• Journal Information: Journal of Nuclear Materials, Journal Name: Journal of Nuclear Materials Vol. 505; ISSN 0022-3115
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English