Title: Flash sintering of stoichiometric and hyper-stoichiometric urania

Abstract

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 sectionsmore » 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.« less

Authors:

Valdez, James Anthony ^[1]; Byler, Darrin David  ^[1];

• Search DOE PAGES for author "Byler, Darrin David"
• Search DOE PAGES for ORCID "0000-0002-5456-8334"

Kardoulaki, Erofili ^[1]; Francis, John stanley Curtis ^[2]; Mcclellan, Kenneth James  ^[1]

• Search DOE PAGES for author "Mcclellan, Kenneth James"
• Search DOE PAGES for ORCID "0000-0002-3503-6754"

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+ Show Author Affiliations

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

Publication Date:

Thu Mar 29 00:00:00 EDT 2018

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Office of Nuclear Energy (NE), Nuclear Fuel Cycle and Supply Chain

OSTI Identifier:

1431082

Alternate Identifier(s):

OSTI ID: 1548514

Report Number(s):

LA-UR-18-20238
Journal ID: ISSN 0022-3115; TRN: US1802427

Grant/Contract Number:  

AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Nuclear Materials

Additional Journal Information:

Journal Volume: 505; Journal ID: ISSN 0022-3115

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Nuclear fuel; Sintering; Urania; Dilatometer; Field assisted sintering; Flash sintering