Report on in-situ studies of flash sintering of uranium dioxide

Technical Report · Mon Jan 23 23:00:00 EST 2017

DOI:https://doi.org/10.2172/1340977· OSTI ID:1340977

Raftery, Alicia Marie ^[1]

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

Flash sintering is a novel type of field assisted sintering that uses an electric field and current to provide densification of materials on very short time scales. The potential for field assisted sintering techniques to be used in producing nuclear fuel is gaining recognition due to the potential economic benefits and improvements in material properties. The flash sintering behavior has so far been linked to applied and material parameters, but the underlying mechanisms active during flash sintering have yet to be identified. This report summarizes the efforts to investigate flash sintering of uranium dioxide using dilatometer studies at Los Alamos National Laboratory and two separate sets of in-situ studies at Brookhaven National Laboratory’s NSLS-II XPD-1 beamline. The purpose of the dilatometer studies was to understand individual parameter (applied and material) effects on the flash behavior and the purpose of the in-situ studies was to better understand the mechanisms active during flash sintering. As far as applied parameters, it was found that stoichiometry, or oxygen-to-metal ratio, has a significant effect on the flash behavior (time to flash and speed of flash). Composite systems were found to have degraded sintering behavior relative to pure UO₂. The critical field studies are complete for UO_2.00 and will be analyzed against an existing model for comparison. The in-situ studies showed that the strength of the field and current are directly related to the sample temperature, with temperature-driven phase changes occurring at high values. The existence of an ‘incubation time’ has been questioned, due to a continuous change in lattice parameter values from the moment that the field is applied. Some results from the in-situ experiments, which should provide evidence regarding ion migration, are still being analyzed. Some preliminary conclusions can be made from these results with regard to using field assisted sintering to fabricate nuclear fuel. First, the pure UO₂-based system shows promising behavior with flash sintering, but composite systems are likely to show better sintering behavior with spark plasma sintering. Efforts to develop these methods should therefore be tailored towards the likelihood of success. Additionally, modeling is a rapidly developing aspect of current flash sintering research and should be used in parallel with experiments. Ultimately, ongoing flash sintering studies on various materials, like those summarized in this report, are rapidly contributing to the feasibility of controlling this method for use in the future.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1340977
• Report Number(s): LA-UR-16-24836
• Country of Publication: United States
• Language: English

Related Subjects

##CAI suggestions##
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
BNL
COMPARATIVE EVALUATIONS
COST
CRITICAL FIELD
CURRENTS
DATA
ECONOMICS
ELECTRIC FIELDS
GAIN
INCUBATION
IONS
LANL
LATTICE PARAMETERS
LOS ALAMOS
MIGRATION
NSLS
NUCLEAR FUELS
OXYGEN
PLASMA
POTENTIALS
SIMULATION
SINTERING
SOCIO-ECONOMIC FACTORS
STOICHIOMETRY
URANIUM
URANIUM DIOXIDE
VELOCITY
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY