U3Si2 and UO2 composites densified by spark plasma sintering for accident-tolerant fuels

Bowen Gong, Tiankai Yao, Penghui Lei, Lu Cai, Kathryn E. Metzger, Edward J. Lahoda, Frank A. Boylan, Afiqa Mohamad, Jason Harp, Andrew T. Nelson, Jie Lian

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32 Scopus citations

Abstract

This work reports the synthesis and characterization of the U3Si2 and UO2 composites sintered by spark plasma sintering (SPS) with controlled microstructures for accident-tolerant fuel application. The U3Si2 and UO2 composites with different silicide and oxide ratios were synthesized by SPS at temperatures from 1000 to 1300 °C for 5 minutes. The microstructure and phase composition of the SPS densified composite fuels were characterized with scanning electron microscopy, X-ray diffraction (XRD), and energy dispersed spectroscopy (EDS). A systematic study of the thermal and mechanical properties was conducted using microhardness testing and laser flash apparatus, along with oxidation resistance measurements using thermogravimetric analysis (TGA). The results show that the synthesis of composite fuels can be achieved with a 90% theoretical density (TD) at 1000 °C and over 95% TD when sintered at 1300 °C. XRD and EDS results confirmed that the dominant phases in the composites are U3Si2 and UO2. Improved physical density generally leads to improved hardness, fracture toughness, thermal diffusivity, and onset temperature during the oxidation process. U3Si2 was found to play a dominant role in determining the mechanical and oxidation properties of the composite fuels, whereas UO2 had a more important impact on controlling the thermal diffusivity of the composites. The composite with 50 wt% UO2 sintered at 1300 °C displayed the onset oxidation temperature of 500 °C by dynamic oxidation testing using TGA at a ramp degree of 10 °C/min. The composite also achieved a high fracture toughness of ∼3.5 MPa m½. These results highlight the potential of composite fuel forms densified by SPS with simultaneously enhanced fissile element density, fracture toughness, thermal transport properties, and oxidation resistance.

Original languageEnglish
Article number152147
JournalJournal of Nuclear Materials
Volume534
DOIs
StatePublished - Jun 2020

Funding

This work was supported by the US Department of Energy’s (DOE’s) Office of Nuclear Energy under a Nuclear Engineer University Program (award number: DE-NE0008532 ) and by Westinghouse Electric Company under the DOE ATF program.

FundersFunder number
Nuclear Energy
Westinghouse Electric Company
U.S. Department of Energy
Nuclear Energy University ProgramDE-NE0008532

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