Hot Hydrogen Testing of W-Coated UN Kernels in a Mo30W Matrix

Journal Article · 14 April 2024 · Nuclear Science and Engineering

DOI: https://doi.org/10.1080/00295639.2024.2332001 · OSTI ID:2340868

Cröll, Arne  ^[1]; Williams, Jamelle P.  ^[2]; Taylor, Brian  ^[2]; Volz, Martin P.  ^[2]; McKinney, Christopher  ^[2]; Coons, Timothy Philip  ^[3]; Rosales, Jhonathan  ^[2]

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1. Univ. of Alabama, Huntsville, AL (United States)
2. NASA Marshall Space Flight Center (MSFC), Huntsville, AL (United States)
3. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Ceramic uranium mononitride (UN) is being considered as a reactor fuel for nuclear thermal propulsion. To avoid or reduce the dissociation of UN at the high temperatures needed, embedding it in a metallic matrix (cermet) has been proposed. To assess the viability of this concept, hot hydrogen testing of tungsten-coated UN kernels embedded in a Mo-30 wt% W (Mo30W) alloy matrix has been performed at temperatures from 1800°C to 2300°C. Both the isolated kernels and kernels consolidated by spark plasma sintering in the Mo30W matrix were tested. In addition to direct observations and mass loss measurements, the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) after each run. The decomposition of UN started at 1800°C despite the coating and matrix, and increased at 2000°C. Uranium seeped through the tungsten grain boundaries of the coating at all temperatures. The consolidated sample expanded irregularly at 2000°C through the formation of voids, and SEM/EDS analysis showed uranium-containing veins in the matrix consisting of U₂Mo according to the XRD data. The observed pore generation at 2000°C was explained by the formation of water vapor from residual oxides and diffused hydrogen. At 2200°C and above, both the kernels and the consolidated samples melted through the formation of uranium or low–melting point uranium-molybdenum alloys.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; National Aeronautics and Space Administration (NASA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 2340868
• Report Number(s): LA-UR--23-20007
• Journal Information: Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Journal Issue: 1 Vol. 199; ISSN 0029-5639
• Publisher: Taylor & FrancisCopyright Statement
• Country of Publication: United States
• Language: English