Abstract
Uranium nitride is an advanced fuel candidate for a wide variety of advanced nuclear reactors. This work summarizes the first characterization of UN kernels by Raman spectroscopy. First-principles density functional theory calculations were performed to predict the Raman spectra of uranium sesquinitride (U2N3), uranium dinitride (UN2), uranium mononitride (UN), uranium monocarbide (UC), as well as U-N-C (UN1-xCx) and a U-N-C-O mixture. A core–shell structure was identified by scanning electron microscopy and Raman spectroscopy imaging. A signal at ∼500 cm−1 was identified on the periphery of the core-shell structure, possibly corresponding to U2N3 and/or UN2. This signal broadens and shifts to 470 cm−1 because of the formation of UNC, UNCO or U2N3+x structures. The culmination of this work demonstrates the feasibility of using Raman spectroscopy to identify variations in composition and phases in UN kernels.
