title: Synthesis of phase-pure U2N3 microspheres and its decomposition into UN.
abstract: Uranium mononitride (UN) is important as a nuclear fuel. Fabrication of UN in its microspherical form also has its own merits since the advent of the concept of accident-tolerant fuel, where UN is being considered as a potential fuel in the form of TRISO particles. However, not many processes have been well established to synthesize kernels of UN. Therefore, a process for synthesis of microspherical UN with a minimum amount of carbon is discussed herein. First, a series of single-phased microspheres of uranium sesquinitride (U2N3) were synthesized by nitridation of UO2+C microspheres at a few different temperatures. Resulting microspheres were of low-density U2N3 and decomposed into low-density UN. The variation of density of the synthesized sesquinitrides as a function of its chemical composition indicated the presence of extra (interstitial) nitrogen atoms corresponding to its hyperstoichiometry, which is normally indicated as α-U2N3. Average grain sizes of both U2N3 and UN varied in a range of 1-2.5 μm. These also had a considerably large amount of pore spacing, indicating the potential sinterability of UN toward its use as a nuclear fuel.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Chinthaka M
authors.initials: CM
authors.lastname: Silva
authors.forename: Rodney D
authors.initials: RD
authors.lastname: Hunt
authors.forename: Lance L
authors.initials: LL
authors.lastname: Snead
authors.forename: Kurt A
authors.initials: KA
authors.lastname: Terrani