Comparing the corrosion of uranium nitride and uranium dioxide surfaces with H2O2

Abstract

Uranium mononitride, UN, is considered a potential accident tolerant fuel due to its high uranium density, high thermal conductivity, and high melting point. Compared with the relatively inert UO 2 , UN has a high reactivity in water, however, studies have not considered the significant effect of radiation, which is known to cause corrosion of UO 2 . This study uses 0.1 M H 2 O 2 to simulate the effects of water radiolysis in order to compare the radiolytic corrosion rates of UO 2 , UN, and U 2 N 3 thin films at room temperature. X-ray reflectivity was used to investigate the changes in film morphology as a function of H 2 O 2 exposure time, allowing changes in film thickness and roughness to be observed on theÅngstrom length-scale. Results showed significant differences between UO 2 , UN, and U 2 N 3 , with corrosion rates of 0.083(3), 0.020(4), and 0.47(8)Å/s, respectively, showing that UN corrodes more slowly than UO 2 in 0.1 M H 2 O 2 .

Synchrotron x-ray scattering of magnetic and electronic structure of UN and U2N3 epitaxial films

“…Since U 6+ is soluble in water and highly reactive, this would explain why the U 2 N 3 is more reactive (in H 2 O 2 ) than either UO 2 or UN, as reported in Ref. [6]. U 6+ would have no associated 5 f electrons, so would not order magnetically, nor should there be any aspherical resonant scattering from U 1 as suggested by the observations in Fig.…”

“…We have recently succeeded in preparing thin epitaxial films [5] of UN and a closely associated material cubic U 2 N 3 , which is almost always found in conjunction with UN, as it represents a byproduct in the oxidation process. We have also reported the corrosion rates (with H 2 O 2 ) [6] of these materials and found that whereas UN is less corrosive than UO 2 , the U 2 N 3 material is at least 20 times more corrosive than UN. Since U 2 N 3 is found at the surface of UN, this higher corrosion rate is a concern, and our work reported here suggests a possible reason for this difference.…”

Towards actinide heterostructure synthesis and science

“…A group currently operating at the University of Bristol employed reactive magnetron sputtering to produce epitaxial films of UO 2 and nanocrystalline films of UO 2 , UN, U 2 N 3 . They studied a range of topics from antiferromagnetism 16 , to corrosion 17 , to phonon linewidths in irradiated specimens 18 . Researchers at Los Alamos National Laboratory have utilized two distinct methods, a polymer-assisted deposition technique to target a range of actinide oxides, carbides, and nitrides 19 and, more recently, pulsed laser deposition to target epitaxial synthesis of uranium oxides: UO 2 , U 3 O 8 , and UO 3 20 .…”

Valence Fluctuation of Uranium Ions in Uranium Sesquinitride Revealed by Dynamical Mean‐field Theory Merged with Density Functional Theory

“…Experimentally, the strong radioactivity and chemical reactivity restrain the direct observations on uranium nitrides. [7] In general, theoretically, the physical, thermodynamical, and mechanical properties of uranium nitrides are governed by the electronic properties, in particular the electronic structure, the chemical bonding and the electronic correlation. [8] In fact, the theoretical investigations in particular the first principle calculations pose a promising candidate for the experimental measurements.…”

“…In general, uranium‐based systems attract extensive interests originating from the correlation of 5 f electrons, [5] the oxidation states of U 3+ /U 4+ , [6] and U 5 f ‐conduction electrons hybridization. Experimentally, the strong radioactivity and chemical reactivity restrain the direct observations on uranium nitrides [7] . In general, theoretically, the physical, thermodynamical, and mechanical properties of uranium nitrides are governed by the electronic properties, in particular the electronic structure, the chemical bonding and the electronic correlation [8] .…”