Stabilization of UO2

Calorimetric determination of energetics of solid solutions of UO2+x with CaO and Y2O3

“…Rather, the oxidation of uranium and formation of complex defect clusters dominate the system and are responsible for the large stabilization. A similar large decrease of activity of UO 2 in solid solution with another trivalent dopant was observed in early work [5] for high concentrations of La 2 O 3 . In general, we conclude that the interaction energies between UO 2+x and trivalent dopants such as yttria or rare earth oxides are strongly negative.…”

“…Doping urania, UO 2 , with different di- [1,2], tri- [3][4][5][6][7][8] and tetravalent [9][10][11] metals has attracted interest primarily in the context of improving the performance and stability of UO 2 in nuclear applications [5,12] and in reactor accident scenarios. More than 30 different elements are produced by fission during the lifetime of fuel rods.…”

On the redox reactivity of doped UO2 pellets – Influence of dopants on the H2O2 decomposition mechanism

“…These new types of surfaces can have altered reactivity and improved mechanical and chemical resistance. For the case of UO 2 , this fact was shown in a previously published work where it was demonstrated that the inclusion of Y 3+ into UO 2 pellets increases the corrosion resistance of the latter when oxidized in air at high temperatures, T = [1375-1750]°C [20]. This fact is explained in a review by McEachern and Taylor [32] where the authors attribute the increased corrosion resistance to the enhanced surface stability of the doped material when compared to the undoped UO 2 .…”

“…Also U 4 O 9 is stabilized and U 3 O 7 is not formed as intermediate [19][20][21]. For aqueous systems, kinetic data on oxidation of doped UO 2 is scarce.…”

A review of acid leaching of uraninite

“…It is isometric (fluorite structure, space group Fm3m, cell parameter a = 5.4682 Å, unit cell volume V = 163.51 Å 3 ) with the U 4+ coordinated by eight O atoms in a face centred cubic arrangement with each O atom bonded to four U 4+ cations at the corner of a regular tetrahedron ( Fig. 1) (Belle, 1969;Fayek et al, 2000;Forster, 1999;Frondel, 1957;He et al, 2010;Kotzer and Kyser, 1993;Krivovichev and Plášil, 2013;Pourcelot and Gauthier-Lafaye, 1998;Wilson et al, 1961). Uraninite that contains exclusively tetravalent U 4+ is unknown in nature.…”