Oxidation of U-10 at% Zr alloy in air at 432–1028 K

Abstract

The oxidation behavior of U 0.90Zr 0.10 alloy (two-phase mixture of α-U and δ-UZr 2 below 890 K, two-phase mixture of ß-U and γ-(U, Zr) at 953 K and single solid solution at 1028 K) was studied by thermogravimetry in the temperature range from 432 to 1028 K in air. During oxidation in the low temperature region (432–515 K), the sample kept its initial shape (a rectangular rod) and the surface of the sample was covered by a black thin adherent UO 2+x oxide layer. On the other hand, by oxidation in the middle temperature region, the sample broke to several pieces of thin plates and fine powder at 728 K and entirely to fine powder at 953 K, all of which were analyzed to be the mixture of U 3O 8 and ZrO 2. By oxidation at 1028 K the sample broke to fine powder, which consisted of U 3O 8 and ZrO 2. Based on the oxidation behavior of U 0.90Zr 0.10 regarding the sample shape, the oxide phase identified after oxidation and the slope value of the bilogarithmic plots of the weight gain against time, the oxidation kinetics was analyzed with a paralinear equation in the low temperature region below 515 K and a linear equation in the middle and high temperature regions above 728 K. The oxidation behavior of U 0.80Zr 0.20 alloy was also investigated at 723 K in argon gas to clarify the effect of oxygen partial pressure.