Characterization of δ-PuGa (1 at%. Ga) Oxidation Under Dry Oxygen Atmosphere Exposure
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The oxidation of δ-stabilized plutonium alloy was studied under dry oxygen exposures for temperatures varying from 100 up to 300 °C and oxygen partial pressures varying from 10 –4 up to 500 mbar. The coupling of X-ray diffraction, Raman spectroscopy and FIB-SEM has allowed to show that the oxide scale is composed of an outer layer of PuO 2 and an inner mixed layer of α + β-Pu 2 O 3 platelets propagating into a metallic zone corresponding to the stable phase of unalloyed Pu. Furthermore, the analysis of Pu oxidation kinetics has displayed first a parabolic growth governed by the diffusion of interstitial oxygen. This step consists of the thickening of the Pu 2 O 3 layer with a decrease in α-Pu 2 O 3 ratio in favor of β-Pu 2 O 3 . Then, a second step occurs consisting of a linear growth of the PuO 2 -layer with the formation of thick nodules which tend to cover the whole oxide surface. Based on the results of this work, a general oxidation mechanism for δ-Pu alloy is provided.
