Studies on the kinetics of oxidation of urania-thoria solid solutions in air

The oxidation behaviour of (UyTh1-y)O-2 powders (y = 0.15, 0.30, 0.72 and 0 .77) was studied by means of thermogravimetry. The oxidation was carried ou t under both isothermal and non-isothermal conditions. The limits of oxygen solubility in terms of O/M ratios of (UyTh1-y)O-2 Solid solutions, derived from the thermogravimetric data, were 2.08, 2.15, 2.35 and 2.36 for y = 0. 15,0.30,0.72 and 0.77, respectively. A single-step oxidation was observed f or (UyTh1-y)O-2 solid solutions with y = 0.15-0.77. The activation energy f or the oxidation of (UyTh1-y)O-2 powders with y = 0.15 and 0.30 (the final product is single-phase), was found to be (48.5 +/- 2.5) kJ mol(-1). The ac tivation energy for the oxidation of (UyTh1-y)O-2 powders with y = 0.72 and 0.77 (the final product is a bi-phasic mixture) was found to be (86.5 +/- 4.5) kJ mol(-1). (C) 2000 Elsevier Science B.V. All rights reserved.