Nonstoichiometric Solid Solutions Research Articles

Oxidation Studies of Urania‐Thoria Solid Solutions

Nonstoichiometric solid solutions in the system UO2‐ThO2 were formed by sintering U3O‐ThO3 and codigested nitrate mixtures in air. The oxygen content of the solid solutions was determined by a weight‐loss method. The changes occurring in oxygen content during solid solution formation and densification were determined for a 70.4 mole % UO2‐29.6 mole % Tho2 composition formed by sintering U3O3‐ThO2 in air. The first evidence of solid solution occurred at 1000° C. and solution was complete above 1250°C. Thermal cycling of solid solutions in air showed a minimum oxygen‐uranium ratio of 2.34 for the compositions studied. The minimum oxygen‐uranium ratio obtained during thermal cycling decreased with increasing Tho2 content.