Application of thermogravimetric analysis in study of solid-state reaction between barium oxalate and uranyl oxalate

Abstract

Alkaline earth metals and their oxides have an important role while deciding the postirradiation processing of irradiated fuels from the reactors. The reaction between uranyl oxalate and barium oxalate has been studied using thermogravimetric analysis. Oxalates of uranium and barium were prepared, and their thermal decomposition in argon environment has been studied. It has been observed that uranyl oxalate decomposes into mixture of U3O8 and UO2.13 with the evolution of carbon monoxide, oxygen and carbon dioxide in the temperature range of 573–673 K, but beyond this temperature U3O8 and UO2.13 appeared as intermediate and the final product has been found to be UO2.12. In case of solid-state reaction of barium oxalates, it has been observed that the reaction pathway of its decomposition is altered in the presence of uranium oxide. Barium oxalate first decomposes to barium carbonate followed by the reaction with uranium oxide at a relatively high temperature during the next step in TG. XRD characterization of the intermediates and end products indicated that BaUO4 is formed which gets partially reduced to BaUO3 at elevated temperature.