Investigation of mechanism and kinetics of thermal decomposition of ammonium uranates in different gaseous media

Thermal decomposition of ammonium polyuranates in various gaseous media (oxygen, nitrogen, argon, air) is studied. Effect of decomposition gaseous products on ammonium uranate thermal decomposition process is demonstrated. Kinetic parameters of separate process stages are determined. Based on data of thermogravimetric, chemical, gas chromatographic and kinetic analysis methods mechanism of ammonium uranate thermal decomposition process is proposed. It is ascertained that ammonium uranate thermal decomposition in air atmosphere occurs in six stages with the formation of U3O8. In the inert atmosphere U3O8 formation process ends at 120-140 deg C lower than in the air one, and in the oxygen atmosphere the same process is shifted to the region of higher temperatures by ∼ 30 deg C