Elaboration of U3O8 by the Modified Direct Denitration process (MDD)

Abstract

This process consists of adding ammonium nitrate to a pure uranyl nitrate solution to form the double salt (NH₄)₂UO₂(NO₃)₄.2H₂O which decomposes by calcination to produce a UO₃ powder. The objective of this work is to study, first, the thermal decomposition of double salt (NH₄)₂UO₂(NO₃)4.2H₂O in nitrogen atmosphere by thermogravimetry in order to determine the formation temperatures of the different phases and second, the determination of the optimal parameters (time and temperature) to prepare stable triuranium octoxide (U₃O₈) using muffle furnace. As results, the MDD product obtained is an orange colored and free flowing UO₃ powder, having a surface area in the target range [5-12 m²/g]. In addition, by calcination of UO₃ powder at 650°C for one hour, U₃O₈ oxide is obtained. The identification of the latter by the O/U ratio gave a value of 2.65, which is in the range [2.6-2.66]. This suggests that the oxide produced under these conditions is β-U₃O₈.