Study of the formation of α-U 2N 3+ x using unstable ammonia — reaction sequence and control of nitrogen activity

Abstract

The formation of α-U 2N 3+ x by the reactions between U and NH 3 or a gas mixture of NH 3 and H 2 was examined at 300 °C. It was found that there were two routes for the reaction process. One route was the direct formation of α-U 2N 3+ x by the reaction of U and NH 3; the other included the formation of UH 3. Although the UH 3 formed in this way was finally converted to α-U 2N 3+ x , the reaction rate was very slow compared with the rates of nitride and hydride formation. It was presumed that the conversion of UH 3 to α-U 2N 3+ x was the rate-determining step in the series of reactions. It was also confirmed that the nitrogen content of α-U 2N 3+ x varied when the composition of the reactant gas mixture was changed. This result implies that the nitrogen activity of the unstable gas mixture is dependent on the composition.