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Phase Relations in the System Uranium—Nitrogen

1964; Wiley; Volume: 47; Issue: 9 Linguagem: Inglês

10.1111/j.1151-2916.1964.tb14429.x

1551-2916

J. Bugl, A.A. Bauer,

Radioactive element chemistry and processing

To supplement efforts to develop UN as a nuclear fuel material, a study of the phase relations in the system uranium‐nitrogen was conducted. The decomposition behavior and melting point of UN was studied in a controlled nitrogen‐pressure apparatus in which cast specimens of UN were heated and observed. UN decomposed at pressures of nitrogen below 2.5 atm at temperatures below 2850° C and melted congruently at 2850° C and pressures of 2.5 atm or greater. The nitrogen content of the liquid uranium phase in equilibrium with UN was determined by heating uranium in a UN crucible and then quenching and analyzing the equilibrated phase. The solubility of nitrogen in atomic percent can be expressed as S = 2.45 × 10 4 exp (‐38,800/RT) for temperatures in OK. Studies in the region U 2 N 3 ‐UN 2 of the system which were performed using a Sievert‐type apparatus showed that although these compounds are structurally dissimilar, they form a series of continuous solid solutions. Only UN 2 formed at high pressures and low temperatures. A pressure‐temperature schematic diagram and a temperature‐composition schematic diagram for a nitrogen pressure of 1 atm for the system uranium‐nitrogen are presented. At this pressure, UN decomposed at 2800° C and U 2 N 3 decomposed at 1345° C.