Preparation of Uranium Nitride from Uranium Metal through by Hydriding and Nitriding Process

Abstract

The RERTR Program (Reduced Enrichment in Research and Test Reactors) is an attempt to utilize uranium fuel enriched below 20% for nuclear research reactors. Since the program was launched by the United States in 1978, the International Atomic Energy Agency (IAEA) has recommended that UxSiy alloys, particularly U3Si2 and U3Si compounds, be used to fuel nuclear research reactors with uranium loading rate up to 4.8 gU/cm3. Unfortunately, there are difficulties in reprocessing U3Si2 and U3Si compounds due to the Si content. To overcome this problem, the IAEA initiated international cooperation to find the best solution in the development of new nuclear fuels to substitute the UxSiy alloys. In order to synthesize nuclear fuel containing high loading of uranium, research in developing uranium nitride (UN) from uranium metal has been conducted by reacting the massive uranium metal with hydrogen gas at a temperature of 573 K followed by dehydriding at a temperature of 773 K under vacuum pressure and nitriding at a temperature of 1073 K by introducing nitrogen gas in the reaction chamber. The X-ray diffraction analysis results showed that the hydriding process caused the uranium metal to turn into a stable compound, UH3, which was identified by the changes of the massive shapes into fine metal powders. Dehydriding process at a temperature of 773 K caused the UH3 compound to decompose into U metal powders, and when the metal powders were reacted with N2 gas at 1073 K a stable phase identified as UN was formed. The results showed that it is possible to produce UN powders by hydriding, dehydriding, and nitriding process, although special handling of UH3 and UN powders is required due to their pyrophoric nature.