Thermodynamic and experimental study of UC powders ignition

• Published in: Journal of nuclear materials Vol. 393; no. 2; pp. 333 - 342
• Main Authors: Le Guyadec, F., Rado, C., Joffre, S., Coullomb, S., Chatillon, C., Blanquet, E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2009; Elsevier
• Subjects: Applied sciences; Chemical Sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Engineering Sciences; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Material chemistry; Materials; Nuclear fuels; Preparation and processing of nuclear fuels; Phase diagram; Thermogravimetry; Nuclear fuel; High temperature; X ray diffraction; Pressure; Reprocessing; Nuclear reactor; Uranium carbide; Thermodynamics; Uranium; Reactor material; Oxidation; Thermal analysis; Plutonium; Handling; uranium-carbon-oxygen; composition range
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2009.06.009

Mixed plutonium and uranium carbide (UPuC) is considered as a possible fuel material for future nuclear reactors. However, UPuC is pyrophoric and fine powders of UPuC are subject to temperature increase due to oxidation with air and possible ignition during conditioning and handling. In a first approach and to allow easier experimental conditions, this study was undertaken on uranium monocarbide (UC) with the aim to determine safe handling conditions for the production and reprocessing of uranium carbide fuels. The reactivity of uranium monocarbide in oxidizing atmosphere was studied in order to analyze the ignition process. Experimental thermogravimetric analysis (TGA) and differential thermal analysis (DTA) revealed that UC powder obtained by arc melting and milling is highly reactive in air at about 200 °C. The phases formed at the various observed stages of the oxidation process were analyzed by X-ray diffraction. At the same time, ignition was analyzed thermodynamically along isothermal sections of the U-C-O ternary diagram and the pressure of the gas produced by the UC + O 2 reaction was calculated. Two possible oxidation schemes were identified on the U-C-O phase diagram and assumptions are proposed concerning the overall oxidation and ignition paths. It is particularly important to understand the mechanisms involved since temperatures as high as 2500 °C could be reached, leading to CO(g) production and possibly to a blast effect.