Uranium carbides melting point

The fuel particles used in these studies were typical pyrolytic carbon-coated thorium-uranium dicarbide, (Th,U)C2, microspheres. The kernels, — 200/i in diameter, were prepared from Th02, U02, and C and converted to the carbide at temperatures below 2200°C., followed by a spheroidization above the melting point, 2450°-2500°C. The bare kernels were coated with a 30-50fi layer of low density (— 1.0 gram/cm.3) buffer pyrolytic carbon, followed by a 40-70/a layer of high density... 

Uranium carbide UC (UC2 and U2C also exist) has a melting point of about 2300 °C and is an important nuclear fuel for high-temperature reactors. It is prepared by reduction of UO2 with carbon, followed by pressing and sintering. It can also be made by hot pressing of mixtures of uranium metal powder with graphite at 1000 to 1100 °C. A mixed carbide with ThC is manufactured in the form of spheroids by melting. As the product is hydrolyzed on exposure to air, it is coated with a protective carbon layer. 

Uranium carbides UC and UCj can be produced by reaction of carbon monoxide with molten uranium. These gray crystals have high melting points of 2790°C and 2350°C, respectively. U2C3 also exists but decomposes at 1700°C. In principle, uranium carbide can replace uranium dioxide in nuclear fuels. 

Uranium nitrides UN and U2N3 form cubic crystals and are quite similar to the carbides in their melting point (UN at 2805°C with a density of 14.3 g cm ). They are formed by reaction of nitrogen with uranium. 

Another promising uranium compound that can be used in nuclear fuels is uranium carbide that has a high melting point and better thermal conductivity than the oxide and in addition does not form oxygen when radiolyzed. Uranium nitride can also be used, but formation of from N could be problematic. In addition, other uranium compounds that can be used as a fuel in a nuclear reactor, ranging from aqueous solutions to molten salts that are brought to a high temperature in order to keep them in a molten state. MOX of uranium and plutonium also serve as a nuclear fuel in some reactors. 

UC2 is a carbide of uranium, which has a high melting point and a high thermal conductivity. UC2 has a body-centered tetragonal (BCT) crystal structure up to the transformation temperature of 1820 20°C, where it transforms to a face-centered cubic (FCC) structure, similar to that of UO2 (Frost, 1963). Frost (1963) has indicated that UC2 has always been found in hypostoichiometric forms such... 

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