Uranium carbide nuclear fuels

Uranium. tetrathiocyanatotetrakis[tris-(dimethylamino)phosphine oxide]-structure, 1.87 Uranium carbide nuclear fuels dissolution, 6, 928 Uranium complexes, 3,1131-1215 carbamic acid... 

The deposition of pyrolytic graphite in a fluidized bed is used in the production of biomedical components such as heart valves, ] and in the coating of uranium- and thorium-carbides nuclear-fuel particles for high temperature gas-cooled reactors, for the purpose of containing the products of nuclear fission.fl" The carbon is obtained from the decomposition of propane (CgHg) or propylene (CgHg) at 1350°C, or of methane (CH4) at 1800°C. Its structure is usually isotropic (see Ch. 4). 

The meyor applications of pyrolytic carbon deposited by fluidized bed are found in the production of biomedical components such as heart valves and in the coating of uranium carbide and thorium carbide nuclear-fuel... 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

As previously stated, uranium carbides are used as nuclear fuel (145). Two of the typical reactors fueled by uranium and mixed metal carbides are thermionic, which are continually being developed for space power and propulsion systems, and high temperature gas-cooled reactors (83,146,147). In order to be used as nuclear fuel, carbide microspheres are required. These microspheres have been fabricated by a carbothermic reduction of UO and elemental carbon to form UC (148,149). In addition to these uses, the carbides are also precursors for uranium nitride based fuels. 

Carbides of the Actinides, Uranium, and Thorium. The carbides of uranium and thorium are used as nuclear fuels and breeder materials for gas-cooled, graphite-moderated reactors (see Nuclearreactors). The actinide carbides are prepared by the reaction of metal or metal hydride powders with carbon or preferably by the reduction of the oxides uranium dioxide [1344-57-6] UO2 tduranium octaoxide [1344-59-8], U Og, or thorium... 

In order to be used as nuclear fuel, carbide microspheres are required. These microspheres have been fabricated by a carbothermic reduction of UO3 and elemental carbon to form UC. In addition to these uses, the carbides are also precursors for uranium nitride based fuels. 

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 (ca. 20% is used as the fuel, but mainly with 239pu in the form of a UO2/PUO2 mixture. The breeding blanket consists of depleted uranium from isotope separation plants or from reprocessing plants for spent nuclear fuels. Axially movable boron carbide absorbers are distributed in the fuel zone for shutting down purposes. The uranium utilized can be ca. 100 times better utilized than e.g. in light-water reactors. 

Brand, G. E. Murbach, E. W., "Experiments on Pyrochemical Reprocessing of Uranium Carbide Fuel" in "Symposium on Reprocessing of Nuclear Fuels, The Metallurgical Society of AIME, Ames, Iowa, August, 1969", Nucl. Metallurgy, Vol. 15, 1969. 

Uranium carbide, UC2, is a binary salt. It is a gray crystal that decomposes in water. It is highly toxic and a radiation risk. Uranium carbide is used as nuclear reactor fuel. 

In recent years a wide variety of inorganic, non-metallic materials has been developed for the electrical, nuclear power, and engineering industries. In the shaping and processing of these products some form of heat treatment is involved, and they too are regarded as ceramic materials. Examples are rutile, a form of titanium dioxide used for making ferroelectric materials steatite or talc, for electrical insulators alumina, zirconia, thoria and beryllia as refractories and electrical insulators, uranium oxide as a nuclear-fuel element, and nitrides and carbides as abrasives or insulators. 

The oxides of uranium and plutonium are now widely used as nuclear fuel, while the carbides and nitrides of these elements possess promising qualities as the fuel of the future. 

The binary systems actually and potentially important as nuclear fuel include oxides, carbides, nitrides, phosphides, and sulfides of uranium, plutonium, and thorium. An increasing amount of detailed information is becoming available on the phase equilibria of these compounds, but the relations existing between the composition (especially nonstoichiometric) and the vapor pressure (or activity) of each component are known only for a limited number of systems. 

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. 

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. 

Grande, L., Villamere, B., Allison, L., Mikhael, S., Rodriguez-Prado, A., Pioro, I., 2011. Thermal aspects of uranium carbide and uranium di-carbide fuels in supercritical water-cooled nuclear reactors. Journal of Engineering for Gas Turbines and Power 133 (2). February, 7 pp. 

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