Uranium Carbide Fuels

Spherical particles of controlled sizes can be used to fabricate high density uranium carbide fuel pins by means of vibratory packing directly into the cladding tube, as with sphere-pac oxide fuel (see 17.3.12.1.1). 

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. 

Material Buddings of Uranium-Carbide-Fueled Graphite Assemblies - Measurements,... 

Critical and subcritical experiments, in support of the Advanced ium Graphite Reactor fASGR) program, . have been performed to determine values of material buckling for graphite assemblies fueled with slightly-enriched (3.02 wt%), uranium carbide-fuel elements. These experiments provide the first data available for comparison with results of calculations. 

The reactor configuration, shown in Fig. t, consists of a large outer cylindrical reflector shell of beryllium, into which the fuel (in the form of a cylindrical shell Of uranium carbide fuel elements) and an inner beryllium reflector are assembled by a ram which lifts them into the reflector. Originallyi the reactor control and safety systems consisted of rotary drums with a 120-deg boron sector running the full length of the core, which resided permanently in the outer beryllium reflector and were spring loaded for fail-safe control. ... 

At the time of this report, no practicable means existed to extract plutonium from the coated fuel particles. Uranium-thorium and uranium carbide fuel could also be used in the AFPR to enhance its proliferation resistance. 

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. 

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

Uranium and plutonium carbide fuels have also been investigated and their dissolution in nitric acid results in the formation of organic acids as well as In the case of (Uo.gPuo.2)C... 

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. 

Thorium carbides (ThC, ThC2) and uranium carbides (UC, UC2) exhibit metallic properties, but in other properties differ significantly from the carbides of the subgroups of the IVth, Vth and Vlth groups of the periodic table. Their hardnesses are substantially lower (see Table 5.6-1), they are pyrophoric and are easily hydrolyzed in water or weak aeids. Their only economic importance is as carbidie fuels in nuelear technology, particularly for high temperature and breeder reactors which are currently in the evaluation phase. 

Carbide powder is manufaetured by carburization of the metal, metal oxide or metal hydride with nuclear-pure graphite at ca. 2000°C. Carbide powder pellets (see Section 5.5.5.1.5) or beads up to 0.6 mm in diameter are formed and sintered using ceramic process technology. Reaction sintering is commonly used for the manufacture of uranium earbide fuel beads, in whieh uranium oxide and carbon are first mixed then annealed to form the carbide and then are sintered to 90 to 95% of the theoretical density. An... 

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