Carbide fuels uranium dicarbide

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... 

The dicatbide, either by itself, mixed with uranium dicarbide, or in solid solution with uranium dicarbide, is used as fuel material in some versions of high-temperature gas-cooled reactors. Like uranium carbides, the thorium carbides react rapidly with water or moist air and must be protected from moisture in storage and fuel fabrication. 

The fuel for the Peach Bottom reactor consisted of a uranium-thorium dicarbide kernel, overcoated with pyrolytic carbon and silicon carbide which were dispersed in carbon compacts (see Section 5), and encased in graphite sleeves [37]. There were 804 fuel elements oriented vertically in the reactor core. Helium coolant flowed upward through the tricusp-shaped coolant channels between the fuel elements. A small helium purge stream was diverted through the top of each element and flowed downward through the element to purge any fission products leaking from the fuel compacts to the helium purification system. The Peach... 

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