Vaporization of ThC and (Th,U)C

Vaporization behavior of thorium carbide fuels, ThC and (Th,U)C, was studied by high temperature mass spectrometry. Both ThC and (Th,U)C were prepared by carbothermic reduction. Vapor pressure of U(g) or, U(g) and Th(g) was measured by using a graphite-linered tantalum Knudsen cell. Besides the absolute vapor pressure, the partial molal enthalpy of vaporization and the partial molar Gibbs energy of Th were evaluated for ThC1±x. For (Th,U)C, activities of ThC and UC in addition to absolute vapor pressures were evaluated. Then, compatibility of ThC with either Ni, Fe or Cr was examined by means of an EPMA analysis of the reaction zone. Only Ni showed significant reaction with ThC. Three reaction layers were identified. Finally, preparation of high density ThC pellet by means of sintering was studied. (author)