Direct measurements of the thermal conductivity of uranium carbide samples by the method of electron bombardment

For the next generation of nuclear physics accelerator facilities, fission targets employing compounds of uranium are being proposed to produce ion species far from stability. With the high power beams proposed for the Rare Isotope Accelerator (RIA) production targets, heat dissipation becomes important. In our two-step target design, neutrons are first generated in the primary target, which then induce fission in a surrounding assembly of uranium carbide. Knowledge of the physical, chemical and, most importantly, the thermal properties of the uranium target material are crucial to the engineering designs under consideration. The interplay of density, grain size, thermal conductivity, and diffusion properties of the uranium carbide must be well understood before a successful target can be built. We present here recent investigations of the thermal conductivity of uranium carbide samples. Thin sample pellets have been produced for measurements of thermal conductivity using the method of electron bombardment. The experimental apparatus consists of a 10 kV vertical electron beam source, which is used to heat the samples while the thermal radiation is observed using a two-color optical pyrometer. Initial results are given and compared with bulk properties as well as to similar measurements made on pellets of uranium carbide obtained via carbothermic reduction starting from the oxide. Slight variations of thermal conductivity with density have been observed for the reduced oxide samples. Experimental investigations of the physical and thermal properties of uranium carbide sample pellets using various binder materials are also being undertaken.