| Popis: |
The thermal conductivities of powders consisting of ThO/sub 2/ or UO/sub 2/ microspheres in He, Ar, N/sub 2/, and Kr were measured by two techniques over a pressure range of 0.03 to 0.6 MPa and a temperature range of 300 to 1300 K. The powders had solid volume packing fractions from 58.5 to 86.6% and were prepared by vibratory compaction and by mixing. The highest thermal conductivity measured was for powder containing three particle sizes at a packing fraction of 86.6% in helium gas. The applicability of the data to practical reactor fuels is limited to the early stages of fuel burnup because of restructing. A theoretical model is derived for heat transfer in powders with spherical particles. |
