Characterization of Oxide Precipitates Observed as a Gray Phase in High-Burnup Mixed Oxide Fuels for Fast Reactor

摘要

It is very important to understand the behavior of the fission products (FPs) for evaluation of the fuel performance. For example, in the high-burnup oxide fuels, some FPs dissolve in the fuel matrix and others form oxide or metallic inclusions, which would affect the physical and chemical properties of the fuels. Here we show the characteristics of the oxide inclusions; especially we focused on (Sr,Ba)-Mo-O ternary compounds because they would take various chemical forms under the different oxygen potentials. We found that the thermal conductivities of (Sr,Ba)MoO_3 are approximately 10 times higher than those of (Sr,Ba)MoO_4. This result could be explained from the viewpoint of Slack's general thermal conductivity theory.