Year
2014
Abstract
238PuO2 is a ceramic material that acts as the heat source in the Radioisotope Power Systems (RPS) used in space exploration. PuO2 exists in the fluorite atomic space grouping ( ¯ ; #225), and one of the well-known properties of the fluorite based oxides is their ability to lose a considerable amount of oxygen (up to several atomic %) when exposed to very high temperatures under a variety of atmospheric conditions, including air. These changes in stoichiometry have been tied to changes in atomic defect structure, lattice constant, and electronic configuration of the fluorite based oxides, but the effect of this highly variable stoichiometry on the ceramic and mechanical properties of these materials is not very well understood. Improvements in ceramic processing of PuO2 will clearly require a deeper understanding of how the stoichiometry of the material impacts its ceramic and mechanical properties. Since destructive testing of 238PuO2 is extremely challenging due to its high activity and corrosive nature, we are performing these initial studies on CeO2, a radiologically cold fluorite based oxide that is frequently used as a surrogate for PuO2. Thermogravimetric analysis with mass spectrometry detection and x-ray diffraction were used to help characterize the CeO2 material. The CeO2 stoichiometry will be varied using thermal treatments in inert atmosphere and air before and after forming the material into a ceramic disk for destructive testing. Results from this long term research project will help guide future decisions about how to improve the ceramic processing of 238PuO2 pellets for use in RPS applications. This progress report will present and discuss the results from this research obtained to date.