Atomic-Scale Characterization of Uranium Oxide Micro-Particles

To ensure the highest quality of analytical measurements, the IAEA’s network of analytical laboratories (NWAL) must manage robust internal quality assurance and control (QA/QC) plans. The International Atomic Energy Agency (IAEA) routinely distributes well-characterized quality control (QC) samples to the NWAL and conducts Interlaboratory Comparison (ILC) studies to periodically assess their analytical performance. Although certified reference materials are available for bulk analytical techniques, the selection of available materials for the QA/QC of analytical methods for particle analysis is limited. As the IAEA needs micrometer-sized nuclear materials (e.g., uranium oxide) with well-characterized properties such as size, density, homogeneity, and elemental and isotopic composition for its NWAL particle analysis laboratories’ QA/QC program, the Pacific Northwest National Laboratory (PNNL), Savannah River National Laboratory (SRNL), and Forschungszentrum Jülich are producing bespoke working reference materials which are useful for a range of QA/QC measurements to meet this need. PNNL’s efforts are focused on hydrothermal synthesis methods for producing particulate uranium oxides and, more recently, mixed actinide oxides (i.e., U1-xThxO2). Herein, the details of PNNL’s particle synthesis strategy and the thorough characterization of elemental composition, crystal structure, spatial elemental homogeneity, and isotopic profile will be discussed.