Characterization of the Aerosol-Based Synthesis of Uranium Particles as a Potential Reference Material for Microanalytical Methods

Abstract

A process for production of micrometer-sized particles composed of uranium oxide using aerosol spray pyrolysis is characterized with respect to the various production parameters. The aerosol is generated using a vibrating orifice aerosol generator providing monodisperse droplets, which are oxidized in a subsequent heat treatment. The final particles are characterized with microanalytical methods to determine size, shape, internal morphology, and chemical and structural properties in order to assess the suitability of the produced particles as a reference material for microanalytical methods, in particular, for mass spectrometry. It is demonstrated that physicochemical processes during particle formation and the heat treatment to chemically transform particles into an oxide strongly influence the particle shape and the internal morphology. Synchrotron μ-X-ray based techniques combined with μ-Raman spectroscopy have been applied to demonstrate that the obtained microparticles consist of a triuranium octoxide phase. Our studies demonstrate that the process is capable of delivering spherical particles with determined uniform size and elemental as well as chemical composition. The particles therefore represent a suitable base material to fulfill the homogeneity and stability requirements of a reference material for microanalytical methods applied in, for example, international safeguards or nuclear forensics.

Synthesis of size-controlled UO2 microspheres from the hydrothermal conversion of U(iv) aspartate

“…First of all, as UO 2 and (U,Pu)O 2 solid solutions are aimed to be used as fuels in future Gen III and/or Gen IV reactors 2 , spherical oxides with tailored size could help to improve the flowing capability of powders used in the fabrication process 3,4 and could enhance the green density of the pellets before the sintering step. The design of uranium oxides particles with controlled shape and size is also required to qualify the analytical methods used for nuclear safeguards 5,6 . Uranium oxide nanospheres have already attracted some attention in view of their catalytic properties, particularly in the framework of the destruction of volatile organic compounds 7 .…”

“…from about 50 to 2000 nm. Physical methods such as aerosol spray pyrolysis appeared to be suitable for the production of monodisperse particles, as their size is directly controlled by the diameter of the droplets forming the aerosol 5 . Nevertheless, this kind of process requires specific equipment, which might be difficult to implement in nuclear facilities aiming to work with radionuclides of high specific activity.…”

Experimental assessment of effectively probed volume in confocal XRF spectrometry using microparticles

“…The uranium particles were produced for internal use in the Quality Control Program of the Environmental Sample Laboratory, Department of Safeguards, International Atomic Energy Agency (IAEA). The particles were produced out of suitable solutions of uranium compounds using a modified vibration aerosol generator . This technique allows to produce monodisperse droplets, which after an oxidation step in a heating column are collected onto suitable substrates.…”

“…The particles were produced out of suitable solutions of uranium compounds using a modified vibration aerosol generator. [19] This technique allows to produce monodisperse droplets, which after an oxidation step in a heating column are collected onto suitable substrates. These particles were characterized with microanalytical methods to determine their size, shape, internal morphology, and chemical and structural properties to assess their suitability as a reference material for microparticle analytical methods by mass spectrometry.…”

Towards the Synthesis of Mixed Actinide Particulate Reference Materials: Microscopy and Spectroscopic Characterization of U/Ce-containing Specimens

“…Both thermal ionization (TIMS) and secondary ion mass spectrometry (SIMS) are primary particle characterization tools for these analyses, but representative particulate (reference and proficiency testing) materials have been historically limited and/or unavailable. This material need is recognized by the IAEA as urgent; with our team and others pursuing the R&D required to reproducibly produce single and mixed element reference particulates [2][3][4][5]. Initial efforts focused on U/Ce as a convenient test surrogate for U/Th and U/Pu materials.…”