Structural Investigation of the Incorporation of Various Dopants into Uranium Oxide – A Systematic Study Regarding the Development of New Composite Reference Microparticles

Year
2022
Author(s)
Shannon Potts - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Philip Kegler - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Giuseppe Modolo - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Simon Hammerich - Institute of Earth Sciences - Heidelberg University
Martina Klinkenberg - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Sidney Niemeyer - Lawrence Livermore National Laboratory
Dirk Bosbach - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Stefan Neumeier - Forschungszentrum Julich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6)
Abstract

In order to verify the compliance of the Member States to their international legal obligations with respect to the Non-Proliferation Treaty to use nuclear materials and technologies only for peaceful purposes, the International Atomic Energy Agency (IAEA) implements technical measures, or safeguards. These technical measures, inter alia, include analytical measurements of individual micrometer- and submicrometer-sized particles on swipe samples taken by IAEA safeguards inspectors during in-field verification activities. The implementation of this measure goes hand in hand with the further development of analytical methods and quality control of the analytical results from particle analysis, including the provision of suitable particle-based reference materials with well-defined properties. To this purpose, an aerosol-based process to produce microparticulate reference materials was developed and established in the laboratories of the Forschungszentrum Juelich. This physical approach supplies well-defined uranium oxide microparticles, which fulfill the IAEA’s requirements. In addition to the production of pure uranium oxide particles, mixed lanthanide/uranium oxide microparticles were produced as first step towards composite reference materials in order to increase in the sensitivity and selectivity of mass spectrometric methods for detecting even small amounts of dopants, e.g., fission products. To understand the incorporation mechanisms of dopants into the uranium oxide structure deeply, bulk-scale comparison materials were produced and doped with lanthanides and thorium by co-precipitation methods and systematically investigated by TG-DSC, XRD, Raman and SEM measurements. This presentation will show some results regarding the incorporation of lanthanides and thorium into U3O8 under the presence of a phase transition from the orthorhombic to the hexagonal U3O8 crystal system. These results will be integrated into the particle production process to design well-defined microparticulate mixed oxide reference materials.