Synthesis of Non-Radioactive Complex Molybdenum Oxides for Thermodynamic Study of Nuclear Materials

Abstract

Understanding nuclear fuel behaviour and the ability to predict nuclear fuel properties under a wide range of conditions is necessary for the progress of the nuclear industry. As part of the Thermodynamics of Advanced Fuels – International Database (TAF-ID), the Nuclear Research Group at the Royal Military College of Canada (NRG-RMC) is committed to providing accurate, reliable, and self-consistent thermodynamic data of the complex oxides present in the grey phases and other nuclear materials of spent nuclear fuel. This data is valuable input for the modelling of nuclear fuel behaviour under normal and abnormal reactor operating conditions. In this presentation, we focus on the advancements made at the NRG-RMC to produce, characterize, and study non-radioactive complex oxides, homologues to nuclear materials. At this stage, results obtained from the study of the following chemical systems will be discussed: Na-Mo-O, Cs-Mo-O, Ca-Mo-O, Sr-Mo-O, Ba-Mo-O, and U-Mo-O. These elements are relevant for the nuclear industry given their high fission yield in nuclear fuels. Synthesis of these materials involves the use of several techniques such as wet chemistry, solid-state, gel crystallization, and combustion syntheses. Using these methods, several of the target compounds within the aforementioned chemical systems have been successfully synthesized (i.e., Na₆Mo₇O₂₄, Sr₃MoO₆, SrMo₅O₈, Sr₃Mo₇O₂₄, SrMoO₃, Ba₂MoO₅, Ba₃MoO₆, BaMo₃O₁₀, Ba₃Mo₇O₂₄, UMoO₆, and others). Subsequent characterization of these materials was performed using several techniques. Where suitable, Powder X-Ray Diffraction (PXRD) is effective for phase identification, whereas Single-Crystal X-Ray Diffraction has proven successful for the characterization of novel phases. Elemental identification is provided by either instrumental or analytical techniques. Additionally, the thermodynamic properties (i.e., heat capacity (CP) and transition temperatures) of some of the synthesized materials have been determined. This data is relevant for the accurate representation of the phase behaviour in thermodynamic models. Finally, the current version of the thermodynamic models for the Sr-Mo-O and Ba-Mo-O systems are presented.