Understanding the characteristics of special nuclear materials in LiCl-KCl eutectic salt is extremely important in terms of effective system operation and material accountability for safeguarding pyroprocessing technology. By considering that uranium (U) is the most abundant and important element in the used nuclear fuel, measurements and analyses of U properties were performed in LiCl-KCl eutectic salt. Therefore, the electrochemical techniques such as cyclic voltammetry (CV), open circuit potential (OCP), Tafel, linear polarization (LP), and electrochemical impedance spectroscopy (EIS) were conducted under different experimental conditions to explore the electrochemical, thermodynamic, and kinetic properties of U in LiCl-KCl eutectic. The ultimate goal of this study was to develop proper methodologies for measuring and analyzing the exchange current density (i0) of U3+/U reaction, which has not been fully studied and understood in literature. In the preliminary study, cerium (Ce) was selected as a surrogate material for uranium and its behavior was being explored with the developments of experimental methods. CV was performed to evaluate Ce properties such as the diffusion coefficients (D), apparent standard reduction potential (E0*), Gibbs free energy (DG), and activity coefficient (g). In addition, EIS methods were adapted and specific experimental procedures were established for the proper i0 measurements providing repeatable and reproducible data sets. The i0 values for Ce3+/Ce pair were ranging from 0.0076 A cm-2 to 0.016 A cm-2, depending on the experimental conditions. These preliminary results give insight in developing the experimental setups and methods to evaluate the properties of U in LiCl-KCl. Plus, Ce is one of the lanthanide (Ln) fission products in electrorefiner (ER) system; therefore, the resulting data values yield useful information of the fundamental behaviors of Ln elements in the system. Based on these developed methodologies, the experimental designs and routines were established to explore the main properties (e.g., D, E0*, etc.) of UCl3 in LiCl-KCl eutectic salt under different concentrations (0.5 wt% to 4 wt% UCl3) and temperatures (723 K to 798 K). Specially, the i0 values of U3+/U were evaluated via EIS, LP, Tafel, and CV methods. All i0 values had linear trends with the change of concentration and temperature; however, these values measured by LP, Tafel, and CV methods were greatly influenced by the change in electrode surface area. Overall, the i0 values agreed within 33% relative error range with the EIS method being the most consistent and accurate in comparison to reported literature values. The measured values of i0 were ranging from 0.0054 A cm-2 to 0.102 A cm-2. Therefore, an extremely reliable database for i0 was provided and it is feasible to anticipate the i0 kinetics in other experimental conditions by using the provided equation models. Furthermore, GdCl3 was added to the LiCl-KCl-UCl3 system to explore the effects of other elements on the U properties such as the diffusion coefficients, thermodynamic properties, and i0 kinetics. The diffusion coefficient was generally decreased by 12 ~ 35% with addition of GdCl3 in LiCl-KCl-UCl3; however, the apparent standard potentials and exchange current density follow the same trends with data obtained without GdCl3 additions. Hence, the results indicate that the thermodynamic and kinetic values for U3+/U reaction in LiCl-KCl eutectic salt are not greatly influenced by the presence of GdCl3.

Rare earth and actinide metals, critical to security, medicine, and the economy, have been processed through methods such as solvent extraction and electrorefining. To minimize radiological waste and improve yield, a 'chloride volatility' process--also known as the chlorination and volatilization process (CVP)--has been proposed and demonstrated for processing rare earths. The process takes advantage of the low vapor pressure of rare earth chlorides (<700 >°C), CaCl2 was added to LaCl3 to lower the melting temperature. LaCl3 electrochemical behavior has not previously been studied in CaCl2. Cyclic voltammetry (CV) and square wave voltammetry (SWV) were applied to LaCl3 salts in CaCl2-LiCl and CaCl2 to study the metal ion behavior. Various electrode materials were compared at low CV scan rates (s-1) to determine compatibility with chlorine gas evolution. Experiments of eutectic LaCl3-CaCl2 were performed and analyzed to determine the efficacy of chlorine gas generation via electrolysis for the CVP. Through galvanostatic electrolysis, oxidation of chloride ions and subsequent chlorination of rare earth was demonstrated, with cerium chosen as the representative rare earth metal. Through a quadrupole mass spectrometer plumbed in line with the electrolytic cell, the quality of the generated gas was analyzed.

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Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge. We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data. The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term. The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour. The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.