Corrosion Dynamics of Carbon Steel in Used Fuel Container Environments

The current Canadian used nuclear fuel container (UFC) design uses a pressure‑grade carbon steel (CS) vessel with its outer surface coated with a thin layer of copper. One concern regarding the structural integrity of the UFC design is the potential internal corrosion of the CS vessel. Moisture trapped inside a UFC could condense within the gap between the hemispherical head and the cylindrical body of the vessel. The internal UFC environment will be exposed to a continuous flux of ionizing radiation arising from the decay of radionuclides trapped in the used UO2 fuel matrix. This thesis research project investigates the effects of physical and chemical solution parameters on CS corrosion, with the aim of developing a corrosion dynamics model that can be used to assess the integrity of the current Canadian UFC design with confidence. The parameters studied in this thesis project were the ratio of solution volume to surface area, pH, dissolved O2, and the presence or absence of γ-radiation. Corrosion dynamics were followed using electrochemical techniques, both conventional and non‑standard techniques developed as part of this project. The electrochemical tests were augmented with post-test surface and solution analyses to study oxides formed on corroded surfaces and to determine the dissolved metal content in the solution phase. The results of this study clearly demonstrated that CS corrosion involves many oxidation steps that lead to the formation and growth of different oxides as well as the dissolution of metal ions. The transfer of Fe atoms between metal, oxide and solution phases provides routes for developing strong systemic feedback that can induce autocatalytic reaction cycles, resulting in oscillatory behaviours that are observable under certain solution conditions. The dynamics of CS corrosion may not approach and reach only one steady state, but continue to evolve and reach different steady states, depending on solution parameters. A mechanism that can explain the CS corrosion dynamics over long time periods under a range of solution conditions has been proposed. The mathematical formulation of a model for the long-term corrosion of CS based on this mechanism has just begun. This study has shown that the corrosion dynamics in the early stages of corrosion can be easily modeled by applying classical electrochemical reaction rate equations coupled with mass transport flux equations. However, for CS in aerated solutions or other oxidizing environments, these classical equations must be formulated for the metal oxidation process rather than the reduction of solution species (oxidant) because the former process is rate determining

Perfect Fluids and Bad Metals: Transport Analogies Between Ultracold Fermi Gases and High TcT_c Superconductors

In this paper, we examine in a unified fashion dissipative transport in strongly correlated systems. We thereby demonstrate the connection between "bad metals" (such as the high temperature superconductors) and "perfect fluids" (such as the ultracold Fermi gases, near unitarity). One motivation of this work is to communicate to the high energy physics community some of the central unsolved problems in high $T_c$ superconductors. Because of interest in the nearly perfect fluidity of the cold gases and because of new tools such as the AdS/CFT correspondence, this better communication may lead to important progress in a variety of different fields. A second motivation is to draw attention to the great power of transport measurements which more directly reflect the excitation spectrum than, say, thermodynamics and thus strongly constrain microscopic theories of correlated fermionic superfluids. Our calculations show that bad metal and perfect fluid behavior is associated with the presence of a normal state excitation gap which suppresses the effective number of carriers leading to anomalously low conductivity and viscosity above the transition temperature $T_c$. Below $T_c$ we demonstrate that the condensate collective modes ("phonons") do not couple to transverse probes such as the shear viscosity. As a result, our calculated shear viscosity at low $T$ becomes arbitrarily small as observed in experiments. In both homogeneous and trap calculations we do not find the upturn in $\eta$ or $\eta/s$ (where $s$ is the entropy density) found in most theories. In the process of these studies we demonstrate compatibility with the transverse sum rule and find reasonable agreement with both viscosity and cuprate conductivity experiments.Comment: 21 pages, 11 figure

Nonlinear Modeling and Verification of a Heaving Point Absorber for Wave Energy Conversion

Although the heaving Point Absorber (PA) concept is well known in wave energy conversion research, few studies focus on appropriate modelling of non-linear fluid viscous and mechanical friction dynamics. Even though these concepts are known to have non-linear effects on the hydrodynamic system, most research studies consider linearity as a starting point and in so doing have a weak approach to modelling the true dynamic behaviour, particularly close to resonance. The sole use of linear modelling leads to limited ability to develop control strategies capable of true power capture optimisation and suitable device operation. Based on a 1/50 scale cylindrical heaving PA, this research focuses on a strategy for hydrodynamic model development and experimental verification. In this study, nonlinear dynamics are considered, including the lumped effect of the fluid viscous and mechanical friction forces. The excellent correspondence between the derived non-linear model and wave tank tested PA behaviours provides a strong background for wave energy tuning and control system design

Search for C=+C=+ charmonium and bottomonium states in e+e−→γ+Xe^+e^-\to \gamma+ X at B factories

We study the production of $C=+$ charmonium states $X$ in $e^+e^-\to \gamma + X$ at B factories with $X=\eta_c(nS)$ (n=1,2,3), $\chi_{cJ}(mP)$ (m=1,2), and $^1D_2(1D)$. In the S and P wave case, contributions of tree-QED with one-loop QCD corrections are calculated within the framework of nonrelativistic QCD(NRQCD) and in the D-wave case only the tree-QED contribution are considered. We find that in most cases the QCD corrections are negative and moderate, in contrast to the case of double charmonium production $e^+e^-\to J/\psi + X$, where QCD corrections are positive and large in most cases. We also find that the production cross sections of some of these states in $e^+e^-\to \gamma + X$ are larger than that in $e^+e^-\to J/\psi + X$ by an order of magnitude even after the negative QCD corrections are included. So we argue that search for the X(3872), X(3940), Y(3940), and X(4160) in $e^+e^-\to \gamma + X$ at B factories may be helpful to clarify the nature of these states. For completeness, the production of bottomonium states in $e^+e^-$ annihilation is also discussed.Comment: 13pages, 4 figure