Chris Cochrane

Canadian Nuclear Safety Commission | CNSC · Directorate of Security and Safeguards

The zirconium alloy Excel has been shown to retain a metastable β phase upon quenching from temperature within the α+β phase field. Using a combination of neutron diffraction and EBSD, we show that it is possible to initiate a phase transformation from β→α during tensile deformation of Excel in the quenched state. We present a model to explain the...

This study investigates the phase stability and redistribution of solute during heating and cooling of a quaternary zirconium alloy, Excel (Zr-3.2Sn-0.8Mo-0.8Nb). Time-of-flight neutron diffraction data are analyzed using a novel Vegard’s law-based approach to determine the phase fractions and location of substitutional solute atoms in situ during...

The determination of inorganic anions in uranium ore concentrates (UOCs) is useful to nuclear forensics for establishing the provenance of sample materials. In this collaborative study, quantitation of inorganic anions was carried out on three UOC reference materials from the National Research Council Canada: UCLO-1 ( https://doi.org/10.4224/crm.20...

The texture evolution of a Zr-2.5wt pctNb alloy pressure tube is characterized after the α→β transformation and the β→α transformation by room temperature EBSD maps and reconstruction of the high temperature β phase. The β phase forms a deformation texture which varies along the radial direction of the tube and changes after thermal cycling. Varian...

We present a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method for trace-element analysis of uranium ore concentrates (UOCs). The method was used to characterize a select number of UOC samples representing 20 different producers from 8 distinct geographic locations. These results were then used to assess the origin of t...

Uranium ore concentrate (UOC) is an important nuclear material of interest for Canada. A large scale analytical program is being led by the Directorate of Security and Safeguards (DSS) of the Canadian Nuclear Safety Commission (CNSC) to establish a reference dataset of UOCs that have passed through and/or are currently under Canadian regulatory con...

Orientation-dependent irradiation hardening phenomena in pure Zr have been studied, and the corresponding mechanisms investigated based on the combined use of SEM, TEM, and CPFEM. Nanoindentation was conducted on ten grains at room temperature before and after ion irradiation (0.3 dpa, 250 °C). The hardness decreases as the declination angle (the a...

The quaternary zirconium alloy, Zr-3.5Sn-0.8Mo-0.8Nb, has shown promise as a possible system for utilization of transformation-induced plasticity. In this study, we investigate the effect of strain rate and stress-relaxation β → α on the phase transformation at room temperature, and present a technique to characterize the thermally-activated deform...

The activation of a phase transformation during plastic deformation of the zirconium alloy, Excel (Zr-3.5Sn-0.8Mo-0.8Nb), has been investigated using a combination of in situ neutron diffraction and electron microscopy. The effect of temperature and tension/compression asymmetry on the activation of the phase transformation is identified. While the...

This study investigates the retention of greater than equilibrium β phase in a two-phase zirconium alloy. We provide experimental data exploring two factors that impact the retention of β phase following heat treatment of a two-phase quaternary zirconium alloy, Zr-3.5Sn-0.8Mo-0.8Nb. Heat treatment temperature and quenching rate are varied to establ...

Understanding the stress state and microstructural features at a growing crack-tip is critical to understanding the failure mechanisms of engineering structures. To investigate the strain and dislocation evolution at a crack-tip, electron backscatter diffraction and geometrically necessary dislocation analysis were performed on fully annealed zirco...

A series of stress relaxation experiments were performed on samples of rolled Zircaloy-2 plate. . In situ synchrotron x-ray diffraction was used to observe changes in interatomic lattice spacing during both deformation and relaxation. The concepts of strain rate sensitivity and activation volume are extended from the macroscopic to the microscopic...

In this paper, 40 MeV Zr ion irradiation of Zr-2.5Nb pressure tube alloy was carried out, delivering a damage layer 6.5 μm deep. Uniaxial micropillar compression experiments along the tube axial (AD) and transverse directions (TD) were conducted. Irradiation was found to alter the deformation mechanisms and to increase the yield strength more in th...

A series of in situ compression tests have been carried out at room temperature on three dual-phase Zr–2.5 wt% Nb alloys with different concentrations of the interstitial alloying elements oxygen and iron. Oxygen and iron are potent strengthening additives in two-phase alloys with a hexagonal-close packed α phase and body-centred cubic β phase, suc...

It is shown that attempts to accurately deduce the magnetic penetration depth λ of overdoped BaFe(1.82)Co(0.18)As₂ single crystals by transverse-field muon spin rotation (TF μSR) are thwarted by field-induced magnetic order and strong vortex-lattice disorder. We explain how substantial deviations from the magnetic field distribution of a nearly per...

It is shown that attempts to accurately deduce the magnetic penetration depth of overdoped BaFe_{1.82}Co_{0.18}As2 single crystals by transverse-field muon spin rotation (TF-muSR) are thwarted by field-induced magnetic order and strong vortex-lattice disorder. We explain how substantial deviations from the magnetic field distribution of a nearly pe...

The doping of charge carriers into the CuO(2) planes of copper oxide Mott insulators causes a gradual destruction of antiferromagnetism and the emergence of high-temperature superconductivity. Optimal superconductivity is achieved at a doping concentration p beyond which further increases in doping cause a weakening and eventual disappearance of su...

It has been proposed that the termination of superconductivity in heavily overdoped copper oxides is caused by the emergence of competing ferromagnetism. We report on a direct examination of this scenario in overdoped La2-xSrxCuO4 using the technique of muon spin relaxation. We detect the onset of static magnetic moments of electronic origin beyond...

We have measured the DC magnetic susceptibility of a heavily overdoped La1.67Sr0.33CuO4 single crystal. In contrast to lower-doped superconducting samples no magnetic anisotropy is observed. However, as previously seen in the normal state, there is a Curie-like term that appears in the susceptibility for strontium content in excess of x˜0.19. This...