Showing papers by "Atomic Energy of Canada Limited published in 1986"
TL;DR: Mise en evidence, par diffusion de neutrons, de l'apparition a frequence finie des excitations les plus basses dans l'antiferromagnetique a spin 1 CsNiCl 3 , dans sa phase a une dimension.
Abstract: Neutron scattering has shown that the lowest spin excitations in the spin-1 antiferromagnet ${\mathrm{CsNiCl}}_{3}$ in its one-dimensional phase occur at finite frequency. After allowance for the known weak interchain coupling the gap is found to be in good agreement with recent numerical calculations. The results support the Haldane conjecture that in integral-spin chains with isotropic interactions a gap separates the ground state from the excitations.
240 citations
TL;DR: In this paper, the critical heat flux (CHF) lookup table is used for predicting CHF for water over a very wide range of conditions and geometries, especially over the ranges where CHF data are scarce.
Abstract: This paper describes the derivation of a critical heat flux (CHF) lookup table, which may be used for predicting CHF for water over a very wide range of conditions. The CHF table is based on the Chalk River Nuclear Laboratories' CHF data bank, which contains more than 15.000 CHF data points for water. A comparison of the prediction accuracy of the CHF lookup table and selected CHF correlations is presented. The table method is not designed to replace ad hoc CHF correlations derived for a given geometry over a narrow range of flow conditions; rather it is designed to provide a reasonable estimate of CHF over a very wide range of flow conditions and geometries, especially over the ranges where CHF data are scarce. It may also be used to predict CHF for nonaqueous fluids by fluid-to-fluid modeling techniques
221 citations
01 Jan 1986-International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry
TL;DR: The rate constant for reaction of hydroxyl radicals with the bicarbonate ion has been determined to be 8.5 × 106 dm3 mol-1s-1.1.
137 citations
TL;DR: In this article, the adsorption of uranyl species onto a well-characterized hematite sol has been studied in the presence of bicarbonate ions and it was shown that the uptake of uranium decreases abruptly with increasing solution pH.
119 citations
TL;DR: The SIMPLE method of Patankar and Spalding and its variants such as SIMPLER, SIMPLEC and SIMPLEX are segregated methods for solving the discrete algebraic equations representing the equations of motion for an incompressible fluid flow as discussed by the authors.
Abstract: The SIMPLE method of Patankar and Spalding and its variants such as SIMPLER, SIMPLEC and SIMPLEX are segregated methods for solving the discrete algebraic equations representing the equations of motion for an incompressible fluid flow. The present paper presents the extension of these methods to the solution of compressible fluid flows within the context of a generalized segregated approach. To provide a framework for better understanding the segregated approach to solving viscous compressible fluid flows an interpretation of the role of pressure in the numerical method is presented. With this interpretation it becomes evident that the linearization of the equation for mass conservation and the approach used to solve the linearized algebraic equations representing the equations of motion are important in determining the performance of the numerical method. The relative performance of the various segregated methods are compared for several subsonic and supersonic compressible fluid flows.Copyright © 1986 by ASME
113 citations
TL;DR: In this article, the Bauschinger effect is defined as the response during the early stages of reverse flow and the reverse flow stress σ r tends to saturate before it begins to rise again, and the rearrangement of dislocation substructure is treated by employing a two-component composite model.
109 citations
79 citations
01 Aug 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the relative mean pulse height produced by 1H, 4He, 7Li and 16O ions in Si surface barrier detectors was measured and a simple model invoking a stopping power dependence of the energy required to create an electron-hole pair was proposed.
Abstract: We report measurements of the relative mean pulse height produced by 1H, 4He, 7Li and 16O ions in Si surface barrier detectors. The data are anomalous in that the pulse height for different ions of the same energy (after window and nonionizing losses are subtracted) increases with atomic number, contrary to observations for fission fragments. A simple model invoking a stopping power dependence of the energy required to create an electron-hole pair is consistent with all experimental data, suggesting that the response of Si detectors is nonlinear with particle energy.
73 citations
69 citations
TL;DR: A novel method of solution of the finite difference equations was deviced and incorporated, and many of the approximations that are common in other stability codes are avoided.
66 citations
TL;DR: In this paper, an analysis of solute diffusion data for α-Zr has been made in terms of atomic size considerations; it suggests a normal value for the activation energy for self-diffusion (3.2 eV).
TL;DR: The phonon-dispersion relations of USe and UTe has been determined by the inelastic scattering of thermal neutrons and Elastic constants, derived from the slopes of the dispersion relations and from ultrasound velocity measurements, have been determined.
Abstract: The phonon-dispersion relations of USe and UTe have been determined by the inelastic scattering of thermal neutrons. All existing phonon measurements for the UX series, viz., UC, UN, UAs, USb, US, USe, and UTe, have been fitted to the rigid-ion and shell models and dispersion relations have been predicted for UP. The U-X force constants dominate the lattice dynamics and are nearly constant for the series, whereas the U-U force constants vary systematically from being large and positive for the compounds with the smallest lattice parameter to being negative for the chalcogenide series. The negative U-U force constant is identified with destabilizing f-d interactions. Elastic constants, derived from the slopes of the dispersion relations and from ultrasound velocity measurements, have been determined. The bulk modulus decreases unusually rapidly as the lattice parameter increases and is in fair agreement with band-structure calculations.
TL;DR: In this article, the authors measured the flooding limits in countercurrent air-water flow through pipe elbows consisting of an upper vertical leg and a lower leg which is horizontal or slightly inclined, and found that flooding is caused by unstable wave formation (slugging) at the hydraulic jump which forms in the lower pipe limb close to the bend.
TL;DR: Results demonstrate the feasibility of using electron beam pretreatment for enzymatic hydrolysis of a softwood and the amount of reducing sugar formed by Trichoderma cellulase increased with increasing level of irradiation.
Abstract: Spruce wood chips were irradiated with 4-MeV electrons using the Chalk River Electron Test Accelerator. The irradiation pretreatment increased the susceptibility of wood to be crushed to a fine powder and consequently increased the surface area for enzymatic action. The amount of reducing sugar formed from treated chips by Trichoderma cellulase increased with increasing level of irradiation and reached a maximum value (over 90%) at approximately 2 mGy. Results demonstrate the feasibility of using electron beam pretreatment for enzymatic hydrolysis of a softwood.
TL;DR: In this article, a comprehensive review of the electromagnetic neutron-atom interactions with particular emphasis on the question of the extent to which the secondary interactions are already included implicitly in the scattering lengths obtained from accurate neutron optical measurements, which one finds listed in data tables, and the conditions under which explicit corrections for the residual secondary interaction are required in the analysis of neutron diffraction and inelastic scattering data for condensed matter.
TL;DR: The boiling crisis is characterized by either a sudden rise in surface temperature, caused by the heated surface being covered by a stable vapor film (film boiling), or by small surface temperature spikes, corresponding to the appearance and disappearance of dry patches (transition boiling).
Abstract: Fuel sheath temperatures in water-cooled nuclear reactors are usually near the saturation temperature of water. However, during an accidental increase in power, or a decrease in flow and pressure, deterioration in heat transfer is possible. It occurs when the surface temperature increases to such a high level that the heated surface can no longer support continuous liquid contact. This phenomenon is usually referred to as the boiling crisis (or dryout) and the corresponding heat flux as the critical heat flux (or CHF). The boiling crisis is characterized by either a sudden rise in surface temperature, caused by the heated surface being covered by a stable vapor film (film boiling), or by small surface temperature spikes, corresponding to the appearance and disappearance of dry patches (transition boiling).
TL;DR: The irreversible rhabdophane → monazite transformations on heating rare earth (La-Dy) phosphates occurred at higher temperatures (500 −900°C) than dehydration (100 −400°C), and were found to be exothermic as discussed by the authors.
TL;DR: In this paper, the adsorption of oxygen on Ni(110) was investigated by nuclear reaction analysis (NRA), XPS, Δφ, temperature programmed reaction spectroscopy (TPRS) and LEED.
TL;DR: The results on light transmission in D2O indicate that a large 1000-Mg heavy water Cherenkov detector constructed for the purpose of neutrino detection is not limited by the attenuation length of radiation in the D1O.
Abstract: A long-path-length transmission cell has been used to measure the attenuation coefficients of purified H2O and D2O at various wavelengths between 250 and 580 nm. The principles governing the procedures and corrections for various sources of light attenuation in the transmission cell components are discussed. Detailed chemical histories of the H2O and D2O samples are given. The measured attenuation coefficients of H2O are lower than those of many previous determinations and, where comparable, are close to the record low values of Quickenden and Irvin [
J. Chem. Phys.72,
4416 (
1980)]. The measured attenuation coefficients of D2O are the lowest yet achieved and range from 32 × 10−4 cm−1 at 254 nm down to 1.1 × 10−4 cm−1 at 578 nm, attesting to the low level of impurities in our D2O. These results on light transmission in D2O indicate that a large 1000-Mg heavy water Cherenkov detector constructed for the purpose of neutrino detection is not limited by the attenuation length of radiation in the D2O.
TL;DR: In this article, the steady state release of active noble gas and iodine from defective fuel elements is described either in terms of a kinetic or a diffusion model, assuming a diffusional release in the fuel.
Abstract: The steady-state release of active noble gas and iodine from defective fuel elements is described either in terms of a kinetic or a diffusion model. Both models assume a diffusional release in the fuel. Transport of fission products in the fuel-to-sheath gas is represented either by a first-order rate process or diffusion process, and is characterized with an escape-rate constant or diffusion coefficient, respectively. The kinetic model predicts a release dependence on the decay constant of lambda /sup -1/2/ to lambda /sup 3/2/. The diffusion model predicts a dependence of lambda /sup -1/. Observed release data from inpile loop experiments, for a wide range of defect states, confirm the predictions of the models. A fitting of the model to the measured data yields estimates of the empirical diffusion coefficient in the fuel matrix, and the scape-rate constant or diffusion coefficient in the fuel-to-sheath gap. Evaluation of the fitted parameters enables the various rate-controlling processes to be deduced as a function of the defect size.
TL;DR: Oxygen hydrate was prepared by reacting oxygen with deuteriated ice at high pressure and its structure was examined with powder neutron diffraction in this paper, where it was found to crystallize in the cubic space group and formed type II structures rather than type I structures.
Abstract: Oxygen hydrate was prepared by reacting oxygen with deuteriated ice at high pressure. Its structure was examined with powder neutron diffraction. It was found to crystallize in the cubic space group
$$Fd\bar 3m$$
witha=17.070(1) A. The formation of the type II structure rather than type I can be attributed to the larger Langmuir constant of sorption for the oxygen molecules in the 12-hedral cages. The encaged oxygen molecules are orientationally disordered. A comparison of the oxygen thermal parameters in both cages suggests the existence of local potential minima in the 16-hedral cages.
TL;DR: In this article, the authors measured the isotope activity ratios in the 238 U decay series for core samples obtained from boreholes up to 1-km depth in the Eye-Dashwa Lakes granite pluton, Atikokan, northwest Ontario, Canada.
Abstract: Measurements of isotope activity ratios in the 238 U decay series have been made for core samples obtained from boreholes up to 1-km depth in the Eye-Dashwa Lakes granite pluton, Atikokan, northwest Ontario, Canada. This work was done to determine the significance of recent radionuclide migration in plutonic rocks for the Canadian Nuclear Fuel Waste Management Programme. Most samples displayed secular equilibrium between 238 U, 234 U, 230 Th and 226 Ra, indicating that there has been no significant radionuclide migration in these samples over periods as long as the last 1 Ma. Disequilibrium was observed in some altered near-surface and deeper fracture-filling mineral samples with 234 U deficiencies of up to 20%. A similar deficiency of 226 Ra was found at ∼ 1-km depth in a gypsum-infilled core sample. These results indicate that U and Ra leaching by groundwater has occurred within periods 1 Ma and 8 ka ago, respectively. One instance of 226 Ra excess was found at 94-m depth, indicating deposition of 226 Ra in the last 8 ka. All cases of disequilibrium involved fracture-infilling minerals or altered granite cores from fracture zones, indicating that radionuclide migration occurred via fractures. Examples were found, however, of altered samples or mineral infillings that showed no detectable disequilibrium. These locations have been closed to migration in the last 1 Ma. Relative age estimates are made for some of the infilling minerals, based on their U-series isotopic characteristics.
TL;DR: In this article, the ability of sphene to retain certain radionuclides over geological time is examined using observed properties and age measurements of natural sphenes, showing that sphene ages and the estimated age of crystallization of the host rocks or vein infillings, except where subsequent metamorphim had reset the sphene age.
TL;DR: Copper, zinc superoxide dismutase was isolated from human red blood cell hemolysate by DEAE-Sepharose and copper chelate affinity chromatography and resulted in a purification factor of about 60-fold.
01 Jan 1986-International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
TL;DR: In the preceding meeting on solid state nuclear track detectors, a qualitative description was given (Ing and Birnboim, 1984) of a novel neutron detector consisting of microscopic droplets of superheated liquid dispersed in a firm elastic polymer as discussed by the authors.
01 Jan 1986-International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
TL;DR: In this article, the response of CR-39 to protons was studied as a function of energy and direction, and the critical angle to the normal, beyond which protons are not detected, is substantially smaller for electrochemical etching than for chemical etching.
01 Mar 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the specific energy loss for 23 carbon targets at low velocity, v < v 0, was measured using a Monte Carlo calculation to determine the elastic energy loss appropriate to the experimental conditions.
Abstract: We have measured the specific energy loss, ΔE/ΔX, for 23 projectiles in carbon targets at low velocity, v < v0. We have used a Monte Carlo calculation to determine the elastic energy loss appropriate to the experimental conditions. The electronic stopping values derived from our measurements show a marked oscillation in Z1, the projectile atomic number, and depend on the target thickness. Our data are compared to other measurements in the same velocity regime.
TL;DR: In this article, the authors developed a theoretical model by which the flooding limits for this elbow geometry can be predicted, assuming that a smooth stratified flow exists in the lower limb of the elbow, with a free outfall at the exit Flooding is assumed to coincide with slug formation just downstream of the bend where the liquid depth is greatest.