Showing papers by "Chalk River Laboratories published in 1986"
TL;DR: In this paper, annealed Zircaloy-2 and 4 irradiated to lower fluences were examined using transmission electron microscopy and showed the presence of long 〈 c 〉 component dislocations not present prior to irradiation.
95 citations
TL;DR: The morphology and composition of oxide films formed on type 304 stainless steel surfaces exposed to 300°C water at pH 10 have been examined in this paper, where a correlation was found between oxide film thickness and average crystallite size.
89 citations
TL;DR: In this article, the effect of sintering heat treatments on the tensile properties of the cobalt-chromium casting alloy specified by ASTM F75-76 was investigated, and two methods were found which would reduce the amount of this brittle solid: modifying the heat treatment to include a slow cooling step to temperatures below that at which incipient melting first occurred; and reducing the carbon content of the alloy.
Abstract: Porous-surface-layered surgical implants may be produced by sintering at elevated temperatures. An investigation was undertaken to determine the effect of these sintering heat treatments on the tensile properties of the cobalt-chromium casting alloy specified by ASTM F75-76. Specimens which were given a sintering treatment and then rapidly cooled from elevated temperature were found to lack ductility. This was due to the incipient melting of an interdendritic material which was subsequently retained in the grain boundaries as a brittle solid after quenching. Two methods were found which would reduce the amount of this brittle solid: (i) modify the heat treatment to include a slow cooling step to temperatures below that at which incipient melting first occurred; and (ii) reduce the carbon content of the alloy. Reduced-carbon alloys gave the greatest post-sintering ductility, but showed a lower 0.2% yield stress. The techniques of thermal activation analysis were used to investigate the effect of second phases upon the initial low-strain work-hardening rates and the 0.2% yield stress. It was found that the work-hardening rate from the elastic limit to a total strain of about 0.01 to 0.02 depends, in part, directly on the volume fraction of second phase.
33 citations
01 Apr 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: The Bi content of several Series II Rutherford backscattering (RBS) standards (Bi-implanted silicon) has been calibrated by comparison with an earlier Series I standard and also by an independent measurement of the absolute RBS yield as mentioned in this paper.
Abstract: The Bi content of several Series II Rutherford backscattering (RBS) standards (Bi-implanted silicon) has been calibrated by comparison with an earlier Series I standard and also by an independent measurement of the absolute RBS yield. Both methods agree within ± 1% on a given sample. Independent measurements at each of CRNL and CBNM Geel indicate Bi implant uniformity better than 1% across each target and good agreement (± 1%) in the absolute Bi content of exchanged samples. Most of the Bi assays agree within the combined counting statistics (± 1%) with Geel's previous Series II calibration value of (4.75 ± 0.07) × 1015 cm−2; however,two targets were found to contain ∼ 4% more Bi. Harwell's implantation records show that the two higher dose samples were both cut from the same implanted wafer and that poor vacuum conditions during implantation may have been responsible for this excess dose. Since the implantation history of each wafer has been well documented, there should be no difficulty in establishing which calibration value is appropriate for an individual standard.
31 citations
01 Apr 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the redistribution of As from a shallow As-implant (5 keV) in Si following oxygen bombardment has been studied by grazing exit RBS, and the results indicate that the As-atoms segregate at the oxide-silicon interface.
Abstract: The redistribution of As from a shallow As-implant (5 keV) in Si following oxygen bombardment has been studied by grazing exit RBS. The oxygen bombardment was performed in an ion implanter (12.5 keV O+, room temperature and 40 K), and a reactive ion elcher (1.7 keV O+2). For 12.5 keV O+ bombardment the As redistributes very rapidly in the sample; displacements up to 50 nm are observed. Implantation at 40 K shows only a very small reduction in spreading of the As distribution indicating a very low activation energy for the defect-induced diffusion. Bombardment with 1.7 keV O+2 does not broaden the internal As distribution as much as at 12.5 keV O+ but our results indicate that the As-atoms segregate at the oxide-silicon interface. Enhanced segregation in the reactive ion etcher results in a much larger decay length than under SIMS-bombardment conditions.
22 citations
TL;DR: In this article, the authors made estimates of transmitted global radiation under a red pine canopy, using three mobile and three stationary pyranometers above the forest floor and one that was placed above the canopy.
21 citations
TL;DR: The thermal neutron capture cross section of 232Th has been measured relative to that of 197Au as discussed by the authors, where gold, thorium metal, and thoria were irradiated together in the NRU reactor thermal column.
Abstract: The thermal neutron capture cross section of 232Th has been measured relative to that of 197Au. Foils of gold, thorium metal, and thoria were irradiated together in the NRU reactor thermal column. ...
20 citations
TL;DR: In this article, a heavy-water Cerenkov detector was proposed to measure the 8B solar neutrino flux, to identify neutrinos oscillations and to watch for gravitational collapse.
Abstract: The proposal to build a heavy-water Cerenkov detector deep underground is discussed. The main physics objectives are to measure the8B solar neutrino flux, to identify neutrino oscillations and to watch for gravitational collapse. The measurements of the sources of background and the optical properties of heavy water, which are necessary to prove the feasibility of the detector, are reported. The present status of the project is indicated.
11 citations
TL;DR: Activities of six enzymes from extracts of separated embryos and gametophytes of tamarack seeds were assayed at various stages of imbibition and germination, with the rate of increase of enzyme activity increasing at a faster rate with emergence of the radicle and subsequent growth of the seedling.
Abstract: Activities of six enzymes from extracts of separated embryos and gametophytes of tamarack [Larix laricina (Du Roi) K. Koch] seeds were assayed at various stages of imbibition and germination. On a per seed part basis, activities of 6-phosphogluconate dehydrogenase (6-PGD, EC 1.1.1.44), glucose-6-phosphate dehydrogenase (G-6-PD, EC 1.1.1.49), malate dehydrogenase (NAD+–MDH, EC 1.1.1.37), isocitrate dehydrogenase (NADP+–IDH, EC 1.1.1.42), soluble peroxidase (PER, EC 1.11.1.7), and acid phosphatase (ACP, EC 3.1.3.2) from both the embryo and gametophyte tissues generally increased slowly, following cold stratification for 30 days and imbibition under germinating conditions for 5 days, but then increased at a faster rate with emergence of the radicle and subsequent growth of the seedling. The rate of increase of enzyme activity was highest for PER. Soluble protein levels also increased with imbibition and germination, with about 3 times greater levels present in the gametophyte than in the embryo. Heat inactivation experiments showed that, except for G-6-PD, activities were stable up to 40°C. Inactivation occurred at lower temperatures for G-6-PD, while higher temperatures were required for PER. Incubation of extracts for 7 days at 4°C indicated that loss of enzyme activity was greatest for G-6-PD (3.9% remaining) and least for PER and ACP (94 and 95% remaining, respectively).
10 citations
TL;DR: Ion beam techniques were applied for detection and depth profiling of hydrogen isotopes (H, D and T) under the surface (∼1 μm) of solid lithium blanket materials (Li 2 0 and LiAlO 2 ).
5 citations
01 Jan 1986
05 Aug 1986
TL;DR: In this article, a pyroelectric or disc calorimeter was placed behind a Beryllium-copper mask to measure the energy parameters required for ablation of different depths of corneal tissue.
Abstract: Nanosecond pulses from CO2 TEA lasers, (A= 10,600nm,T = 3ns, 4Ons and 200ns), HF lasers (X= 2,744nm,1'= 300ns) and excimer lasers (N= 193nm,T= 15ns) were focussed (either through cylindrical quartz lens or 0.001" thick Beryllium-copper mask etched with slits of various widths) onto the corneas of enucleated dog eyes. Pulse energies were measured with a pyroelectric or disc calorimeter, placed behind the mask. The mask unit area and the number of pulses were varied to determine energy parameters required for ablation of different depths of corneal tissue. Ultrastructural studies of corneal incisions made with knife were compared with those made by laser pulses.
TL;DR: A method is described for determining stable cobalt concentrations in fish flesh and bone using polarized Zeeman effect graphite furnace atomic absorption spectrometry (ZAAS) and the mean cobalt content calculated was 4.23 +/- 1.0 microgram Co.
Abstract: A method is described for determining stable cobalt concentrations in fish flesh and bone using polarized Zeeman effect graphite furnace atomic absorption spectrometry (ZAAS). Cobalt analysis on freshwater fish flesh samples (log dry weight) required predigestion and wet-ashing at 70–80°C. Cobalt is chelated with ammonium pyrrolidine dithiocarbamate (APDC) extracted with methyl isobutyl ketone (MIBK) and analysed by ZAAS. The mean cobalt content calculated from the standard additions method using three replicate fish flesh samples was 4.23 ± 1.0 μg Co. Kg−1 (dry weight) Analyses were also carried out on flesh and bone samples from similar sized fish, of the same species, taken from three area lakes.
TL;DR: In this article, a combination of measurements of the O and P shell internal conversion coefficients of the 35.8 keVγ-line in198Au and of197Au Mossbauer spectra in thin films of metallic gold, Au0.20Sc 0.72 and Au 0.06Cr 0.92, the 6s electron density at the gold nuclei in these hosts was derived.
Abstract: From a combination of measurements of the O and P shell internal conversion coefficients of the 35.8 keVγ-line in198Au and of197Au Mossbauer spectra in thin films of metallic gold, Au0.20Sc0.72 and Au0.06Cr0.92, the 6s electron density at the gold nuclei in these hosts was derived and an estimate of the change of the nuclear charge radius for the Mossbauer transition was made. The result is considerably larger than previously derived values, with which it can only be reconciled if a large shielding effect of the 5d electrons on inner shells exists.
01 Apr 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the range and range straggling of 132 Xe + ions in Al and Si were calculated from implantation profiles obtained by Rutherford backscattering of 4 He +.
Abstract: The range and range straggling of 132 Xe + ions in Al and Si were calculated from implantation profiles obtained by Rutherford backscattering of 4 He + . The data are compared with LSS calculations [1] and some earlier results [2].
01 Oct 1986-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the enhancement in ion backscattering surface peak yield at 180° has been measured for 0.5 MeV and 1.0 MeV He + incident upon the direction of a near (110)Au single crystal at 40 K, 170 K, and 300 K.
Abstract: The enhancement in ion backscattering surface peak yield at 180° has been measured for 0.5 MeV and 1.0 MeV He + incident upon the 〈110〉 and 〈112〉 directions of a near (110)Au single crystal at 40 K, 170 K, and 300 K. The normal (RBS) surface peak yield observed at 150° is in agreement with that calculated by computer simulation using a modified 1 × 2 surface structure for (110)Au, including the effects of enhanced vibrations in the surface layers and vibration correlations. A theoretical description of the enhanced yield at 180°, based on a two-atom scattering model, is given. The theoretical enhancement from a 1 × 2 surface is in good agreement with the observations.
TL;DR: In this article, a part of the rich medium-spin (I ⩽ 35 2 ) level structure observed can be characterized to belong to shell model multiplets v f 3 7 2, v h 9 2 f 2 7 2 and v f 7 2 × 3 −.
TL;DR: In this article, the authors address three aspects of the surface analytical experiment which are felt to be particularly crucial in characterizing corrosion mechanisms: chemical speciation, microscopic analysis and improved control of experimental conditions.
Abstract: This paper addresses three aspects of the surface analytical experiment which are felt to be particularly crucial in characterizing corrosion mechanisms: chemical speciation, microscopic analysis and improved control of experimental conditions. X-ray Photoelectron Spectroscopy (XPS or ESCA) has been particularly effective in differentiating chemical species. The major chemical use of XPS is limited however to the outer surface of the film. Depth profiling by ion bombardment frequently degrades the chemical information available in the film interior and at the metal-oxide interface, and this is often where corrosion mechanisms are established. Mechanical methods of film penetration are thus encouraged to use XPS to its maximum capability. Microscopic analysis of corrosion surfaces using Scanning Auger Microscopy (SAM) or Secondary Ion Mass Spectrometry can reveal effects such as grain boundary segregation and oxide nucleation. Another important aspect of corrosion film analysis is the preparation of the metal surface itself. The oxidized surface can be strongly influenced by preparation artefacts such as cold work or impurities. Three different studies are used to illustrate these aspects: (i) the analysis of a molybdenum inhibitor layer on a steel surface; (ii) the study of corrosion product release from 304-stainless steel; and (iii) the effects of H+ ion bombardment to anneal mechanical work on Ni-Cr alloy surfaces, prior to oxidation.
01 Jan 1986
TL;DR: In this paper, the authors proposed a solar neutrino observatory in a nickel mine near Sudbury, Canada, which is both attractive and timely because of the temporary surplus of over 1000 Mg of D2O stockpiled for the Canadian-designed nuclear power reactors.
Abstract: The construction of a solar neutrino observatory in a nickel mine near Sudbury, Canada, has been proposed[1]. This proposal is both attractive and timely because of the temporary surplus of over 1000 Mg of D2O stockpiled for the Canadian-designed nuclear power reactors, of the large rock overburden at the INCO mine and of the scientific interest in the solar neutrino flux and neutrino oscillations. The primary objective of the experiment is to measure the incident electron neutrino (νe) spectrum above 5 MeV in real time with energy and directional resolution. It is also expected that the total neutrino (νx) flux above 2.2 MeV can be measured thereby providing important information concerning neutrino oscillations. The observatory will also be a sensitive instrument for measuring neutrinos produced by cosmic rays, solar flares and collapsing stars.
01 Jan 1986
TL;DR: In this article, the authors describe the importance of estimating the exposures that might arise and their occurrence frequencies for planning to meet such emergencies to have estimates of the exposures and of their occurrence frequency.
Abstract: Specifying the temporal and spatial variability of atmospheric dispersivity is an important part of a general understanding of the meteorological aspects of air pollution and its social and economic implications. There are several reasons why, two of which may be mentioned here. For steady sources the occasional occurrence of pollutant concentrations well in excess of the long-term mean may be, and often are, the main cause of resulting harm or nuisance. Accidental releases of toxic substances over relatively short periods can produce locally serious threats to the population. It is important for planning to meet such emergencies to have estimates of the exposures that might arise and of their occurrence frequencies.
01 Jan 1986
TL;DR: In this paper, the authors used a wind rose to predict the ranges of potential exposures in the surrounding area, particularly the upper ranges, in the case of a new or planned installation, where on-site data do not exist.
Abstract: There is currently much interest in planning responses to accidental releases of toxic materials to the atmosphere. To do this effectively requires prior knowledge of the magnitudes and occurrence frequencies of potential exposures. This in turn requires some knowledge of what might be called the ‘climatology’ of air pollution events. Several workers have reported the frequency distributions of concentrations of tracer materials in urban centres or around single isolated stacks. Various well known statistical distributions have been fitted to such data to describe the observations in terms of a small number of parameters. Such studies dealt with observed concentrations but in the case of a new or planned installation, on-site data do not exist and it is then necessary to predict the ranges, particularly the upper ranges, of potential exposures in the surrounding area. Climatological data from which can be derived estimates of the occurrence frequencies of weather or stability classes, and a wind rose are used for the purpose.