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Nuclear Science, IEEE Transactions on

Issue 1 • Date Feb. 1972

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Displaying Results 1 - 25 of 145
  • [Front cover]

    Page(s): c1
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  • IEEE Transactions on Nuclear Science

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  • Table of contents

    Page(s): 1 - 6
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  • Symposium Committee

    Page(s): 7
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  • Session Chairmen

    Page(s): 8
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  • The Nucleus

    Page(s): 9
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  • The Significance of Tritium Releases to the Environment

    Page(s): 27 - 39
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    Tritium is produced naturally and was present in low concentrations in precipitation and natural bodies of water before atmospheric testing of nuclear weapons. Other sources of tritium are now present from which tritium is released to the environment. Nuclear reactor tritium production, according to recent estimates, will equal natural tritium production before the year 2000. Predicted increases of tritium in the environment will take place first on a local ecological level and then appear on a biospheric level. Tritium introduced into the environment as THO will move through ecological systems in the same manner as stable water. Tritium will enter the hydrologic cycle either via evapo-transpiration or the surface bodies of water. Ecological experiments have been conducted to determine the movement of tritium in the environment. Field-grown plants were exposed to liquid and vapor THO for periods of one-half and one hours. Tritium concentrations were determined in leaf samples collected after exposure for periods of time up to 45 days. Tritium decays rapidly in the plant species studied and exhibited a three component half-life when plants were exposed to THO vapor. The length of exposure, and sources of THO in the soil affect the half-time of tritium in the plant tissues. Data produced in ecological experiments on tritium movement are used in a theoretical consideration of acute and chronic vapor releases of tritium in an agricultural environment. View full abstract»

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  • Computer Processing of Radiographic Images with the Finite Fourier Transform

    Page(s): 40 - 45
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    This paper considers the optimal design and implementation of two-dimensional, nonrecursive digital filters for use in the processing of radiographic images. A stochastic system model is used for the image-forming process, and the filter is designed to a mean-square error criterion. Both the design algorithm and filter realization are mechanized by using a Fast Fourier Transform code, thereby ensuring the computational efficiency of the method. View full abstract»

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  • Laminographic Excitation Camera for Thyroid Imaging

    Page(s): 46 - 50
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    We describe a camera for the laminographic imaging of the thyroid without administration of radiopharmaceuticals to the patient. An external source of gamma-rays is used to excite the characteristic x-rays of natural iodine in the patient's thyroid, source geometry limiting excitation to well-defined planes. The camera consists of a parallel hole collimator and a xenon-filled proportional wire chamber with digitized readout of coordinates. Pulse height selection is provided to limit events in the image display to a selected energy range. We estimate that the system will obtain high resolution laminography for local exposures on the order of 1 to 5 rad, with exposure times of a few minutes for each laminogram. View full abstract»

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  • Avalanche Detector Arrays for in Vivo Measurement of Plutonium and Other Low Activity, Low Energy Emitters

    Page(s): 55 - 63
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    Arrays of silicon avalanche detectors are being used for Ti vivo detection and measurement of low energy radiation in very small activities at room and body temperatures. Plutonium may be measured (via the 13.5-20 keV daughter uranium L x-rays) with an array of three 1 cm2 avalanche detectors in the esophagus, examining the thoracic lymph nodes which accumulate inhaled PuO2. The three detectors used in this array together provide uniformity of sensitivity to a source at any angle around the longitudinal axis of the array; using three independent signal processing systems, the array can also provide localization information. Plutonium scratches and puncture wounds may be inspected for contamination and the plutonium may be localized using a specially fabricated 1/8 inch diameter avalanche detector. With this configuration, the Minimum Detectable Amount (MDA) of Plutonium-238 (84% confidence level and four minute count) measured through 2 mm of tissue is 1 nCi. Early results of improved uniformity and resolution with the avalanche detector have shown promise of increased efficiency per unit area of detector face. A step toward unambiguous detection by making better use of the nanosecond speed of avalanche is described. View full abstract»

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  • Instruments and Methods for Characterizing Radioactive Aerosols

    Page(s): 64 - 75
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    The importance of characterizing aerosol properties in evaluating the behavior and potential hazards of radioactive aerosols is emphasized. The instruments and techniques for studying the properties of radioactive aerosols including special properties such as chemical form, solubility, and state of electrostatic charge are discussed. The uses of electrostatic and thermal precipitators for electron-microscopic observations and measurements, and of various aerodynamic samplers such as impactors, centripeters, cyclones, and aerosol centrifuges for study of size distribution, particle density and shape factors, and relative specific activity are reviewed. The conventional terminology for describing particle size and size distributions is described with emphasis on the relationships to the factors associated with the potential hazards of inhaling radioactive aerosols. View full abstract»

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  • A Gamma Ray Probe for the Detection of Ocular Melanomas

    Page(s): 76 - 80
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    A specially designed scintillation probe has been assembled and applied in a promising diagnostic study of malignant melanoma in the human eye. When used in conjunction with a new radiopharmaceutical agent recently developed at The University of Michigan, 125I labeled chloroquine analog, the probe permits simple and nonsurgical gamma ray counting as a substitute for more elaborate techniques required in 32p beta scanning for the same prupose. Preferential uptake of the agent in ocular melanomas has been previously reported using a modified 5-inch NaI (Tl) crystal scanner as the detector. We have realized a substantial improvement in both sensitivity and reproducibility by substituting a hand-held probe placed in contact with the patient's closed eyelid. The counting rate over each eye is followed for a period ranging from 3 to 21 days after dosage. A melanoma in one eye gives rise to an enhanced rate over that eye. Data are presented on a total of 12 patients, including two with confirmed ocular melanomas. In both of these cases, the involved eye consistently shows a significantly greater activity than the opposite eye. In the remaining cases considered "negative", measured eye-to-eye asymmtries are much lower, and a measure of the variance associated with these cases is presented. View full abstract»

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  • An Improved X-Ray Intensifying Screen

    Page(s): 81 - 86
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    It is shown experimentally that a new x-ray phosphor Gb2O2S: Tb used as an intensifying screen with the common blue-sensitive x-ray photographic film can increase sensitivity to medical x rays by about a factor of 2 relative to CaWO4 which is currently used. It is also shown that a sensitivity increase of about 20 is possible if photographic film is optimized to the Gd2O2S: Tb emission. View full abstract»

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  • An Interactive Chromosone Scanning System

    Page(s): 87 - 90
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    To the relatively few groups actively engaged in automated chromosome studies, the title of this paper is rather self explanatory because it proposes to address a problem which has become apparent to all of us who have sought to automate cell analysis. The need for human interaction implies that our automated procedures are not error free and require some degree of human verification and correction within the procedure. Indeed this is so. The fact that a problem exists may be attributed to an over-optimistic concept of the capability of machines to duplicate apparently simple human activity. It follows that certainly one purpose of this paper would be to discuss the need for human interaction in automated chromosome analysis and to suggest an approach to the question of where and how interaction should be implemented. However, so that others who may be unfamiliar with automated chromosome analysis can achieve a better understanding, the format of this paper includes a brief overview of human cytogenetics along with an attempt to treat the significance of chromosome abnormalities in terms of the need for population studies. Unfortunately, the justification for automated procedures in cytogenetics has been based upon the need to reduce the labor and tedium involved in large studies without the need for the large studies themselves being clearly established on a cytogenetic basis. View full abstract»

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  • A Survey of Radiation Damage in Semiconductor Detectors

    Page(s): 91 - 99
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    Examples of radiation damage in lithium-drifted detectors, lithium-drifted silicon detectors, and high-purity germanium detectors are discussed. The general patterns of damage, lithium-precipitation, annealing and recovery of detectors are outlined, and the observations are discussed. View full abstract»

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  • Electronic System Hardening Approaches

    Page(s): 100 - 103
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    First Page of the Article
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  • Environmental Radiation, Past, Present, and Future

    Page(s): 104 - 106
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    At present, as in the past, the bulk of environmental radiation comes from natural sources, cosmic radiation, and natural radioactivity. The normal dose to man from natural sources ranges from about 60 to 250 mrads/year. Fallout from weapons testing has provided as much as 20 to 25 mrads/year during the early to mid-1960's. At present, medical uses provide 20 to 100 mrads/year to the average individual in the U.S. Radiation to the general population from nuclear power is insignificant at present. With the trend toward improved technology in the control and containment of radioactivity from nuclear facilities, future levels should not exceed those observed from fallout. Improvements in radiological procedures should materially reduce unnecessary exposure from this application. View full abstract»

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  • Sensitivity Problems in Biological and Environmental Counting

    Page(s): 107 - 116
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    Analysis of biological and environmental samples differs from other physics applications in the need for very high sensitivity. A number of factors, including efficiency, geometry, resolution, and an interrelation of these, all affect sensitivity. An analysis, based on both experimental data and computations, indicates that in the range of equal detector volumes < 40 cm3, planar detectors are to be preferred over coaxial detectors due to their much better ability to quantitate data at energies below 500 keV without loss of performance at higher energies. For equal detector volumes in excess of 40 cm3, coaxial detectors may be preferred for high energy use due to their better resolution, but performance at lower energies will still favor the planar detectors. View full abstract»

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  • The Measurement of Environmental Levels of Rare Gas Nuclides and the Treatment of Very Low-Level Counting Data

    Page(s): 119 - 126
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    The radioactive isotopes of the rare gases provide unique geophysical and mete-orological information concerning the properties and history of our (atmospheric) environment. The extremely low activity levels, however, require very special methods of measurement, experiment design, and data interpretation. Following an examination of the decay characteristics and atmospheric abundances of Kr and Ar radioisotopes, the question of experiment planning and data interpretation in the "extreme Poisson" (few counts) region is considered. A reduced activity plot is offered as an aid for making rapid evaluations and decisions in this region. The concept of an effectively zero background is illustrated by means of atmospheric 37Ar data. Finally, the problem of the blank is examined, and the merits and deficiencies of three alternative approaches are discussed, again with special emphasis on the measurement of 37Ar in Nature. View full abstract»

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  • The Direct Evaluation of Low Level Counting Techniques Employing Ge(Li) Detectors

    Page(s): 127 - 134
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    The low level counting capabilities and critical parameters of Ge(Li) gamma ray spectrometers are investigated using an expression for the spectrometer sensitivity limit. The significance of the counting parameters involved and the practical means by which they may be optimised have also been considered. A comparison method is used to evaluate the effectiveness and behaviour of several available counting techniques (e.g. coincidence and anti-coincidence methods). View full abstract»

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  • Investigation on the Background of a Ge(Li) Detector

    Page(s): 135 - 140
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    An experimental study has been performed to investigate the ultimate limit of the intrinsic background of a Ge(Li) detector. The results obtained in three runs under different experimental conditions are compared and discussed. A tentative interpretation of the various sources of background and of their relative contribution is given. From the measurements performed in an underground laboratory with an attenuation factor for cosmic rays of 106, the ultimate background level appears almost completely due to radioactivity present in the structural materials of the cryostat and shield. An important contribution is attributable to airborne radioactivity due to 222Rn daughters. View full abstract»

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IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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