Gamma-ray Scanning Research Articles

Automatic quality sorting of Picea abies logs with a gamma ray log scanner

A quality index for quality sorting of Norway spruce (Picea abies) has been developed. The quality index expresses the expected mean quality of the centerboards from the log. This quality index is based on property variables obtained when using a gamma ray scanner. A multivariate calibration method, PLS (partial least squares models in latent variables), was used. A training set of 2 000 graded centerboards coming from 1 000 selected spruce logs was used to create the model between measured property variables and the expected quality output. The model is tested with crossvalidation within the training set, and expected precision of aim is 65% overall correct classification and a 70% correct classification for dimensions 150 to 225 mm. It can be utilized when sorting logs automatically with respect to the quality of the center boards.

Detection of Occlusion and Wall Degradation in Fire Protection Piping Systems Using Non-Invasive Gamma-Ray Techniques

Water piping occlusion categories are reviewed. Determination of sprinkler piping occlusions and pipe wall degradation are investigated by using a non-invasive gamma-ray scanning technique. Theoretical and experimental investigations illustrate that the technique is capableof revealing the thickness, location, density and shape of substantial solid occlusions without requiring any prior knowledge about the pipe interior. Major degradation of the pipe wall can also be determined with this technique, provided the scanning speed and collimator thickness are selected properly. While theoretically feasible, determination of thin and porous occlusions could not be achieved experimentally. In theory, if the beam of gamma-ray is very thin and the scanning speed is very small, thin and porous occlusions can be detected.

Upward displacement of the centre of gravity in paraplegic patients

The centres of gravity of 44 complete chronic spinal cord injured patients and 24 normal subjects were measured using a gamma ray scanner (Barycentremetre). The results are expressed as a percentage of body length and as anatomical level. The mean weight of paraplegic patients was 12kg less than the controls. The centre of gravity was 5% of body length higher in the paraplegic patients than in the controls, equivalent to 3 to 4 vertebrae level. The importance of such changes in the centre of gravity for the design of stable wheelchairs is discussed.

Isometric representation of data obtained using a Compton gamma-ray scanner : Bridge, B.; Harirchian, F.; Imrie, D.C.; Mehrabi, Y.; Meragi, A.R. Nondestructive testing communications, Vol. 4, No. 1, pp. 1–10 (1988)

Isometric representation of data obtained using a Compton gamma-ray scanner : Bridge, B.; Harirchian, F.; Imrie, D.C.; Mehrabi, Y.; Meragi, A.R. Nondestructive testing communications, Vol. 4, No. 1, pp. 1–10 (1988)

Heat and Moisture Transfer Characteristics of Compacted Mackenzie Silt

Abstract The heat and moisture transfer characteristics of a silt from the Mackenzie River Valley have been determined in a laboratory investigation. A dual gamma-ray scanner was used to measure the changes in density and volumetric moisture content along the soil samples. The coefficients of soil-water diffusivity under isothermal conditions and under temperature gradients have been obtained. The development of a calibration curve for the analysis of gamma-ray readings has been described. The shortcomings of the procedures used for the measurement of transport coefficients have been discussed.

Visualization on full spine radiographs of the anatomical connections of the centres of the segmental body mass supported by each vertebra and measured in vivo.

A gamma-ray scanner has been used to develop in vivo a rapid, noninvasive technique for the estimation of the mass of successive body scans, and the positions of the centres of those masses. The integrated data are computed to calculate the mass supported by each vertebra and the coordinates of the centre of these masses. These coordinates are transferred from the coordinate system of the gamma ray table to the coordinate system of the X-ray radiographs. In this way, the anatomical relations of the centres of these masses are visualized on the frontal and sagittal full spine radiographs. The method allowed the estimation of various biomechanical parameters such as the height of half the body mass or the compressive load on a specific vertebra. These new parameters were found to be similar to equivalent parameters in the literature. Therefore, these comparisons validate the method. Fourteen normal subjects were tested, and their mean data are proposed as reference.

A Mobile Gamma Scanning System for Detecting Radiation Anomalies

A mobile gamma-ray scanning system has been developed by Oak Ridge National Laboratory for use in the U.S. Department of Energy's remedial action survey programs. The unit consists of NaI(Tl) detectors housed in a specially equipped van. The system is operator controlled through an on-board minicomputer with data output provided on the computer video screen, strip chart recorders, and an on-line printer. Data storage is provided on floppy disk. Multichannel analysis capabilities are included for qualitative radionuclide identification. A /sup 226/Ra-specific algorithm is currently employed to identify locations containing residual radium-bearing materials.

A tomographic gamma-ray scanner for industrial applications

An experimental computerised tomographic (CT) gamma-ray scanner is being developed for the non-destructive testing of industrial objects. A micro-computer controlled traversing system steps the test object across a collimated gamma-ray beam the transmitted intensity of which is measured by a NaI(Tl) detector for a large number of beam paths both through the object and the surrounding air. These data are used to reconstruct an image of the scanned section in terms of a two-dimensional distribution of linear attenuation coefficients at the gamma-ray energy used. A 100 mCi 241Am source of 59.6 keV gamma-rays has been used initially in order to compare the performance with medical CT X-ray scanners.

A CAMAC gamma-ray scanning system

A flexible gamma-ray scanning system, based on a LeCroy 3500 multichannel analyzer and CAMAC modules, is described. The system is designed for making simultaneous passive and active scans of objects of interest to nuclear safeguards. The scanner is a stepping-motor-driven carriage; the detectors, a bismuth-germanate scintillator and a high-purity germanium detector. A total of sixteen peaks in the two detector-produced spectra can be integrated simultaneously, and any scan can be viewed during data acquisition. For active scanning, the 2615 keV gamma-ray line from a 232U source and the 4439 keV gamma-ray line from 9Be( α, n) 12C were selected. The system can be easily reconfigured to accommodate up to seven detectors because it is based on CAMAC modules and FORTRAN. The system is designed for field use and is easily transported. We present and discuss examples of passive and active scans.

Multi-energy gamma-ray automated scanning system

A CAMAC-based gamma-ray scanning system was used to measure the transmission through stacked attenuators for up to 16 different gamma rays. For each measurement, we obtained the transmission for gamma rays ranging in energy from 77 to 2614 keV. These transmission measurements were used to produce a set of linear equations that may be solved for either thickness or density of the discrete attenuators comprizing a given stacked assembly.

Correlation of the Cesium-134/Cesium-137 Ratio to Fast Reactor Burnup

The correlation of 134Cs/137Cs to burnup in irradiated fast reactor fuel pins was investigated using nondestructive precision gamma-ray scanning. This correlation was significant within individual ...

AN ATTEMPT AT EXPERIMENTAL VALIDATION OF MACROSCOPIC-SCALE MODELS OF SOIL MOISTURE EXTRACTION BY ROOTS

An experiment was conducted to test the validity of a mechanistic simulation model describing the process of soil moisture extraction by root systems, and to assess the quantitative importance of root hydraulic resistance in this process. Close-growing stands of ryegrass were raised in tubes packed with sand and loam, with and without the presence of a water table. The pattern of water uptake was monitored by gamma-ray scanning and tensiometry. Correspondence between measured and independently predicted uptake patterns could be greatly improved by assigning a relatively high value of root resistivity. Further improvement of the mechanistic model's predictive capability may require explicit formulation of conductive (axial) resistance in addition to absorptive (radial) resistance, as well, perhaps, as such important subsidiary factors as aeration, mechanical impedance, and distribution of nutrients in the soil profile.

Gamma-ray scanning of neutron activated geological sediments for studying elemental profile distributions

Gamma-ray scanning for application to elemental profile studies of geological samples was studied with a neutron activated Baltic Shield sediment. Profile distributions for seven elements were measured. The capabilities and limitations of gamma-ray scanning are discussed by comparing the results with profiles obtained after the mechanical subdivision of the sample and the activation of the appropriately sized separates.

Comparative studies on plastic scintillators — applications to low energy high rate photon detection

The possible uses of plastic crystals in high rate single counting experiments have been investigated. Two different plastic crystals were studied: a conventional plastic crystal (NE 111) and a tinloaded plastic crystal (5% Sn, NE140). It was found that the tinloaded plastic crystal had the same total absorption efficiency as a NaI(Tl) crystal of the same size for gamma energies below 60 keV. Both crystals have a decay time of a few nanoseconds. At 120 keV the total absorption efficiency relative to NaI(Tl) was about 40%. The high detection efficiency, in addition to the excellent time properties imply that the tinloaded plastic crystals are well suited for low energy high count rate experiments such as tomographic X- and gamma-ray scanning.

The effect of height of sample and confinement on the moisture characteristic of an aggregated swelling clay soil

The pore pressure/moisture content relationship of 0.5-1.0 mm aggregates of Narrabri soil, initially 1.66 cm high, was examined at 1/3 cm height intervals by means of dual source gamma ray scanning, for confined and unconfined conditions. In the unconfined sample, absorption and desorption of water to or from the interaggregate pore space occurred at less negative pore water pressures than in the confined sample. In the latter, the swelling aggregates deformed into the inter-aggregate pore space during absorption and reduced the size of the pores. In the unconfined sample, absorption into the inter-aggregate pore space occurred at less negative water pressures with increasing height in the sample. During absorption, bulk density decreased with height in the sample, and bulk density at all points within the sample decreased until pore water pressures were between -20 to - 10 cmH2O. At pore water pressures closer to zero, bulk density increased as the sample compacted under its own weight. During desorption, bulk density increased at all heights as the pore water pressures decreased from zero to - 8 cmH2O, because of isotropic stress imparted by the hanging water column. During this phase normal shrinkage occurred, therefore overburden potentials, and hence moisture potentials, could be calculated. Between - 10 and - 50 cmH2O, the inter-aggregate pore space drained rapidly, and no further increase in bulk density was detectable and hence moisture potential equates to manometric pressure. It was found that the derived moisture characteristics (� versus �) are different for different heights in the aggregate mass. This result is of consequence to the theory of hydrostatics in swelling media. In the unconfined sample, no differences in the pore water pressure/moisture content relationships occurred with height during absorption or desorption, and bulk density remained constant throughout. The application of these results to the behaviour of swelling soils in the field is briefly discussed. The use of dual source gamma ray scanning seems an essential tool for further investigations.

Gamma-Ray Scanning System for Barrels Containing Plutonium Waste

A system designed to perform quantitative assay of plutonium waste material in 30 to 55 gallon barrels is described. The system uses up to eight 2 in. × 2 in. NaI(Tl) detectors to make a detailed gamma ray scan of the barrel to be assayed. Barrels of 55 gallon size containing 239Pu waste and 30 gallon barrels containing 238Pu waste (from 238PuO2 isotopic heat source production) have been scanned with this system. Experience has shown that a barrel assay can be performed in 10 to 15 minutes to an accuracy of ±10%. The sensitivity of the system is one gram or better for 239Pu or 238Pu in low to medium density waste material.

Slow Pulses from Germanium Detectors

Slow pulses from various types of Ge(Li) detectors, i.e., a planar, a coaxial, a thin p+-contact planar, and a 'back-to-back' double planar detector, have been studied by using a gamma-ray scanning technique and a risetime selector. A large and abrupt increase in the counting rates of the slow pulses were observed when the n+-i and the i-p boundaries of these detectors were irradiated by a collimated gamma-ray beam. Slow pulses contributed to background counts in the pulse height distributions. Slow pulses from a deeply depleted n+-p detector made from a high-purity p-type germanium crystal were also investigated.

Insensitive zones in the intrinsic region of Ge(Li) coaxial detectors

Insensitive regions in the intrinsic volume of a double open ended coaxial Ge(Li) detector have been put in evidence and evaluated by using the gamma ray scanning technique with photons of different energy. Insensitive zones have been observed at both open ends of the diode, having circular geometry with a thickness increasing from the p core to the n + electrode. Their size is sensitive to the detector bias and can be reduced by a suitable warm up and by redrift cycles. Their existence is probably related to local imperfect compensation of the Li drifted germanium.

Characteristics of Coaxial Ge(Li) Detectors through Warm-Up and Re-Drift Cycles

Studies have been made of several cylindrical coaxial Ge(Li) detectors through various cycles of warming to room temperature and subsequent 'cleanup' redrift - all in high vacuum. Conventional double-openend detectors with an n+-layer on the outside and a p-type core were used. Using the gamma-ray scanning technique it was observed that (1) When not fully cleaned up (capacitance decreasing with increasing voltage) the i-layer thickness increased from the n-layer towards the p-core as voltage was increased. (2) After a warm-up period, part of the i-layer nearest the core was lost with a reduction in efficiency (18% at 500V for one detector after an 8 hour warmup period). (3) Cleanup re-drift following a warm-up period restored the original characteristics but the cleanup time varied with the crystal from which the detector was made.

GAMMA RAYS CAN SPOT INVISIBLE AIR MOVEMENT

School Science and MathematicsVolume 66, Issue 4 p. 330-330 GAMMA RAYS CAN SPOT INVISIBLE AIR MOVEMENT First published: April 1966 https://doi.org/10.1111/j.1949-8594.1966.tb15006.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume66, Issue4April 1966Pages 330-330 RelatedInformation