inverse problem has been fonnulated. The method is suitable for on-line automated quality-control measurements.

39909 Bushlin. Y.; Notea. A. Sizing of slits by digital radiography NDT International, Vol. 21, No.6, pp. 397-402 (Dec. 1988)

A method for the sizing of cracks from radiographic images is presented. Interpretation is based on a description of the radiographic image generation by theoretical models and characteristics functions detennined from experimental results. The crack was simulated by a rectangular slit The inclination of the crack was expressed by a suitable locally dependent operator, while blurring effects were expressed by a convolutable function. The method has been successfully applied to digitized radiographs of a lucite block containing slits less than I mm wide. The influence of slit size and inclination on the probability of detection has been analysed. The method is suitable for real-time radiographic systems.

39908 Bespalov. V.I.; Zaitsev. A.K.; Kononov. M.Y.; Kuleshov. V.K. Inherent unsbarpness in a gas-discharge converter operating with high- energy X rays Soviet Journal of Nondestructive Testing, Vol. 24, No. I, pp. 59-64 (Jan. 1988)

Monte Carlo simulation has been applied to electron and photon transport in calculating absorbed-energy radial distributions in gas­discharge converters in order to estimate the inherent unsharpness for x-ray beams having maximum energies of 6 and 30 Me V. The unsharpness is related to the thickness and material in the front electrode, the gas pressure, and the distance between electrodes. Calculations for 6 MeV are compared with measurements.

39628 Heut. J.; Pauton. M.; Thomas. G.; Casagrande. J.M.; Lagnier. P.; Glasser. F. The industrial X-ray tomography study of high resolution analyzers Proceedings of the 4th European Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2133-2141. Pergamon Press, 3173 pp. (1988)

In conjunction with the CEA Company, the INTERCONTROLE Company has made two models of 420 kV X-ray scanners. The characteristics of these machines, some recent results and the high X-ray energy development are presented.

39476 Brase. J.M.; Waltjen. K.E.; Martz. H.E. Research in computed tomography Lawrence Livermore National Laboratory, UCRL-53868-87 (Thrust Area Report FY87), Section 9, pp. 14-19 (Apr. 1988)

The use of computed tomography (Cn imaging has been researched for evaluating materials of interest at LLNL. A microfocus CT system has been demonstrated aimed at high-resolution applications, as well as a pencil­beam cr system for quantitative material evaluation. Given a model of the x-ray imaging system, algorithms have been developed for enhancing the resolution of images. A new reconstruction algorithm has been developed that can easily incorporate a priori knowledge of the specimen being imaged. Reconstruction programs have been used on several systems to compare their performance and have begun to develop an algorithm for the SPRINT architecture.

39475 Christian. J.M.; Mueller. K. Jr.; Schwalbe. L. High-energy nash radiography of two axisymmetric copper explosively formed penetrators International Advances in Nondestructive Testing, Vol. 13, pp. 365-396 (1987). Edited by W,J. McGonnagle. Gordon and Breach Science Publishers.

In-flight radiographic data is presented from two explosively fonned penetrators (EFPs) of copper. The data were obtained with Ector, a high-energy, pulsed x-ray source operating at effective mean energies selectable in the range 0.5-1.5 MeV. The Ector-produced radiation has enough energy and intensity to penetrate several centimeters of copper, and the 50-ns pulse is short enough that motion blur is negligible from objects traveling at 2-3 mm/microsec. The radiographs were first digitized and then subjected to numerical analyses. The results of this work include tomographic reconstructions and accurate detenninations of the internal and external contours of the EFPs, as well as their masses and center-of-mass coordinates. Along with the experimental data, the original design specifications of the two warheads has been made available. The combined information allows detailed comparisons with the results of design code simulations. The data should serve as useful tests for theoretical models of material strength, fracture, and equations of state.

NOT & E International Volume 25 Number 4/5 1992

39466 Fry. DA.; Pearsall. C.R.; Guu. A.C. Design considerations for an industrial diode array digital radiographic system Transactions of the American Nuclear Society, Vol. 56, Supplement No.3, p. 70-72 (Conference on Industrial and Radioisotope Measurement Applications, Pinehurst, North Carolina, 7-9 Sep. 1988)

Work in the U.S.A. on the evaluation of line-scan diode array radiography (DADR) for a wide variety of industrial applications (welds, castings and electronic assemblies) is described. The advantages of digital overfilm radiography are discussed. Two prototype DADR systems have been constructed and evaluated and a computer model has been developed for perfonnance prediction. This paper concentrates on the inspection of steel welds. The DADR system is described and results given. Image quality and scan rates will be improved in the future.

39465 Gentle. D.J.; Spyrou, N.M.; Dhani. A.; Hutchinson. I.G.; Huddleston. J. Scattering and attenuation corrections in emission tomography in nuclear industry applications Transactions of the American Nuclear Society, Vol. 56, Supplement No.3, p. 81-82 (Conference on Industrial and Radioisotope Measurement Applications, Pinehurst, North Carolina, 7-9 Sep. 1988)

This prototype scanning rig for use in the nuclear industry will use scattering and attenuation corrections in emission tomography for examining nuclear materials such as fuel rods or radionuclides in waste containers. The rig, which works essentially as a simulator, is controlled by a BBC microcomputer and data is acquired in a single or multichannel analyzers. Image reconstruction is performed using a filtered back­projection program on the micro-computer and on a main frame which provides image processing facilities. Results using the high purity Gennanium detector are superior to those using the sodium iodide detector. The reasons for this are explored.

39464 Sheppard. G A. Development of a high-resolution inert high-explosives tomography phantom Transactions of the American Nuclear Society, Vol. 56, Supplement No.3, p. 82 (Conference on Industrial and Radioisotope Measurement Applications, Pinehurst, North Carolina, 7·9 Sep. 1988)

Work is being carried out in the U.S.A. which aims to use X ray computerised tomography to characterise the density uniformity of chemical high explosives (HE). Safety considerations preclude the actual use of these materials during the system's development, so inert calibration phantoms (test objects for calibration and reference purposes) are also being developed. Density and mass attenuation must both be similar to the HE materials they mimic. Equipment and procedures are described. A suitable phantom density calibration standard called Viton A has been identified and further experiments concerned with radial placement within the sample are planned.

39386 Morgner. W.; Tutzschky. G. Assessment of defect detectability by statistical models Proceedings of the 4th European conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 2, pp. 844-852. Pergamon Press, 3173 pp. (1988)

It is lightweight construction and the role of materials economy with ever rising demands on materials which compel the designer to make increasing use of the safety reserves of materials. In this light there is an enhancing impetus on the reliability of nondestructive inspection methods. It can be appraised by characterising the equivalent flaw size as a random variable and studying its distribution function. Analyzing the patterns of the latter usually reveals markedly asymmetrical distributions which are induced by two components. viz. frequency of the actual flaw size and defect detectability by the particular inspection method. Adopting the probability theory for assessing the outcome of weld inspection by radiography as well as magnetic and potential drop crack testing along with light and electron microscopy, it is demonstrated for definite examples how the reliability of actual test results can be assessed.

38942 Cox. L.D.; Hammer. K.W. The NDT reference standard Materials Evaluation. Vol. 46, No.6, pp. 702-704 (May 1988)

The design, manufacture and use of reference standards in nondestructive testing for ultrasound, radiography and other methods is re-examined critically in this paper.

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