Radiography in Modern Industry - Kodak

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Neutron radiography is suitable for a number of tasks impossible for conventional radiography--for example, the examination of great thicknesses of high atomic number material. Several inchesof lead can be radiographed with neutrons using exposure times of a few minutes. The transferexposure method is well adapted to the radiography of highly radioactive materials such asirradiated nuclear fuel elements. Since the converter foil is unaffected by the intense beta andgamma radiation given off by the fuel element itself, the image is formed only by the differentialattenuation of the neutrons incident on the element. The disadvantages of neutron radiographyare primarily associated with the comparative rarity and great cost of nuclear reactors and, to asomewhat lesser degree, the small diameter of available neutron beams.AutoradiographyAn autoradiograph is a photographic record of the radioactive material within an object, producedby putting the object in contact with a photographic material. In general, autoradiography is alaboratory process applied to microtome sections of biological tissues that contain radioisotopes,metallographic samples, and the like. Highly specialized techniques and specialized photographicmaterials--including liquid emulsions--are usually required.However, certain autoradiographic techniques resemble those used in industrial radiography.Almost entirely limited to the nuclear energy field, they include the determination of the fueldistribution and of cladding uniformity of unirradiated fuel elements, and the measurement offission-product concentration in irradiated fuel elements.The first two applications involve comparatively low levels of radioactivity, and usually require thefastest types of x-ray film. The fuel element is placed in intimate contact with a sheet of film. Theexposure time must be determined by experiment, but may be several hours. In the case of anonuniformly loaded fuel element with uniform cladding, the densities recorded can be correlatedwith concentration of radioactive material in the element. In the case of a uniformly loaded plate,density can be correlated to the thickness of cladding. In either case, calibration exposures to oneor more fuel elements of known properties are necessary, and ideally a calibration exposureshould be processed with each batch of autoradiographic exposures.If the nuclear fuel is unclad, a large part of the exposure to the film is caused by beta radiation.The thinnest material that gives adequate mechanical and light protection should be usedbetween the specimen and the film. It is essential, however, that this material be exceedinglyuniform in thickness. Variations in thickness will cause differences in electron transmission, andthe result can easily be an "electron radiograph" of the protective material rather than a record ofconcentration of radioactive material in the specimen.If the fuel element is clad, the exposure to the film is almost entirely the result of gammaradiation. Conventional exposure holders or cassettes can be used, and lead foil screens oftenprovide substantial savings in time.The autoradiographic determination of fission-product concentration in an irradiated fuel elementusually involves exceedingly high degrees of radioactivity. The slower types of industrial x-ray filmare most suitable. As in the radiography of radioactive materials, this technique places a greatpremium on bringing film and specimen together quickly at the start of the exposure andseparating them quickly at its termination (See "Radiography Of Radioactive Materials"). As inother radiographic measurement techniques, calibration exposures or rigid control of all exposureand processing variables is needed. Some means is also usually needed to protect the film or theexposure holder from radioactive contamination during the exposure to the irradiated fuelelement. Thin plastic sheeting, which can be discarded after one use, has been found suitable.This, of course, is in addition to the elaborate personnel-protection measures--beyond the scopeof this publication--that are also necessary.Radiography in Modern Industry 158
Duplicating RadiographsSimultaneous RadiographyIf it is known beforehand that a duplicate radiograph will be required, the easiest and mosteconomical way of obtaining it is to expose two x-ray films of the same type simultaneously in theoriginal exposure. Thus two essentially identical radiographs are produced at little or no extra costin exposure time.If lead-foil screen techniques are used, it is usually advisable to put both films between a singlepair of screens. If each film is placed between a pair of screens, the absorption of the back andfront screens, which separate the two films, results in a lower density on the back film. When twofilms are used between a single pair of screens, an increase in exposure is normally requiredbecause each film receives the intensification from only a single screen instead of from two. Theexposure increase required must in most cases be determined by tests because it depends onboth the kilovoltage and the specimen.If envelope-packed film with integral lead oxide screens is used, two envelopes can besuperimposed since the absorption of the lead oxide layers within the package is relatively low.With direct exposure techniques, both films should be put into the same exposure holder, eitherwithout interleaving paper or with both sheets in the same interleaving folder. With directexposure techniques it may sometimes be found, especially at the higher kilovoltages, thatexposure time must be slightly decreased to achieve the same density as obtained on a singlefilm. This is because each film acts as an intensifying screen for the other. The effect is small, butmay be puzzling if unexpected.Two or more films in factory-sealed envelopes may be exposed simultaneously. No adjustment ofexposure is required because the intensifying radiation from the films is largely absorbed in thematerial of the envelopes.In direct exposure techniques, if it should be necessary to use separate cardboard or plasticexposure holders for each film, care should be taken to remove any lead backing from the frontexposure holder. The presence of the lead will cause a marked difference in density betweenfilms.In general, observance of these rules results in two identical radiographs of equal density.Copying RadiographsWhen copies of existing radiographs are needed, they can be produced by contact printing onspecial duplicating film. This is a direct-positive film, which produces a duplicate-tone facsimile.The characteristic curve of a typical duplicating film is shown in Figure 98. The negative slopeindicates that increasing the exposure to light decreases developed density. Thus, if a sheet ofthis film is exposed to light through a radiograph and then processed, the dark parts of theradiograph (which transmit little light to the duplicating film) are reproduced as high densities, andthe low density areas of the original are reproduced as low densities.Radiography in Modern Industry 159
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RadiographyinModernIndustry
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RadiographyinModernIndustryFOURTH E
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ContentsIntroduction...............
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Chapter 1: The Radiographic Process
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Intensifying ScreensX-ray and other
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makes it a very suitable material f
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Figure 6: Typical voltage waveforms
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Table I - Typical X-ray Machines an
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The wavelengths (or energies of rad
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Table III - Industrial Gamma-Ray So
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1. The source of light should be sm
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B and H in the Figure 13 show the e
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Figure 14: Geometric construction f
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Figure 17: Pinhole pictures of the
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The kilovoltage applied to the x-ra
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Figure 21: Schematic diagram of som
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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Figure 70 indicates the direction t
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the lead letters on a radiation-abs
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Therefore, protection requirements
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5. Avoid pressure damage caused by
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Paddles or plunger-type agitators a
Page 107 and 108: slow, and the development time reco
Page 109 and 110: ubbles make their way to the surfac
Page 111 and 112: When development is complete, the f
Page 113 and 114: soften considerably with prolonged
Page 115 and 116: Figure 77: The roller transport sys
Page 117 and 118: Rapid Access to Processed Radiograp
Page 119 and 120: Figure 78: Film-feeding procedures
Page 121 and 122: Chapter 11: Process ControlUsers of
Page 123 and 124: 3. Age of the developer replenisher
Page 125 and 126: Figure 80: Control chart below for
Page 127 and 128: DiscussionDensitometric data and pr
Page 129 and 130: Figure 82: Plan of a manual x-ray p
Page 131 and 132: Figure 83: A schematic diagram of a
Page 133 and 134: loading-bench activities are carrie
Page 135 and 136: KODAK Quinone-Thiosulfate Intensifi
Page 137 and 138: Methylene-Blue MethodTwo variations
Page 139 and 140: KODAK Hypo Test Solution HT-2Avoird
Page 141 and 142: In summary, use of the test papers
Page 143 and 144: narrow angle would be very thick, e
Page 145 and 146: When radiation passes through a spe
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149 and 150: Figure 90: The amount of gamma radi
Page 151 and 152: The radiograph exposed in the right
Page 153 and 154: To illustrate, let us assume that t
Page 155 and 156: Figure 95: High-speed x-ray picture
Page 157: Figure 97: Two methods of neutron r
Page 161 and 162: Sometimes, as when sets of referenc
Page 163 and 164: PhotofluorographyIn photofluorograp
Page 165 and 166: discontinuities or of segregation i
Page 167 and 168: from the camera or by reaching down
Page 169 and 170: Figure 106: Schematic diagram of th
Page 171 and 172: valuable technique, for instance, i
Page 173 and 174: The position of the spots is determ
Page 175 and 176: Powder Diffraction File, Internatio
Page 177 and 178: Processing TechniquesRadiographs on
Page 179 and 180: Since this formula applies only to
Page 181 and 182: such that it does not distort the i
Page 183 and 184: Figure 113: A: Representation of a
Page 185 and 186: Figure 115: Characteristic curve of
Page 187 and 188: film fairly well. If high densities
Page 189 and 190: Density = 1.5 Density = 2.5Film Rel
Page 191 and 192: In most industrial radiography, the
Page 193 and 194: e noted here. Although the average
Page 195 and 196: Chapter 17: Film Graininess; Signal
Page 197 and 198: The ratio of signal to noise has a
Page 199 and 200: Chapter 18: The Photographic Latent
Page 201 and 202: Thus, the change that makes an expo
Page 203 and 204: Figure 130: Stages in the developme
Page 205 and 206: electrons by successive Compton int
Page 207 and 208: Development is essentially a chemic
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Chapter 19: ProtectionOne of the mo
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duct is brought into the x-ray room
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