Radiography in Modern Industry - Kodak

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structures that lie above and below that plane are blurred. It is fairly common in medicalradiography, and has a few specialized applications in industrial radiography.Figure 88: Basic principle of tomography. The source-specimen distance has beenunrealistically shortened and the specimen-film distance increased, in order to show theprinciples of the system more clearly.The principle can be understood by reference to Figure 88, which shows one of the simpler andmore frequently used methods. The tube and film holder are linked at the ends of a lever pivotedat the level of the plane it is desired to render. The film and tube move horizontally during thecourse of the exposure. As the focal spot moves to the right from X 1 to X 2 and the film to the leftfrom F 1 to F m2 , the image (P 1 ) of the point P remains stationary with respect to the film. However,the images of points above (A) and below (B) the point P move with respect to the film (from A 1 toA 2 and B 1 to B 1 ) and hence are blurred on the radiograph as shown in Figure 89.The excursion of tube and film determines the thickness of the layer that is sharply imaged. Smallmotions render structures within a relatively thick section of the specimen; large motions render athin section in sharp "focus."Figure 88 a simple linear motion of tube and film, for the sake of illustrative clarity. In actualpractice, the motions are often more complicated--circular, spiral, or hypocycloidal.Radiography in Modern Industry 146
Figure 89: Demonstration of the effect obtained with tomography. The test object (below)is a series of plastic "shelves", each holding a lead letter. The first radiography (top, right)was made with conventional radiographic equipment. The second radiography (bottom,right), made with tomographic equipment, shows level C clearly, while the other levels areblurred.Radiography Of Radioactive MaterialsExamination of radioactive materials is complicated by the fact that the film is exposed to theemission of the specimen as well as to the imaging radiation. The exposure from the specimenitself is usually uniform over the whole film area, and thus has effects similar to, and in addition to,scattered radiation from the specimen. Best radiographic results are obtained when theproportion of this "fogging" radiation to the total radiation (fogging plus imaging) affecting the filmis made as small as possible.In general, the only radiation from the specimen that needs to be considered is the gammaradiation; any beta or alpha radiation can easily be absorbed in any material between thespecimen and the film. This material may be the coating, cladding, or container of the radioactivematerial, separate filters introduced between specimen and film, the front of the exposure holder,or any front screen used.A number of techniques are available for minimizing the deleterious effects of the gammaradiation on the final radiograph. Which, or what combination, of these techniques is useddepends on the requirements of the inspection and particularly on the activity of the specimen. Asactivity increases, more measures, and more complicated ones, must be employed. Becauseexaminations of this type are highly specialized, no general directions can be given. Rather, a listof techniques, ranging from the simpler to the more expensive and complex, will be given, not allof which are necessarily applicable to every radiographic problem. It should be emphasized againthat the consideration should be directed not to reducing the absolute amount of foggingradiation, but rather to reducing the proportion it bears to the imaging radiation.Speed of OperationThe most obvious way to minimize the effect of radiation from the specimen itself is to workquickly. The film is exposed to fogging radiation during the setup, exposure, and takedown times,but to the imaging radiation only during the exposure time. It is therefore advisable that the filmRadiography in Modern Industry 147
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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
Page 95 and 96: Chapter 9: Industrial X-ray FilmsMo
Page 97 and 98: Figure 70 indicates the direction t
Page 99 and 100: the lead letters on a radiation-abs
Page 101 and 102: Therefore, protection requirements
Page 103 and 104: 5. Avoid pressure damage caused by
Page 105 and 106: 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: When radiation passes through a spe
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 and 158: Figure 97: Two methods of neutron r
Page 159 and 160: Duplicating RadiographsSimultaneous
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
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The ratio of signal to noise has a
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Chapter 18: The Photographic Latent
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Thus, the change that makes an expo
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Figure 130: Stages in the developme
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electrons by successive Compton int
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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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Radiography in Modern Industry - Kodak

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