1、Designation: E 1114 03Standard Test Method forDetermining the Focal Size of Iridium-192 IndustrialRadiographic Sources1This standard is issued under the fixed designation E 1114; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the focalsize of an iridium-192 radiographic source. The determi
3、nationis based upon measurement of the image of the iridium metalsource in a projection radiograph of the source assembly andcomparison to the measurement of the image of a referencesample in the same radiograph.1.2 This standard does not purport to address all of thesafety concerns, if any, associa
4、ted with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 999 Guide for Controlling the Quality of Industrial Ra-diog
5、raphic Film Processing2E 1316 Terminology for Nondestructive Examinations2E 1815 Test Method for Classification of Film Systems forIndustrial Radiography23. Terminology3.1 For definitions of terms relating to this test method, referto Terminology E 1316.4. Significance and Use4.1 One of the factors
6、affecting the quality of a radiographicimage is geometric unsharpness. The degree of geometricunsharpness is dependent upon the focal size of the source, thedistance between the source and the object to be radiographed,and the distance between the object to be radiographed and thefilm. This test met
7、hod allows the user to determine the focalsize of the source and to use this result to establish source toobject and object to film distances appropriate for maintainingthe desired degree of geometric unsharpness.5. Apparatus5.1 Subject Iridium-192 Source, the focal size of which is tobe determined.
8、 The appropriate apparatus and equipment forthe safe storage, handling, and manipulation of the subjectsource, such as a radiographic exposure device (also referred toas a gamma ray projector or camera), remote control, sourceguide tube, and source stop are also required.5.2 Reference Sample (see Fi
9、gs. 1-3)The referencesample shall be of material which is not radioactive. Therecommended material is iridium. However, substitutes such asplatinum, tungsten or other material of similar radiopacity maybe used. The sample should be of the same geometric shape asthe subject source, should be approxim
10、ately the same size asthe subject source, and should be positioned on or within ashim or envelope to simulate the source capsule wall. Theresulting radiographic contrast, with reference to adjacentbackground density of the image of the reference sample,should be approximately the same as that of the
11、 subject source.The actual dimensions of the reference sample should bedetermined to the nearest 0.025 mm 0.001 in.5.3 X-ray Generator, capable of producing a radiationintensity (roentgen per hour at one metre) at least ten timesgreater than that produced by the subject source. Examples oftypical X-
12、ray generator output requirements that satisfy thiscriterion are presented in Table 1.5.4 Film systemsOnly film systems having cognizantengineering organization approval or meeting the system classrequirements of Test Method E 1815, for system classes I, II orSpecial, shall be used. Selection of fil
13、m systems should bedetermined by such factors as the required radiographic qualitylevel, equipment capability, materials and so forth. The filmsystem selected shall be capable of demonstrating the requiredimage quality. No intensifying screens shall be used. Radio-graphic films shall be processed in
14、 accordance with GuideE 999.1This test method is under the jurisdictioin of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.01 onRadiology (X and Gamma) Method.Current edition approved March 10, 2003. Published May 2003. Originallyapproved in 1986. La
15、st previous edition approved in 1997 as E 1114 92 (1997)e1.2Annual Book of ASTM Standards, Vol 03.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5 Image Measurement ApparatusThis apparatus is usedto measure the size of the imag
16、e of the focal spot. Theapparatus shall be an optical comparator with built-in graticulewith 0.1 mm divisions or 0.001 in. divisions and magnificationof 53 to 103.6. Procedure6.1 Set up the exposure arrangement as shown in Figs. 4-7.Position the X-ray tube directly over the center of the film. Thefi
17、lm plane must be normal to the central ray of the X-ray beam.The X-ray focal spot should be 0.90 m 36 in. from the film.Position the reference sample and apparatus used to locate thesubject source (source stop) as close together as possible anddirectly over the center of the film. The plane of the s
18、ource stopand reference sample must be parallel to the film and normal tothe central ray of the X-ray beam. The source stop andreference sample should be 0.15 m 6 in. from the film. Thesource stop should be connected to the radiographic exposuredevice by the shortest source guide tube practicable in
19、 order tominimize fogging of the film during source transit.6.2 Place identification markers to be imaged on the film toidentify, as a minimum, the identification (serial number) of thesubject source, the size of the reference sample, the identifi-cation of the organization performing the determinat
20、ion, andFIG. 1 Reference Sample in Standard Source EncapsulationFIG. 2 Alternate Reference Sample ArrangementFIG. 3 Alternate Reference Sample ArrangementTABLE 1 Examples of Typical X-ray Generator OutputRequirements for Related Iridium192Source ActivitiesSubject Iridium192SourceRadiationTypical X-r
21、ay GeneratorOutput RequirementsActivity(Curie)Output(R/h at 1 m)Potential Current30 14.4 160 kV 5 mAor 200 kV 3 mA100 48.0 160 kV 10 mAor 250 kV 4 mA200 96.0 160 kV 20 mAor 250 kV 8 mAor 300 kV 6 mAE1114032the date of the determination. Care should be taken to ensurethat the images of the subject so
22、urce and reference sample willnot be superimposed on the image of the identification mark-ers.6.3 ExposureSelect the X-ray tube potential (kV), X-raytube current (mA) and exposure time such that the density inthe image of the envelope surrounding the reference sampledoes not exceed 3.0 and that the
23、density difference between theimage of the reference sample and the image of the envelopesurrounding the reference sample is at least 0.10.NOTE 1The actual parameters that will produce acceptable resultsmay vary between X-ray units, and trial exposures may be necessary.6.3.1 Energize the X-ray gener
24、ator and, at the same time,manipulate the subject source into the exposure position in thesource stop. It is important that this be performed as quickly aspossible to minimize fogging of the film.6.3.2 At the conclusion of the exposure time, deenergize theX-ray generator and, at the same time, retur
25、n the subject sourceto the proper shielded storage position.6.3.3 Process the film.7. Measurement of Focal Dimensions7.1 View the radiograph with sufficient light intensity foradequate viewing. Using an optical comparator with built-ingraticule as described in 5.5, measure the linear dimensions ofth
26、e image of the focal spot of the subject source and thereference sample. Take measurements from the perceptibleedges of the image. When performing the physical measure-ments with the optical comparator, the actual measured valuesshall be to the nearest graduation on the graticule scale beingused.7.2
27、 The focal size for a given technique is the maximumprojected dimension of the source in the plane perpendicular toa line drawn from the source to the object being radiographed.Therefore, sufficient measurements of the image of the iridiummust be made to determine the focal size of the source in any
28、orientation. Sections 7.2.1-7.2.4 serve as examples.7.2.1 Uniform Right Circular Cylinder (see Fig. 8)Determine the focal size of a uniform right circular cylindricalsource by measuring the diameter, d, the height, h, and thediagonal, m, as illustrated in Fig. 8 and computing the actualdimensions as
29、 described in 8.1.7.2.2 Sphere (see Fig. 9)Determine the focal size of aspherical source by measuring the diameter, d, as illustrated inFig. 9 and computing the actual dimension as described in 8.1.7.2.3 Nonuniform Stack of Right Circular Cylinders (seeFig. 10)Determine the focal size of a nonunifor
30、m stack ofright circular cylindrical components of a source by measuringthe intrinsic diameter, d, the height, h, and the effectivemaximum dimension, m, as illustrated in Fig. 10 and comput-ing the actual dimensions as described in 8.1.7.2.4 Separated Stack of Right Circular Cylinders (see Fig.11)De
31、termine the focal size of a separated stack of rightcircular cylindrical components of a source by measuring theintrinsic diameter, d, the effective height, h, and the effectivemaximum dimension, m, as illustrated in Fig. 11 and comput-ing the actual dimensions as described in 8.1.8. Calculation and
32、 Evaluation8.1 Measure the linear dimension of interest in the subjectsource image and measure the same linear dimension in thereference sample image (that is, the diameter of each). Theactual dimension of the subject source is computed from thefollowing:FIG. 4 Typical Exposure ArrangementFIG. 5 Typ
33、ical Arrangement Using a Specially Designed GuideTubeFIG. 6 Typical Arrangement Using a Standard Guide Tube andSpecial Positioning FixtureE1114033a 5 bc/dwhere:a = actual dimension of the subject source,b = actual dimension of the reference sample,c = measured dimension of the subject source image,
34、andd = measured dimension of the reference sample image.9. Report9.1 A report of the focal size of an iridium-192 sourceshould indicate the model number and serial number of thesource, the name of the organization making the determination,the date the determination was made, a description of the sha
35、peof the source (or an appropriate sketch), and the calculatedactual dimensions. The actual radiograph should accompanythe report.10. Keywords10.1 cylinder(s); focal size; iridium 192; radiographicsource; reference sample; sphereFIG. 7 Typical Arrangement Using Reference Sample Positioning DeviceFIG
36、. 8 Uniform Right Circular CylinderFIG. 9 SphereFIG. 10 Nonuniform Cylindrical StackFIG. 11 Separated Cylindrical StackE1114034ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are
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39、may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E1114035
