ASTM E1496-97

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Designation: E 1496 – 97
Standard Test Method for
Neutron Radiographic Dimensional Measurements
This standard is issued under the fixed designation E1496; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method provides a technique for extracting
quantitative dimensional information on an object from its
neutron radiograph. The technique is based on the identifica-
tion of changes in film density caused by material changes
whereacorrespondingdiscontinuityinfilmdensityexists.This
test method is designed to be used with neutron radiographs
made with a well-collimated beam. The film densities in the
vicinity of the edge must be in the linear portion of the density
versus exposure curve. The accuracy of this test method may
FIG. 1 Typical Microdensitometer Film Density Traces Associated
with Three Rectangular Material Discontinuities: (a) Edge of
be affected adversely in installations with high-angular-
Object, (b) Thickness Variation, and (c) Dissimilar Material
divergence neutron beams or with large object-to-film dis-
Boundary
tances.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions—Definitions of the many terms relative to
priate safety and health practices and determine the applica-
radiography (for example, X, gamma, and neutron radiogra-
bility of regulatory limitations prior to use.
phy) can be found in Terminology E1316.
2. Referenced Documents 3.2 Definitions of Terms Specific to This Standard:
3.2.1 extremum—the point on the linear response portion of
2.1 ASTM Standards:
the curve of smoothed density versus location at which the
E94 Guide for Radiographic Testing
slope is a maximum.
E748 Practices for Thermal Neutron Radiography of Ma-
3.2.2 extremum slope criterion—the criterion that specifies
terials
the edge of a defect or an object, located at the spatial position
E803 Method for Determining the L/D Ratio of Neutron
corresponding to the extremum as determined from examina-
Radiography Beams
tion of a radiograph.
E1316 Terminology for Nondestructive Examination
3.2.3 linear response—a radiographic response where the
2.2 Other Documents:
film density across an edge within an object is contained in the
SNT-TC-1A Recommended Practice for Nondestructive
linear part of the density versus exposure curve.
Testing Personnel Qualification and Certification
3.2.4 traveling-stage microdensitometer—a densitometer
ANSI/ASNT CP-189 ASNT Standard for Qualification and
3 withasmallaperture(typicallybetween10to25µmby200to
Certification of Nondestructive Testing Personnel
300 µm) that has the capability of scanning a radiograph in a
MIL-STD-410 Nondestructive Testing Personnel Qualifica-
4 continuousorsteppedmannerandgeneratingeitheradigitalor
tion and Certification
an analog mapping of the film density of the radiograph as a
function of position.
4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee E-7 on
Nondestructive Testing and is the direct responsibility of Subcommittee E07.05 on
4.1 All radiation used in radiography is attenuated in its
Radiology (Neutron) Method.
passage through an object according to its thickness and
Current edition approved May 10, 1997. Published February 1998. Originally
magnitude of the material attenuation properties appropriate to
published as E1496–92. Last previous edition E1496–92.
Annual Book of ASTM Standards, Vol 03.03.
the type and energy of radiation. Additionally, significant
Available from American Society for Nondestructive Testing, 1711 Arlingate
spatial spreading occurs due to the system imperfections,
Plaza, PO Box 28518, Columbus, Ohio 43228-0518.
nonsymmetric radiation transport, and image formation pro-
Available from Standardization Documents Order Desk, Building 4 Section D,
700 Robbins Avenue, Philadelphia, PA 19111-5904, Attn: NPODS. cess.Significantvariationsintherecordedradiationnearedges
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1496–97
extremum slope criterion. These have been confirmed by
careful experimentation (1-3).
5. Significance and Use
5.1 Many requirements exist for accurate dimensional in-
formation in industrial quality control. Frequently, this infor-
mation cannot be measured directly, may be very uncertain, or
is expensive to obtain. If a radiograph of the object in question
displays a sufficient film density variation near the edge of
interest, however, dimensional radiography methods may be
applied. This test method provides a technique for extracting
quantitative dimensional information from the neutron radio-
graph of an object. Guide E94 and Practices E748 are helpful
FIG. 2 Typical Microdensitometer Traces of Film Density for (a)
for understanding the principles involved in obtaining a high-
Rectangular Objects and (b) Cylindrical Objects; Note
quality neutron radiograph.
Placements of Edges x and x on the Traces
+ −
5.2 Dimensional radiography appears to be particularly
relevant in determination of the following: (1) diameters of
and material discontinuities therefore occur and manifest spent radioactive fuel, (2) gap sizes in contact-circuit mecha-
themselves by film density variations in the radiograph, as nisms of shielded components, and (3) prescribed spacings
illustrated in Fig. 1.
between distinct materials.
4.2 A graph of detector response (film density) versus 5.3 While this test method addresses dimensional measure-
location across an interface is similar in form for many
ments using neutron radiography, the methods and techniques
differenttypesofinterface,providedthatthedetectorresponds of dimensional radiography are also equally applicable to
linearlytoincreasedexposureovertheentireregionofinterest.
varioustypesofradiography,suchasx-ray, g-ray,andneutron.
Typical radiographic responses are shown in Fig. 2 (a) and (b). 5.4 Afundamentalassumptionofthistestmethodisthatthe
4.3 Both theoretical and experimental studies in neutron
userwillhaveaccesstoasystemthatpermitstheattainmentof
radiography have established that under commonly encoun- data describing the density response of the radiograph. Al-
tered high-quality linear-response radiographic conditions, the
though a system may include any digitization equipment
edge of an object corresponds to that point on the smoothed capable of providing the spatial resolutions recommended in
experimentally obtained microdensitometer trace at which the
6.1.1,atypicalsystemwillincludeahigh-resolutiontraveling-
slopeisamaximum,asillustratedinFig.3.Thispointiscalled stage microdensitometer and a neutron radiograph of the
theextremum,andtherelationshipbetweenthespatialposition
object.
of the extremum and location of the edge is called the 5.5 An object with accurately known dimensions must be
available to calibrate the equipment used to measure the
radiographic response, that is, the traveling-stage microdensi-
tometer (or other digitization system capable of spatial resolu-
tion comparable to that of the detector).
6. Basis of Application
6.1 Personnel Qualification—If specified in the contractual
agreement, NDT personnel shall be qualified in accordance
with a nationally recognized NDT personnel qualification
practice or standard such as ANSI/ASNT CP-189, SNT-TC-
1A, MIL STD-410, or a similar document. The practice or
standard used and its applicable revision shall be specified in
the contractual agreement between the using parties.
6.2 Qualification of Nondestructive Agencies—If specified
in the contractual agreement, NDT agencies shall be qualified
and evaluated as described in Practice E543. The applicable
edition of Practice E543 shall be specified in the contractual
agreement.
6.3 Procedures and Techniques—The procedures and tech-
niques to be utilized shall be as described in this test method
FIG. 3 Depiction of Various Slopes on a Smoothed
Microdensitometer Trace; The Object Edge Coordinate, x ,
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
+
Corresponds to the Extremum Slope Point on the Trace this test method.
E1496–97
unless otherwise specified. Specific techniques may be speci- 9.2.2 Obtain a high-quality continuous or digital microden-
fied in the contractual agreement. sitometer trace along the traverse, ensuring that the traveling
stage is set for a speed or pixel dimension that scales the film
7. Apparatus
densityvar
...