ASTM C1718-10(2019)
(Test Method)Standard Test Method for Nondestructive Assay of Radioactive Material by Tomographic Gamma Scanning
Standard Test Method for Nondestructive Assay of Radioactive Material by Tomographic Gamma Scanning
SIGNIFICANCE AND USE
5.1 The TGS provides a nondestructive means of mapping the attenuation characteristics and the distribution of the radionuclide content of items on a voxel by voxel basis. Typically in a TGS analysis a vertical layer (or segment) of an item will be divided into a number of voxels. By comparison, a segmented gamma scanner (SGS) can determine matrix attenuation and radionuclide concentrations only on a segment by segment basis.
5.2 It has been successfully used to quantify 238Pu, 239Pu, and 235U. SNM loadings from 0.5 g to 200 g of 239Pu (5, 6), from 1 g to 25 g of 235U (7), and from 0.1 to 1 g of 238Pu have been successfully measured. The TGS technique has also been applied to assaying radioactive waste generated by nuclear power plants (NPP). Radioactive waste from NPP is dominated by activation products (for example, 54Mn, 58Co, 60Co, 110mAg) and fission products (for example, 137Cs, 134Cs). The radionuclide activities measured in NPP waste is in the range from 3.7E+04 Bq to 1.0E+07 Bq. Some results of TGS application to non-SNM radionuclides can be found in the literature (8).
5.3 The TGS technique is well suited for assaying items that have heterogeneous matrices and that contain a non-uniform radionuclide distribution.
5.4 Since the analysis results are obtained on a voxel by voxel basis, the TGS technique can in many situations yield more accurate results when compared to other gamma ray techniques such as SGS.
5.5 In determining the radionuclide distribution inside an item, the TGS analysis explicitly takes into account the cross talk between various vertical layers of the item.
5.6 The TGS analysis technique uses a material basis set method that does not require the user to select a mass attenuation curve apriori, provided the transmission source has at least 2 gamma lines that span the energy range of interest.
5.7 A commercially available TGS system consists of building blocks that can easily be configured to operate the system in the ...
SCOPE
1.1 This test method describes the nondestructive assay (NDA) of gamma ray emitting radionuclides inside containers using tomographic gamma scanning (TGS). High resolution gamma ray spectroscopy is used to detect and quantify the radionuclides of interest. The attenuation of an external gamma ray transmission source is used to correct the measurement of the emission gamma rays from radionuclides to arrive at a quantitative determination of the radionuclides present in the item.
1.2 The TGS technique covered by the test method may be used to assay scrap or waste material in cans or drums in the 1 to 500 litre volume range. Other items may be assayed as well.
1.3 The test method will cover two implementations of the TGS procedure: (1) Isotope Specific Calibration that uses standards of known radionuclide masses (or activities) to determine system response in a mass (or activity) versus corrected count rate calibration, that applies to only those specific radionuclides for which it is calibrated, and (2) Response Curve Calibration that uses gamma ray standards to determine system response as a function of gamma ray energy and thereby establishes calibration for all gamma emitting radionuclides of interest.
1.4 This test method will also include a technique to extend the range of calibration above and below the extremes of the measured calibration data.
1.5 The assay technique covered by the test method is applicable to a wide range of item sizes, and for a wide range of matrix attenuation. The matrix attenuation is a function of the matrix composition, photon energy, and the matrix density. The matrix types that can be assayed range from light combustibles to cemented sludge or concrete. It is particularly well suited for items that have heterogeneous matrix material and non-uniform radioisotope distributions. Measured transmission values should be available to permit valid attenuation corrections, but are not n...
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1718 − 10 (Reapproved 2019)
Standard Test Method for
Nondestructive Assay of Radioactive Material by
Tomographic Gamma Scanning
This standard is issued under the fixed designation C1718; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope mission values should be available to permit valid attenuation
corrections, but are not needed for all volume elements in the
1.1 This test method describes the nondestructive assay
container, for example, if interpolation is justified.
(NDA) of gamma ray emitting radionuclides inside containers
using tomographic gamma scanning (TGS). High resolution
1.6 The values stated in SI units are to be regarded as
gamma ray spectroscopy is used to detect and quantify the
standard. No other units of measurement are included in this
radionuclidesofinterest.Theattenuationofanexternalgamma
standard.
ray transmission source is used to correct the measurement of
1.7 This standard does not purport to address all of the
the emission gamma rays from radionuclides to arrive at a
safety concerns, if any, associated with its use. It is the
quantitative determination of the radionuclides present in the
responsibility of the user of this standard to establish appro-
item.
priate safety, health, and environmental practices and deter-
1.2 The TGS technique covered by the test method may be
mine the applicability of regulatory limitations prior to use.
used to assay scrap or waste material in cans or drums in the 1
1.8 This international standard was developed in accor-
to500litrevolumerange.Otheritemsmaybeassayedaswell.
dance with internationally recognized principles on standard-
1.3 The test method will cover two implementations of the
ization established in the Decision on Principles for the
TGS procedure: (1) Isotope Specific Calibration that uses
Development of International Standards, Guides and Recom-
standards of known radionuclide masses (or activities) to
mendations issued by the World Trade Organization Technical
determine system response in a mass (or activity) versus
Barriers to Trade (TBT) Committee.
corrected count rate calibration, that applies to only those
specific radionuclides for which it is calibrated, and (2)
2. Referenced Documents
Response Curve Calibration that uses gamma ray standards to
determine system response as a function of gamma ray energy
2.1 ASTM Standards:
and thereby establishes calibration for all gamma emitting
C1030TestMethodforDeterminationofPlutoniumIsotopic
radionuclides of interest.
Composition by Gamma-Ray Spectrometry
1.4 This test method will also include a technique to extend C1128Guide for Preparation of Working Reference Materi-
the range of calibration above and below the extremes of the als for Use in Analysis of Nuclear Fuel Cycle Materials
measured calibration data. C1156Guide for Establishing Calibration for a Measure-
ment Method Used toAnalyze Nuclear Fuel Cycle Mate-
1.5 The assay technique covered by the test method is
rials
applicable to a wide range of item sizes, and for a wide range
C1490GuidefortheSelection,TrainingandQualificationof
of matrix attenuation. The matrix attenuation is a function of
Nondestructive Assay (NDA) Personnel
the matrix composition, photon energy, and the matrix density.
C1592/C1592MGuide for Making Quality Nondestructive
The matrix types that can be assayed range from light
Assay Measurements (Withdrawn 2018)
combustibles to cemented sludge or concrete. It is particularly
C1673Terminology of C26.10 NondestructiveAssay Meth-
well suited for items that have heterogeneous matrix material
ods
and non-uniform radioisotope distributions. Measured trans-
1 2
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Destructive Assay. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2019. Published February 2019. Originally the ASTM website.
approved in 2010. Last previous edition approved in 2010 as C1718–10. DOI: The last approved version of this historical standard is referenced on
10.1520/C1718-10R19. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1718 − 10 (2019)
2.2 ANSI Standards: 3.1.7 grab (or view), n—a single measurement of the scan,
ANSI N15.37Guide to the Automation of Nondestructive where the scan sequence consists of measurements at various
Assay Systems for Nuclear Materials Control heights, rotational positions, and translation positions of the
assay item.
2.3 Nuclear Regulatory Commission (NRC) Guides
NRC Guide 5.9Guidelines for Germanium Spectroscopy 3.1.8 map (transmission and emission), n—avoxelbyvoxel
record of the matrix density or linear attenuation coefficient
Systems for Measurement of Special Nuclear Material,
Revision 2, December 1983 (transmission map) or a voxel by voxel record of radionuclide
content (emission map).
NRC Guide 5.53Qualification, Calibration, and Error Esti-
mation Methods for Nondestructive Assay, Revision 1,
3.1.9 material basis set (or MBS), n—the method where the
February 1984
linear attenuation coefficient map for a matrix material is
determined in terms of 2 or 3 basis elements that span the Z
3. Terminology
range of interest (4).
3.1 Definitions:
3.1.10 non-negative least squares (NNLS), n—constrained
3.1.1 Terms shall be defined in accordance with Terminol-
least squares fitting algorithm used in TGS analysis to obtain
ogy C1673 except for the following:
an initial estimate of the transmission map.
3.1.2 Algebraic Reconstruction Technique (ART), n—image
3.1.11 pre-scan, n—a preliminary scan of an assay item
reconstruction technique typically used in the TGS method to
employed by some TGS implementations to optimize the scan
obtainthetransmissionmapasafunctionofatomicnumber(Z)
protocol on an item-by-item basis.
and gamma ray energy (1).
3.1.12 scan, n—sequence of measurements at various
3.1.3 aperture, n—the terminology applies to the width of
heights, rotational positions, and translation positions of the
thedetectorcollimator.Inthecaseofadiamondcollimator,the
assay item.
apertureisdefinedasthedistancebetweentheparallelsidesof
3.1.13 response function, n—detectorefficiency(absoluteor
the diamond. In some designs, the detector collimator can be a
relative) as a function of measurement locus and gamma ray
truncated diamond that consists of flat trim pieces at the left
energy.
and right corners of the diamond. This type of collimator is
usually designed with the distance between the trim pieces set 3.1.14 tomography, n—the mathematical method in which
gammaraymeasurementsareusedtodeterminetheattenuation
equal to the distance between the parallel surfaces (aperture).
and emission characteristics of an item on a voxel-by-voxel
3.1.4 voxel, n—volume element; the three-dimensional ana-
basis.
log of a two-dimensional pixel. Typically 5 cm on a side for a
3.1.15 translation, n—the relative motion in the horizontal
208 L drum.
direction of the item to be measured perpendicular to the
3.1.4.1 Discussion—The full container volume will be di-
transmission source-detector axis.
vided into a number of smaller volume elements (typically
100–2000 or typically 0.1% of the total container volume),
3.1.16 TGS Number, n—uncalibrated result of aTGS analy-
which are not necessarily rectilinear.
sisrepresentingcountratecorrectedforgeometricalefficiency,
gamma ray attenuation, and rate loss at a given emission
3.1.5 Beers Law, n—the law states that the fraction of
gamma ray energy, proportional to the mass or activity of a
uncollided gamma rays transmitted through layers of equal
specific radionuclide.
thickness of an absorber is a constant. Mathematically, Beer’s
Law can be expressed as follows:
3.1.17 view, n—see grab.
I µ
T 5 5 exp 2 ·ρ·t
H J
4. Summary of Test Method
I ρ
In the above equation, I is the intensity of a pencil beam of
4.1 Assay of the radionuclides of interest is accomplished
gamma rays incident on a uniform layer of absorber, I is the
by measuring the intensity of one or more characteristic
transmitted intensity through the layer, µ/ρ is the mass at-
gamma rays from each radionuclide utilizing TGS techniques.
tenuation coefficient of the absorber material, ρ is the density
TGS techniques include translating, rotating and vertically
of the absorber and t is the thickness of the layer. For a het-
erogeneous material the exponent would be integrated along scanning the assay item such that a 3-dimensional (3D) image
the ray path.
can be reconstructed from the data. Generally two 3D images
are constructed; a transmission image and a passive emission
3.1.6 expectation maximization (EM), n—image reconstruc-
image. Corrections are made for count rate-related losses and
tion technique typically used in the TGS method to solve for
attenuation by the matrix in which the nuclear material is
the emission map as a function of gamma ray energy (2, 3).
dispersed. The calibration then provides the relationship be-
tween observed gamma ray intensity and radionuclide content.
4.2 Calibration is performed using standards containing the
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
radionuclidestobeassayedorusingamixtureofradionuclides
AvailablefromU.S.NuclearRegulatoryCommission,Washington,DC20555-
emittinggammaraysthatspantheenergyrangeofinterest.The
0001, http://nrc.gov.
activities or masses of the radionuclides and the gamma ray
The boldface numbers in parentheses refer to a list of references at the end of
this standard. yields are traceable to a national measurement database.
C1718 − 10 (2019)
4.2.1 Using a traceable mixed gamma ray standard that item will be divided into a number of voxels. By comparison,
spanstheenergyrangeofinterestwillenablethedetermination a segmented gamma scanner (SGS) can determine matrix
of theTGS calibration parameters at any gamma ray energy of attenuation and radionuclide concentrations only on a segment
interest, not just those that are present in the calibration by segment basis.
standard. A calibration curve is generated that parameterizes 238 239
5.2 It has been successfully used to quantify Pu, Pu,
235 239
the variation of the TGS calibration factor as a function of
and U. SNM loadings from 0.5 g to 200 g of Pu (5, 6),
gamma ray energy. 235 238
from1gto25gof U (7), and from 0.1 to1gof Pu have
4.3 The assay item is rotated about its vertical axis. been successfully measured.TheTGS technique has also been
Concurrently, the relative position of the assay item and applied to assaying radioactive waste generated by nuclear
detector are translated. This is repeated for every vertical powerplants(NPP).RadioactivewastefromNPPisdominated
segment.Duringthisprocess,aseriesofmeasurements(grabs) by activation products (for ex-
54 58 60 110m
are taken of gamma rays corresponding to the transmission ample, Mn, Co, Co, Ag) and fission products (for
137 134
source and the emission sources. A transmission scan is example, Cs, Cs).Theradionuclideactivitiesmeasuredin
performed with the transmission source exposed. A separate NPP waste is in the range from 3.7E+04 Bq to 1.0E+07 Bq.
emission scan is performed with the transmission source Some results of TGS application to non-SNM radionuclides
can be found in the literature (8).
shielded.
4.3.1 Fromthetransmissionmeasurements,a3Dmapofthe
5.3 TheTGStechniqueiswellsuitedforassayingitemsthat
average linear attenuation coefficient across of each voxel is
have heterogeneous matrices and that contain a non-uniform
determined.
radionuclide distribution.
4.3.2 From the emission measurements, a 3D map of the
5.4 Since the analysis results are obtained on a voxel by
location of the gamma emitting radionuclides is determined.
voxel basis, the TGS technique can in many situations yield
These 3D maps are typically low spatial resolution (for
more accurate results when compared to other gamma ray
example, approximately ⁄10 th the diameter would be a typical
techniques such as SGS.
characteristic dimension).
5.5 In determining the radionuclide distribution inside an
4.3.3 Through a voxel by voxel application of Beer’s Law,
the emission source strength is corrected for the attenuation of item, the TGS analysis explicitly takes into account the cross
talk between various vertical layers of the item.
the matrix material.
5.6 The TGS analysis technique uses a material basis set
4.4 Count rate-dependent losses from pulse pile-up and
method that does not require the user to select a mass
analyzer deadtime are monitored and corrected.
attenuation curve apriori, provided the transmission source has
4.5 The TGS determines an estimate of the average attenu-
at least 2 gamma lines that span the energy range of interest.
ation coefficient of each voxel in a layer of matrix using an
5.7 AcommerciallyavailableTGSsystemconsistsofbuild-
over determined set of transmission measurements.
ing blocks that can easily be configured to operate the system
4.6 Acollimatorisusedinfrontofthedetectortorestrictthe
in the SGS mode or in a far-field geometry.
measurement to a well-defined solid angle.
5.8 The TGS provides 3-dimensional maps of gamma ray
4.7 The TGS technique assumes the following item charac-
attenuation and radionuclide concentration within an item that
teristics:
can be used as a diagnostic tool.
4.7.1 The particles containing the radionuclides of interest
5.9 Item preparation is limited to avoiding large quantities
are small enough to minimize self-absorption of emitted
of heavily attenuating materials (such as lead shielding) in
gamma radiation. Corrections to self-attenuation may be ap-
ordertoallowsufficienttransmissionthroughthecontainerand
plied post TGS analysis, but is outside the scope of this
the matrix.
standard.
4.7.2 The mixture of material within each item voxel is
6. Interferences
sufficiently uniform that an attenuation correction factor, com-
6.1 Radionuclides may be present in an item that produce
putedfromameasurementofgammaraytransmissionthrough
gamma rays with energies the same
...
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