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ASTM C1726/C1726M-10(2018)

(Guide)

Standard Guide for Use of Modeling for Passive Gamma Measurements

Standard Guide for Use of Modeling for Passive Gamma Measurements

SIGNIFICANCE AND USE
5.1 The following methods assist in demonstrating regulatory compliance in such areas as safeguards (Special Nuclear Material), inventory control, criticality control, decontamination and decommissioning, waste disposal, holdup and shipping.  
5.2 This guide can apply to the assay of radionuclides in containers, whose gamma-ray absorption properties can be measured or estimated, for which representative certified standards are not available. It can be applied to in situ measurements, measurement stations, or to laboratory measurements.  
5.3 Some of the modeling techniques described in the guide are suitable for the measurement of fall-out or natural radioactivity homogenously distributed in soil.  
5.4 Source-based efficiency calibrations for laboratory geometries may suffer from inaccuracies due to gamma rays being detected in true coincidence. Modeling can be an advantage since it is unaffected by true coincidence summing effects.
SCOPE
1.1 This guide addresses the use of models with passive gamma-ray measurement systems. Mathematical models based on physical principles can be used to assist in calibration of gamma-ray measurement systems and in analysis of measurement data. Some nondestructive assay (NDA) measurement programs involve the assay of a wide variety of item geometries and matrix combinations for which the development of physical standards are not practical. In these situations, modeling may provide a cost-effective means of meeting user’s data quality objectives.  
1.2 A scientific knowledge of radiation sources and detectors, calibration procedures, geometry and error analysis is needed for users of this standard. This guide assumes that the user has, at a minimum, a basic understanding of these principles and good NDA practices (see Guide C1592/C1592M), as defined for an NDA professional in Guide C1490. The user of this standard must have at least a basic understanding of the software used for modeling. Instructions or further training on the use of such software is beyond the scope of this standard.  
1.3 The focus of this guide is the use of response models for high-purity germanium (HPGe) detector systems for the passive gamma-ray assay of items. Many of the models described in this guide may also be applied to the use of detectors with different resolutions, such as sodium iodide or lanthanum halide. In such cases, an NDA professional should determine the applicability of sections of this guide to the specific application.  
1.4 Techniques discussed in this guide are applicable to modeling a variety of radioactive material including contaminated fields, walls, containers and process equipment.  
1.5 This guide does not purport to discuss modeling for “infinite plane” in situ measurements. This discussion is best covered in ANSI N42.28.  
1.6 This guide does not purport to address the physical concerns of how to make or set up equipment for in situ measurements but only how to select the model for which the in situ measurement data is analyzed.  
1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.8 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.9 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.

General Information

Status
Published
Publication Date
31-Mar-2018
ICS
17.240 - Radiation measurements
Technical Committee
C26 - Nuclear Fuel Cycle
Drafting Committee
C26.10 - Non Destructive Assay
Current Stage
Ref Project

Relations

Refers
ASTM C1673-10a(2018) - Standard Terminology of C26.10 Nondestructive Assay Methods
Effective Date
01-Apr-2018
Referred By
ASTM C1592/C1592M-21 - Standard Guide for Making Quality Nondestructive Assay Measurements
Effective Date
01-Apr-2018

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ASTM C1726/C1726M-10(2018) - Standard Guide for Use of Modeling for Passive Gamma MeasurementsASTM C1726/C1726M-10(2018) - Standard Guide for Use of Modeling for Passive Gamma Measurements
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ASTM C1726/C1726M-10(2018) - Standard Guide for Use of Modeling for Passive Gamma Measurements
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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: C1726/C1726M − 10 (Reapproved 2018)
Standard Guide for
1
Use of Modeling for Passive Gamma Measurements
This standard is issued under the fixed designation C1726/C1726M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 This guide does not purport to address the physical
concerns of how to make or set up equipment for in situ
1.1 This guide addresses the use of models with passive
measurements but only how to select the model for which the
gamma-ray measurement systems. Mathematical models based
in situ measurement data is analyzed.
on physical principles can be used to assist in calibration of
1.7 The values stated in either SI units or inch-pound units
gamma-ray measurement systems and in analysis of measure-
are to be regarded separately as standard. The values stated in
ment data. Some nondestructive assay (NDA) measurement
programs involve the assay of a wide variety of item geom- each system may not be exact equivalents; therefore, each
system shall be used independently of the other. Combining
etries and matrix combinations for which the development of
physical standards are not practical. In these situations, mod- values from the two systems may result in non-conformance
with the standard.
eling may provide a cost-effective means of meeting user’s
data quality objectives.
1.8 The values stated in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical
1.2 A scientific knowledge of radiation sources and
conversions to SI units that are provided for information only
detectors, calibration procedures, geometry and error analysis
and are not considered standard.
isneededforusersofthisstandard.Thisguideassumesthatthe
user has, at a minimum, a basic understanding of these
1.9 This international standard was developed in accor-
principles and good NDA practices (see Guide C1592/
dance with internationally recognized principles on standard-
C1592M),asdefinedforanNDAprofessionalinGuideC1490.
ization established in the Decision on Principles for the
The user of this standard must have at least a basic understand-
Development of International Standards, Guides and Recom-
ing of the software used for modeling. Instructions or further
mendations issued by the World Trade Organization Technical
training on the use of such software is beyond the scope of this
Barriers to Trade (TBT) Committee.
standard.
2. Referenced Documents
1.3 The focus of this guide is the use of response models for
2
2.1 ASTM Standards:
high-purity germanium (HPGe) detector systems for the pas-
C1490 GuidefortheSelection,TrainingandQualificationof
sive gamma-ray assay of items. Many of the models described
Nondestructive Assay (NDA) Personnel
in this guide may also be applied to the use of detectors with
C1592/C1592M Guide for Making Quality Nondestructive
different resolutions, such as sodium iodide or lanthanum
3
Assay Measurements (Withdrawn 2018)
halide. In such cases, an NDA professional should determine
C1673 Terminology of C26.10 Nondestructive Assay Meth-
the applicability of sections of this guide to the specific
ods
application.
4
2.2 Other Standard:
1.4 Techniques discussed in this guide are applicable to
ANSI N42.28 Performance Standard for the Calibration of
modeling a variety of radioactive material including contami-
Germanium Detectors for In Situ Gamma-Ray Measure-
nated fields, walls, containers and process equipment.
ments
1.5 This guide does not purport to discuss modeling for
3. Terminology
“infinite plane” in situ measurements. This discussion is best
3.1 See Terminology C1673.
covered in ANSI N42.28.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
1
This guide is under the jurisdiction ofASTM Committee C26 on Nuclear Fuel Standards volume information, refer to the standard’s Document Summary page on
Cycle and is the direct responsibility of Subcommittee C26.10 on Non Destructive the ASTM website.
3
Assay. The last approved version of this historical standard is referenced on
Current edition approved April 1, 2018. Published May 2018. Originally www.astm.org.
4
approved in 2010. Last previous edition approved in 2010 as C1726/C1726M – 10. Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
DOI: 10.1520/C1726_C1726M-10R18. 4th Floor, New York, NY 10036, http://www.ansi.org.
C
...

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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.  
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5.1 Refer to Guide E844 for the selection, irradiation, and quality control of neutron dosimeters.  
5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors.  
5.3 Pure aluminum in the form of foil or wire is readily available and easily handled. 27Al has an abundance of 100 % (1).3  
5.4 24Na has a half-life of 14.958 (2)4 h (2) and emits gamma rays with energies of 1.368630 (5) and 2.754049 (13) MeV (2).  
5.5 Fig. 1 shows a plot of the International Reactor Dosimetry and Fusion File (IRDFF-II) cross section (3, 4) versus neutron energy for the fast-neutron reaction  27Al(n,α) 24Na (3) along with a comparison to the current experimental database (5, 6). While the RRDF-2008 and IRDFF-1.05 cross sections extend from threshold up to 60 MeV, due to considerations of the available validation data, the energy region over which this standard recommends use of this cross section for reactor dosimetry applications only extends from threshold at ~4.25 MeV up to 20 MeV. This figure is for illustrative purposes and is used to indicate the range of response of the  27Al(n,α) reaction. Refer to Guide E1018 for recommended sources for the tabulated dosimetry cross sections.
FIG. 1 27Al(n,α)24Na Cross Section, from IRDFF-II Library, with EXFOR Experimental Data  
5.6 Two competing activities, 28Al (2.25 (2) minute half-life) and 27Mg (9.458 (12) minute half-life), are formed in the reactions 27Al(n,γ)28Al and 27Al(n,p)27Mg, respectively, but these can be eliminated by waiting 2 h before counting.
SCOPE
1.1 This test method covers procedures measuring reaction rates by the activation reaction  27Al(n,α)24Na.  
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1.3 With suitable techniques, fission-neutron fluence rates above 106 cm−2·s−1 can be determined.  
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6 – 11  
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Standard Practice for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver

SIGNIFICANCE AND USE
3.1 This practice uses one monitor (cobalt) with a nearly 1/v absorption cross-section curve and a second monitor (silver) with a large resonance peak so that its resonance integral is large compared to its thermal cross section. The pertinent data for these two reactions are given in Table 1. The equations are based on the Westcott formalism ((2, 3) and Practice E261) and determine a Westcott 2200 m/s neutron fluence rate nv0 and the Westcott epithermal index parameter  . References (4-6) contain a general discussion of the two-reaction test method. In this practice, the absolute activities of both cobalt and silver monitors are determined. This differs from the test method in the references wherein only one absolute activity is determined.  (A) The numbers in parentheses following given values are the uncertainty in the last digit(s) of the value; 0.729 (8) means 0.729 ± 0.008, 70.8(1) means 70.8 ± 0.1.(B) The decay constant, λ, is defined as ln(2) / t1/2 with units of sec–1, where t1/2 is the nuclide half-life in seconds.(C) Calculated using Eq 10.(D) In Fig. 1, Θ = 4ErkT/AΓ2 = 0.2 corresponds to the value for 109Ag for T = 293 K, ∑r = N0σr,max,T=0Kσr,max,T=0K = 31138.03 barn at 5.19 eV (13). The value of σr,max,T=0K = 31138.03 barns is calculated using the Breit-Wigner single-level resonance formula  where the 109Ag atomic mass is A = 108.9047558 amu (14), the ENDF/B-VIII.0 (MAT = 4731) (13) resonance parameters are: resonance total width Γ = 0.1427333 eV, formation neutron width Γn = 0.0127333 eV, and radiative/decay width Γγ = 0.13 eV, with a resonance spin J=1, and the statistical spin factor  where s1 = 1/2 and s2 = 1/2 are the spins of the two particles (neutron and 109Ag ground state (15)) forming resonance.  
3.2 The advantages of this approach are the elimination of four difficulties associated with the use of cadmium: (1) the perturbation of the field by the cadmium; (2) the inexact cadmium cut-off energy; (3) the low melting temperature of cadmium; a...
SCOPE
1.1 This practice covers a suitable means of obtaining the thermal neutron fluence rate, or fluence, in nuclear reactor environments where the use of cadmium, as a thermal neutron shield as described in Test Method E262, is undesirable for reasons such as potential spectrum perturbations or due to temperatures above the melting point of cadmium.  
1.2 The reaction 59Co(n,γ )60Co results in a well-defined gamma emitter having a half-life of 5.2711 years2 (8)3 (1).4 The reaction 109Ag(n,γ)110mAg results in a nuclide with a well-known, complex decay scheme with a half-life of 249.78 (2) days (1). Both cobalt and silver are available either in very pure form or alloyed with other metals such as aluminum. A reference source of cobalt in aluminum alloy to serve as a neutron fluence rate monitor wire standard is available from the National Institute of Standards and Technology (NIST) as Standard Reference Material (SRM) 953.5 The competing activities from neutron activation of other isotopes are eliminated, for the most part, by waiting for the short-lived products to die out before counting. With suitable techniques, thermal neutron fluence rate in the range from 108 cm−2·s−1 to 3 × 1015 cm−2·s−1 can be measured. Two calculational practices are described in Section 9 for the determination of neutron fluence rates. The practice described in 9.3 may be used in all cases. This practice describes a means of measuring a Westcott neutron fluence rate in 9.2 (Note 1) by activation of cobalt- and silver-foil monitors (see Terminology E170). For the Wescott Neutron Fluence Convention method to be applicable, the measurement location must be well moderated and be well represented by a Maxwellian low-energy distribution and an (1/E) epithermal distribution. These conditions are usually only met in positions surrounded by hydrogenous moderator without nearby strongly multiplying or absorbing materials.
Note 1: Westcott fluence rate    ...

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