ASTM C1268-23

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Designation: C1268 − 15 C1268 − 23
Standard Test Method for
Quantitative Determination of Am in Plutonium by
Gamma-Ray Spectrometry
This standard is issued under the fixed designation C1268; 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
1.1 This test method covers the quantitative determination of Am by gamma-ray spectrometry in plutonium nitrate solution
samples that do not contain significant amounts of radioactive fission products or other high specific activity gamma-ray emitters.
1.2 This test method can be used to determine the Am in samples of plutonium metal, oxide and other solid forms, when the
solid is appropriately sampled and dissolved.
1.3 The values stated in SI units are to be regarded as standard. Additionally, the non-SI units of electron volts, kiloelectron volts,
and liters are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
C758 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-
Grade Plutonium Metal
C759 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-
Grade Plutonium Nitrate Solutions
C859 Terminology Relating to Nuclear Materials
C1009 Guide for Establishing and Maintaining a Quality Assurance Program for Analytical Laboratories Within the Nuclear
Industry
C1168 Practice for Preparation and Dissolution of Plutonium Materials for Analysis
C1592/C1592M Guide for Making Quality Nondestructive Assay Measurements
E181E3376 GuidePractice for Detector Calibration and Analysis of Radionuclides Usage of Germanium Detectors in Radiation
Metrology for Reactor Dosimetry
This test method is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of Test.
Current edition approved June 1, 2015Oct. 1, 2023. Published July 2015November 2023. Originally approved in 1994. Last previous edition approved in 20082015 as
C1268 – 94 (2008).C1268 – 15. DOI: 10.1520/C1268-15.10.1520/C1268-23.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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2.2 U.S. Nuclear Regulatory Commission Regulatory Guides:
Regulatory Guide 5.9, Rev. 2—Guidelines for Germanium Spectroscopy Systems for Measurement of Special Nuclear
MaterialsMaterial
Regulatory Guide 5.53, Rev. 1—Qualification, Calibration, and Error Estimation Methods for Nondestructive Assay
3. Terminology
3.1 Except as otherwise defined herein, definitions of terms are as given in Terminology C859.
4. Summary of Test Method
4.1 An aliquot of the sample that contains about 1010 ng to 100 ng of Am is analyzed by measuring the intensity of the
characteristic 59.5 keV gamma ray emitted by Am.
4.2 Multiple sample geometries may be used if an appropriate calibration for each geometry is made.
4.3 The sample geometry must be reproducible. This includes the physical characteristics of the sample container, the positioning
of the sample, and the volume of sample viewed by the gamma-ray detector.
4.4 Electronic corrections are made, if required, for the effects of pulse pile-up and dead time losses due to the activity of the
sample. The necessity of dead time and pulse pile-up corrections can be reduced by sample dilution to control count rates.
4.5 A correction is made for the contribution to the 59.5 keV intensity due to gamma rays produced in the decay of U.
4.6 The relationship between the measured gamma-ray intensity and the Am content is determined by the use of appropriate
standards.
5. Significance and Use
5.1 This test method allows the determination of Am in a plutonium solution without separation of the americium from the
plutonium. It is generally applicable to any solution containing Am.
5.2 The Am in solid plutonium materials may be determined when these materials are dissolved (see Practice C1168).
5.3 When the plutonium solution contains unacceptable levels of fission products or other materials, this method may be used
following a tri-n-octylphosphine oxide (TOPO) extraction, ion exchange or other similar separation techniques (see Test Methods
C758 and C759).
5.4 This test method is less subject to interferences from plutonium than alpha counting since the energy of the gamma ray used
for the analysis is better resolved from other gamma rays than the alpha particle energies used for alpha counting.
5.5 The minimal sample preparation reduces the amount of sample handling and exposure to the analyst.
5.6 This test method is applicable only to homogeneous solutions. This test method is not suitable for solutions containing solids.
241 −5 241
5.7 Solutions containing Am at concentrations as little as 1 × 10 g/L Am may be analyzed using this method. The lower
limit depends on the detector used and the counting geometry. Solutions containing high concentrations may be analyzed following
an appropriate dilution.
6. Interferences
6.1 The presence of other radioactive nuclides in the sample or in the vicinity of the detector may produce interferences. These
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C1268 − 23
may be due to the Compton scattering of high energy gamma rays which contribute to the background in the region of interest or
from gamma rays with energies close to the energies used for the analysis.
6.2 The presence of U will interfere if a correction is not applied. This interference will lead to an over estimation of the amount
of Am present. This interference is especially pronounced in plutonium from which the americium has recently been separated.
6.3 The presence of radioactive materials in the vicinity of the gamma-ray detector which are not in the sample may create
interferences if detector shielding is not adequate. These interferences may be due to the Compton scattering of high energy gamma
rays which contribute to the background in the region of interest or from gamma rays with energies close to the energies used for
the analysis.
7. Apparatus
7.1 High-Resolution Gamma Ray Counting System—A high resolution gamma-ray counting system is required. General guidelines
for the selection of detectors and signal processing electronics are discussed in NRC Regulatory Guide 5.9. Data acquisition
systems are addressed in NRC Regulatory Guide 5.9. This system should include the following items as a minimum.
7.1.1 Germanium Photon Detector with Integral Preamplifier—A coaxial type detector should typically have a full width at half
maximum resolution of 850 eV or less at 122 keV 122 keV and 2.0 keV or less at 1332 keV. A planar type detector should typically
have a full width at half maximum resolution of 600 eV or less at 122 keV. Consideration should be given to the use of a high
efficiency detector to enhance the ability to analyze low levels of americium.
7.1.2 High Voltage Power Supply—A high voltage power supply with voltage range and current output compatible with the
detector selected is required. It is desirable that the voltage output be continuously adjustable.
7.1.3 Nuclear Spectroscopy Amplifier—Select a nuclear spectroscopy amplifier with pulse shaping, baseline restoration, and pulse
pile-up rejection circuitry.
7.1.4 Multichannel Pulse Height Analyzer (MCA)—Select an MCA with a minimum of 2048 channels. It is desirable that the MCA
be compatible with computerized operations so that data acquisition and analysis may be automated. The analog to digital
converter (ADC) associated with the MCA should have a clock rate of at least 100 MHz and the capability of digitizing the input
voltage range into a minimum of 2048 channels (other types of ADC’s which provide equivalent capabilities can be used). The
ADC should also have dead time and pulse pile-up correction capabilities.
7.2 Sample Holder, incorporating shielding to limit the interferences from background radiation sources, is required. Collimation
to restrict the view of the detector to a portion of the sample may be required. The sample holder may incorporate more than one
sample position. The sample holder shall provide reproducible positioning for each sample position so that a consistent volume
or portion of the sample is viewed by the detector.
7.3 Sample Vials of sufficient volume to contain the desired sample as described in 10.2 are required. The sample vials should be
made of low density materials and have reproducible dimensions such as wall thickness and internal diameter. Vials with identical
dimensions should be used for samples and standards.
8. Hazards
8.1 Plutonium and americium bearing materials are radioactive and toxic. Adequate laboratory facilities, gloveboxes, fume hoods,
and so forth, along with safe techniques must be used in handling samples containing these materials. A detailed discussion of all
the precautions necessary is beyond the scope of this test method; however, personnel who handle these materials should be
familiar with such safe handling practices.This standard involves work with nuclear materials. The unique hazards and controls
required to conduct the work contained in this standard from a safety, environmental, and security standpoint is the responsibility
of the facility operators, in compliance with any applicable regulations. Any information given for handling these types of materials
contained herein is meant only as a guide for consideration of the user and not a requirement.
8.2 Solutions and solids containing radioactive materials represent a potential for high radiation exposure to personnel handling
them. Appropriate sample shielding, sample handling procedures, and radiation monitoring should be employed to ensure
personnel protection.
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9. Calibration and Standardization
9.1 Calibrate the counting system for energy (eV/channel) in the range 00 keV to 300 keV using a radioactive source or sources
which emit gamma rays with well known energies. A plutonium source is an obvious choice. See MethodsPractice E181E3376,
Guide C1592/C1592M, and U.S. NRC Regulatory Guide 5.53 for further guidance.
9.2 Determine the relative detection efficiency (counts/emitted gamma ray) of the counting system in the 0 to 300 keV 0 keV to
300 keV range. Specifically, the efficiency at 59.5 keV and 208 keV 59.5 keV and 208 keV needs to be determined. See
MethodsPractice E181E3376, Guide C1592/C1592M and U.S. NRC Regulatory Guide 5.53 for further guidance.
9.3 The relationship between the mass of Am and the number of 59.5 keV 59.5 keV gamma rays is established through
fundamental physics and basic nuclear constants, that is, the number of 59.5 keV gamma rays/sec/gram 59.5 keV gamma rays per
241 10
second per gram of Am = 4.543 × 10Am equals 4.543 × 10 .
10. Procedure
10.1 If necessary, prepare a plutonium solution from a solid sample following the procedure in Practice C1168 or other dissolution
procedure.
10.2 Determine the amount of solution and the dilution required to provide 1010 ng to 100 ng of Am in the selected sample
volume. The sample volume viewed by the detector should be consistent for the samples and standards used, regardless of the
concentration.
10.3 Determine the counting time necessary to achieve the desired statistical counting precision. Samples which contain more
americium will generally require less time to achieve the same statistical precision.
10.4 Quantitatively transfer the predetermined volume of solution from 9.210.2 into a sample vial and close.
10.5 Place the vial in the counting system sample holder and acquire a spectrum. The detector should see a consistent portion of
the sample volume. The same counting geometry and sample size as used for the standards must be used.
10.6 Record the sample counting time, sample volume, dilution factor, and counting geometry used if more than one is available.
11. Calculation
11.1 Using the same methods as used for the calibration, determine the background corrected net count rates for the 59.5 keV
59.5 keV gamma ray and the 208 keV gamma ray using the spectral data acqui
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