ASTM C1415-18

Standard Test Method for ²³⁸Pu Isotopic Abundance By Alpha Spectrometry

SIGNIFICANCE AND USE
5.1 This test method is used when the determination of  238Pu isotopic abundance is required for plutonium samples.
SCOPE
1.1 This test method covers the use of alpha spectrometry for determining the  238Pu isotopic abundance in plutonium samples. It is particularly useful for samples in which the  238Pu content is less than 1 % of the total plutonium content. For such samples, mass spectrometric results are vulnerable to bias because of potential interference from any  238U isobar remaining after ion exchange.  
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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-May-2018
• ICS: 71.060.10 - Chemical elements
• Technical Committee: C26 - Nuclear Fuel Cycle
• Drafting Committee: C26.05 - Methods of Test

Relations

• Replaces: ASTM C1415-14 - Standard Test Method for ²³⁸Pu Isotopic Abundance By Alpha Spectrometry
• Effective Date: 01-Jun-2018
• Refers: ASTM C859-24 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C1672-23 - Standard Test Method for Determination of the Uranium, Plutonium or Americium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
• Effective Date: 01-Dec-2023
• Refers: ASTM C1168-23 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Oct-2023
• Refers: ASTM C1411-20 - Standard Practice for The Ion Exchange Separation of Uranium and Plutonium Prior to Isotopic Analysis
• Effective Date: 01-Jul-2020
• Refers: ASTM C1672-17 - Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
• Effective Date: 01-Jan-2017
• Refers: ASTM C697-16 - Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Plutonium Dioxide Powders and Pellets
• Effective Date: 01-Jun-2016
• Refers: ASTM C1816-16 - Standard Practice for The Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium Prior to Isotopic Abundance and Content Analysis
• Effective Date: 15-Jan-2016
• Refers: ASTM C1168-15 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Sep-2015
• Refers: ASTM C1816-15 - Standard Practice for The Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium Prior to Isotopic Abundance and Content Analysis
• Effective Date: 01-Jun-2015
• Refers: ASTM C859-14a - Standard Terminology Relating to Nuclear Materials
• Effective Date: 15-Jun-2014
• Refers: ASTM C859-14 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 15-Jan-2014
• Refers: ASTM C1672-07(2014) - Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
• Effective Date: 01-Jan-2014
• Refers: ASTM C1411-14 - Standard Practice for The Ion Exchange Separation of Uranium and Plutonium Prior to Isotopic Analysis
• Effective Date: 01-Jan-2014
• Refers: ASTM C859-13a - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jun-2013

Overview

ASTM C1415-18 is a standardized test method developed by ASTM International for determining the isotopic abundance of plutonium-238 (^238Pu) in plutonium samples using alpha spectrometry. This standard is particularly valuable when ^238Pu content is below 1% of the total plutonium content, where mass spectrometric methods may be susceptible to bias due to potential interference from residual uranium isobars. The method includes essential guidance for sample preparation, purification, spectrometric analysis, and calculation of isotopic abundance, all conducted in compliance with internationally recognized standardization principles.

Key Topics

• Alpha Spectrometry: Use of alpha spectrometry for quantifying ^238Pu isotopic abundance, based on measurement of alpha activity ratios.
• Sample Preparation and Purification: Guidance on purification steps to eliminate interferences, especially from uranium and americium, using anion-exchange techniques.
• Apparatus Requirements: Specification of suitable equipment, such as silicon-based alpha detectors, light-tight chambers, and multichannel analyzers, for accurate alpha spectroscopy.
• Reagents and Materials: Establishing reagent grade chemical requirements, especially for water and nitric acid, as well as the use of specific anion-exchange resins.
• Calibration and Quality Control: Protocols for calibration of the alpha spectrometer, including periodic checks and background measurements to ensure accuracy and reliability.
• Precision and Bias: Evaluation of measurement precision and bias by repeated analysis of certified reference materials.

Applications

This test method is widely used in nuclear laboratories, nuclear fuel processing facilities, and other research or regulatory environments where the isotopic composition of plutonium must be determined accurately. Its practical applications include:

• Nuclear Safeguards: Supporting the tracking and accountability of special nuclear material in compliance with national and international oversight.
• Nuclear Forensics: Providing high-precision isotopic data critical for tracing the origin and history of plutonium samples.
• Nuclear Waste Management: Assisting in the characterization of nuclear materials for disposal or reprocessing.
• Quality Assurance: Enabling laboratories to verify the ^238Pu composition in materials used for reactor fuel, medical, or industrial applications.

Key benefits of this method include its reliability in cases where ^238Pu content is low and where mass spectrometry may be less accurate due to interfering isotopes.

Related Standards

For comprehensive plutonium and uranium analysis, the following ASTM standards are referenced and often used alongside ASTM C1415-18:

• ASTM C697: Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Plutonium Dioxide Powders and Pellets
• ASTM C859: Terminology Relating to Nuclear Materials
• ASTM C1168: Preparation and Dissolution of Plutonium Materials for Analysis
• ASTM C1411: Ion Exchange Separation of Uranium and Plutonium Prior to Isotopic Analysis
• ASTM C1625: Uranium and Plutonium Concentrations and Isotopic Abundances by Thermal Ionization Mass Spectrometry
• ASTM C1672: Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
• ASTM C1816: Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium Prior to Isotopic Analysis
• ASTM D1193: Specification for Reagent Water

These complementary standards help ensure rigorous, reproducible plutonium isotopic analyses within the nuclear industry.

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Keywords: alpha spectrometry, plutonium-238, isotopic abundance, ASTM C1415-18, nuclear material analysis, ion exchange, nuclear safeguards, nuclear forensics, standard test method.

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: C1415 − 18
Standard Test Method for
238 1
Pu Isotopic Abundance By Alpha Spectrometry
This standard is issued under the fixed designation C1415; 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 C1625 Test Method for Uranium and Plutonium Concentra-
tions and Isotopic Abundances by Thermal Ionization
1.1 This test method covers the use of alpha spectrometry
238 Mass Spectrometry
for determining the Pu isotopic abundance in plutonium
238 C1672 Test Method for Determination of Uranium or Pluto-
samples.Itisparticularlyusefulforsamplesinwhichthe Pu
nium Isotopic Composition or Concentration by the Total
contentislessthan1 %ofthetotalplutoniumcontent.Forsuch
Evaporation Method Using a Thermal Ionization Mass
samples, mass spectrometric results are vulnerable to bias
238 Spectrometer
because of potential interference from any U isobar remain-
C1816 Practice for The Ion Exchange Separation of Small
ing after ion exchange.
Volume Samples Containing Uranium, Americium, and
1.2 The values stated in SI units are to be regarded as the
Plutonium Prior to Isotopic Abundance and Content
standard. The values given in parentheses are for information
Analysis
only.
D1193 Specification for Reagent Water
1.3 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 Except as otherwise defined herein, definitions of terms
priate safety, health, and environmental practices and deter-
are as given in Terminology C859.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
4. Summary of Test Method
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the 4.1 Thisdeterminationmethodinvolvesthemeasurementof
238 239 240
Development of International Standards, Guides and Recom- thealpha-activityratioof Puand Pu+ Pu.Theisotopic
analysis of plutonium for the Pu isotope requires the prior
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. separation of potentially interfering species. After dissolution
of the sample (see Practice C1168), the plutonium is separated
2. Referenced Documents
from interferences by purification techniques such as given in
this test method or in Practices C1411 or C1816.
2.1 ASTM Standards:
C697 Test Methods for Chemical, Mass Spectrometric, and
4.2 In this test method, nitric acid (HNO ) is used to adsorb
Spectrochemical Analysis of Nuclear-Grade Plutonium
theplutoniumfractionontheresin.Interferingions,principally
Dioxide Powders and Pellets
uranium and americium, are not adsorbed. The plutonium is
C859 Terminology Relating to Nuclear Materials
then eluted with dilute HNO (0.1 M).
C1168 PracticeforPreparationandDissolutionofPlutonium
4.3 Because an alpha-activity ratio is used, quantitative
Materials for Analysis
recovery of the plutonium is not required. The alpha spectrum
C1411 Practice for The Ion Exchange Separation of Ura-
in the 5 to 6-MeV region is obtained. The total counts in the
nium and Plutonium Prior to Isotopic Analysis
238 239 240
Pu and the Pu + Pu peaks are obtained and corrected
for background. The Pu abundance is calculated from the
238 239
ratio of the alpha activity due to Pu and that due to Pu +
This test method is under the jurisdiction ofASTM Committee C26 on Nuclear
240 239 240
Pu. The abundance of Pu and Pu is determined by
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Test. mass spectrometry (see Test Methods C697, C1625,or C1672)
CurrenteditionapprovedJune1,2018.PublishedJuly2018.Originallyapproved
on a separate portion of the purified sample.
in 1999. Last previous edition approved in 2014 as C1415 – 14. DOI: 10.1520/
C1415-18.
5. Significance and Use
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.1 This test method is used when the determination of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Pu isotopic abundance is required for plutonium samples.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1415 − 18
6. Interferences 8. Reagents and Materials
6.1 Am-241 is always present as a result of Pu decay and 8.1 Purity of Reagents—Reagent grade chemicals are used
is a direct interference that must be removed prior to the in all tests and conform to the specifications of the Committee
238 230 3
determination of Pu. The very small amount of Th and on Analytical Reagents of the American Chemical Society.
Th which could be present causes insignificant interference
8.2 Purity of Water—Unless otherwise indicated, references
with the determination of Pu at the level of uncertainty of
to water shall be understood to mean distilled or deionized
this test method. Other nuclides that could interfere, such as
water in conformance with Specification D1193, Type I.
238 243 245 249
U, Am, Cm, and Bk, are removed by purification
8.3 Nitric acid (HNO ). Concentrated (sp gr 1.42).
prior to analysis. Any residual uranium, while it does not
directly interfere with the alpha-pulse height determination, 8.4 Nitric acid, 4 M. Add 250 mLof nitric acid (sp gr 1.42)
can raise the salt content of the sample.Ahigh salt content can
to <750 mL of water and dilute to 1 L.
decrease the resolution of the alpha spectra, and, consequently,
8.5 Nitric acid, 0.1 M.Add6.2mLofnitricacid(spgr1.42)
decrease the accuracy of the test method.
to <950 mL of water and dilute to 1 L.
7. Apparatus
8.6 Anion-exchange resin and column, 74-149 µm (100-200
mesh) dry size, containing quaternary ammonium functional
7.1 Counting disks of polished platinum, tantalum, or stain-
groups.
less steel, sized to fit the detection chamber. A disk 25 mm in
diameter and 0.5 mm thick has been found to be acceptable.
9. Calibration of the Alpha Spectrometer
7.2 Alpha spectrometer. This instrument may consist of the
following individual components but more typically as an 9.1 Initial Calibration—Set the amplifier so that channel
zero is about 4.75 MeV. Use a standard alpha source such as
integrated system that is readily interfaced to a computer:
the 5.30 MeV particle of Po, or the 5.49 MeV particle of
7.2.1 Silicon based alpha detector, with an active area of at
2 241
Am, for energy calibration. Establish the system gain at
least 100 mm , a depletion depth of 100 µm or more, and a
someconvenientvaluethatwillcovertheneededenergyrange.
resolution of 50 keV or less full width at half maximum
(FWHM) (for Am 5.486 MeV alpha).
9.2 Resolution—Count the standard source and determine
the energy span at half the peak height. A full width half
NOTE 1—A FWHM of 30 keV or less is desirable, but a FWHM up to
50 keV can be tolerated.
maximum of 30 keVor less is desirable, but a FWHM up to 50
keV can be tolerated.
7.2.2 Evacuable, light-tight chamber in which the detector
and the counting plate on its support can be mounted.
9.3 Background—Obtain a background spectrum with a
7.2.3 Preamplifier (charge-sensitive field-effect transistor)
clean counting disk in the chamber.
with noise less than 4.6 keV when used with above detector
9.4 Frequency of Calibration—The energy calibration and
(100 pF capacitance).
energy resolution should be checked periodically, to maintain
7.2.4 Detector bias supply, 0 to 150 V, continuously
the same operating conditions and to check whether the
variable, well-regulated and stable, with noise and ripple less
spectrometer has deteriorated. Daily or similarly frequent
than 0.0002 %.
background counting is advisable, to ensure that neither the
7.2.5 Main spectroscopy amplifier, low noise, with variable
chamber nor the detector has been overly contaminated and
shaping constants and baseline restoration.
that an appropriate background correction is accomplished.
7.2.6 Biased amplifier and pulse stretcher, with continu-
ously adjustable post-gain and automatic pile-up rejection.
10. Procedure
7.2.7 Multichannel pulse-height analyzer. A multichannel
NOTE 2—Procedure steps 10.2 through 10.7 were developed based on
analyzer is most versa
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C1415 − 14 C1415 − 18
Standard Test Method for
238 1
Pu Isotopic Abundance By Alpha Spectrometry
This standard is issued under the fixed designation C1415; 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 use of alpha spectrometry for determining the Pu isotopic abundance in plutonium samples.
It is particularly useful for samples in which the Pu content is less than 1 % of the total plutonium content. For such samples,
mass spectrometric results are vulnerable to bias because of potential interference from any U isobar remaining after ion
exchange.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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:
C697 Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Plutonium Dioxide
Powders and Pellets
C859 Terminology Relating to Nuclear Materials
C1168 Practice for Preparation and Dissolution of Plutonium Materials for Analysis
C1411 Practice for The Ion Exchange Separation of Uranium and Plutonium Prior to Isotopic Analysis
C1625 Test Method for Uranium and Plutonium Concentrations and Isotopic Abundances by Thermal Ionization Mass
Spectrometry
C1672 Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total
Evaporation Method Using a Thermal Ionization Mass Spectrometer
C1816 Practice for The Ion Exchange Separation of Small Volume Samples Containing Uranium, Americium, and Plutonium
Prior to Isotopic Abundance and Content Analysis
D1193 Specification for Reagent Water
3. Terminology
3.1 For Except as otherwise defined herein, definitions of pertinent terms not listed here, seeterms are as given in Terminology
C859.
4. Summary of Test Method
238 239 240
4.1 This determination method involves the measurement of the alpha-activity ratio of Pu and Pu + Pu. The isotopic
analysis of plutonium for the Pu isotope requires the prior separation of potentially interfering species. After dissolution of the
sample (see Practice C1168), the plutonium is separated from interferences by purification techniques such as given in this test
method or in Practices C1411 or C1816.
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, 2014June 1, 2018. Published July 2014July 2018. Originally approved in 1999. Last previous edition approved in 20072014 as
C1415 – 01a (2007).C1415 – 14. DOI: 10.1520/C1415-14.10.1520/C1415-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1415 − 18
4.2 In this test method, nitric acid (HNO ) is used to adsorb the plutonium fraction on the resin. Interfering ions, principally
uranium and americium, are not adsorbed. The plutonium is then eluted with dilute HNO (0.1 M).
238 239 240
4.3 This determination method involves the measurement of the alpha-activity ratio of Pu and Pu + Pu. The isotopic
analysis of plutonium for the Pu isotope requires the prior separation of potentially interfering species. After dissolution of the
sample (see Practice C1168), the plutonium is separated from interferences by an anion-exchange purification technique. Nitric
acid (HNO ) is used to adsorb the plutonium fraction on the resin. Interfering ions, principally uranium and americium, are not
adsorbed. The plutonium is then eluted with dilute HNO (0.1 M). Because an alpha-activity ratio is used, quantitative recovery
of the plutonium is not required. The alpha spectrum in the 5 to 6-MeV region is obtained. The total counts in the Pu and the
239 240 238
Pu + Pu peaks are obtained and corrected for background. The Pu abundance is calculated from the ratio of the alpha
238 239 240 239 240
activity due to Pu and that due to Pu + Pu. The abundance of Pu and Pu is determined by mass spectrometry (see
Test Methods C697, C1625, or C1672) on a separate portion of the purified sample.
5. Significance and Use
5.1 This test method is used when the determination of Pu isotopic abundance is required for plutonium samples.
6. Interferences
6.1 Am-241 is always present as a result of Pu decay and is a direct interference that must be removed prior to the
238 230 232
determination of Pu. The very small amount of Th and Th which could be present causes insignificant interference with
238 238 243
the determination of Pu at the level of uncertainty of this test method. Other nuclides that could interfere, such as U, Am,
245 249
Cm, and Bk, are removed by the anion-exchange separation. purification prior to analysis. Any residual uranium, while it
does not directly interfere with the alpha-pulse height determination, can raise the salt content of the sample. A high salt content
can decrease the resolution of the alpha spectra, and, consequently, decrease the accuracy of the test method.
7. Apparatus
7.1 Counting disks of polished platinum, tantalum, or stainless steel, sized to fit the detection chamber. A disk 25 mm in
diameter and 0.5 mm thick has been found to be acceptable.
7.2 Alpha spectrometer. This instrument may consist of the following individual components but more typically as an integrated
system that is readily interfaced to a computer:
7.2.1 Silicon surface barrierbased alpha detector, with an active area of at least 100 mm , a depletion depth of greater than 100
μm,100 μm or more, and a resolution of 3050 keV or less full width at half maximum (FWHM) (for Am 5.486 MeV alpha).
NOTE 1—A FWHM of 30 keV or less is desirable, but a FWHM up to 50 keV can be tolerated.
7.2.2 Evacuable, light-tight chamber in which the detector and the counting plate on its support can be mounted.
7.2.3 Preamplifier (charge-sensitive field-effect transistor) with noise less than 4.6 keV when used with above detector (100 pF
capacitance).
7.2.4 Detector bias supply, 0 to 150 V, continuously variable, well-regulated and stable, with noise and ripple less than
0.0002 %.
7.2.5 Main spectroscopy amplifier, low noise, with variable shaping constants and baseline restoration.
7.2.6 Biased amplifier and pulse stretcher, with continuously adjustable post-gain and automatic pile-up rejection.
7.2.7 Multichannel pulse-height analyzer. A A multichannel analyzer is most versatile and convenient, since it can be used for
the acquisition of data from one to four detectors, simultaneously. Even if only one detector is used, such an analyzer has the
advantages that background may be stored in another subgroup and subtracted electronically from the spectrum of interest, and
that several spectra can be stored and compared. An analyzer that permits the analyst to set windows around the peaks of interest
and perform electronic integration is especially convenient. The analyzer should accept pulses 0 to 10 V and 3 to 6 μs in width
and should have a capacity of at least 10 counts full scale per channel.
7.3 Heat lamp.
7.4 Bunsen burner, or similar heat source device.
7.5 Sample beaker, 30-mL, borosilicate glass.
7.6 Bottles or vials.
7.7 Hot plate.
C1415 − 18
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals are used in all tests and conform to the specifications of the Committee on
Analytical Reagents of the American Chemical Society.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean distilled or deionized water
(Specification in conformance with Specification D1193). , Type I.
8.3 Nitric acid (HNO ). Concentrated (sp gr 1.42).
8.4 Nitric acid, 4 M. Add 250 mL of nitric acid (sp gr 1.42) to <750 mL of water and dilute to 1 L.
8.5 Nitric acid, 0.1 M. Add 6.2 mL of nitric acid (sp gr 1.42) to <950 mL of water and dilute to 1 L.
8.6 Anion-exchange resin and column, 100-200 mesh, 74-149 μm
...