ASTM C1307-21

Standard Test Method for Plutonium Assay by Plutonium (III) Diode Array Spectrophotometry

SIGNIFICANCE AND USE
5.1 This test method is designed to determine whether a given material meets the purchaser's specification for plutonium content. This method may also be used, with sufficient qualification, for process control or accountability measurements associated with nuclear materials processing.
SCOPE
1.1 This test method describes the determination of total plutonium as plutonium(III) in nitrate and chloride solutions. The technique is applicable to solutions resulting from plutonium dioxide powders and pellets (Test Methods C697), nuclear grade mixed oxides (Test Methods C698), plutonium metal (Test Methods C758), and plutonium nitrate solutions (Test Methods C759). Solid samples are dissolved using the appropriate dissolution techniques described in Practice C1168. The use of this technique for other plutonium-bearing materials has been reported (1-6),2 but final determination of applicability must be made by the user. The applicable concentration range for plutonium sample solutions is 10 to 200 g Pu/L.
Note 1: As directly measured in the spectrophotometer, concentrations will be approximately 0.8 to 4.0 g Pu/L. Sample solutions are diluted to reach this target range. For solid samples, select the sample size and dissolved solution weight to yield sample solutions in the 10 to 30 g Pu/L range. With special preparation and spectral analysis techniques, the method has been applied to nitrate solutions in the 0.1 to 10 g Pu/L range.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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: 14-Feb-2021
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: C26 - Nuclear Fuel Cycle
• Drafting Committee: C26.05 - Methods of Test

Relations

• Refers: ASTM C859-24 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C1168-23 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Oct-2023
• Refers: ASTM D6122-23 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, Field and Laboratory Infrared Spectrophotometer, and Raman Spectrometer Based Analyzer Systems
• Effective Date: 01-Jul-2023
• Refers: ASTM D6122-19b - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jun-2019
• Refers: ASTM D6122-19a - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-May-2019
• Refers: ASTM D6122-19 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jan-2019
• Refers: ASTM C759-18 - Standard Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Plutonium Nitrate Solutions
• Effective Date: 01-Sep-2018
• Refers: ASTM C758-18 - Standard Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Plutonium Metal
• Effective Date: 01-Sep-2018
• Refers: ASTM D6122-18 - Standard Practice for Validation of the Performance of Multivariate Online, At-Line, and Laboratory Infrared Spectrophotometer Based Analyzer Systems
• Effective Date: 01-Jul-2018
• Refers: ASTM E2617-17 - Standard Practice for Validation of Empirically Derived Multivariate Calibrations
• Effective Date: 15-Dec-2017
• Refers: ASTM C698-16 - Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Mixed Oxides ((U, Pu)O<inf>2</inf>)
• Effective Date: 01-Jun-2016
• 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 C757-16 - Standard Specification for Nuclear-Grade Plutonium Dioxide Powder for Light Water Reactors
• Effective Date: 01-Apr-2016
• Refers: ASTM C1168-15 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Sep-2015
• Refers: ASTM E169-04(2014) - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 01-Aug-2014

Overview

ASTM C1307-21 is the Standard Test Method for Plutonium Assay by Plutonium (III) Diode Array Spectrophotometry, published by ASTM International. This standard specifies a robust laboratory methodology for determining total plutonium content as plutonium(III) in nitrate and chloride solutions using diode array spectrophotometry. It is crucial for assessing whether a given plutonium-bearing material meets purchaser specifications and may also support process control and accountability measurements during nuclear materials processing.

The scope of this method primarily covers solutions prepared from plutonium dioxide powders and pellets, nuclear-grade mixed oxides, plutonium metal, and plutonium nitrate solutions. With the correct preparation techniques, it is also applicable to select other plutonium-bearing materials. Applicability must always be validated by the end-user for their specific material.

Key Topics

• Plutonium (III) Diode Array Spectrophotometry: The standard describes the approach of using diode array spectrophotometers to analyze the characteristic absorbance of plutonium(III) in solution.
• Sample Preparation: Solid plutonium sources (oxide, metal, mixed oxide) are dissolved using ASTM Practice C1168 before measurement. Solutions must be properly diluted for accurate quantitation.
• Analytical Range: The method generally applies to plutonium solution concentrations from 10 to 200 g Pu/L, with specialized approaches available for lower concentrations.
• Reduction Chemistry: For nitrate matrices, ferrous sulfamate is used as a reductant; for chloride matrices, ascorbic acid is preferred. Correct selection and preparation of matrix solution is essential.
• Spectral Analysis: Measurement relies on absorbance in the blue-green region (516-640 nm), with multivariate calibration and specialized software used to determine the plutonium content and assess spectral fit quality.
• Interference Management: The method outlines approaches for managing interference from other absorbing species, undissolved particulates, and matrix effects, as well as the importance of proper calibration and spectral pre-processing.
• Quality Control: Routine use of standards and blanks, calibration curve validation, and ongoing monitoring for instrument drift are required for reliable results.
• Precision and Accuracy: Procedures align with national measurement systems and published quality assessment data.

Applications

• Material Specification Verification: Assure material batches meet specified plutonium content, supporting quality assurance for nuclear fuel manufacturers and suppliers.
• Nuclear Materials Process Control: Provide accurate, timely measurements of plutonium during conversion, purification, and fabrication steps, supporting process optimization and compliance.
• Nuclear Safeguards and Accountability: Deliver reliable quantitative plutonium assay data essential for regulatory reporting and nuclear materials management.
• Research and Development: Used in laboratories investigating plutonium chemistry, isotope separation, and advanced nuclear fuels.
• Environmental and Safety Monitoring: Supports the quantitation of plutonium in dissolved samples for safety, environmental, and waste management evaluation.

Related Standards

For a comprehensive, compliant analytical program, referencing the following related ASTM standards is recommended:

• ASTM C697 - Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Plutonium Dioxide Powders and Pellets
• ASTM C698 - Analysis of Nuclear-Grade Mixed Oxides ((U, Pu)O₂)
• ASTM C758 - Analysis of Nuclear-Grade Plutonium Metal
• ASTM C759 - Analysis of Nuclear-Grade Plutonium Nitrate Solutions
• ASTM C1168 - Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• ASTM C833, C859 - Material and Terminology Standards
• ASTM D6122, E60, E169, E1655, E2617 - Practices and guidelines for spectrophotometry and multivariate quantitative analysis

ASTM C1307-21 is an internationally recognized standard fundamental to nuclear fuel cycle laboratories, research facilities, and industrial operators seeking precise and reliable plutonium assay by spectrophotometric methods. Its protocols enable consistent results critical for safety, regulatory compliance, and operational excellence in plutonium assay and nuclear material management.

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: C1307 − 21
Standard Test Method for
Plutonium Assay by Plutonium (III) Diode Array
Spectrophotometry
This standard is issued under the fixed designation C1307; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method describes the determination of total
plutonium as plutonium(III) in nitrate and chloride solutions. C697 Test Methods for Chemical, Mass Spectrometric, and
Spectrochemical Analysis of Nuclear-Grade Plutonium
The technique is applicable to solutions resulting from pluto-
nium dioxide powders and pellets (Test Methods C697), Dioxide Powders and Pellets
C698 Test Methods for Chemical, Mass Spectrometric, and
nuclear grade mixed oxides (Test Methods C698), plutonium
metal (Test Methods C758), and plutonium nitrate solutions Spectrochemical Analysis of Nuclear-Grade Mixed Ox-
ides ((U, Pu)O )
(Test Methods C759). Solid samples are dissolved using the
appropriate dissolution techniques described in Practice C757 Specification for Nuclear-Grade Plutonium Dioxide
Powder for Light Water Reactors
C1168. The use of this technique for other plutonium-bearing
materials has been reported (1-6), but final determination of C758 Test Methods for Chemical, Mass Spectrometric,
Spectrochemical, Nuclear, and RadiochemicalAnalysis of
applicability must be made by the user. The applicable con-
centration range for plutonium sample solutions is 10 to 200 g Nuclear-Grade Plutonium Metal
Pu/L. C759 Test Methods for Chemical, Mass Spectrometric,
NOTE 1—As directly measured in the spectrophotometer, concentra-
Spectrochemical, Nuclear, and RadiochemicalAnalysis of
tionswillbeapproximately0.8to4.0gPu/L.Samplesolutionsarediluted
Nuclear-Grade Plutonium Nitrate Solutions
to reach this target range. For solid samples, select the sample size and
C833 Specification for Sintered (Uranium-Plutonium) Diox-
dissolved solution weight to yield sample solutions in the 10 to 30 g Pu/L
ide Pellets for Light Water Reactors
range. With special preparation and spectral analysis techniques, the
C859 Terminology Relating to Nuclear Materials
method has been applied to nitrate solutions in the 0.1 to 10 g Pu/Lrange.
C1168 PracticeforPreparationandDissolutionofPlutonium
1.2 The values stated in SI units are to be regarded as
Materials for Analysis
standard. No other units of measurement are included in this
D6122 Practice for Validation of the Performance of Multi-
standard.
variate Online, At-Line, Field and Laboratory Infrared
1.3 This standard does not purport to address all of the
Spectrophotometer, and Raman Spectrometer Based Ana-
safety concerns, if any, associated with its use. It is the
lyzer Systems
responsibility of the user of this standard to establish appro-
E60 Practice for Analysis of Metals, Ores, and Related
priate safety, health, and environmental practices and deter-
Materials by Spectrophotometry
mine the applicability of regulatory limitations prior to use.
E169 PracticesforGeneralTechniquesofUltraviolet-Visible
1.4 This international standard was developed in accor-
Quantitative Analysis
dance with internationally recognized principles on standard-
E1655 Practices for Infrared Multivariate Quantitative
ization established in the Decision on Principles for the
Analysis
Development of International Standards, Guides and Recom-
E2617 Practice for Validation of Empirically Derived Mul-
mendations issued by the World Trade Organization Technical
tivariate Calibrations
Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms related to nuclear materials,
This test method is under the jurisdiction ofASTM Committee C26 on Nuclear
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
refer to Terminology C859.
Test.
Current edition approved Feb. 15, 2021. Published May 2021. Originally
approved in 1995. Last previous edition approved in 2015 as C1307 – 15. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C1307-21. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1307 − 21
3.1.2 For definition of terms related to UV-visible technique variations. The software package selected should
spectrophotometry, refer to Practice E60. include a feature that indicates the quality of the analysis, such
3.1.3 For definitions of terms related to multivariate asmetricsthatindicatethesimilarityofthesamplespectrumto
calibration, refer to Practices E1655 and E2617. those in the calibration set. The user may thereby assess the
measurement reliability and the presence of interferences that
4. Summary of Method
absorb light or otherwise alter the plutonium(III) spectrum
without requiring supplemental measurements.
4.1 The concentration of plutonium in a solution is deter-
mined by the spectrophotometric measurement of the absor-
4.4 In nitrate solutions, plutonium will form a distribution
bance of visible light by plutonium(III).
of complexes with nitrate anions. For plutonium(III), these
3-x
4.1.1 In a spectrophotometric measurement, the substance
complexes will be of the form Pu(NO ) , with x tending to
3 x
being determined absorbs light at wavelengths characteristic of
increase at higher nitrate concentration. Each plutonium nitrate
that substance. This characteristic pattern is an absorbance
complex has a distinct absorbance spectrum, and the total
spectrum. The Beer-Lambert Law provides that the magnitude
spectrum will be the sum of the spectra of the individual
of the absorbance is proportional to the concentration of the
complexes, weighted by their relative concentration in the
absorber.The absorbance spectrum of a solution is equal to the
solution.Asimilar process occurs in chloride matrices, but the
sum of the absorbance spectra of all species in the solution.
chloride complexes have similar spectra and the overall effect
Where the absorbance spectra of multiple species overlap,
on the total absorbance is less significant.
accurate measurement of the species of interest requires
4.5 The scope of this method is restricted to the spectropho-
distinguishing the absorbance of that species from the absor-
tometric analysis of plutonium in the (III) oxidation state.
bances of other species. The characteristic wavelengths at
Other spectrophotometric techniques have been reported to
which a substance absorbs will depend on the physical and
measure Pu in the (IV) or (VI) oxidation state, or for the
chemical characteristics of the substances.
simultaneous measurement of Pu as a mixture of several
4.2 Reduction to plutonium(III) is accomplished by the
oxidation states. (9, 10). The user must distinguish the suit-
addition of a measured quantity of reductant solution to the
ability of this method versus another method for the intended
sample aliquant
application.
4.2.1 For nitrate solutions, ferrous sulfamate is the recom-
mended reductant. Aliquants (1 mL or less) of the sample
5. Significance and Use
solution are diluted with 10 mL of a ferrous reductant/matrix
5.1 This test method is designed to determine whether a
solution to 1 g Pu/L and measured.
given material meets the purchaser’s specification for pluto-
4.2.2 For chloride solutions, ascorbic acid is the recom-
nium content. This method may also be used, with sufficient
mended reductant. Aliquants of the sample solution, each
qualification, for process control or accountability measure-
containing 50 to 100 mg of plutonium, are diluted with 2 mL
ments associated with nuclear materials processing.
of zirconium solution to complex fluoride ions, 2 mL ascorbic
acid reductant solution, and 1.0 M HCl to a total volume of
6. Interferences
25 mL, yielding 2 to 4 g Pu/L solutions for measurement.
6.1 Materials meeting the applicable material specifications
4.3 Plutonium concentration is determined from absorbance
oftheASTMstandardforwhichthisprocedurewasdeveloped,
measurements taken on the sample solution from 516 to
when dissolved and diluted without introduction of interfering
640 nm (blue-green region) where a broad doublet band is
contaminants as described in Practice C1168, will contain no
observed (7, 8). Guidelines for the operation and maintenance
interfering elements or species.
of ultravioletvisible spectrophotometers is provided elsewhere
NOTE 2—Fluoride, if present, would interfere if the zirconium, rou-
(see Practices E60 and E169). Multivariate analysis software is
tinely added to the sample solution aliquant for the chloride matrix, were
used to calculate the plutonium concentration from measured
omitted from the procedure. Zirconium may be added to the ferrous
spectra. The analysis is based on prediction models derived
sulfamate reductant solution to handle fluorides if present in a nitrate
from a set of standard calibration solutions that encompass the
matrix.Zirconium,whenused,shouldbeaddedtoallsamples,blanks,and
standards to obtain a consistent matrix. Refer to Specifications C833 and
range of expected solution conditions (plutonium
C757.
concentration, potential complexing agents and interferents,
etc.)Thissoftwareiscommerciallyavailableandinsomecases 6.2 Interferences and measurement biases are caused by: (1)
is provided with the spectrophotometer. The users of this materials that absorb light in the region of the plutonium
procedureareresponsibleforselectingorcustomizing,orboth, absorption, (2) undissolved solids that cause light scattering,
the multivariate analysis (and instrument control) software that (3) strong oxidizing or complexing agents that prevent com-
best meets their individual measurement methodology and pletereductionoftheplutoniumtotheplutonium(III)oxidation
needs. Guidelines for creating and validating multivariate state, (4) anions that competitively form complexes with
analysis calibrations provided elsewhere (see Practices E1655 plutoniumandshiftthespectrumawayfromthoseexpectedfor
and E2617). Guidelines and principles for the creation and nitrate or chloride matrices, and (5) variance of other solution
maintenance of a spectrophotometer-based analysis method conditions (ionic strength, temperature) outside the range(s)
can be found in Practice D6122. This procedure is intended to encompassed in the calibration model.
address key measurement requirements and to allow users 6.2.1 Absorptionoflightinthespectralregionofinterestby
discretion in establishing appropriate procedural details and another species is a potential interference. Identification and
C1307 − 21
inclusion of potentially interfering species in the multivariate and shifts in the spectrum due to complexing agents are also
analysis calibration set will significantly reduce their effect.At indicated by increases in the spectral curve fitting error.
a minimum, sample measurements should be flagged when the
6.2.4 The presence of other anions may alter the absorbance
higher than normal fitting error occurs, resulting from the spectrum by competitively forming complexes with plutonium
presence of unidentified absorbing species. Absorbance limits
(7). This effect may be mitigated by including the expected
should be established within the region of interest to ensure range of anion identities and concentrations in the multivariate
that the instrument response remains reliable. calibration set or by using appropriate spectral fitting features
that identify and correct for the effect.
NOTE 3—Specific species of concern will depend on the source of the
6.2.5 Solution temperature and ionic strength are also
plutonium and the concentration of the species. For example, nitric
known to influence the absorption spectra of actinides, likely
acid-based dissolution of stainless steel-clad fuels may lead to significant
3+ 2+ 3+
amounts of Cr ,Ni , and Fe . Sample cleanup, as part of the
through changing the equilibrium of complex formation (11).
separations process or in the laboratory, can mitigate the effects of these
As with other anions, these effects should be included in
species.
multivariate calibration sets.
NOTE4—Caremustbetakeninthechoiceofthepreprocessingmethods
(derivatives, mean centering, autoscaling, wavelength selection, or com-
6.3 A study was conducted at the Los Alamos National
binations thereof) as these may affect the robustness of the final model,
Laboratory to determine the immunity of the Pu(III) spectro-
particularly with regard to unknown interferences. Double derivatives of
photometric assay method to a diverse species of potential
the spectra often ameliorate the effect of interferents. Use of residual
interferences. The elements studied were atomic numbers 1, 9,
analysis will not always detect unknown interferences and results will
11 to 13, 17, 19, 22 to 31, 35, 42, 44 to 46, 48, 50, 53, 57, 58,
vary depending on the preprocessing methods and models employed.
Even within the calibration set, fit residuals will vary significantly, with
60, 62, 73, 74, 76, 77, 79, 83, 90, 92, 93, and 95. Potential
correlations to the concentrations of both the plutonium and the interfer-
interferences from nitrate, phosphate, sulfate, and oxalic acid
ents. Identification of high fit residuals should prompt the user to further
are also documented (12).
investigate the spectral quality.
NOTE 5—As light intensities approach intrinsic noise and background
7. Apparatus
levels, instrument response will start to become nonlinear. As commonly
used multivariate analysis methods based on principal components analy-
7.1 Spectrophotometer—Wavelength range 190 to 820 nm;
sis are intrinsically linear, low light throughput during a measurement will
wavelength accuracy 62 nm; wavelength reproducibility
lead to errors in the analysis results.
60.05 nm; full dynamic range 0.0022 to 3.3 AU; photometric
6.2.2 This spectrophotometric assay method should not be
accuracy at 1 AU with a NBS 931 filter at 512 nm is
used on turbid (cloudy) solutions or solutions containing
60.005 AU; baseline flatness <0.0013AU; noise at 500 nm is
undissolved material. In addition to visual or turbidity meter
0.0002 AU RMS; stray light measured with a Hoya O-56 filter
measurements, or both, the presence of undissolved solids may
at 220 nm <0.05 %.
be identified by the resulting shifts in the spectral baseline and
by elevated spectral fitting errors. NOTE 7— The optical specifications listed in 7.1 are for instruments
used in previous reports (2, 3, and 5) and have been found to provide
NOTE 6—Plutonium oxides, mixed oxides, and plutonium metals
satisfactory results. Instrument resolution should allow for each absor-
meeting the material specifications for which this test method is intended,
bance feature to be sampled by multiple diode array pixels without
will dissolve when procedures in Practice C1168 are followed. Failure to
interpolation. In addition to these specifications, an acceptable spectrom-
achieve dissolution is an indication that the material does not meet the
eter system should also provide multivariate analysis and computer
specifications, and the application of this test method for plutonium assay
control. Optical fiber capabilities will facilitate sample handing in radio-
must be verified by the user. The user and customer are cautioned: when
logical containment. Although the wavelength range for plutonium re-
undissolved solids that persist after exhaustive dissolution efforts are to be
quires only a fraction of the 190 to 820 nm range specified (plutonium
removed by filtration through filter paper or other inert material of
absorption spectrum is measured over the 520 to 634 nm region)
appropriate porosity, the subsequent plutonium assay measurements
spectrophotometers with significantly smaller range would be of little
require close scrutiny. While filtration of undissolved solids may permit
general use to the purchaser.
the reliable measurement of the concentration of plutonium in the filtrate,
7.2 Sample Handling—Quartz cuvettes with pathlengths
the resulting analysis may not be representative of their source material.
from 1 to 4 cm are recommended. The use of a flow-through
Solids may indicate incomplete dissolution of the plutonium in the sample
material, not necessarily a plutonium-free refractory residue. When this
cuvette4eliminatespathlengthvariabilitybetweensamples.To
technique is utilized in support of reprocessing operations, process
that effect, plastic disposable cuvettes should be used with
solutions containing solids may be an indication of incomplete dissolution
reservation, as pathlength variability can lead to increased
of the plutonium-bearing material being processed or of an error in
measurement uncertainty. Flow systems and operating proce-
process operations. In addition to process control considerations, the
undissolved solids may represent accountability and criticality control dures should ensure complete sample exchange between mea-
problems.
surements.
6.2.3 Strong oxidizing agents and complexing agents in
7.3 Analytical Balance—Readability of 0.1 mg; linearity
sufficientconcentrationtopreventcompletereductiontypically
0.1 mg over any 10 g range and 0.2 mg over 160 g full scale.
are not present in plutonium nitrate samples. Appreciable
7.4 Solution Density Meter—Readability of 0.1 mg/mL;
concentrations of fluoride and sulfate anions have been found
precision of 0.3 mg/mL; linearity and accuracy 0.5 mg/mL
to interfere. The concentration of hydrofluoric acid, added to
over the range 0 to 2.0 g/mL.
catalyze dissolution of oxides, may be removed by evaporation
prior to measurement to ensure that the zirconium effectively 7.5 Adjustable, Fixed-volume Pipetters—Calibrated to de-
complexes the t
...

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: C1307 − 15 C1307 − 21
Standard Test Method for
Plutonium Assay by Plutonium (III) Diode Array
Spectrophotometry
This standard is issued under the fixed designation C1307; 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 describes the determination of total plutonium as plutonium(III) in nitrate and chloride solutions. The
technique is applicable to solutions of resulting from plutonium dioxide powders and pellets (Test Methods C697), nuclear grade
mixed oxides (Test Methods C698), plutonium metal (Test Methods C758), and plutonium nitrate solutions (Test Methods C759).
Solid samples are dissolved using the appropriate dissolution techniques described in Practice C1168. The use of this technique
for other plutonium-bearing materials has been reported (1-56), but final determination of applicability must be made by the user.
The applicable concentration range for plutonium sample solutions is 10–200 10 to 200 g Pu/L.
NOTE 1—As directly measured in the spectrophotometer, concentrations will be approximately 0.8 to 4.0 g Pu/L. Sample solutions are diluted to reach
this target range. For solid samples, select the sample size and dissolved solution weight to yield sample solutions in the 10 to 30 g Pu/L range. With
special preparation and spectral analysis techniques, the method has been applied to nitrate solutions in the 0.1 to 10 g Pu/L range.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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
C698 Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Mixed Oxides ((U,
Pu)O )
C757 Specification for Nuclear-Grade Plutonium Dioxide Powder for Light Water Reactors
C758 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-
Grade Plutonium Metal
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 Jan. 1, 2015Feb. 15, 2021. Published January 2015May 2021. Originally approved in 1995. Last previous edition approved in 20142015 as
C1307 – 14.C1307 – 15. DOI: 10.1520/C1307-15.10.1520/C1307-21.
For solid samples, select the sample size and dissolved solution weight to yield sample solutions in the 10–30 g Pu/L range. With special preparation and spectral analysis
techniques, the method has been applied to nitrate solutions in the 0.1–10 g Pu/L range.The boldface numbers in parentheses refer to a list of references at the end of this
standard.
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
C1307 − 21
C759 Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-
Grade Plutonium Nitrate Solutions
C833 Specification for Sintered (Uranium-Plutonium) Dioxide Pellets for Light Water Reactors
C859 Terminology Relating to Nuclear Materials
C1168 Practice for Preparation and Dissolution of Plutonium Materials for Analysis
D6122 Practice for Validation of the Performance of Multivariate Online, At-Line, Field and Laboratory Infrared
Spectrophotometer, and Raman Spectrometer Based Analyzer Systems
E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry
E169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
E1655 Practices for Infrared Multivariate Quantitative Analysis
E2617 Practice for Validation of Empirically Derived Multivariate Calibrations
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms related to nuclear materials, refer to Terminology C859.
3.1.2 For definition of terms related to UV-visible spectrophotometry, refer to Practice E60.
3.1.3 For definitions of terms related to multivariate calibration, refer to Practices E1655 and E2617.
4. Summary of Method
4.1 In a diode array spectrophotometric measurement, as in a conventional spectrophotometric measurement, the substance being
determined absorbs light at frequencies characteristic of that substance. The amount of light absorbed at each wavelength is directly
proportional to the concentration of the species of interest. The absorption is a function of the oxidation state and the complexation
obtained in the solution matrix selected for measurement. Beer’s Law permits quantifying the species of interest relative to a
traceable standard when both solutions are measured under the same conditions. The array of photosensitive diodes permits the
(virtually) simultaneous collection of spectral information over the entire range of the instrument, for example, 190–820 nm (or
any selected portion of the range). An entire absorption spectrum can be obtained in 0.1 s; however, optimum precision is obtained
from multiple spectra collected over a 4-s period.The concentration of plutonium in a solution is determined by the
spectrophotometric measurement of the absorbance of visible light by plutonium(III).
4.1.1 In a spectrophotometric measurement, the substance being determined absorbs light at wavelengths characteristic of that
substance. This characteristic pattern is an absorbance spectrum. The Beer-Lambert Law provides that the magnitude of the
absorbance is proportional to the concentration of the absorber. The absorbance spectrum of a solution is equal to the sum of the
absorbance spectra of all species in the solution. Where the absorbance spectra of multiple species overlap, accurate measurement
of the species of interest requires distinguishing the absorbance of that species from the absorbances of other species. The
characteristic wavelengths at which a substance absorbs will depend on the physical and chemical characteristics of the substances.
4.2 Reduction to plutonium(III) is accomplished by the addition of a measured quantity of reductant solution to the sample
aliquant.aliquant
4.2.1 For nitrate solutions, ferrous sulfamate is the recommended reductant. Aliquants (1 mL or less) of the sample solution are
diluted with 10 mL of a ferrous reductant/matrix solution to 1 g Pu/L,Pu/L and measured.
4.2.2 For chloride solutions, ascorbic acid is the recommended reductant. Aliquants of the sample solution, each containing
50–100 50 to 100 mg of plutonium, are diluted with 2 mL of zirconium solution to complex fluoride ions, 2 mL ascorbic acid
reductant solution, and 1.0 M HCl to a total volume of 25 mL, yielding 2–4 25 mL, yielding 2 to 4 g Pu/L solutions for
measurement.
4.3 Plutonium concentration is determined from light absorption absorbance measurements taken on the sample solution in the
blue-green region from 516 to 640 nm 640 nm (blue-green region) where a broad doublet band is observed.observed Spectral(7,
8quantifying). software capable of fitting the sample spectrum with spectral information fromGuidelines for the operation and
maintenance of ultravioletvisible spectrophotometers is provided elsewhere (see Practices E60 standardand E169solutions is ).
Multivariate analysis software is used to calculate the plutonium concentration. Both concentration from measured spectra. The
analysis is based on prediction models derived from a set of standard calibration solutions that encompass the range of expected
solution conditions (plutonium concentration, potential complexing agents and interferents, etc.) This software is commercially
C1307 − 21
available (6)and custom-designedin (some7-12) spectral fitting software have been developed which may be used for plutonium
measurements. cases is provided with the spectrophotometer. The users of this procedure are responsible for selecting or
customizing, or both, the spectral fittingmultivariate analysis (and instrument control) software that best meets their individual
measurement methodology and needs. Software selection will dictate many Guidelines for creating and validating multivariate
analysis calibrations provided elsewhere (see Practices E1655 and E2617of the procedural specifics not included in this).
Guidelines and principles for the creation and maintenance of a spectrophotometer-based analysis method can be found in Practice
D6122procedure. This procedure is intended to address key measurement requirements and to allow users discretion in
establishing appropriate procedural details and technique variations. The software package selected should include a feature that
indicates the quality of spectral fit, thereby providing information on the analysis, such as metrics that indicate the similarity of
the sample spectrum to those in the calibration set. The user may thereby assess the measurement reliability and the presence of
interferences that absorb light or otherwise alter the plutonium(III) spectrum without requiring supplemental measurements.
4.4 In nitrate solutions, plutonium will form a distribution of complexes with nitrate anions. For plutonium(III), these complexes
3-x
will be of the form Pu(NO ) , with x tending to increase at higher nitrate concentration. Each plutonium nitrate complex has a
3 x
distinct absorbance spectrum, and the total spectrum will be the sum of the spectra of the individual complexes, weighted by their
relative concentration in the solution. A similar process occurs in chloride matrices, but the chloride complexes have similar spectra
and the overall effect on the total absorbance is less significant.
4.5 The scope of this method is restricted to the spectrophotometric analysis of plutonium in the (III) oxidation state. Other
spectrophotometric techniques have been reported to measure Pu in the (IV) or (VI) oxidation state, or for the simultaneous
measurement of Pu as a mixture of several oxidation states. (9, 10). The user must distinguish the suitability of this method versus
another method for the intended application.
5. Significance and Use
5.1 This test method is designed to determine whether a given material meets the purchaser’s specification for plutonium content.
This method may also be used, with sufficient qualification, for process control or accountability measurements associated with
nuclear materials processing.
6. Interferences
6.1 Materials meeting the applicable material specifications of the ASTM standard for which this procedure was developed, when
dissolved and diluted without introduction of interfering contaminants as described in Practice C1168, will contain no interfering
elements or species.
NOTE 2—Fluoride, if present, would interfere if the zirconium, routinely added to the sample solution aliquant for the chloride matrix, were omitted from
the procedure. Zirconium may be added to the nitrate matrix. Ferrous-Reductant Solutionferrous sulfamate reductant solution to handle fluorides if
present. present in a nitrate matrix. Zirconium, when used, should be added to all samples, blanks, and standards to obtain a consistent matrix. Refer to
Specifications C833 and C757.
6.2 Interferences and measurement biases are caused by: (1(1)) materials that absorb light in the region of the plutonium
absorption, (2(2)) undissolved solids that cause light scattering, (3(3)) strong oxidizing or complexing agents that prevent complete
reduction of the plutonium to the plutonium(III) oxidation state, (4)and ( anions that competitively form complexes with plutonium
and shift the spectrum away from those expected for nitrate or chloride matrices, and 4(5)) anions that shift the spectrum. variance
of other solution conditions (ionic strength, temperature) outside the range(s) encompassed in the calibration model.
6.2.1 Absorption of light in the spectral region of interest by another species is a potential interference. Identification and inclusion
of potentially interfering species and inclusion of their spectra in the spectral curve fitting processin the multivariate analysis
calibration set will significantly reduce their effect. At a minimum, sample measurements should be flagged when the higher than
normal fitting error occurs, resulting from the presence of unidentified absorbing species. Enhancement of the spectral curve fitting
capabilities of the DAS can be achieved by taking double derivatives of the spectrum collected. The spectral curve fitting software
of the DAS is then used to quantitate the mathematically manipulated spectrum.Absorbance limits should be established within
the region of interest to ensure that the instrument response remains reliable.
NOTE 3—Specific species of concern will depend on the source of the plutonium and the concentration of the species. For example, nitric acid-based
3+ 2+ 3+
dissolution of stainless steel-clad fuels may lead to significant amounts of Cr , Ni , and Fe . Sample cleanup, as part of the separations process or in
the laboratory, can mitigate the effects of these species.
C1307 − 21
NOTE 4—Care must be taken in the choice of the preprocessing methods (derivatives, mean centering, autoscaling, or channel wavelength selection, or
combinations thereof) as these may affect the robustness of the final model, particularly with regard to unknown interferences. Double derivatives of the
spectra often ameliorate the effect of interferents. Use of residual analysis will not always detect unknown interferences and results will vary depending
on the preprocessing methods and models employed. Even within the calibration set, fit residuals will vary significantly, with correlations to the
concentrations of both the plutonium and the interferents. Identification of high fit residuals should prompt the user to further investigate the spectral
quality.
NOTE 5—As light intensities approach intrinsic noise and background levels, instrument response will start to become nonlinear. As commonly used
multivariate analysis methods based on principal components analysis are intrinsically linear, low light throughput during a measurement will lead to
errors in the analysis results.
6.2.2 This spectrophotometric assay method should not be used on turbid (cloudy) solutions or solutions containing undissolved
material. In addition to visual or turbidity meter measurements, or both, the presence of undissolved solids may be identified by
the resulting shifts in the spectral baseline and by elevated spectral fitting errors.
NOTE 6—Plutonium oxides, mixed oxides, and plutonium metals meeting the material specifications for which this test method is intended, will dissolve
when procedures in Practice C1168 are followed. Failure to achieve dissolution is an indication that the material does not meet the specifications, and
the application of this test method for plutonium assay must be verified by the user. The user and customer are cautioned: when undissolved solids that
persist after exhaustive dissolution efforts are to be removed by filtration through filter paper or other inert material of appropriate porosity, the subsequent
plutonium assay measurements require close scrutiny. While filtration of undissolved solids may permit the reliable measurement of the concentration
of plutonium in the filtrate, the resulting analysis may not be representative of their source material. Solids may indicate incomplete dissolution of the
plutonium in the sample material, not necessarily a plutonium-free refractory residue. When this technique is utilized in support of reprocessing
operations, process solutions containing solids may be an indication of incomplete dissolution of the plutonium-bearing material being processed or of
an error in process operations. In addition to process control considerations, the undissolved solids may represent accountability and criticality control
problems.
6.2.3 Strong oxidizing agents and complexing agents in sufficient concentration to prevent complete reduction typically are not
present in plutonium nitrate samples. Appreciable concentrations of fluoride and sulfate anions have been found to interfere. The
concentration of hydrofluoric acid, added to catalyze dissolution of oxides, may be removed by evaporation prior to measurement
to ensure that the zirconium effectively complexes the traces of fluoride ion. Changes in the plutonium spectrum from incomplete
reduction due to oxidizing agents and shifts in the spectrum due to complexing agents are also indicated by increases in the spectral
curve fitting error.
6.2.4 Anion identity and concentration will shift the location and alter the shape of the absorption curve. The system
calibrationThe presence of other anions may alter the absorbance spectrum by competitively forming complexes with plutonium
must(7). include the anion shift effect by encompassingThis effect may be mitigated by including the expected range of anion
identities and concentrations in the multivariate calibration set or by using appropriate spectral fitting features that identify and
correct for the effect.
6.2.5 Solution temperature and ionic strength are also known to influence the absorption spectra of actinides, likely through
changing the equilibrium of complex formation (11). As with other anions, these effects should be included in multivariate
calibration sets.
6.3 A study was conducted at the Los Alamos National Laboratory to determine the immunity of the Pu(III) spectrophotometric
assay method to a diverse species of potential interferences. The elements studied were elementatomic numbers 1, 9, 11–13, 11
to 13, 17, 19, 22–31, 22 to 31, 35, 42, 44–46, 44 to 46, 48, 50, 53, 57, 58, 60, 62, 73, 74, 76, 77, 79, 83, 90, 92, 93, and 95. Potential
interferenceinterferences from nitrate, phosphate, sulfate, and oxalic acid isare also documented (1312).
7. Apparatus
7.1 Diode Array Spectrophotometer (DAS)—Spectrophotometer—Wavelength range 190–820 190 to 820 nm; wavelength
accuracy6 2accuracy 62 nm; wavelength reproducibility 60.05 nm; full dynamic range 0.0022 to 3.3; 3.3 AU; photometric
accuracy at 1 AU with a NBS 931 filter at 512 nm is 60.005 AU; 60.005 AU; baseline flatness <0.0013 AU; noise at 500 nm
is 0.0002 AU 0.0002 AU RMS; stray light measured with a Hoya 056O-56 filter at 220 nm 220 nm <0.05 %.
NOTE 7— The optical specifications listed in 7.1 are for instruments used in previous reports (2, 3, and 5) and have been found to provide satisfactory
results. Instrument resolution should allow for each absorbance feature to be sampled by multiple diode array pixels without interpolation. In addition
to these specifications, an acceptable spectrometer system should also provide multivariate analysis and computer control. Optical fiber capabilities will
facilitate sample handing in radiological containment. Although the wavelength range for plutonium requires only a fraction of the 190 to 820 nm range
specified (plutonium absorption spectrum is measured over the 520 to 634 nm region) spectrophotometers with significantly smaller range would be of
little general use to the purchaser.<0.05 %;
C1307 − 21
7.2 Sample Handling—Quartz cuvettes with pathlengths from 1 to 4 cm are recommended. The use of a flow-through cuvette 4
eliminates pathlength variability between samples. To that effect, plastic disposable cuvettes should be used with reservation, as
pathlength variability can lead to increased measurement uncertainty. Flow systems and operating procedures should ensure
complete sample exchange between measurements.
7.3 Analytical Balance—Readability of 0.1 mg; linearity 0.1 mg 0.1 mg over any 10 g range and 0.2 mg over 160 g full scale.
7.4 Solution Density Meter—Readability of 0.1 mg/mL; precision of 0.3 mg/mL; linearity and accuracy 0.5 mg/mL over the range
0 to 2.0 g/mL.
7.5 Adjustable, Fixed-VolumeFixed-volume Pipetters—Calibrated to deliver the desired range of volumes for sample and
matrix-reductant solutions.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean distilled or deionized water.
8.3 Ascorbic Acid-Reductant Solution (C H O , aminoguanidine bicarbonate (CH N ·H CO ), 0.4 M in each reagent)—Prepare
6 8 6 6 4 2 3
fresh daily by dissolving 7 g of ascorbic acid and 5.5 g aminoguanidine bicarbonate in 80 mL of 1 M HCl, then dilute to a final
volume of 100-mL 100 mL 1 M HCl.
NOTE 8—The ascorbic acid is stabilized by the addition of aminoguanidine (Guanylhydrazine:HN:C(NH )NHNH ). The stabilized reductant solution has
2 2
been found to be effective when ascorbic acid stability problems are encountered.
8.4 Ferrous-ReductantFerrous-reductant Solution (ferrous sulfamate, 0.05 M; sulfamic acid, 0.25 M; nitric acid, 1.0 M)—Prepare
fresh weekly by adding 12 mL of freshly prepared ferrous sulfamate (2 M) to 90 mL of sulfamic acid (1.5 M). Stir, then add 175
mL of nitric acid (3.0 M) and dilute to 500 mL with water.
8.5 Ferrous Sulfamate (Fe(NH SO ) , 2.0 M)—Prepare fresh for the preparation of the ferrous-reductant solution. Add 220 g of
2 3 2
solid sulfamic acid to 450 mL of water, stir, and heat at 70–80°C 70 to 80 °C until dissolved. Continue stirring and heating, while
adding approximately 0.5-g 0.5 g portions of iron metal powder (Fe ) until 56 g of iron have been dissolved in the heated sulfamic
acid. Filter the solution while hot; allow to cool; then dilute to a final volume of 50 mL.
NOTE 9—The dissolution of the sulfamic acid need not be quantitative before beginning the addition of the iron powder. Excessive heating beyond the
time required to achieve the dissolution of the sulfamic acid/iron powder or at temperatures above 80°C80 °C will cause excessive decomposition of the
sulfamic acidacid.
8.6
...