ASTM C1307-95
(Test Method)Standard Test Method for Plutonium Assay by Plutonium (III) Diode Array Spectrophotometry
Standard Test Method for Plutonium Assay by Plutonium (III) Diode Array Spectrophotometry
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 plutonium dioxide powders and pellets (Test Methods C 697), nuclear grade mixed oxides (Test Methods C 698), plutonium metal (Test Methods C 758), and plutonium nitrate solutions (Test Methods C 759). Solid samples are dissolved using the appropriate dissolution techniques described in Practice C 1168. The use of this technique for other plutonium-bearing materials has been reported (1-5), but final determination of applicability must be made by the user. The applicable concentration range for plutonium sample solutions is 10-200 g Pu/L.
1.2 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 health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 1307 – 95
Standard Test Method for
Plutonium Assay by Plutonium (III) Diode Array
Spectrophotometry
This standard is issued under the fixed designation C 1307; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope C 833 Specification for Sintered (Uranium-Plutonium) Di-
oxide Pellets
1.1 This test method describes the determination of total
C 1168 Practice for Preparation and Dissolution of Pluto-
plutonium as plutonium(III) in nitrate and chloride solutions.
nium Materials for Analysis
The technique is applicable to solutions of plutonium dioxide
2.2 American Chemical Society Standard:
powders and pellets (Test Methods C 697), nuclear grade
Reagent Chemicals, American Chemical Society Specifica-
mixed oxides (Test Methods C 698), plutonium metal (Test
tions
Methods C 758), and plutonium nitrate solutions (Test Meth-
ods C 759). Solid samples are dissolved using the appropriate
3. Summary of Method
dissolution techniques described in Practice C 1168. The use of
3.1 In a diode array spectrophotometric measurement, as in
this technique for other plutonium-bearing materials has been
a conventional spectrophotometric measurement, the substance
reported (1-5), but final determination of applicability must be
being determined absorbs light at frequencies characteristic of
made by the user. The applicable concentration range for
2 that substance. The amount of light absorbed at each wave-
plutonium sample solutions is 10–200 g Pu/L.
length is directly proportional to the concentration of the
1.2 This standard does not purport to address all of the
species of interest. The absorption is a function of the oxidation
safety concerns, if any, associated with its use. It is the
state and the complexation obtained in the solution matrix
responsibility of the user of this standard to establish appro-
selected for measurement. Beer’s Law permits quantifying the
priate safety and health practices and determine the applica-
species of interest relative to a traceable standard when both
bility of regulatory limitations prior to use.
solutions are measured under the same conditions. The array of
2. Referenced Documents photosensitive diodes permits the (virtually) simultaneous
collection of spectral information over the entire range of the
2.1 ASTM Standards:
instrument, for example, 190–820 nm (or any selected portion
C 697 Test Methods for Chemical, Mass Spectrometric, and
of the range). An entire absorption spectrum can be obtained in
Spectrochemical Analysis of Nuclear-Grade Plutonium
0.1 s; however, optimum precision is obtained from multiple
Dioxide Powders and Pellets
spectra collected over a 4-s period.
C 698 Test Methods for Chemical, Mass Spectrometric, and
3.2 Reduction to plutonium(III) is accomplished by the
Spectrochemical Analysis of Nuclear-Grade Mixed Oxides
addition of a measured quantity of reductant solution to the
((U, Pu)O )
sample aliquant.
C 757 Specification for Nuclear-Grade Plutonium Dioxide
3.2.1 For nitrate solutions, ferrous sulfamate is the recom-
Powder, Sinterable
mended reductant. Aliquants (1 mL or less) of the sample
C 758 Test Methods for Chemical, Mass Spectrometric,
solution are diluted with 10 mL of a ferrous reductant/matrix
Spectrochemical, Nuclear, and Radiochemical Analysis of
3 solution to 1 g Pu/L, and measured.
Nuclear-Grade Plutonium Metal
3.2.2 For chloride solutions, ascorbic acid is the recom-
C 759 Test Methods for Chemical, Mass Spectrometric,
mended reductant. Aliquants of the sample solution, each
Spectrochemical, Nuclear, and Radiochemical Analysis of
containing 50–100 mg of plutonium, are diluted with 2 mL of
Nuclear-Grade Plutonium Nitrate Solutions
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 g Pu/L solutions for measurement.
This test method is under the jurisdiction of ASTM Committee C-26 on Nuclear
3.3 Plutonium concentration is determined from light ab-
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Test.
sorption measurements taken on the sample solution in the
Current edition approved Sept. 10, 1995. Published November 1995.
blue-green region from 516 to 640 nm where a broad doublet
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. “Reagent Chemicals, American Chemical Society Specifications,” American
Annual Book of ASTM Standards, Vol 12.01. Chemical Society, Washington, D.C.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 1307
NOTE 1—Plutonium oxides, mixed oxides, and plutonium metals meet-
band is observed. Spectral quantifying software capable of
ing the material specifications for which this test method is intended, will
fitting the sample spectrum with spectral information from
dissolve when procedures in Practice C 1168 are followed. Failure to
standard solutions is used to calculate the plutonium concen-
achieve dissolution is an indication that the material does not meet the
tration. Both commercially available (6) and custom-designed
specifications, and the application of this test method for plutonium assay
(7-12) spectral fitting software have been developed for pluto- 6
must be verified by the user.
nium measurements. The users of this procedure are respon-
5.2.3 Strong oxidizing agents and complexing agents in
sible for selecting or customizing, or both, the spectral fitting
sufficient concentration to prevent complete reduction typically
(and instrument control) software that best meets their indi-
are not present in plutonium nitrate samples. Appreciable
vidual measurement methodology and needs. Software selec-
concentrations of fluoride and sulfate anions have been found
tion will dictate many of the procedural specifics not included
to interfere. The concentration of hydrofluoric acid, added to
in this procedure. This procedure is intended to address key
catalyze dissolution of oxides, may be removed by evaporation
measurement requirements and to allow users discretion in
prior to measurement to ensure that the zirconium effectively
establishing appropriate procedural details and technique varia-
complexes the traces of fluoride ion. Changes in the plutonium
tions. The software package selected should include a feature
spectrum from incomplete reduction due to oxidizing agents
that indicates the quality of spectral fit, thereby providing
and shifts in the spectrum due to complexing agents are also
information on the measurement reliability and the presence of
indicated by increases in the spectral curve fitting error.
interferences that absorb light or otherwise alter the pluto-
5.2.4 Excessive anion concentration will shift the location
nium(III) spectrum without requiring supplemental measure-
and alter the shape of the absorption curve. The system
ments.
calibration must include the anion shift effect by using matrix-
4. Significance and Use
matched standards for calibration or by using appropriate
spectral fitting features that identify and correct for the effect.
4.1 This test method is designed to determine whether a
5.3 A study was conducted at the Los Alamos National
given material meets the purchaser’s specification for pluto-
Laboratory to determine the immunity of the Pu(III) spectro-
nium content.
photometric assay method to a diverse species of potential
5. Interferences
interferences. The elements studied were element numbers 1,
5.1 Materials meeting the applicable material specifications
9, 11–13, 17, 19, 22–31, 35, 42, 44–46, 48, 50, 53, 57, 58, 60,
of the ASTM standard for which this procedure was developed,
62, 73, 74, 76, 77, 79, 83, 90, 92, 93, and 95. Potential
when dissolved and diluted without introduction of interfering
interference from nitrate, phosphate, sulfate, and oxalic acid is
contaminants as described in Practice C 1168, will contain no
also documented (13).
interfering elements or species.
6. Apparatus
5.2 Interferences are caused by: 1) materials that absorb
6.1 Diode Array Spectrophotometer (DAS)—wavelength
light in the region of the plutonium absorption, 2) undissolved
range 190–820 nm; wavelength accuracy6 2 nm; wavelength
solids that cause light scattering, 3) strong oxidizing or
reproducibility 60.05 nm; full dynamic range 0.0022 to 3.3;
complexing agents that prevent complete reduction of the
photometric accuracy at 1 AU, 512 nm, NBS 931 filters
plutonium to the plutonium(III) oxidation state, and 4) anions
60.005 AU; baseline flatness <0.0013 AU; noise at 500 nm
that shift the spectrum.
0.0002 AU RMS; stray light measured with Hoya at 220 nm
5.2.1 Absorption of light in the region of interest by another
<0.05 %; stray light measured with a 056 filter <0.05 %.
species is a potential interference. Identification of potentially
6.2 Analytical Balance—readability of 0.1 mg; linearity 0.1
interfering species and inclusion of their spectra in the spectral
mg over any 10 g range and 0.2 mg over 160 g full scale.
curve fitting process will significantly reduce their effect. At a
minimum, sample measurements should be flagged when the
higher than normal fitting error, resulting from the presence of 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
unidentified absorbing species, occurs. Enhancement of the
other inert material of appropriate porosity, the subsequent plutonium assay
spectral curve fitting capabilities of the DAS can be achieved
measurements require close scrutiny. While filtration of undissolved solids may
by taking double derivatives of the spectrum collected. The
permit the reliable measurement of the concentration of plutonium infiltrate, the
resulting analysis may not be representative of their source material. Solids may
spectral curve fitting software of the DAS is then used to
indicate incomplete dissolution of the plutonium in the sample material, not
quantitate the mathematically manipulated spectrum.
necessarily a plutonium-free refractory residue. When this technique is utilized in
5.2.2 This spectrophotometric assay method should not be
support of reprocessing operations, process solutions containing solids may be an
indication of incomplete dissolution of the plutonium-bearing material being
used on turbid (cloudy) solutions or solutions containing
processed or of an error in process operations. In addition to process control
undissolved material. In addition to visual or turbidity meter
considerations, the undissolved solids may represent accountability and criticality
measurements, or both, the presence of undissolved solids may
control problems.
be identified by the resulting shifts in the spectral baseline and
Hewlett-Packard 8451A and 8452A has been found to have satisfactory optical
characteristics and Multicomponent spectral quantitating software. These two
by elevated spectral fitting errors.
spectrophotometers are easily controlled by computer and readily remoted via fiber
optics. Fiber Optic Coupler, Fibers, and 1, 3, and 4-cm Flow Cell/Pump System
Fluoride, if present, would interfere if the zirconium, routinely added to the have been developed and reported on (2, 3, 5). Specifications listed are those of the
sample solution aliquant for the chloride matrix, were omitted from the procedure. HP-8451A and the HP-8452A. Although the wavelength range for plutonium
Zirconium may be added to the nitrate matrix, Ferrous-Reductant Solution to handle requires only a fraction of the 190–820 nm range specified (plutonium absorption
fluorides if present. Zirconium, when used, should be added to all samples, blanks, spectrum is measured over the 520–634 nm region) spectrophotometers with
and standards to obtain a consistent matrix. Refer to Specifications C 833 and C 757. significantly smaller range would be of little general use to the purchaser.
C 1307
6.3 Solution Density Meter—readability of 0.1 mg/mL; 7.11 Plutonium Standard Solutions—Prepare standards
precision of 0.3 mg/mL; linearity and accuracy 0.5 mg/mL traceable to the national measurement system, which cover the
over the range 0 to 2.0 g/mL. range of concentrations over which sample measurements will
8 11
6.4 Adjustable, Fixed-Volume Pipetters —calibrated to de- be performed.
liver the desired range of volumes for sample and matrix- 7.12 Sulfamic Acid (NH SO H, 1.5 M)—Dissolve 145 g of
2 3
reductant solutions. solid sulfamic acid in 900 mL of water with stirring. Filter, then
dilute with water to a final volume of 1 L.
7. Reagents and Materials
7.13 Zirconium Reagent (ZrOCl –8H O, 0.75 M)—
2 2
7.1 Purity of Reagents—Reagent grade chemicals shall be
Dissolve 120.5 g zirconium chloride octahydrate in 450 mL of
used in all tests. Unless otherwise indicated, it is intended that
1.0 M HCl; dilute to a final volume of 500 mL of 1.0 M HCl.
all reagents conform to the specifications of the Committee on
Analytical Reagents of the American Chemical Society where 8. Calibration and Standardization of Instrument
such specifications are available. Other grades may be used,
8.1 Calibrate the system prior to each use. To calibrate,
provided it is first ascertained that the reagent is of sufficiently
prepare several aliquants of at least two different plutonium
high purity to permit its use without lessening the accuracy of
standard solutions in the same concentration range as the
the determination.
samples to be measured in accordance with the preparation
7.2 Purity of Water—Unless otherwise indicated, references
procedure described in Section 9. At least one of the standard
to water shall be understood to mean distilled or deionized
solutions prepared will be used independently to ensure the
water.
accuracy of the calibration and should not be used in generat-
7.3 Ascorbic Acid-Reductant Solution (C H O , ami-
6 8 6
ing the calibration curve.
noguanidine bicarbonate (CH N ·H CO ), 0.4 M in each
6 4 2 3
8.2 Following spectral referencing, measure each of the
reagent)—Prepare fresh daily by dissolving7gof ascorbic
aliquants from one or more of the standard solutions. Quanti-
acid and 5.5 g aminoguanidine bicarbonate in 80 mL of 1 M
tate each of the resulting spectra using appropriate software
HCl, then dilute to a
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