ASTM C1165-90(2000)e1
(Test Method)Standard Test Method for Determining Plutonium by Controlled-Potential Coulometry in H2SO4 at a Platinum Working Electrode
Standard Test Method for Determining Plutonium by Controlled-Potential Coulometry in H<sub>2</sub>SO<sub>4</sub> at a Platinum Working Electrode
SCOPE
1.1 This test method describes the determination of milligram quantities of plutonium in unirradiated uranium-plutonium mixed oxide having a U/Pu ratio range of 0.1 to 10. This test method is also applicable to plutonium metal, plutonium oxide, uranium-plutonium mixed carbide, various plutonium compounds including fluoride and chloride salts, and plutonium solutions.
1.2 The recommended amount of plutonium for each aliquant in the coulometric analysis is 5 to 10 mg. Precision worsens for lower amounts of plutonium, and elapsed time of electrolysis becomes impractical for higher amounts of plutonium.
1.3 The values stated in SI units are to be regarded as standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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e1
Designation:C1165–90(Reapproved 2000)
Standard Test Method for
Determining Plutonium by Controlled-Potential Coulometry
in H SO at a Platinum Working Electrode
2 4
This standard is issued under the fixed designation C1165; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Section 2 and footnote 6 were editorially updated in July 2000.
1. Scope C1009 Guide for Establishing a Quality Assurance Pro-
gram for Analytical Chemistry Laboratories Within the
1.1 This test method describes the determination of milli-
Nuclear Industry
gram quantities of plutonium in unirradiated uranium-
C1068 Guide for Qualification of Measurement Methods
plutonium mixed oxide having a U/Pu ratio range of 0.1 to 10.
by a Laboratory Within the Nuclear Industry
This test method is also applicable to plutonium metal,
C1108 Test Method for Plutonium by Controlled-Potential
plutonium oxide, uranium-plutonium mixed carbide, various
Coulometry
plutonium compounds including fluoride and chloride salts,
C1128 Guide for Preparation of Working Reference Mate-
and plutonium solutions.
rials for Use in the Analysis of Nuclear Fuel Cycle
1.2 The recommended amount of plutonium for each ali-
Materials
quant in the coulometric analysis is 5 to 10 mg. Precision
C1156 Guide for Establishing Calibration for a Measure-
worsens for lower amounts of plutonium, and elapsed time of
ment Method Used to Analyze Nuclear Fuel Cycle Mate-
electrolysis becomes impractical for higher amounts of pluto-
rials
nium.
C1168 Practice for Preparation and Dissolution of Pluto-
1.3 The values stated in SI units are to be regarded as
nium Materials for Analysis
standard.
C1210 Guide for Establishing a Measurement System
1.4 This standard does not purport to address all of the
Quality Control Program for Analytical Chemistry Labo-
safety concerns, if any, associated with its use. It is the
ratories Within the Nuclear Industry
responsibility of the user of this standard to establish appro-
C1297 Guide for Qualification of Laboratory Analysts for
priate safety and health practices and determine the applica-
the Analysis of Nuclear Fuel Cycle Materials
bility of regulatory limitations prior to use. Specific precau-
tionary statements are given in Section 8.
3. Summary of Test Method
2. Referenced Documents 3.1 In controlled-potential coulometry, the analyte reacts at
an electrode having a maintained potential that precludes
2.1 ASTM Standards:
reactionsofasmanyimpuritycomponentsasisfeasible.Inthe
C757 Specification for Nuclear-Grade Plutonium Dioxide
2 electrolysis, current decreases exponentially as the reaction
Powder, Sinterable
proceeds until a selected background current is reached. The
C758 Test Methods for Chemical, Mass Spectrometric,
quantity of analyte reacted is calculable by Faraday’s law.
Spectrochemical, Nuclear, and RadiochemicalAnalysis of
Detailed discussions of the theory and applications of this
Nuclear-Grade Plutonium Metal
technique are presented in Refs (1) and (2).
C759 Test Methods for Chemical, Mass Spectrometric,
3.2 Plutonium and many impurity element ions are initially
Spectrochemical, Nuclear, and RadiochemicalAnalysis of
reduced in a 0.5 M H SO electrolyte at a platinum working
2 4
Nuclear-Grade Plutonium Nitrate Solutions
electrode (3) maintained at+0.310 V versus a saturated
C833 Specification for Sintered (Uranium-Plutonium) Di-
calomelelectrode(SCE).PlutoniumisthenoxidizedtoPu(IV)
oxide Pellets
at a potential of+0.670 V. The quantity of plutonium is
C859 Terminology Relating to Nuclear Materials
calculatedfromthenumberofcoulombsrequiredforoxidation
according to Faraday’s law.
t
1 Q 5 * idt 5 nwF/M (1)
o
ThistestmethodisunderthejurisdictionofASTMCommitteeC-26onNuclear
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Test.
Current edition approved Nov. 30, 1990. Published July 1991. The boldface numbers in parentheses refer to a list of references at the end of
Annual Book of ASTM Standards, Vol 12.01. the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1165
Rearrangement to solve for w gives: oxidation of Pu(III) to Pu(IV), organic matter, anions that
complex plutonium, and oxygen.
w 5 MQ/nF (2)
5.2 The major interfering metallic impurity element, of
where:
those usually included in specifications for FBR mixed oxide
w 5 weight of Pu(III) oxidized to Pu(IV), g,
fuel,isiron(4).Inthe 0.5MH SO electrolyte, the
2 4
M 5 gram-molecular mass of plutonium (adjusted for iso-
Fe(II)−Fe(III) and Pu(III)−Pu(IV) couples have essentially
o
topic composition), grams/equivalent,
the same E value of+0.490 V. The iron interference, there-
Q 5 number of coulombs to oxidize Pu(III) to Pu(IV),
fore, is quantitative and is corrected based on its measured
coulombs,
value that can be determined by a spectrophotometric method
n 5 number of electron change to oxidize Pu(III) to
(5). Alternatively, other techniques such as ICP, DCP or
Pu(IV) 51, and
emission spectrometry can also be used if the iron content is
F 5 Faraday constant, coulomb/equivalent.
sufficiently low. When the iron result is <20µ g/g, the lower
3.3 An electrolyte of sulfuric acid, that selectively com-
limit of the spectrophotometric method, no correction is
plexes Pu(IV), provides very reproducible electrolysis of
necessary. The best available method for iron determination is
Pu(III) to Pu(IV). In a 0.5 M H SO electrolyte, the reduction
2 4
recommended since the uncertainty in the iron correction
potential of+0.310 V for conversion of Pu(IV and VI) to
contributes to the uncertainty in the plutonium value.
Pu(III) and the oxidation potential of+0.670Vfor conversion
5.3 Organic matter usually is not present in calcined mixed
of Pu(III) to Pu(IV) accounts for about 99.9% (as calculated
oxide fuel pellets nor in mixed oxide powder blends prepared
from the Nernst equation) conversion of the total plutonium in
using calcined uranium oxide and calcined plutonium oxide.
solution. There are few interferences at the selected potentials
However, it may be introduced as an impurity in reagents.The
ofthemetallicimpuritiesusuallylistedinspecificationsforfast
sulfuric acid fuming of reference material and of samples that
breederreactor(FBR)mixedoxidefuel.Achemicalcalibration
precedes the coulometric analysis volatilizes most organic
of the coulometric system using the selected potentials tech-
components.
nique is necessary to correct for the less than 100% conver-
5.4 The sulfuric acid fuming volatilizes nitrate, nitrite,
sions of Pu(III) and Pu(IV).
fluoride, and chloride, that are introduced by the use of a
3.4 Sulfuric acid is a convenient electrolyte since it is used
nitric-hydrofluoric acid mixture or acid mixtures containing
for preliminary fuming of samples to volatilize interfering
chloride for the dissolution of samples and interfere in the
components (see 5.3 and 5.4). The preliminary fuming with
coulometric determination of plutonium.
sulfuric acid also serves to depolymerize any polymeric
5.5 Oxygen interferes and must be purged continuously
plutonium species, which tend to be electrolytically inactive
from both the solution and atmosphere in the electrolysis cell
(3).
with an oxygen-free inert gas before and during the electroly-
sis.
4. Significance and Use
NOTE 1—The purge gas tube extends through the cell cover and is
4.1 Thistestmethodistobeusedtoascertainwhetherornot
positioned approximately 1 cm above the sample solution in the cell.The
materials meet specifications for plutonium content or pluto-
inert gas flow is maintained at a flow rate that causes a dimple to be seen
nium assay, or both.
on the surface of the solution with the stirrer off. The inert gas flow rate
4.2 A chemical calibration of the coulometer is necessary should be such that no splashing occurs.
for accurate results.
6. Apparatus
5. Interferences 6.1 Controlled-Potential Coulometer—A potentiostat hav-
ing stable potential control at approximately 200 mAand 20V
5.1 Categories of interferences are diverse metal ions that
and an integrator capable of 0.05% reproducibility are re-
oxidize or reduce at the potential of+0.670 V used for the
quired. The linearity of the integrator should be better than
0.1% for the selected range.
NOTE 2—To obtain maximum precision, it is recommended that the
referenceandsamplealiquantscontainapproximatelythesameamountof
plutonium.
6.2 Cell Assembly— A cell assembly similar to the one
describedinRef(5)hasbeenusedsatisfactorily.Celldesignis
very critical in controlled-potential coulometry. There are
many factors that must be considered in choosing or designing
a cell assembly. It is beyond the scope of this test method to
describe all of the factors that should be considered. A
thorough detailed discussion of electrolysis cell design is
presented in Ref (2).
FIG. 1 Example of a Cell Design Used at Los Alamos National Apparatus manufactured by the EG&G PrincetonApplied Research Corp., has
Laboratory (LANL) been found satisfactory for this purpose.
C1165
NOTE 3—Drawing (see Fig. 1) of a cell design that has been success-
8. Safety Precautions
fully used at the Los Alamos National Laboratory. The titration cell
8.1 Committee C-26 Safeguards Statement :
consists of a 50 mL cut off beaker.
8.1.1 The materials (nuclear grade plutonium metal, pluto-
6.3 Timer or stopwatch for measuring electrolysis times
nium oxide powder, plutonium nitrate solutions, and mixed
(capable of measuring in seconds).
oxide and carbide powders and pellets) to which this test
method applies, are subject to nuclear safeguards regulations
7. Reagents
governing their possession and use. This test method has been
designated as technically acceptable for generating safeguards
7.1 Purity of Reagents—Reagent grade chemicals shall be
accountability measurement data.
used in all tests. Unless otherwise indicated, it is intended that
8.1.2 When used in conjunction with appropriate certified
all reagents conform to the specifications of the Committee on
reference materials (CRMs), this test method can demonstrate
Analytical Reagents of theAmerican Chemical Society where
traceability to the national measurements base. However,
such specifications are available. Other grades may be used,
adherencetothistestmethoddoesnotautomaticallyguarantee
provided it is first ascertained that the reagent is of sufficiently
regulatory acceptance of the resulting safeguards measure-
high purity to permit its use without lessening the accuracy of
ments. It remains the sole responsibility of the user of this test
the determination.
method to ensure that its application to safeguards has the
7.2 Purity of Water— Unless otherwise indicated, refer-
approval of the proper regulatory authorities.
ences to water shall be understood to mean distilled or
deionized water.
9. Preparation of Apparatus
7.3 Argon, Oxygen-Free (99.99%)—Helium, nitrogen, or
9.1 Verify proper equipment operation by performing an
other pure inert gas may be used.
electrical calibration according to manufacturers’ specifica-
7.4 Hydrochloric Acid (HCl, 6 M)—Add 500 mL of con-
tions on each day that the instrument is used.
centrated HCl (sp gr 1.19) to less than 500 mL of water and
dilute to 1 L with water.
10. Calibration
7.5 Sulfuric Acid (sp gr 1.84)—Concentrated H SO (sp gr
2 4
10.1 If not done previously as recommended in 7.8.1,
1.84).
completely transfer one of the dispensed aliquants, containing
7.6 Sulfuric Acid (3 M)—Add 168 mL of concentrated
5to10mgofplutoniumoftheplutoniumreferencesolution,to
HSO (sp gr 1.84) to water, while stirring, and dilute to 1 L
a cell using 0.5 M H SO rinses and place platinum working
2 4
with water.
electrode in the cell. Using 0.5 M H SO , completely immerse
2 4
7.7 Sulfuric Acid (0.5 M)—Add 28 mL of concentrated
the working electrode. (See Note 8.)
HSO (sp gr 1.84) to water, while stirring, and dilute to 1 L
2 10.2 Rinsetheexteriorsurfacesofthecounterandreference
with water.
electrode salt bridges (for example, high-silica tubes) with 0.5
7.8 Plutonium Reference Solution—Dissolve a weighed
MH SO .
2 4
quantity (balance capable of weighing to 0.01 mg) of 0.5 to 1
10.3 Raisethecellintopositionfirmlyagainstthecellcover
g of NBL CRM 126 metal (or its replacement) cleaned per
to ensure a tight fit. Purge the cell atmosphere with flowing
certificate directions in 6 M HCl. Use a sufficient amount of 6
argon or other inert gas. (See Note 1.)
M HCl to maintain an acid concentration of 1 to 2 molar.
10.4 Immediatelyconnectthecellelectrodestothecoulom-
Completely transfer the solution with 0.5 M H SO rinses to a
2 4
eter; begin stirring.
tared container, dilute to 100 to 200 g with 0.5 M H SO (to
2 4
10.5 Reduce Pu(IV) to Pu(III) at+0.310Vuntil the current
give a plutonium concentration of 5 mg/g), and weigh.
decreases to 30 µA.
10.6 Reset the integrator and start timer.
NOTE 4—A tared polyethylene bottle has been used successfully to
10.7 OxidizePu(III)toPu(IV)at+0.670Vuntilthecurrent
dispense weighed aliquants.
decreases to 30 µA. Record the coulomb accumulation and
7.8.1 Dispense weighed 1 to 2 g aliquants, each containing
elapsed time.
accurately known 5 to 10 mg quantities of plutonium, to
NOTE 5—All standards (reference material) and samples should be
individual electrolysis cells or vials for subsequent use in
freshly fumed (within 4 h) prior to analysis.
chemical calibration.
7.8.2 Prior to using, add 0.5 mLof 3 M H SO and fume to 10.8 Remove the solution and thoroughly rinse the cell and
2 4
dryness. electrodes with 0.5 M H SO .
2 4
10.9 Repeat 10.1-10.8 to attain a desired precision level for
7.8.3 After cooling, redissolve using a minimal amount of
the calibration.
0.5MH SO and again fume to dryness.
2 4
7.8.4 Repeat 7.8.3.
NOTE 6—A recommended practice would be to intersperse standards
(reference material) and samples during the time the analyses are being
done.
10.10 Calculate the calibration factor F by
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals,BDHLtd.,Poole,Dorset,U.K.,andtheUnitedStatesPharmacopeiaand Based upon Committee C26 Safeguards Matrix (C1009, C1068, C1128,
NationalFormulary,U.S.PharmaceuticalConvention,Inc.(USPC),Rockville,MD. C1156, C1210, and C1297).
...
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