ASTM C1108-99(2006)
(Test Method)Standard Test Method for Plutonium by Controlled-Potential Coulometry
Standard Test Method for Plutonium by Controlled-Potential Coulometry
SIGNIFICANCE AND USE
Factors governing selection of a method for the determination of plutonium include available quantity of sample, sample purity, desired level of reliability, and equipment.
4.1.1 This test method determines 5 to 10 mg of plutonium with prior dissolution using Practice C 1168.
4.1.2 This test method calculates plutonium assay using physical constants as reference standards.
4.1.3 Chemical standards are used for quality control when prior chemical separation of plutonium is necessary to remove interferences (9).
Committee C-26 Safeguards Statement4 :
4.2.1 The materials (plutonium metal, plutonium oxide or mixed oxide [(U, Pu) O2] powders and pellets) to which this test method applies are subject to nuclear safeguards regulations governing their possession and use. Materials for use by the commercial nuclear community must also meet compositional specifications.
4.2.2 The analytical method in this test method both meets U. S. Department of Energy guidelines for acceptability of a measurement method for generation of safeguards accountability measurement data and also provides data that may be used to demonstrate specification compliance in buyer-seller interactions.
SCOPE
1.1 This test method describes the determination of plutonium in solutions of unirradiated nuclear-grade (that is, high-purity) materials by controlled-potential coulometry. Controlled-potential coulometry may be performed in a choice of supporting electrolytes, such as 0.9 M HNO3, 1 M HClO 4, 1 M HCl, 5 M HCl, and 0.5 M H2SO4. Limitations on the use of selected supporting electrolytes are discussed in Section 5. Optimum quantities of plutonium for this procedure are 5 to 10 mg.
1.2 Plutonium-bearing materials are radioactive and toxic. Adequate laboratory facilities, such as gloved boxes, fume hoods, controlled ventilation, etc., along with safe techniques must be used in handling specimens containing these materials.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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: C1108 − 99 (Reapproved2006)
Standard Test Method for
Plutonium by Controlled-Potential Coulometry
This standard is issued under the fixed designation C1108; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope ment Method Used toAnalyze Nuclear Fuel Cycle Mate-
rials
1.1 This test method describes the determination of pluto-
C1168PracticeforPreparationandDissolutionofPlutonium
nium in solutions of unirradiated nuclear-grade (that is, high-
Materials for Analysis
purity) materials by controlled-potential coulometry.
C1210Guide for Establishing a Measurement System Qual-
Controlled-potential coulometry may be performed in a choice
ity Control Program for Analytical Chemistry Laborato-
ofsupportingelectrolytes,suchas0.9 MHNO,1 MHClO,1
3 4
ries Within the Nuclear Industry
M HCl, 5 M HCl, and 0.5 M H SO . Limitations on the use of
2 4
C1297Guide for Qualification of Laboratory Analysts for
selected supporting electrolytes are discussed in Section 5.
the Analysis of Nuclear Fuel Cycle Materials
Optimumquantitiesofplutoniumforthisprocedureare5to10
E691Practice for Conducting an Interlaboratory Study to
mg.
Determine the Precision of a Test Method
1.2 Plutonium-bearing materials are radioactive and toxic.
Adequate laboratory facilities, such as gloved boxes, fume
3. Summary of Test Method
hoods, controlled ventilation, etc., along with safe techniques
3.1 In a controlled-potential coulometric measurement, the
mustbeusedinhandlingspecimenscontainingthesematerials.
substancebeingdeterminedreactsatanelectrode,thepotential
1.3 The values stated in SI units are to be regarded as the
ofwhichismaintainedatsuchavaluethatunwantedelectrode
standard. The values given in parentheses are for information
reactions are precluded under the prevailing experimental
only.
conditions. Those substances which have reduction-oxidation
(redox) potentials near that of the ion being determined
1.4 This standard does not purport to address all of the
constitute interferences. Electrolysis current decreases expo-
safety concerns, if any, associated with its use. It is the
nentially as the reaction proceeds, until constant background
responsibility of the user of this standard to establish appro-
current is obtained. Detailed discussions of the theory and
priate safety and health practices and determine the applica-
applications of this technique have been published (1, 2, 3, 4,
bility of regulatory limitations prior to use.
5, 6). The control-potential adjustment technique (7) can be
2. Referenced Documents
used to terminate the electrolysis of the specimen at constant
background current without exhaustive electrolysis with con-
2.1 ASTM Standards:
siderable reduction in operating time. Use of the control-
C1009Guide for Establishing a QualityAssurance Program
potential adjustment technique requires that the coulometer
forAnalytical Chemistry Laboratories Within the Nuclear
integrator be capable of operations in a bipolar mode and that
Industry
the plutonium-containing solution be of high purity, that is,
C1068Guide for Qualification of Measurement Methods by
nuclear grade.
a Laboratory Within the Nuclear Industry
C1128Guide for Preparation of Working Reference Materi-
3.2 Plutonium(IV) is reduced to Pu(III) at a working elec-
als for Use in Analysis of Nuclear Fuel Cycle Materials
trode maintained at a potential more negative than the formal
C1156Guide for Establishing Calibration for a Measure-
redox potential. Plutonium(III) is oxidized to Pu(IV) at a
potential more positive than the formal redox potential. The
quantity of plutonium electrolyzed is calculated from the net
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear
number of coulombs required for the electrolysis, according to
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Faraday’s law. Corrections for incomplete reaction, derived
Test.
Current edition approved July 1, 2006. Published October 2006. Originally from the Nernst equation, must be applied for electrolysis of
approved in 1988. Last previous edition approved in 1999 as C1108–99. DOI:
the sample aliquot (7, 8).
10.1520/C1108-99R06.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the ASTM website. this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1108 − 99 (2006)
Q 2 Q M 5.4 Iron—In 0.5 M H SO supporting electrolyte, iron is
~ !
s b
2 4
W 5 (1)
nFf reduced and oxidized at essentially the same formal redox
potentials as the Pu(III)-Pu(IV) couple and thus constitutes a
where:
direct interference. Iron must be removed by prior separation,
W = grams of plutonium,
or the effect of its presence must be corrected by a separate
Q = coulombs required by the electrolysis,
s
measurement of the iron concentration in the sample solution.
Q = coulombs of background current,
b
In 1 M HCl, 1 M HNO,or1 M HClO , iron interferes to a
3 4
M = gram-atomic weight of plutonium (must be adjusted
much lesser extent. The effect of iron in these supporting
for isotopic composition),
electrolytes may be minimized by the choice of redox
n = number of electrons involved in the electrode reaction
potentials, by a secondary titration (10), or by electrochemical
(for Pu(III) → Pu(IV), n=1),
correction (12, 13).
F = Faraday constant, coulombs/equivalent, and
f = fraction of plutonium electrolyzed.
5.5 Nitrites—Nitrites are electrochemically active;
therefore, saturated sulfamic acid solution should be added to
4. Significance and Use
the electrolyte in the cell to destroy any interfering nitrites.
4.1 Factors governing selection of a method for the deter-
5.6 Sulfate—Becauseofthecomplexingactionofsulfateon
mination of plutonium include available quantity of sample,
Pu(IV) and the resultant shift in the redox potential of the
sample purity, desired level of reliability, and equipment.
Pu(III)-Pu(IV) couple, only small amounts of sulfate are
4.1.1 This test method determines 5 to 10 mg of plutonium
tolerable in HNO , HCl, and HClO electrolytes. When using
with prior dissolution using Practice C1168. 3 4
these supporting electrolytes, specimens should be fumed to
4.1.2 This test method calculates plutonium assay using
dryness to assure adequate removal of excess sulfate (see
physical constants as reference standards.
10.1.3).
4.1.3 Chemical standards are used for quality control when
prior chemical separation of plutonium is necessary to remove
NOTE 1—Interference from a sulfate concentration of >0.004 M in 1 M
interferences (9).
HClO has been reported (10).
4.2 Committee C-26 Safeguards Statement :
5.7 Fluoride—Freefluoridecannotbetoleratedandmustbe
4.2.1 The materials (plutonium metal, plutonium oxide or
removed from the specimen. Evaporation of the specimen in
mixed oxide [(U, Pu) O ] powders and pellets) to which this
HNO toalowvolumeandfumingwithH SO areeffectivein
3 2 4
test method applies are subject to nuclear safeguards regula-
removing fluoride.
tions governing their possession and use. Materials for use by
the commercial nuclear community must also meet composi- 5.8 Oxygen—In HNO , HCl, and HClO supporting
3 4
electrolytes,oxygenmaybeaninterference.InH SO ,oxygen
tional specifications.
2 4
4.2.2 The analytical method in this test method both meets does interfere and must be removed. Purging the specimen
with high-purity argon prior to and during the coulometric
U. S. Department of Energy guidelines for acceptability of a
measurementmethodforgenerationofsafeguardsaccountabil- determination is recommended for all electrolytes.
ity measurement data and also provides data that may be used
to demonstrate specification compliance in buyer-seller inter- 6. Apparatus
actions.
6.1 Controlled-Potential Coulometer—A coulometer with
the following specifications is recommended to achieve highly
5. Interferences
precise and accurate results. (Room temperature stability of
5.1 Interferenceiscausedbyionsthatareelectrochemically
61°C is recommended to ensure optimum instrument perfor-
active in the range of redox potentials used or by species that
mance. Instruments with smaller output current or smaller
prevent attainment of 100% current efficiency (for example,
voltage span may be satisfactory.)
reductants, oxidants, and organic matter).
Potentiostat (6)
5.2 Polymer—Polymerized plutonium is not electrochemi- Output voltage >25 V
Output current >200 mA
cally active (10) and thus is neither reduced nor oxidized. The
Open-loop response d-c gain >10
presence of polymerized plutonium will give low results. The
Unity-gain bandwidth >300 kHz
Full-power response >10 kHz (slewing rate 0.5 V/µs)
polymer may be converted to electrochemically active species
Voltage zero offset stability >1-mV long term
by HF treatment (10).
Input d-c resistance >50 MΩ
Input d-c current <50 nA
5.3 Pu(VI)—Plutonium(VI) is only partially reduced to
d-c control voltage span ±4 V
Pu(III) in 1 M HNO , HCl, or HClO supporting electrolyte
3 4
Resolution, hum, and drift <1 mV
solutions; therefore, the presence of Pu(VI) can lead to
Stability through extreme of line and ±5 mV
load variation
inaccurate results when present even as a small fraction of the
Digital Integrator (14)
totalplutonium.Plutonium(VI)iscompletelyreducedin0.5 M
Nonlinearity of V/F converter <0.01 % full scale
H SO (10) or 5.5 M HCl (11) supporting electrolyte.
Full scale error adjustable to zero
2 4
Input offset voltage error adjustable to zero
Output readability <1 µg Pu
Integrating capacity >10 C
BaseduponCommitteeC26SafeguardsMatrix(C1009,C1068,C1128,C1156,
Accuracy <0.01 %
C1210, and C1297).
C1108 − 99 (2006)
FIG. 2 Working Electrode (Top View)
FIG. 1 Exploded View of Cell Assembly: (a) Counter Electrode,
6.3.2 Counter Electrode and Salt Bridge Tube—Thecounter
(b) Cell Head, (c) Counter Electrode Frit Tube, (d) Reference Elec-
electrode is a coiled length of 0.51-mm (0.020-in.) diameter
trode Frit Tube, (e) NBL-Designed S-Shaped Stirrer, (f) Working
Electrode, (g) Sample Cell, (h) Stirrer Motor, (i) Motor Pedestal
platinumwire.Thesaltbridgetubeisunfiredhigh-silicaglass
and Bearing, and (j) Stirrer Shaft
filled with the supporting electrolyte solution.
6.3.3 Reference Electrode and Salt Bridge Tube—The ref-
erence electrode is a miniature saturated-calomel electrode
(SCE). The salt bridge is identical to the salt bridge described
6.2 Digital Voltmeter, 15-V range, 5 ⁄2 digits accurate to
10 5
in 6.3.2 and is also filled with supporting electrolyte solution.
0.01% of full scale on all ranges. Input resistance >10 Ω.
6.3.4 Working Electrode, fabricated from either 8Au8-5/0
6.3 Cell Assembly—Thesuccessofcontrolled-potentialcou-
expanded annealed-gold metal or from 45-mesh platinum
lometric methods is strongly dependent on the design of the
gauze (Fig. 2). Storage of either electrode in 8 M HNO when
cell. The cell dimensions, electrode area, spacing, and stirring
not in use and rinsing with 8 M HNO between specimens are
rateareimportantparametersinadesignthatwillminimizethe
normally adequate to maintain satisfactory electrode response.
time required for titration. The following components are
(Satisfactory response may be defined as the ability of the
required for the recommended cell assembly (Fig. 1).
electrode to oxidize and reduce the supporting electrolyte to 1
6.3.1 Cell—The coulometry cell is fabricated from a cut-off
to 2 µA in about 3 min with the current following an
50-mL borosilicate glass beaker with an inside diameter of 38
exponential curve.) If such electrode response is not obtained,
mm and a height of 42 mm; the cut edges are rounded and
polished smooth. Other cells conforming to these dimensions
EitheratesttubewithunfiredVycorbottomsofType7930glassobtainedfrom
are satisfactory.
Corning GlassWorks, or a 0.5 cm long, 0.5-cm diameter rod of unfiredVycorType
7930 sealed into one end of a glass tube with heat-shrinkable TFE-fluorocarbon
tubing, has been found satisfactory for this application.
5 7
AHewlett-Packard3455ADVMhasbeenfoundtoexceedthesespecifications. AFisher Calomel Reference Electrode Catalog No. 13-639-79 has been found
satisfactory.
C1108 − 99 (2006)
nous motor is recommended.
6.3.6 Inert Gas Inlet Tube—A polyvinyl chloride tube,
approximately 3 mm in outside diameter (1 mm in inside
diameter), is inserted so that its tip is about 10 mm above the
surface of the electrolyte solution. The gas flow is adjusted so
that the surface of the solution is depressed almost 3 mm. The
gas is high-purity argon. While inert gas is not required for all
electrolytes, it is recommended for this procedure.
6.4 Quartz Heating Lamps—Optimum heating or evaporat-
ing efficiency without bumping of solutions, or both, is
obtained using overhead heating with quartz heat lamps
controlled by a variable power supply. However, with proper
care, other conventional means of heating may be used.
6.5 Hot Plate—Recommended for heating during the pluto-
nium oxidation state adjustment with hydrogen peroxide.
6.6 Quartz Clock Timer, accurate to 0.001 s.
6.7 100-Ω Precision Resistor, accurate to better than
0.01%.
7. Reagents and Materials
7.1 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 theAmerican Chemical Society where
Other grades may be used,
such specifications are available.
provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
the determination.
FIG. 3 S-Shaped Stirrer
7.2 Argon, greater than 99.99% purity.
7.3 Hydrochloric Acid, concentrated hydrochloric acid
the following electrode reconditioning treatments, in increas-
(HCl, specific gravity 1.19).
ing order of severity, have been found to be successful in
7.4 Hydrochloric Acid (1 M), prepare by diluting 85 mL of
restoring response.
hydrochloric acid to 1 L with water.
6.3.4.1 Thegoldelectrodemaybe:(1)brieflydippedincold
7.5 Hydrochloric Acid-Nitric Acid-Hydrofluoric Acid Mix-
concentrated HCl and thoroughly rinsed with 8 M HNO;(2)
ture (5.4 M HCl-1.6 M HNO -0.01
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:C 1108–99 Designation: C1108 – 99 (Reapproved 2006)
Standard Test Method for
Plutonium by Controlled-Potential Coulometry
This standard is issued under the fixed designation C1108; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method describes the determination of plutonium in solutions of unirradiated nuclear-grade (that is, high-purity)
materials by controlled-potential coulometry. Controlled-potential coulometry may be performed in a choice of supporting
electrolytes,suchas0.9 MHNO ,1 MHClO ,1 MHCl,5 MHCl,and0.5 MH SO .Limitationsontheuseofselectedsupporting
3 4 2 4
electrolytes are discussed in Section 5. Optimum quantities of plutonium for this procedure are 5 to 10 mg.
1.2 Plutonium-bearing materials are radioactive and toxic. Adequate laboratory facilities, such as gloved boxes, fume hoods,
controlled ventilation, etc., along with safe techniques must be used in handling specimens containing these materials.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.
2. Referenced Documents
2.1 ASTM Standards:
C1009 GuideforEstablishingaQualityAssuranceProgramforAnalyticalChemistryLaboratoriesWithintheNuclearIndustry
C1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear Industry
C1128 Guide for Preparation of Working Reference Materials for Use in the Analysis of Nuclear fuelFuel Cycle Materials
C1156 Guide for Establishing Calibration for a Measurement Method Used to Analyze Nuclear Fuel Cycle Materials
C1168 Practice for Preparation and Dissolution of Plutonium Materials for Analysis
C1210 Guide for Establishing a Measurement System Quality Control Program forAnalytical Chemistry Laboratories Within
the Nuclear Industry
C1297 Guide for Qualification of Laboratory Analysts for the Analysis of Nuclear Fuel Cycle Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Summary of Test Method
3.1 In a controlled-potential coulometric measurement, the substance being determined reacts at an electrode, the potential of
which is maintained at such a value that unwanted electrode reactions are precluded under the prevailing experimental conditions.
Thosesubstanceswhichhavereduction-oxidation(redox)potentialsnearthatoftheionbeingdeterminedconstituteinterferences.
Electrolysis current decreases exponentially as the reaction proceeds, until constant background current is obtained. Detailed
discussionsofthetheoryandapplicationsofthistechniquehavebeenpublished (1, 2, 3, 4, 5, 6). Thecontrol-potentialadjustment
technique (7) can be used to terminate the electrolysis of the specimen at constant background current without exhaustive
electrolysis with considerable reduction in operating time. Use of the control-potential adjustment technique requires that the
coulometerintegratorbecapableofoperationsinabipolarmodeandthattheplutonium-containingsolutionbeofhighpurity,that
is, nuclear grade.
3.2 Plutonium(IV) is reduced to Pu(III) at a working electrode maintained at a potential more negative than the formal redox
potential. Plutonium(III) is oxidized to Pu(IV) at a potential more positive than the formal redox potential. The quantity of
This test method is under the jurisdiction ofASTM Committee C-26 C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods
of Test.
Current edition approved Jan. 10, 1999. Published February 1999. Originally published as C 1108–88. Last previous edition C 1108–93.
Current edition approved July 1, 2006. Published October 2006. Originally approved in 1988. Last previous edition approved in 1999 as C1108–99. DOI:
10.1520/C1108-99R06.
A Julie 100-V precision resistor number NB102A, accurate to 0.0015%, has been found satisfactory.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Annual Book of ASTM Standards, Vol 12.01.
The boldface numbers in parentheses refer to the list of references at the end of this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1108 – 99 (2006)
plutonium electrolyzed is calculated from the net number of coulombs required for the electrolysis, according to Faraday’s law.
Corrections for incomplete reaction, derived from the Nernst equation, must be applied for electrolysis of the sample aliquot (7,
8).
~Q 2 Q ! M
s b
W 5 (1)
nFf
where:
W = grams of plutonium,
Q = coulombs required by the electrolysis,
s
Q = coulombs of background current,
b
M = gram-atomic weight of plutonium (must be adjusted for isotopic composition),
n = number of electrons involved in the electrode reaction (for Pu(III)→ Pu(IV), n=1),
F = Faraday constant, coulombs/equivalent, and
f = fraction of plutonium electrolyzed.
4. Significance and Use
4.1 Factors governing selection of a method for the determination of plutonium include available quantity of sample, sample
purity, desired level of reliability, and equipment.
4.1.1 This test method determines 5 to 10 mg of plutonium with prior dissolution using Practice C 1168C1168.
4.1.2 This test method calculates plutonium assay using physical constants as reference standards.
4.1.3 Chemical standards are used for quality control when prior chemical separation of plutonium is necessary to remove
interferences (9).
4.2 Committee C-26 Safeguards Statement :
4.2.1 The materials (plutonium metal, plutonium oxide or mixed oxide [(U, Pu) O ] powders and pellets) to which this test
method applies are subject to nuclear safeguards regulations governing their possession and use. Materials for use by the
commercial nuclear community must also meet compositional specifications.
4.2.2 The analytical method in this test method both meets U. S. Department of Energy guidelines for acceptability of a
measurement method for generation of safeguards accountability measurement data and also provides data that may be used to
demonstrate specification compliance in buyer-seller interactions.
5. Interferences
5.1 Interference is caused by ions that are electrochemically active in the range of redox potentials used or by species that
prevent attainment of 100% current efficiency (for example, reductants, oxidants, and organic matter).
5.2 Polymer—Polymerized plutonium is not electrochemically active (10) and thus is neither reduced nor oxidized. The
presence of polymerized plutonium will give low results. The polymer may be converted to electrochemically active species by
HF treatment (10).
5.3 Pu(VI)—Plutonium(VI) is only partially reduced to Pu(III) in 1 M HNO , HCl, or HClO supporting electrolyte solutions;
3 4
therefore, the presence of Pu(VI) can lead to inaccurate results when present even as a small fraction of the total plutonium.
Plutonium(VI) is completely reduced in 0.5 M H SO (10) or 5.5 M HCl (11) supporting electrolyte.
2 4
5.4 Iron—In 0.5 M H SO supporting electrolyte, iron is reduced and oxidized at essentially the same formal redox potentials
2 4
as the Pu(III)-Pu(IV) couple and thus constitutes a direct interference. Iron must be removed by prior separation, or the effect of
itspresencemustbecorrectedbyaseparatemeasurementoftheironconcentrationinthesamplesolution.In1 MHCl,1 MHNO ,
or 1 M HClO , iron interferes to a much lesser extent.The effect of iron in these supporting electrolytes may be minimized by the
choice of redox potentials, by a secondary titration (10), or by electrochemical correction (12, 13) .
5.5 Nitrites—Nitritesareelectrochemicallyactive;therefore,saturatedsulfamicacidsolutionshouldbeaddedtotheelectrolyte
in the cell to destroy any interfering nitrites.
5.6 Sulfate—Because of the complexing action of sulfate on Pu(IV) and the resultant shift in the redox potential of the
Pu(III)-Pu(IV) couple, only small amounts of sulfate are tolerable in HNO , HCl, and HClO electrolytes. When using these
3 4
supporting electrolytes, specimens should be fumed to dryness to assure adequate removal of excess sulfate (see 10.1.3).
NOTE 1—Interference from a sulfate concentration of >0.004 M in 1 M HClO has been reported (10).
5.7 Fluoride—Freefluoridecannotbetoleratedandmustberemovedfromthespecimen.EvaporationofthespecimeninHNO
to a low volume and fuming with H SO are effective in removing fluoride.
2 4
5.8 Oxygen—In HNO , HCl, and HClO supporting electrolytes, oxygen may be an interference. In H SO , oxygen does
3 4 2 4
interfere and must be removed. Purging the specimen with high-purity argon prior to and during the coulometric determination is
recommended for all electrolytes.
Annual Book of ASTM Standards, Vol 14.02.
Based upon Committee C26 Safeguards Matrix (C1009, C1068, C1128, C1156, C1210, and C1297).
C1108 – 99 (2006)
6. Apparatus
6.1 Controlled-Potential Coulometer—A coulometer with the following specifications is recommended to achieve highly
precise and accurate results. (Room temperature stability of 61°C is recommended to ensure optimum instrument performance.
Instruments with smaller output current or smaller voltage span may be satisfactory.)
Potentiostat (6)
Output voltage >25 V
Output current >200 mA
Open-loop response d-c gain >10
Unity-gain bandwidth >300 kHz
Full-power response >10 kHz (slewing rate 0.5 V/µs)
Voltage zero offset stability >1-mV long term
Input d-c resistance >50 MV
Input d-c current <50 nA
d-c control voltage span 64V
Resolution, hum, and drift <1 mV
Stability through extreme of line and 65mV
load variation
Digital Integrator (14)
Nonlinearity of V/F converter <0.01 % full scale
Full scale error adjustable to zero
Input offset voltage error adjustable to zero
Output readability <1 µg Pu
Integrating capacity >10 C
Accuracy <0.01 %
FIG. 1 Exploded View of Cell Assembly: (a) Counter Electrode,
(b) Cell Head, (c) Counter Electrode Frit Tube, (d) Reference
Electrode Frit Tube, (e) NBL-Designed S-Shaped Stirrer, (f)
Working Electrode, (g) Sample Cell, (h) Stirrer Motor, (i) Motor
Pedestal and Bearing, and (j) Stirrer Shaft
C1108 – 99 (2006)
FIG. 2 Working Electrode (Top View)
10 5
6.2 Digital Voltmeter, 15-V range, 5 ⁄2 digits accurate to 0.01% of full scale on all ranges. Input resistance >10 V.
6.3 Cell Assembly—The success of controlled-potential coulometric methods is strongly dependent on the design of the cell.
The cell dimensions, electrode area, spacing, and stirring rate are important parameters in a design that will minimize the time
required for titration. The following components are required for the recommended cell assembly (Fig. 1).
6.3.1 Cell—The coulometry cell is fabricated from a cut-off 50-mLborosilicate glass beaker with an inside diameter of 38 mm
andaheightof42mm;thecutedgesareroundedandpolishedsmooth.Othercellsconformingtothesedimensionsaresatisfactory.
6.3.2 Counter Electrode and Salt Bridge Tube—The counter electrode is a coiled length of 0.51-mm (0.020-in.) diameter
platinum wire. The salt bridge tube is unfired high-silica glass filled with the supporting electrolyte solution.
6.3.3 Reference Electrode and Salt Bridge Tube—The reference electrode is a miniature saturated-calomel electrode (SCE).
The salt bridge is identical to the salt bridge described in 6.3.2 and is also filled with supporting electrolyte solution.
6.3.4 Working Electrode,fabricatedfromeither8Au8-5/0expandedannealed-goldmetalorfrom45-meshplatinumgauze(Fig.
2).Storageofeitherelectrodein8 MHNO whennotinuseandrinsingwith8 MHNO betweenspecimensarenormallyadequate
3 3
to maintain satisfactory electrode response. (Satisfactory response may be defined as the ability of the electrode to oxidize and
reduce the supporting electrolyte to 1 to 2 µAin about 3 min with the current following an exponential curve.) If such electrode
response is not obtained, the following electrode reconditioning treatments, in increasing order of severity, have been found to be
successful in restoring response.
6.3.4.1 The gold electrode may be: ( 1) briefly dipped in cold concentrated HCl and thoroughly rinsed with 8 M HNO;(2)
briefly dipped in hot HCl and thoroughly rinsed with HNO;(3) briefly dipped in aqua regia and thoroughly rinsed with HNO ;
3 3
or (4) soaked 10 min in the sulfuric acid-hydrofluoric acid mixture (7.16), the residual acid removed by fuming and the hot
The boldface numbers in parentheses refer to the list of references at the end of this test method.
A Hewlett-Packard 3455A DVM has been found to exceed these specifications.
Based upon Committee C-26 Safeguards Matrix (C 1009C 1009, C 1068C 1068, C 1128C 1128, C 1156C 1156, C 1210C 1210, and C 1297C 1297).
Either a test tube with unfiredVycor bottoms ofType 7930 glass obtained from Corning GlassWorks, or a 0.5 cm long, 0.5-cm diameter rod of unfiredVycorType 7930
sealed into one end of a glass tube with heat-shrinkable TFE-fluorocarbon tubing, has been found satisfactory for this application.
A Hewlett-Packard 3455A DVM has been found to exceed these specifications.
A Fisher Calomel Reference Electrode Catalog No. 13-639-79 has been found satisfactory.
C1108 – 99 (2006)
electrode quenched in 8 M HNO . After each treatment, the electrode is stored in 8 M HNO overnight. Following overnight
3 3
storage, conditioning, that is, alternating reduction and oxidation of the supporting electrolyte with and without plutonium, may
be required to achieve desired electrode performance.
6.3.4.2 The platinum electrode may be subjected to any of the above treatments, or it may be: (1) heated to red heat in a gas
flame and quenched in 8 M HNO or (2) heated in a furnace to 900°C and quenched in 8 M HNO .
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