ASTM C1204-14(2023)

Standard Test Method for Uranium in Presence of Plutonium by Iron(II) Reduction in Phosphoric Acid Followed by Chromium(VI) Titration

SIGNIFICANCE AND USE
4.1 Factors governing selection of a method for the determination of uranium include available quantity of sample, sample purity, desired level of reliability, and equipment availability.  
4.2 This test method is suitable for samples between 20 mg to 300 mg of uranium, is applicable to fast breeder reactor (FBR)-mixed oxides having a uranium to plutonium ratio of 2.5 and greater, is tolerant towards most metallic impurity elements usually specified for FBR-mixed oxide fuel, and uses no special equipment.  
4.3 The ruggedness of the titration method has been studied for both the volumetric (6) and the weight (7) titration of uranium with dichromate.
SCOPE
1.1 This test method covers unirradiated uranium-plutonium mixed oxide having a uranium to plutonium ratio of 2.5 and greater. The presence of larger amounts of plutonium (Pu) that give lower uranium to plutonium ratios may give low analysis results for uranium (U) (1)2, if the amount of plutonium together with the uranium is sufficient to slow the reduction step and prevent complete reduction of the uranium in the allotted time. Use of this test method for lower uranium to plutonium ratios may be possible, especially when 20 mg to 50 mg quantities of uranium are being titrated rather than the 100 mg to 300 mg in the study cited in Ref (1). Confirmation of that information should be obtained before this test method is used for ratios of uranium to plutonium less than 2.5.  
1.2 The amount of uranium determined in the data presented in Section 12 was 20 mg to 50 mg. However, this test method, as stated, contains iron in excess of that needed to reduce the combined quantities of uranium and plutonium in a solution containing 300 mg of uranium with uranium to plutonium ratios greater than or equal to 2.5. Solutions containing up to 300 mg uranium with uranium to plutonium ratios greater than or equal to 2.5 have been analyzed (1) using the reagent volumes and conditions as described in Section 10.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 8.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Dec-2022
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: C26 - Nuclear Fuel Cycle
• Drafting Committee: C26.05 - Methods of Test

Relations

• Refers: ASTM C1168-23 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Oct-2023
• Refers: ASTM C1168-15 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Sep-2015
• Refers: ASTM C1128-15 - Standard Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle Materials
• Effective Date: 01-Feb-2015
• Refers: ASTM C852-09 - Standard Guide for Design Criteria for Plutonium Gloveboxes
• Effective Date: 01-Jun-2009
• Refers: ASTM C1128-01(2008) - Standard Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle Materials
• Effective Date: 01-Jun-2008
• Refers: ASTM C1168-08 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 01-Jan-2008
• Refers: ASTM C1128-01 - Standard Guide for Preparation of Working Reference Materials for Use in the Analysis of Nuclear Fuel Cycle Materials
• Effective Date: 10-Oct-2001
• Refers: ASTM C1168-01 - Standard Practice for Preparation and Dissolution of Plutonium Materials for Analysis
• Effective Date: 10-Jan-2001
• Refers: ASTM C852-93(1997) - Standard Guide for Design Criteria for Plutonium Gloveboxes (Withdrawn 2006)
• Effective Date: 10-Dec-1997

Overview

ASTM C1204-14(2023) provides a standard test method for the determination of uranium in the presence of plutonium. This method utilizes iron(II) reduction in phosphoric acid followed by chromium(VI) titration. Developed by ASTM International, the standard is widely used in the nuclear industry, especially for analyzing unirradiated uranium-plutonium mixed oxides with a uranium to plutonium ratio of 2.5 or greater. The methodology offers a reliable, accurate, and equipment-efficient means for uranium quantification, which is essential for quality control, regulatory compliance, and safeguarding processes within nuclear fuel production and research.

Key Topics

• Uranium Determination in Plutonium-Containing Samples: The standard is specifically designed for uranium analysis in samples where plutonium is present in significant amounts.
• Applicable Sample Range: Suitable for samples containing between 20 mg and 300 mg of uranium, particularly in fast breeder reactor (FBR) mixed oxide (MOX) fuel materials.
• Impurity Tolerance: Accommodates most metallic impurity elements commonly found in FBR-MOX fuels, ensuring accurate results under typical operating conditions.
• No Special Equipment Required: The procedure does not depend on specialized equipment, making it accessible for a broad range of laboratory environments.
• Method Robustness: The ruggedness of this titration technique has been explored for both volumetric and gravimetric titrations, confirming its reliability and repeatability.
• Safety and Regulatory Considerations: Addresses the critical need for proper safety, health, and environmental practices due to the handling of radioactive and toxic materials.

Applications

• Nuclear Fuel Cycle Laboratories: Used extensively in facilities producing or managing MOX fuel, where accurate uranium content determination is critical to safety, efficiency, and regulatory reporting.
• Quality Control of Mixed Oxide Fuels: Ensures that uranium concentration in FBR-MOX fuel meets strict industry and safety standards.
• Regulatory and Safeguard Compliance: Supports nuclear safeguards and accountability requirements, meeting traceability needs for international standards and national oversight bodies.
• Research and Development: Facilitates R&D projects that require precise measurement of uranium in uranium-plutonium oxide matrices, contributing to advances in reactor fuel technology and safety studies.
• Interlaboratory Comparisons: Provides a common test method for collaborative benchmarking and quality assurance among nuclear analytical laboratories.

Related Standards

The following ASTM standards and guides are frequently referenced alongside ASTM C1204-14(2023):

• ASTM C852: Guide for Design Criteria for Plutonium Gloveboxes, useful for safe sample handling.
• ASTM C1128: Guide for Preparation of Working Reference Materials for Analysis of Nuclear Fuel Cycle Materials, supporting traceable solution preparation.
• ASTM C1168: Practice for Preparation and Dissolution of Plutonium Materials for Analysis, referenced for sample preparation and dissolution protocols.

Practical Value

This standard delivers practical value through its robust, versatile approach to determining uranium in challenging mixed oxide matrices without needing specialized equipment. Its broad impurity tolerance and adaptability to standard laboratory settings make it a practical choice for routine analysis in nuclear sectors worldwide. The method’s documented reliability and compatibility with international standards position it as a cornerstone in nuclear material verification, quality control, and regulatory compliance.

Keywords

Uranium analysis, plutonium presence, iron(II) reduction, chromium(VI) titration, mixed oxide fuel (MOX), fast breeder reactor, nuclear fuel analysis, ASTM C1204, uranium to plutonium ratio, safeguard measurement, regulatory compliance.

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: C1204 − 14 (Reapproved 2023)
Standard Test Method for
Uranium in Presence of Plutonium by Iron(II) Reduction in
Phosphoric Acid Followed by Chromium(VI) Titration
This standard is issued under the fixed designation C1204; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 Thistestmethodcoversunirradiateduranium-plutonium
mendations issued by the World Trade Organization Technical
mixed oxide having a uranium to plutonium ratio of 2.5 and
Barriers to Trade (TBT) Committee.
greater. The presence of larger amounts of plutonium (Pu) that
give lower uranium to plutonium ratios may give low analysis
2. Referenced Documents
results for uranium (U) (1) , if the amount of plutonium
2.1 ASTM Standards:
together with the uranium is sufficient to slow the reduction
C852Guide for Design Criteria for Plutonium Gloveboxes
step and prevent complete reduction of the uranium in the
C1128Guide for Preparation of Working Reference Materi-
allotted time. Use of this test method for lower uranium to
als for Use in Analysis of Nuclear Fuel Cycle Materials
plutoniumratiosmaybepossible,especiallywhen20mgto50
C1168PracticeforPreparationandDissolutionofPlutonium
mg quantities of uranium are being titrated rather than the
Materials for Analysis
100mg to 300 mg in the study cited in Ref (1). Confirmation
of that information should be obtained before this test method
3. Summary of Test Method
is used for ratios of uranium to plutonium less than 2.5.
3.1 Samples are prepared by dissolution techniques detailed
1.2 Theamountofuraniumdeterminedinthedatapresented
in Practice C1168 and Ref (2). Aliquants containing 20mg to
in Section 12 was 20mg to 50 mg. However, this test method,
300 mg of uranium, as selected by the facility procedure, are
as stated, contains iron in excess of that needed to reduce the
prepared by weight. The sample is fumed to incipient dryness
combined quantities of uranium and plutonium in a solution
after the addition of sulfuric acid. The sample is dissolved in
containing 300 mg of uranium with uranium to plutonium
dilute sulfuric acid prior to titration.
ratios greater than or equal to 2.5. Solutions containing up to
3.2 Uranium is reduced to uranium(IV) by excess ferrous
300 mg uranium with uranium to plutonium ratios greater than
(iron(II)) in concentrated phosphoric acid (H PO ) containing
or equal to 2.5 have been analyzed (1) using the reagent 3 4
sulfamic acid. The excess iron(II) is selectively oxidized by
volumes and conditions as described in Section 10.
nitric acid (HNO ) in the presence of molybdenum(VI) cata-
1.3 The values stated in SI units are to be regarded as
lyst. After the addition of vanadium(IV), the uranium(IV) is
standard. No other units of measurement are included in this
titratedwithchromium(VI)toapotentiometricendpoint (3, 4).
standard.
3.3 A single chromium(VI) titrant delivered manually on a
1.4 This standard does not purport to address all of the
weight or volume basis is used. The concentration of the
safety concerns, if any, associated with its use. It is the
chromium(VI) solution is dependent upon the amount of
responsibility of the user of this standard to establish appro-
uranium being titrated (see 7.8).Automated titrators that have
priate safety, health, and environmental practices and deter-
comparable precisions can be used.
mine the applicability of regulatory limitations prior to use.
NOTE 1—An alternative ceric (V) sulfate or nitrate titrant may also be
For specific hazard statements, see Section 8.
used, providing that the user demonstrates equivalent performance to the
1.5 This international standard was developed in accor-
dichromate titrant.
dance with internationally recognized principles on standard-
3.4 For the titration of uranium alone, the precision of the
modified Davies and Gray titration method has been signifi-
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear
cantly improved by increasing the amount of uranium titrated
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
Test.
Current edition approved Jan. 1, 2023. Published January 2023. Originally
approved in 1991. Last previous edition approved in 2014 as C1204–14. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C1204-14R23. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this test method. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1204 − 14 (2023)
to 1 g and delivering about 90% of the titrant on a solid mass 6.2 pH Meter,withindicator(platinumhasbeenfoundtobe
basis followed by titration to the end point with a dilute titrant satisfactory) and reference (saturated calomel has been found
(5). This modification has not been studied for the titration of to be satisfactory) electrodes.
uranium in the presence of plutonium, and confirmation of its
NOTE 2—The indicator electrode should be changed or cleaned if there
applicability should be obtained by the facility prior to its use.
is a titration problem such as less distinct than normal end point break or
end point drift, or, if desired, prior to use when more than a week has
3.5 The modification of the Davies and Gray titration
passed since its last use. Suggested cleaning procedures for platinum
method,asdescribedoriginallyinRef (4),maybeusedinstead
electrodes are detailed in Appendix X2.
of the method described herein, where laboratories have
NOTE3—Thereferenceelectrodeshouldbecoveredwitharubbertipor
demonstrated no plutonium interference at the uranium to
submerged in a solution (saturated potassium chloride solution for the
calomel electrode) for overnight storage.
plutonium ratios and amounts titrated at that facility. If any
modificationismadetotheprocedureinRef (4)forapplication
7. Reagents
at the facility to uranium, plutonium mixed oxides, confirma-
tion that the modification does not degrade the analysis
7.1 Purity of Reagents—Reagent grade chemicals shall be
technique as stated should be demonstrated prior to its use. used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
4. Significance and Use
Analytical Reagents of theAmerican Chemical Society where
4.1 Factors governing selection of a method for the deter-
such specifications are available. Other grades of reagents
mination of uranium include available quantity of sample,
may be used, provided it is first ascertained that the reagent is
sample purity, desired level of reliability, and equipment
of sufficiently high purity to permit its use without lessening
availability.
the accuracy of the determination.
4.2 This test method is suitable for samples between 20mg
7.2 Purity of Water—Unless otherwise indicated, references
to 300 mg of uranium, is applicable to fast breeder reactor
to water shall be understood to mean laboratory accepted
(FBR)-mixed oxides having a uranium to plutonium ratio of
demineralized or deionized water.
2.5 and greater, is tolerant towards most metallic impurity
7.3 Ferrous Sulfate (1.0 M)—Add 100 mL of sulfuric acid
elements usually specified for FBR-mixed oxide fuel, and uses
(H SO , sp gr 1.84) to 750 mL of water as the solution is
2 4
no special equipment.
stirred. Add 280 g of ferrous sulfate heptahydrate
4.3 The ruggedness of the titration method has been studied
(FeSO ·7H O), and dilute the solution to 1 L with water.
4 2
for both the volumetric (6) and the weight (7) titration of
Prepare ferrous sulfate reagent fresh on a weekly basis. See
uranium with dichromate.
Note 6 on combination of this reagent.
7.4 Nitric Acid (HNO ),8M—Add 500 mLof HNO (sp gr
5. Interferences
3 3
1.42) to less than 500 mL of water and dilute to 1 L.
5.1 Interfering elements are not generally present in signifi-
7.5 Nitric Acid (8 M)-Sulfamic Acid (0.15 M)-Ammonium
cant quantities in mixed uranium, plutonium oxide product
Molybdate (0.4%)—Dissolve4gof ammonium molybdate
material. However, elements that cause bias when present in
[(NH ) Mo O ·4H O]in400mLofwater,andadd500mLof
milligram quantities are silver (Ag), vanadium (V), plutonium
4 6 7 24 2
nitric acid (HNO , sp gr 1.42). Mix and add 100 mL of 1.5 M
(Pt),ruthenium(Ru),osmium(Os),andiodine(I).Interference
sulfamic acid solution (see 7.9) and mix.
fromtin(Sn),arsenic(As),antimony(Sb),molybdenum(Mo),
manganese (Mn), fluorine (F), chlorine (Cl), and bromine (Br)
7.6 Orthophosphoric Acid (H PO ), 85 %—Test and treat
3 4
are eliminated when the preparation procedure is followed as
for reducing substances prior to use (see Annex A2).
given (4, 8, 9, 10, 11, 12) in this titrimetric method. Of the
7.7 Potassium Dichromate Solution (2 %)—Dissolve 2 g of
metallic impurity elements usually included in specifications
K Cr O in water, and dilute to 100 g with water.
2 2 7
for FBR-mixed oxide fuel, silver, manganese, lead (Pb), and
vanadium interfere. 7.8 Potassium Dichromate Titrant (0.0045 M and 0.045
M)—Dissolve 2.65 g of reagent grade or purer grade K Cr O
2 2 7
5.2 Other interfering metallic elements are gold (Au), mer-
inwater;transferthissolutiontoapre-weighed,2Lvolumetric
cury (Hg), iridium (Ir), and palladium (Pd). Elimination of
flaskanddilutetovolume;thissolutionisforuseintitrationof
their interference requires their separation from uranium by
20 to less than 100 mg uranium aliquants. Dissolve 26.5 g of
such techniques as ion exchange and solvent extraction (13,
reagent grade or purer grade K Cr O in water; transfer this
2 2 7
14).
solution to a pre-weighed, 2L flask and dilute to volume; this
5.3 An initial fuming with sulfuric acid removes such
solution is for use in titration of 100mg to 300 mg uranium
impurityelementsasthehalidesandvolatilemetallicelements.
aliquants.
5.4 The effects of impurities and their removal are listed in
TableA1.1 of AnnexA1, and the details are given in Refs (4,
8, 9, 10, 11, 12, 13, 14, 15). ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
6. Apparatus DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
6.1 Buret—Polyethylenebottle(preparationinstructionscan
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
be found in Appendix X1), glass weight, or volumetric. copeial Convention, Inc. (USPC), Rockville, MD.
C1204 − 14 (2023)
7.8.1 If potassium dichromate traceable to a national stan- sulfate dihydrate (VOSO ·2H O) crystals, mix the solid with
4 2
dards laboratory (for example the National Institute of Stan- the temperature equilibrated sulfuric acid, and dilute the
dards Technology (NIST) in the U.S. or the Federal Institute solution to 2 L. The vanadyl sulfate concentration should
for Materials Research and Testing (BAM) in Germany) was provide 75mg to 125 mg VOSO ·2H O per titration, but the
4 2
used, proceed as in 7.8.1.1 and 7.8.1.2 before going to 7.8.3; concentration is not critical (see Refs (6) and (7)).
otherwise go to 7.8.2. 7.13.1 The vanadyl sulfate solution is not stable (16);
7.8.1.1 Allow the solution to equilibrate to room H SO stabilizes the vanadium(IV) oxidation state, but the
2 4
temperature, weigh the solution, and compute the uranium H SO concentrationisnotcritical.TheVOSO ·2H Osolution
2 4 4 2
equivalenttitrationfactoraftercorrectingtheweightofdichro- should be prepared at suitable intervals to prevent vanadi-
mate for buoyancy (see 11.1.1) and for oxidizing power (see um(V) interference (24-h intervals for preparation are sug-
11.1.2). gested).
7.8.1.2 Verifythepreparationaccuracyofthedichromateor 7.13.2 Alternatively, crystalline vanadyl sulfate dihydrate
ceric titrant solution by titration with a standard uranium (75mg to 125 mg per titration) may be used with a water
solution (see 7.12) within laboratory accepted error limits. diluent in place of the solution (see 10.13).
7.8.2 Ifareagentgradedichromateorcerictitrantwasused,
8. Hazards
allow the solution to equilibrate to room temperature and
8.1 Since plutonium- and uranium-bearing materials are
standardizethedichromatesolutionagainstCRMuranium(see
radioactive and toxic, adequate laboratory facilities, gloved
7.12).
boxes, fume hoods, etc., along with safe techniques, must be
7.8.3 Store the dichromate solution in one or more borosili-
usedinhandlingsamplescontainingthesematerials.Adetailed
cate glass bottles with poly-seal tops, or equivalent containers,
discussion of all precautions necessary is beyond the scope of
to prevent concentration changes due to evaporation.
this test method. However, personnel who handle radioactive
7.9 Sulfamic Acid (1.5 M)—Dissolve 146 g of sulfamic acid
materials should be familiar with such safe handling practices
(NH SO H) in water, filter the solution, and dilute to 1 L.
2 3
as are given in Guide C852 and Refs (17) and (18).
7.10 Sulfuric Acid (1 M)—Add56mLofH SO (spgr1.84)
2 4
8.2 Committee C-26 Safeguards Statement:
to water, while stirring, and dilute to 1 L with water.
8.2.1 The materials (nuclear grade mixed oxides (U, Pu)O
7.11 Sulfuric Acid (0.05 M)—Add 2.8 mL of H SO (sp gr powders and pellets) to which this test method applies are
2 4
1.84) to water, while stirring, and dilute to 1 L with water. subject to nuclear safeguard regulations governing their pos-
session and use. The analytical method in this test method
7.12 Uranium Reference Solution—Guide C1128, Section
meets U.S. Department of Energy guidelines for acceptability
X3.4 may be used to prepare working reference solutions, or
of a measurement method for generation of safeguards ac-
solutions may be prepared with appropriate in-house proce-
countability measurement data.
dures from certified uranium metal.
8.2.2 When used in conjunction with the appropriate stan-
7.12.1 Clean the surface of the uranium metal, New Bruns-
dard or certified reference materials (SRMs or CRMs), this
wick Laboratory CRM 112-A or its replacement, following
procedurecandemonstratetraceabilitytothenationalmeasure-
the instructions on the certificate.
ment base. However, use of this test method does not auto-
7.12.2 Weigh the metal by difference to 0.01 mg making
matically guarantee regulatory acceptance of the resulting
buoyancy and purity corrections detailed in 11.1.1 and 11.1.2,
safeguards measurements. It remains the sole responsibility of
respectively.
the user of this test method to ensure that its application to
7.12.3 Prepare the uranium standard solution in accordance
safeguards has the approval of the proper regulatory authori-
with Guide C1128 or by the procedure approved for use by
ties.
each facility. There are many methods of uranium metal
dissolution that are successful; methods that reproduce the
9. Calibration
uranium assay value on the certificate of analysis for the
9.1 If potassium dichromate traceable to a national stan-
referencematerialareacceptable.Anexampleofanacceptable
dards laboratory is used, only solution preparation, verification
dissolution method is given in Appendix X4.
titrations are needed. Use of an uncertified potassium dichro-
7.12.4 Equilibrate the uranium solution to room
mate requires calibration of the dichromate using a standard
temperature, and weigh the solution to give the same number
uraniummaterialtraceabletoanationalmeasurementbase(for
of significant figures as the metal weight.
example, New Brunswick Laboratory’s CRM 112-A uranium
7.12.5 Calculatethesolutionconcentrationinmguranium/g
metal standard). See Section 9.2 below.
uranium solution using the calculation in 11.2.2.
9.1.1 The potassium dichromate should be prepared as
7.13 Vanadyl Sulfate Dihydrate in Solution (0.0038 M
instructedonthecertificate,weighedto0.01mg,andcorrected
vanadium(IV)-0.18 M H SO )—Add 20 mL concentrated sul-
for buoyancy and purity using the calculations in 11.1.1 and
2 4
furic acid (sp gr 1.84) to less than 980 mL water with stirring
11.1.2.
and equilibrate to room temperature. Weigh 1.5 g of vanadyl
9.1.2 Thedichromatesolutionconcentrationiscalculatedin
mg K Cr O /g solution using the calculation in 11.2.1.
2 2 7
9.1.3 The titration factor (mg uranium/g dichromate solu-
tion) is calculated for the dichromate solution using the
New Brunswick Laboratory Certified Reference Materials Catalog, current
issue, U.S. Department of Energy. calculation in 11.3.1.
C1204 − 14 (2023)
9.2 If reagent grade potassium dichromate or ceric titrant is 10.6 Add 5 mL of 1.5 M sulfamic acid to the beaker, and
used, the solution must be standardized against a primary mix by swirling. Use the reagent to rinse the sides of the
uranium standard for traceability to a national measurement beaker.
base.
10.7 Add 40 mLof H PO (85%), treated with dichromate
3 4
9.2.1 Analyze individually dispensed aliquants of the ura-
(see AnnexA2), directly into the sample.The splashing of any
niumreferencesolutioninaccordancewith10.3–10.14.4.See
solution onto the side of the beaker should be avoided.
Appendix X3 for analysis control recommendations.
10.8 Add7mLofferroussolution,andswirlbriefly.Donot
9.2.2 Calculate the uranium titration factor (mg uranium/g
allowtheferroussolutiontotouchthesidesofthebeakerwhile
dichromate solution) for the standardized potassium dichro-
dispensing this reagent.
mate solution using the calculation in 11.3.2.
NOTE6—TheferrousreagentmaybecombinedwiththeH PO in10.7
3 4
and added as a combined reagent.
10. Procedure
10.9 Add a TFE-fluorocarbon coated magnet without
NOTE 4—Satisfactory analysis results will only be attained if the
temperatureofthereagents(usuallyatroomtemperature)usedare>23°C
splashing, place the beaker on a magnetic stirrer, and initiate
(74°F).
stirring at a slow rate (avoid splashing) for 5 min.
10.9.1 If a visible precipitate is present at the end of 5 min,
10.1 Weigh the sample (0.5 g or more) to 0.1 mg. Dissolve
increase the stirring time to 7 to 8 min.
the sample following the procedures in Ref (2) and Practice
10.9.2 Ifaprecipitateisstillvisibleafter7to8min,prepare
C1168.
anewsample,butincreasethe0.05 MH SO to25mLandthe
2 4
10.2 Quantitatively transfer the weighed, dissolved sample
H PO to 65 mL.
3 4
to a weighed bottle for mixing prior to sample splitting. See
10.10 Add 10 mL of nitric-sulfamic-molybdate solution.
10.2.1 for plastic bottles or 10.2.2 for glass bottles.
Use the solution to rinse down the sides of the beaker.
10.2.1 A low-density polyethylene narrow mouth bottle,
10.11 Mix the solution at a moderate stirrer speed. Imme-
with a one-piece polypropylene special seal-ring screw closure
diatelyupondisappearanceoftheblackcolor,begintimingthe
topreventleakage,maybeused,oranyotherleak-proofbottle.
oxidation period (3 min).
Ifpolyethylenebottlesareused,long-term(weeksandmonths)
storage will not maintain sample integrity because of transpi-
10.12 Weigh the dichromate solution in the weight buret if
ration through the bottle walls (19).
a gravimetric titration is to be used; otherwise, zero the buret.
10.2.1.1 Mix the solution by inverting and equilibrate to
10.13 Stop the stirring, add 100 mL of the vanadyl sulfate
room temperature.
solution or water diluent if solid vanadyl sulfate is used.
10.2.1.2 Weigh the solution to the number of significant
10.13.1 If vanadyl sulfate is added as a solid (75mg to 125
figures equivalent to the sample weight.
mg), add it after the diluent.
10.2.1.3 Calculate the sample dilution factor (g sample/g
10.13.2 Use the vanadyl sulfate solution or diluent to rinse
solution). Go to 10.3.
the sides of the beaker.
10.2.2 Glass bottles with poly-cone seals may also be used
10.14 Increase the rate of stirring to form a vortex in the
for sample mixing.
solution.
10.2.2.1 Cover the glass bottles with parafilm during tem-
10.14.1 Insert the electrodes into the solution, and titrate
peratureequilibration,addthepoly-conesealtopstothebottles
rapidly with dichromate to a potential of 450mV to 480 mV
justpriortomixingtoavoidpressurebuild-upduetoradiolysis
versus a calomel reference electrode or the equivalent voltage
by plutonium, and mix the solution by inverting the bottle.
for other reference electrodes. If the polyethylene weight buret
10.2.2.2 Continue with sample preparation as in 10.2.1.2
is used, remove the reduced size tip used in the final end point
and 10.2.1.3 before going to 10.3.
approach before beginning the addition of dichromate.
10.14.2 Decrease the rate of dichromate additions to large
10.3 Deliver an aliquant, weighed to 0.1 mg accuracy,
drops, 1 to 2 drop portions; titrate to a potential of 500 mV or
containing 20mg to 300 mg of uranium, into the titration
the equivalent for reference electrodes other than calomel.
vessel (400mL beakers are satisfactory).
10.14.3 Begin smaller drop-size additions (for the polyeth-
10.4 Add 1 mL of 1 M H SO to the aliquant, and fume to
ylene weight buret, place the micro-tip on the weight buret),
2 4
near dryness.
and titrate to the potential break, or if a second derivative
technique is to be used, skip to 10.14.4.
NOTE 5—The acid tolerances (4, 20) for a sample aliquant to be
10.14.3.1 The maximum time elapsed between the addition
analyzed by this test method are 4 mL H SO (sp gr 1.84), 3 mL HNO
2 4 3
(sp gr 1.42), no HCl, and 0.5 mLfree HF (sp gr 1.18).Aliquants fumed to
of the vanadyl sulfate or diluent and the completion of 99+%
dryness or near dryness with sulfuric acid should not require further
of the titration should be 7 min.
treatment to satisfy these requirements.
10.14.3.2 Better precision will be attained if the time is
10.5 Dissolve the sample in 15 mL of 0.05 M H SO . Use limited to 3 to 5 min elapsed time.
2 4
the reagent to rinse down the sides of the beaker. The total 10.14.3.3 The variation in the final potential readings to
dissolution of the sample at this point is critical to accurate maintain acceptable precision should be 590 mV 6 20 mV or
analysis;awaitof30minto1hisrecommendedtoensuretotal equivalent potentials for reference electrodes other than the
dissolution. calomel.
C1204 − 14 (2023)
10.14.4 If a dou
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