ASTM C1267-17(2022)

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

SIGNIFICANCE AND USE
5.1 Factors governing selection of a method for the determination of uranium include available quantity of sample, homogeneity of material sampled, sample purity, desired level of reliability, and facility available equipment.  
5.2 This uranium assay method is referenced in the Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium Dioxide Powders and Pellets (Test Methods C696) and in the Test Methods for Chemical, Mass Spectrometric, and Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Uranyl Nitrate Solutions (Test Methods C799). This uranium assay method may also be used for uranium hexafluoride and uranium ore concentrate. This test method determines 20 mg to 200 mg of uranium; is applicable to product, fuel, and scrap material after the material is dissolved; is tolerant towards most metallic impurity elements usually specified in product and fuel; and uses no special equipment.  
5.3 The ruggedness of the titration method has been studied for both the volumetric (6) and the weight (7)  titration of uranium with dichromate.  
5.4 Fitness for Purpose of Safeguards and Nuclear Safety Application—Methods intended for use in safeguards and nuclear safety applications shall meet the requirements specified by Guide C1068 for use in such applications.  
5.4.1 When used in conjunction with the appropriate certified reference materials (SRM6 or CRM), this procedure can demonstrate traceability to the national measurement base. However, use of the test method does not automatically guarantee regulatory acceptance of the resulting safeguards measurements. It remains the sole responsibility of the user of this test method to assure that its application to safeguards has the approval of the proper regulatory authorities.
SCOPE
1.1 This test method, commonly referred to as the Modified Davies and Gray technique, covers the titration of uranium in product, fuel, and scrap materials after the material is dissolved. The test method is versatile and has been ruggedness tested. With appropriate sample preparation, this test method can give precise and unbiased uranium assays over a wide variety of material types (1, 2).2 Details of the titration procedure in the presence of plutonium with appropriate modifications are given in Test Method C1204.  
1.2 Uranium levels titrated are usually 20 mg to 50 mg, but up to 200 mg uranium can be titrated using the reagent volumes stated in this test method.  
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 safeguard and safety precaution statements, see Section 5.  
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: 30-Jun-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 C859-24 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C696-19 - Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium Dioxide Powders and Pellets
• Effective Date: 01-Nov-2019
• Refers: ASTM C799-19 - Standard Test Methods for Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Uranyl Nitrate Solutions
• Effective Date: 01-Jul-2019
• Refers: ASTM C1346-19 - Standard Practice for Dissolution of UF<inf>6</inf> from P-10 Tubes
• Effective Date: 01-Feb-2019
• 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 C859-14a - Standard Terminology Relating to Nuclear Materials
• Effective Date: 15-Jun-2014
• Refers: ASTM C859-14 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 15-Jan-2014
• Refers: ASTM C1346-08(2014) - Standard Practice for Dissolution of UF<inf>6</inf> from P-10 Tubes
• Effective Date: 01-Jan-2014
• Refers: ASTM C859-13a - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Jun-2013
• Refers: ASTM C859-13 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-May-2013
• Refers: ASTM C696-11 - Standard Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium Dioxide Powders and Pellets
• Effective Date: 01-Sep-2011
• Refers: ASTM C1068-03(2011) - Standard Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear Industry
• Effective Date: 01-Jun-2011
• Refers: ASTM C859-10b - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Nov-2010
• Refers: ASTM C859-10a - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Aug-2010
• Refers: ASTM C859-10 - Standard Terminology Relating to Nuclear Materials
• Effective Date: 01-Feb-2010

Overview

ASTM C1267-17(2022) is the globally recognized Standard Test Method for Uranium by Iron (II) Reduction in Phosphoric Acid Followed by Chromium (VI) Titration in the Presence of Vanadium. Developed and maintained by ASTM International, this standard provides a precise and unbiased method, commonly called the Modified Davies and Gray technique, for the determination of uranium content in a wide range of materials associated with the nuclear fuel cycle. Applicable to products, fuels, and scrap materials, this method is essential in the chemical, spectrochemical, and mass spectrometric analysis of nuclear-grade uranium and related compounds.

Key Topics

• Versatile Uranium Assay: Permits the determination of uranium in a variety of material forms-oxides, nitrates, hexafluorides, ore concentrates, and dissolved products-by titrating uranium concentrations typically from 20 mg to 200 mg.
• Modified Davies and Gray Technique: Based on reducing uranium with iron (II) in phosphoric acid, then titrating uranium(IV) with chromium(VI) in the presence of vanadium, resulting in high precision and tolerance to most metallic impurities.
• Sample and Equipment Flexibility: Requires conventional laboratory equipment and reagents, making it accessible and cost-effective for nuclear and analytical laboratories.
• Traceability and Regulatory Value: When combined with certified reference materials, the method can demonstrate traceability to national measurement standards, supporting safeguards and nuclear safety applications.
• Interference Management: Addresses common element interferences such as silver, manganese, vanadium (in high oxidation states), and platinum group metals, with recommended strategies for their removal or correction.
• Safety and Compliance: Emphasizes the importance of rigorous laboratory safety practices due to the handling of radioactive and toxic substances, and the need for laboratory-specific regulatory acceptance.

Applications

• Nuclear Fuel and Product Analysis: Supports uranium assays required for the production and quality assurance of nuclear fuel pellets, powders, and secondary products, ensuring compliance with specifications and safety standards.
• Safeguards and Nuclear Material Accounting: Integral in meeting requirements for measurement accuracy and traceability in nuclear material stewardship, supporting international safeguards and facility accountability.
• Analytical Chemistry and Laboratory QA/QC: Useful as both a routine quality control tool and as part of method validation in laboratories engaged in uranium analysis.
• Support for Dissolution and Preparation Procedures: Facilitates uranium determination after dissolution of product, fuel, and scrap materials, including procedures referenced in other ASTM standards for sample dissolution and preparation.

Related Standards

• ASTM C696: Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Uranium Dioxide Powders and Pellets.
• ASTM C799: Test Methods for Chemical, Mass Spectrometric, and Spectrochemical, Nuclear, and Radiochemical Analysis of Nuclear-Grade Uranyl Nitrate Solutions.
• ASTM C1204: Test Method for Uranium in Presence of Plutonium by Iron(II) Reduction in Phosphoric Acid Followed by Chromium(VI) Titration.
• ASTM C859: Terminology Relating to Nuclear Materials.
• ASTM C1346 & C1347: Practices for dissolution and preparation of uranium materials for analysis.
• ASTM 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 Analysis of Nuclear Fuel Cycle Materials.

Practical Value

Adopting ASTM C1267-17(2022) streamlines uranium assay methods, improves precision and compliance, and ensures laboratories meet international nuclear quality assurance and safety requirements. Its flexibility, reliability, and global acceptance make it a cornerstone test method in the nuclear fuel cycle and uranium analysis sectors.

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: C1267 − 17 (Reapproved 2022)
Standard Test Method for
Uranium by Iron (II) Reduction in Phosphoric Acid Followed
by Chromium (VI) Titration in the Presence of Vanadium
This standard is issued under the fixed designation C1267; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method, commonly referred to as the Modified
C696Test Methods for Chemical, Mass Spectrometric, and
Davies and Gray technique, covers the titration of uranium in
SpectrochemicalAnalysis of Nuclear-Grade Uranium Di-
product, fuel, and scrap materials after the material is dis-
oxide Powders and Pellets
solved. The test method is versatile and has been ruggedness
C799Test Methods for Chemical, Mass Spectrometric,
tested. With appropriate sample preparation, this test method
Spectrochemical,Nuclear,andRadiochemicalAnalysisof
can give precise and unbiased uranium assays over a wide
Nuclear-Grade Uranyl Nitrate Solutions
variety of material types (1, 2). Details of the titration
C859Terminology Relating to Nuclear Materials
procedure in the presence of plutonium with appropriate
C1068Guide for Qualification of Measurement Methods by
modifications are given in Test Method C1204.
a Laboratory Within the Nuclear Industry
1.2 Uranium levels titrated are usually 20mg to 50mg, but
C1128Guide for Preparation of Working Reference Materi-
up to 200mg uranium can be titrated using the reagent
als for Use in Analysis of Nuclear Fuel Cycle Materials
volumes stated in this test method.
C1204Test Method for Uranium in Presence of Plutonium
by Iron(II) Reduction in Phosphoric Acid Followed by
1.3 The values stated in SI units are to be regarded as
Chromium(VI) Titration
standard. No other units of measurement are included in this
C1346Practice for Dissolution of UF from P-10 Tubes
standard.
C1347Practice for Preparation and Dissolution of Uranium
1.4 This standard does not purport to address all of the
Materials for Analysis
safety concerns, if any, associated with its use. It is the
2.2 NIST Standard:
responsibility of the user of this standard to establish appro-
SRM 136ePotassium Dichromate (Oxidimetric Standard)
priate safety, health, and environmental practices and deter-
2.3 NBL Standard:
mine the applicability of regulatory limitations prior to use.
CRM 112AUranium Metal Standard
For specific safeguard and safety precaution statements, see
3. Terminology
Section 5.
1.5 This international standard was developed in accor- 3.1 Except as otherwise defined herein, definitions of terms
dance with internationally recognized principles on standard-
are as given in Terminology C859.
ization established in the Decision on Principles for the
4. Summary of Test Method
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4.1 Samplesarepreparedbydissolutiontechniquesdetailed
Barriers to Trade (TBT) Committee.
in Practices C1346, C1347, or Refs (2), (3), and (4). Appro-
priate uncertainties for sampling and weight determination
1 3
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Test. Standards volume information, refer to the standard’s Document Summary page on
CurrenteditionapprovedJuly1,2022.PublishedJuly2022.Originallyapproved the ASTM website.
in 1994. Last previous edition approved in 2017 as C1267–17. DOI: 10.1520/ Available from National Institute of Standards and Technology (NIST), 100
C1267-17R22. Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
2 5
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof NewBrunswickLaboratory(NBL)CertifiedReferenceMaterialsCatalog(U.S.
this standard. Department of Energy), http://science.energy.gov/nbl.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1267 − 17 (2022)
should be applied to the overall precision and bias calculations 5.4.1 When used in conjunction with the appropriate certi-
for the final result. Aliquants containing 20mg to 200 mg of fied reference materials (SRM or CRM), this procedure can
uranium are prepared by weight. The sample is fumed to demonstrate traceability to the national measurement base.
dryness after the appropriate acid treatment. The sample is However, use of the test method does not automatically
guarantee regulatory acceptance of the resulting safeguards
dissolved in dilute nitric acid or water prior to titration.
measurements. It remains the sole responsibility of the user of
4.2 Uraniumisreducedtouranium(IV)byexcessiron(II)in
this test method to assure that its application to safeguards has
concentrated phosphoric acid (H PO ) containing sulfamic
3 4
the approval of the proper regulatory authorities.
acid. The excess iron(II) is selectively oxidized by nitric acid
(HNO ) in the presence of a molybdenum(VI) catalyst. After
6. Interferences
the addition of a vanadium(IV) solution, the uranium(IV) is
6.1 Interferingelementsarenotgenerallypresentinproduct
titrated with chromium(VI) to a potentiometric end point.
and fuel material in quantities which cause interference in the
4.3 Thechromium(VI)titrantmaybedeliveredmanuallyon
titration.
a weight or on a volumetric basis as specified by the facility
6.1.1 Of the metallic impurity elements usually included in
titration procedure.
specifications for product and fuel, silver, manganese, and
4.3.1 If the titrant is delivered on a volumetric basis, vanadium (in the V oxidation state) interfere when present in
correctionstothevolumeoftitrantmaybeneededtoadjustfor amounts of 10 mg or greater of impurity per 100 mg of
the difference between the temperature of preparation and the uranium (2, 8).
ambient temperature. 6.1.2 Silver and vanadium (in the V oxidation state) cause
positive bias when present in milligram quantities in the
4.3.2 Automated titrators are facility specific and are not
sample. The aliquant treatment adjusts the oxidation state of
explicitly addressed in this test method. However, automated
any vanadium(V) present in the sample (2). To remove silver,
titrators which have comparable bias and precision may be
the sample must be treated prior to titration (8).
used.
6.1.3 Manganese was originally found to cause a negative
4.3.3 There is an alternate, high precision (;0.005% RSD)
bias (2), but this bias is eliminated when the titration aliquant
modified Davies and Gray titration, which is similar to the
preparation procedure is followed as given (9, 10) in this
method covered in this procedure. In the high precision
titrimetric method.
method, the amount of uranium titrated is increased and about
90%ofthetitrantisdeliveredonasolidweightbasisfollowed 6.2 Interferences with the Modified Davies and Gray
titration, which may be present in some uranium materials,
by titration to the end point with a dilute titrant. Details of this
alternate method are available in Ref (5). have been systematically studied.
6.2.1 The non-interference of copper, titanium, cobalt,
nickel, cerium, and samarium was demonstrated (11) at the
5. Significance and Use
50mg impurity level for 100 mg of uranium.
5.1 Factors governing selection of a method for the deter-
6.2.2 The effects of the following elements in milligram
mination of uranium include available quantity of sample,
quantities were studied: silver, gold, lead, iodine, arsenic,
homogeneity of material sampled, sample purity, desired level
antimony, and bismuth (8).
of reliability, and facility available equipment.
6.2.2.1 Gold, lead, arsenic(V), antimony(V), and bismuth
do not interfere when present in amounts of 10 mg for 100 mg
5.2 This uranium assay method is referenced in the Test
of uranium.
Methods for Chemical, Mass Spectrometric, and Spectro-
6.2.2.2 Silver, iodine, arsenic(III), and antimony(III) inter-
chemical Analysis of Nuclear-Grade Uranium Dioxide Pow-
fere seriously in the determination of uranium and must be
ders and Pellets (Test Methods C696) and in the Test Methods
eliminated prior to titration.
for Chemical, Mass Spectrometric, and Spectrochemical,
6.2.3 The effects of impurities on the titration of uranium
Nuclear,andRadiochemicalAnalysisofNuclear-GradeUranyl
continued with the platinum metals (ruthenium, rhodium,
Nitrate Solutions (Test Methods C799). This uranium assay
palladium, osmium, iridium, and platinum), chloride, bromide
method may also be used for uranium hexafluoride and
(12), fluoride (13), and technetium (14).
uraniumoreconcentrate.Thistestmethoddetermines20mgto
6.2.3.1 Ruthenium, palladium, osmium, iridium, and plati-
200 mg of uranium; is applicable to product, fuel, and scrap
num cause serious positive errors in the determination of
materialafterthematerialisdissolved;istoleranttowardsmost
uranium. Rhodium alone among the platinum metals does not
metallic impurity elements usually specified in product and
cause any significant error.
fuel; and uses no special equipment.
6.2.3.2 Chloride and bromide interfere with the assay
5.3 The ruggedness of the titration method has been studied
through their effect on the platinum indicator electrode.
for both the volumetric (6) and the weight (7) titration of
6.2.3.3 Small amounts of fluoride, less than 400 mg as
uranium with dichromate.
hydrofluoric acid (HF) or 600 mg if HNO is present, can be
tolerated by the titration.
5.4 Fitness for Purpose of Safeguards and Nuclear Safety
Application—Methods intended for use in safeguards and
nuclear safety applications shall meet the requirements speci-
fied by Guide C1068 for use in such applications. SRM is a registered trademark.
C1267 − 17 (2022)
6.2.3.4 Technicium,foundinhightemperaturereactorgrade of sufficiently high purity to permit its use without lessening
recycle (htgr) fuel, interferes with the titration and must be the accuracy of the determination.
removed before titration.
8.2 Purity of Water—Unless otherwise indicated, references
6.3 The removal of certain interferences in the modified
to water shall be understood to mean laboratory accepted
Davies and Gray titration has also been studied.
demineralized or deionized water.
6.3.1 The initial fuming of titration aliquants with sulfuric
8.3 Ferrous Sulfate Heptahydrate (FeSO ·7 H O, 1.0 M)—
4 2
acidremovesimpurityelementssuchasthehalidesandvolatile
Add 100 mLof sulfuric acid (H SO , sp gr 1.84) to 750 mLof
2 4
metallic elements (2, 12, 13).
waterasthesolutionisstirred.Add280gofFeSO ·7H O,and
4 2
6.3.2 Arsenic(III) and antimony(III) can be eliminated in
dilute the solution to 1Lwith water. Prepare the FeSO ·7 H O
4 2
theH PO bypotassiumdichromate(K Cr O )oxidationprior
3 4 2 2 7
reagentfresh,weekly.SeetheNote5in11.8oncombinationof
to its addition to the titration medium (8).
this reagent with the H PO .
3 4
6.3.3 Elimination of interferences in the titration by
mercury, platinum, and palladium by means of a copper
8.4 Nitric Acid(HNO ,8M)—Add500mLofHNO (spgr
3 3
column was evaluated (15).
1.42) to <500 mL of water, and dilute to 1L.
6.3.4 Elimination of interferences by solvent extraction of
8.5 HNO , 1 M—Add 64 mL of HNO (sp gr 1.42) to
3 3
the uranium from the impurities has also been studied (16).
<900mL of water, and dilute to 1L.
6.4 A list of impurities with brief references to their treat-
8.6 HNO (8 M)—Sulfamic Acid (NH SO H, 0.15 M)—
ment for elimination is given in Table A1.1 in AnnexA1, and
3 2 3
Ammonium Molybdate ((NH ) Mo O ·4H O, 0.4 %)—
the details are given in Refs 2, 8, 9, 10, and 12-16.
4 6 7 24 2
Dissolve4gof(NH ) Mo O ·4H O in 400 mLof water, and
4 6 7 24 2
7. Apparatus
add 500 mL of HNO (sp gr 1.42). Mix and add 100mL of
1.5 M NH SO H solution (see 8.10) and mix.
7.1 Buret, polyethylene bottle (preparation instructions can 2 3
be found in Appendix X1), glass weight, or glass volumetric.
8.7 Orthophosphoric Acid (H PO ), 85%—Test for reduc-
3 4
7.2 pH Meter, with indicator (a 16-gauge platinum wire has ing substances prior to use (see Annex A2).
beenfoundtobesatisfactory)andreference(saturatedcalomel
8.8 Potassium Dichromate (K Cr O ) Solution (2%)—
2 2 7
has been found to be satisfactory) electrodes.
Dissolve2gofK Cr O in water, and dilute to 100 g with
2 2 7
7.2.1 The indicator electrode should be changed or cleaned
water.
if there is a titration problem such as less distinct than normal
end point break or end point drift, or, if desired, prior to use
8.9 K Cr O (0.0045 M)—Dissolve 2.65 g of reagent grade
2 2 7
whenmorethanaweekhaspassedsinceitslastuse.Suggested or purer grade K Cr O in water; transfer this solution to a
2 2 7
cleaning procedures for platinum wire electrodes are detailed
pre-weighed, 2L volumetric flask or suitable alternative and
in Appendix X2. dilute to volume, or use equivalent weight/volume ratios for
7.2.2 Asbestos and glass bead tipped saturated calomel
larger quantities of solution.
electrodescanbeplaceddirectlyinthetitrationsolution.Glass
8.9.1 If National Institute of Standards and Technology
frit tipped saturated calomel electrodes may have a faster leak
(NIST) standard reference material K Cr O (SRM 136e or its
2 2 7
rate and may need to be used with a separator tube containing
equivalent) was used, proceed as in 8.9.1.1 and 8.9.1.2 before
the electrolyte to prevent titration problems due to chloride.
going to 8.9.3; otherwise go to 8.9.2.
7.2.3 The reference electrode should be covered with a
8.9.1.1 Allow the solution to equilibrate to room
rubber tip or submerged in a solution (saturated potassium
temperature, obtain the weight of the solution. Compute the
chloride solution for the calomel electrode) for overnight
dichromate concentration (11.2.2) and the uranium titration
storage.
factor (12.3.2) after correcting the weight of dichromate for
7.3 Magnetic Stirrer and TFE-Fluorocarbon Coated Mag-
buoyancy (12.1.2) and for purity (12.1.3).
net.
8.9.1.2 As a good quality practice, a check on the material
handling of the K Cr O solution within laboratory accepted
2 2 7
8. Reagents
uncertaintiesmaybedonebytitrationwithaworkingreference
8.1 Purity of Reagents—Reagent grade chemicals shall be
uraniumsolution.Forguidanceinthepreparationofaworking
used in all tests. Unless otherwise indicated, it is intended that
reference uranium solution, see Guide C1128. If the titrations
all reagents conform to the specifications of the Committee on
do not agree within laboratory accepted uncertainties, verifi-
Analytical Reagents of theAmerican Chemical Society where
cation titrations for SRM 136e or its equivalent may be done
such specifications are available. Other grades of reagents
usingNewBrunswickLaboratory(NBL)CRM112-Auranium
may be used, provided it is first ascertained that the reagent is
metal or its equivalent, prepared in 8.12, or the K Cr O
2 2 7
solution should be discarded.
8.9.2 If a reagent grade K Cr O was used, allow the
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
2 2 7
Standard-Grade Reference Materials, American Chemical Society, Washington,
solutiontoequilibratetoroomtemperatureandstandardizethe
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
K Cr O solution against CRM 112-A uranium metal or its
2 2 7
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
equivalent prepared in 8.12 (see Appendix X3). Compute the
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. uranium titration factor as in 12.3.3.
C1267 − 17 (2022)
8.9.3 StoretheK Cr O solutioninoneormoreborosilicate 9. Hazards
2 2 7
glass bottles with a poly-seal top or an equivalent container to
9.1 Since enriched uranium-bearing materials are radioac-
prevent concentration changes due to evaporation.
tive and toxic, adequate laboratory facilities and fume hoods
along with safe techniques must be used in handling samples
8.10 NH SO H (1.5 M)—Dissolve 146 g of NH SOHin
2 3 2 3
water, filter the solution, and dilute to 1 L. containing these materials.Adetailed discussion of all precau-
tions necessary is beyond the scope of this test method.
8.11 Sulfuric Acid(H SO ,1M)—Add56mLofH SO (sp
2 4 2 4
However, personnel who handle radioactive materials should
gr 1.84) to water, while stirring, and dilute to 1 L with water.
be familiar with the safe handling practices of the facility.
8.12 Uranium Standard (CRM) Solution:
9.2 In the absence of data about the bioavailability of the
8.12.1 Clean the surface of the uranium metal (CRM 112-A 8
chromium(VI) in K Cr O , the facility policy for handling of
2 2 7
or its equivalent) following the instructions on the certificate.
K Cr O should be followed. In some facilities K Cr O has
2 2 7 2 2 7
8.12.2 Obtain the weight of the metal by difference to
been identified as a “select carcinogen” as a conservative
0.01mg making buoyancy and purity corrections detailed in
policy.
12.1.2 and 12.1.3, respectively.
9.3 Warning—Hydrofluoric acid is highly corrosive acid
8.12.3 Prepare the uranium standard solution. There are
that can severely burn skin, eyes, and mucous membranes.
manysuccessfulmethodsofuraniummetaldissolution(noneis
Hydrofluoric acid differs from the other acids because the
specified on the CRM 112-A certificate); methods which
fluoride ion readily penetrates the skin, causing destruction of
reproduce the uranium assay value on the certificate are
deep tissue layers. Unlike other acids that are rapidly
acceptable. An example of an acceptable method is given in
neutralized, hydrofluoric acid reactions with tissue may con-
Appendix X4.
tinue for days if left untreated. Familiarization and compliance
8.12.4 Equilibrate the uranium solution to room
with the Safety Data Sheet is essential.
temperature, and obtain the weight of the solution to give the
same number of significant figures as the metal’s weight.
10. Calibration
8.12.4.1 Calculate the solution concentration in mg U/g
10.1 Traceabilitytoanationalorinternationalmeasurement
uranium solution using the calculation in 12.2.3.
base may be demonstrated by the use of standard reference
8.12.4.2 As a good quality practice, a check on the material
materials, for example, NIST standard SRM 136e or its
handling of the uranium solution within laboratory accepted
equivalent (potassium dichromate), or NBL standard CRM
uncertaintiesmaybedonebytitrationwithaworkingreference
112-A (uranium metal standard).
K Cr O solution.Forguidanceinthepreparationofaworking
2 2 7
reference K Cr O solution, see Guide C1128. If the titrations
10.2 ThestandardK Cr O shouldbepreparedasinstructed
2 2 7
2 2 7
do not agree within laboratory accepted uncertainties, verifi-
onthecertificate;theweightshouldbeobtainedto0.01mgand
cation titrations for CRM 112-A or its equivalent may be done
corrected for buoyancy and purity using the calculations in
usingK Cr O SRM136eoritsequivalent,aspreparedin8.9,
2 2 7 12.1.2 and 12.1.3.
or the uranium solution should be discarded.
10.2.1 If a K Cr O solution is prepared from the solid
2 2 7
K Cr O , the solution should be equilibrated to room
2 2 7
8.13 Vanadyl Sulfate Dihydrate—(VOSO ·2H O) Solution
4 2
temperature, and the weight should be obtained to give a
(0.0038M—0.18MH SO )—Add20mLconcentratedH SO
2 4 2 4
numberofsignificantfiguresequaltothatofthesolid’sweight.
(spgr1.84)to<980mLwaterwithstirring;equilibratetoroom
10.2.2 The K Cr O solution concentration is calculated in
temperature. Weigh 1.5 g of VOSO ·2H O crystals, mix the 2 2 7
4 2
mg K Cr O /g K Cr O solution using the calculation in
solid with the temperature equilibrated H SO solution, and 2 2 7 2 2 7
2 4
12.2.2.Thetitrationfactor(mguranium/gK Cr O solution)is
dilute the solution to 2 L. The VOSO ·2H O concentration 2 2 7
4 2
calculated for the K Cr O solution using the calculation in
should provide 75mg to 125 mg VOSO ·2H O per titration, 2 2 7
4 2
12.3.2.
but the concentration is not critical. See Refs (6) and (7).
8.13.1 TheVOSO ·2H O solution is not stable (17);H SO
4 2 2 4 10.3 If reagent grade K Cr O is used, the material must be
2 2 7
stabilizes the V(IV) oxidation state, but the H SO concentra-
standardized against the NBL uranium metal standard (CRM
2 4
tion is not critical. The VOSO ·2H O solution should be
4 2 112-A or its equivalent) to provide traceability to the national
prepared at suitable intervals to prevent V(V) interference
measurement base.
(24h intervals for preparation are suggested) since this solu-
NOTE 2—Caution: Satisfactory analysis results will only be attained if
tion is added after the aliquant treatment stage.
the temperature of the reagents (usually at room temperature) used are
8.13.2 Alternatively, crystalline VOSO ·2H O (75mg to
4 2 within the range of 23°C to 31°C.
125mgpertitration)maybeusedwithawaterdiluentinplace
10.3.1 Analyze individually dispensed aliquants of the ura-
of the solution (see 11.13).
nium reference solution per 11.3 – 11.14.4. See Appendix X3
NOTE 1—There is more than one crystalline form of vanadyl sulfate; for analysis control recommendations.
there are problems with slow dissolving forms particularly when the
vanadylsulfateisaddedasasolid.Sincevendorsarenowsellingvanadyl
sulfate with an unspecified hydration number, that is, VOSO ·xH O, note
4 2
thatthematerialshouldbebrightblueincolorandhaveawetappearance.
Overall Evaluations of Carcinogenicity: An Updating of International Agency
The difficult-to-dissolve crystalline form is light blue and dry in appear- for Research on Cancer (IARC) Monographs, Supplement 7, World Health
ance. Organization, International Agency for Research on Cancer, 1987, p. xvii.
C1267 − 17 (2022)
NOTE5—TheFeSO ·7H OsolutionmaybecombinedwiththeH PO
10.3.2 Calculate the uranium titration factor (mg U/g
4 2 3 4
in 11.7 and added as a combined reagent.
K Cr O solution)forthestandardizedK Cr O solutionusing
2 2 7 2 2 7
the calculation in 12.3.2.
11.9 Add a TFE-fluorocarbon coated magnet without
splashing, place the beaker on a magnetic stirrer, and initiate
11. Titration Procedure
stirring at a slow rate (avoid splashing) for 30 s.
NOTE 3—Caution: Satisfactory analysis results will only be attained if
the temperature of the reagents (usually at room temperature) used are
11.10 Add 10 mL of nitric-sulfamic-molybdate solution.
within the range of 23°C to 31°C.
Use the solution to rinse down the sides of the beaker.
11.1 Obtain the weight of the sample (0.5 g or more) to
11.11 Mix the solution at a moderate stirrer speed. Imme-
0.1mg. When necessary, especially for oxides, include errors
diatelyupondisappearanceoftheblackcolor,begintimingthe
due to weight determination in the calculation of the overall
oxidation period of 3 min; the solution may or may not be
measurement uncertainty. Dissolve the sample following the
stirred during the 3 min time period.
procedures in Practices C1346, C1347, or Refs 2-4.
11.12 Obtain the weight of the dichromate in the weight
11.2 To prepare aliquants, quantitatively transfer the dis-
buretifagravimetrictitrationistobeused;otherwise,zerothe
solvedsamplewithanaccuratelydeterminedweighttoabottle
buret.
with an accurately determined weight for mixing prior to
sample splitting.
11.13 Stop the stirring, add 100 mL of the VOSO ·2H O
4 2
11.2.1 A low-density polyethylene narrow mouth bottle
solution, or add the diluent (water) if crystallineVOSO ·2H O
4 2
with a one-piece polypropylene seal-ring screw closure to
is used.
prevent leakage, or any other leak-proof bottle may be used. If
11.13.1 If crystalline VOSO ·2H O (75mg to 125mg) is
4 2
polyethylene bottles are used, long-term (weeks and months)
used, add it after the diluent.
storage will not maintain sample integrity because of bottle
11.13.2 Use the VOSO ·2H O solution or diluent to rinse
4 2
respiration (18).
the sides of the beaker.
11.2.2 Equilibrate the solution to room temperature, and
11.14 Increase the rate of stirring to form a vortex in the
weigh the solution to the number of significant figures equiva-
solution.
lent to the sample’s weight.
11.14.1 Insert the electrodes into the solution, and titrate
11.2.3 Invert and shake the solution to insure a homoge-
rapidly with K Cr O to a potential of 450mV to 480 mV
2 2 7
neous solution prior to aliquanting.
versus a calomel reference electrode or to the equivalent
11.2.4 Calculate the sample dilution factor (g sample/g
voltage for other reference electrodes. If the polyethylene
solution).
weight buret is used, remove the reduced size tip used in the
11.3 Deliver an aliquant, with a weight determined to
final end point approach before beginning the
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