ASTM C1267-00

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Designation: C 1267 – 00
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope C1204 Test Method for Uranium in the Presence of Pluto-
nium by Iron(II) Reduction in Phosphoric Acid Followed
1.1 This test method, commonly referred to as the Modified
by Chromium(VI) Titration
Davies and Gray technique, covers the titration of uranium in
C1346 Practice for Dissolution of UF from P-10 Tubes
product, fuel, and scrap materials after the material is dis- 6
C1347 PracticeforPreparationandDissolutionofUranium
solved. The test method is versatile and has been ruggedness
Materials for Analysis
tested. With appropriate sample preparation, this test method
can give precise and unbiased uranium assays over a wide
3. Summary of Test Method
variety of material types (1, 2). Details of the titration
3.1 Samples are prepared by dissolution techniques detailed
procedure in the presence of plutonium with appropriate
in Practices C1346, C1347, or Refs (2), (3), and (4) .
modifications are given in Test Method C1204.
Appropriate uncertainties for sampling and weight determina-
1.2 Uranium levels titrated are usually 20 to 50 mg, but up
tion should be applied to the overall precision and bias
to 200 mg uranium can be titrated using the reagent volumes
calculations for the final result.Aliquants containing 20 to 200
stated in this test method.
mgofuraniumarepreparedbyweight.Thesampleisfumedto
1.3 This standard does not purport to address all of the
dryness after the appropriate acid treatment. The sample is
safety concerns, if any, associated with its use. It is the
dissolved in dilute nitric acid or water prior to titration.
responsibility of the user of this standard to establish appro-
3.2 Uraniumisreducedtouranium(IV)byexcessiron(II)in
priate safety and health practices and determine the applica-
concentrated phosphoric acid (H PO ) containing sulfamic
3 4
bility of regulatory limitations prior to use. For specific
acid. The excess iron(II) is selectively oxidized by nitric acid
safeguard and safety precaution statements, see Section 4.
(HNO ) in the presence of a molybdenum(VI) catalyst. After
2. Referenced Documents the addition of a vanadium(IV) solution, the uranium(IV) is
titrated with chromium(VI) to a potentiometric end point.
2.1 ASTM Standards:
3.3 Thechromium(VI)titrantmaybedeliveredmanuallyon
C696 TestMethodsforChemical,MassSpectrometric,and
a weight or on a volumetric basis as specified by the facility
Spectrochemical Analysis of Nuclear-Grade Uranium Di-
titration procedure.
oxide Powders and Pellets
3.3.1 If the titrant is delivered on a volumetric basis,
C799 TestMethodsforChemical,MassSpectrometric,and
correctionstothevolumeoftitrantmaybeneededtoadjustfor
Spectrochemical, Nuclear, and RadiochemicalAnalysis of
3 the difference between the temperature of preparation and the
Nuclear-Grade Uranyl Nitrate Solutions
ambient temperature.
C1128 Guide for Preparation of Working Reference Mate-
3.3.2 Automated titrators are facility specific and are not
rials for Use in the Analysis of Nuclear Fuel Cycle
explicitly addressed in this test method. However, automated
Materials
titrators which have comparable bias and precision may be
used.
3.3.3 There is an alternate, high precision (;0.005 % RSD)
ThistestmethodisunderthejurisdictionofASTMCommitteeC-26onNuclear
modified Davies and Gray titration, which is similar to the
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
method covered in this procedure except that the amount of
Test.
Current edition approved Jan. 10, 2000. Published March 2000. Originally
uranium titrated is increased and about 90% of the titrant is
published as C1267-94. Last previous edition C1267-94.
delivered on a solid weight basis followed by titration to the
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
end point with a dilute titrant. Details of this alternate proce-
the test method.
Annual Book of ASTM Standards, Vol 12.01. dure are available in Ref (5).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1267
4. Significance and Use 5.2 Interferences with the Modified Davies and Gray titra-
tion, which may be present in some uranium materials, have
4.1 Factors governing selection of a method for the deter-
been systematically studied.
mination of uranium include available quantity of sample,
5.2.1 The non-interference of copper, titanium, cobalt,
homogeneity of material sampled, sample purity, desired level
nickel, cerium, and samarium was demonstrated (11) at the 50
of reliability, and facility available equipment.
mg impurity level for 100 mg of uranium.
4.2 This uranium assay method is referenced in the Test
5.2.2 The effects of the following elements in milligram
Methods for Chemical, Mass Spectrometric, and Spectro-
quantities were studied: silver, gold, lead, iodine, arsenic,
chemical Analysis of Nuclear-Grade Uranium Dioxide Pow-
antimony, and bismuth (8).
dersandPellets(C696)andintheTestMethodsforChemical,
5.2.2.1 Gold, lead, arsenic(V), antimony(V), and bismuth
Mass Spectrometric, and Spectrochemical, Nuclear, and Ra-
diochemical Analysis of Nuclear-Grade Uranyl Nitrate Solu- do not interfere when present in amounts of 10 mg for 100 mg
of uranium.
tions (C799).This uranium assay method may also be used for
uranium hexafluoride and uranium ore concentrate. This test
5.2.2.2 Silver, iodine, arsenic(III), and antimony(III) inter-
method determines 20 to 200 mg of uranium; is applicable to fere seriously in the determination of uranium and must be
product,fuel,andscrapmaterialafterthematerialisdissolved;
eliminated prior to titration.
is tolerant towards most metallic impurity elements usually
5.2.3 The effects of impurities on the titration of uranium
specified in product and fuel; and uses no special equipment.
continued with the platinum metals (ruthenium, rhodium,
4.3 The ruggedness of the titration method has been studied
palladium, osmium, iridium, and platinum), chloride, bromide
for both the volumetric (6) and the weight (7) titration of
(12), fluoride (13), and technetium (14).
uranium with dichromate.
5.2.3.1 Ruthenium, palladium, osmium, iridium, and plati-
4.4 Committee C-26 Safeguards Statement:
num cause serious positive errors in the determination of
4.4.1 The materials (nuclear grade uranium in product, fuel,
uranium. Rhodium alone among the platinum metals does not
and scrap) to which this test method applies are subject to
cause any significant error.
nuclear safeguard regulations governing their possession and
5.2.3.2 Chloride and bromide interfere with the assay
use.The analytical method in this standard meets U.S. Depart-
through their effect on the platinum indicator electrode.
ment of Energy guidelines for acceptability of a measurement
5.2.3.3 Small amounts of fluoride, less than 400 mg as
method for generation of safeguards accountability measure-
hydrofluoric acid (HF) or 600 mg if HNO is present, can be
ment data.
tolerated by the titration.
4.4.2 When used in conjunction with the appropriate certi-
5.2.3.4 Technicium,foundinhightemperaturereactorgrade
fied reference materials (SRM or CRM), this procedure can
recycle (htgr) fuel, interferes with the titration and must be
demonstrate traceability to the national measurement base.
removed before titration.
However, use of the test method does not automatically
5.3 The removal of certain interferences in the modified
guarantee regulatory acceptance of the resulting safeguards
Davies and Gray titration has also been studied.
measurements. It remains the sole responsibility of the user of
5.3.1 The initial fuming of titration aliquants with sulfuric
this test method to assure that its application to safeguards has
acidremovesimpurityelementssuchasthehalidesandvolatile
the approval of the proper regulatory authorities.
metallic elements (2, 12, 13).
5.3.2 Arsenic(III) and antimony(III) can be eliminated in
5. Interferences
theH PO bypotassiumdichromate(K Cr O )oxidationprior
3 4 2 2 7
5.1 Interferingelementsarenotgenerallypresentinproduct
to its addition to the titration medium (8).
and fuel material in quantities which cause interference in the
5.3.3 Elimination of interferences in the titration by mer-
titration.
cury, platinum, and palladium by means of a copper column
5.1.1 Of the metallic impurity elements usually included in
was evaluated (15).
specifications for product and fuel, silver, manganese, and
5.3.4 Elimination of interferences by solvent extraction of
vanadium (in the V oxidation state) interfere when present in
the uranium from the impurities has also been studied (16).
amounts of 10 mg or greater of impurity per 100 mg of
5.4 A list of impurities with brief references to their treat-
uranium (2, 8).
ment for elimination is given in Table A1.1 in Annex A1, and
5.1.2 Silver and vanadium (in the V oxidation state) cause
the details are given in Refs 2, 8, and 12-16.
positive bias when present in milligram quantities in the
sample. The aliquant treatment adjusts the oxidation state of
6. Apparatus
any vanadium(V) present in the sample (2). To remove silver,
the sample must be treated prior to titration (8).
6.1 Buret, polyethylene bottle (preparation instructions can
5.1.3 Manganese was originally found to cause a negative
be found in Appendix X1), glass weight, or volumetric.
bias (2), but this bias is eliminated when the titration aliquant
6.2 pH Meter, with indicator (a 16 gage platinum wire has
preparation procedure is followed as given (9, 10) in this
beenfoundtobesatisfactory)andreference(saturatedcalomel
titrimetric method.
has been found to be satisfactory) electrodes.
6.2.1 The indicator electrode should be changed or cleaned
if there is a titration problem such as less distinct than normal
SRM is a registered trademark. end point break or end point drift, or, if desired, prior to use
C 1267
whenmorethanaweekhaspassedsinceitslastuse.Suggested 7.9.1 If National Institute of Standards and Technology
cleaning procedures for platinum wire electrodes are detailed (NIST)standardreferencematerialK Cr O (SRM 136eorits
2 2 7
in Appendix X2. equivalent) was used, proceed as in 7.9.1.1 and 7.9.1.2 before
6.2.2 Asbestos and glass bead tipped saturated calomel going to 7.9.3; otherwise go to 7.9.2.
electrodescanbeplaceddirectlyinthetitrationsolution.Glass 7.9.1.1 Allow the solution to equilibrate to room tempera-
frit tipped saturated calomel electrodes may have a faster leak ture, obtain the weight of the solution, and compute the
rate and may need to be used with a separator tube containing uranium equivalent titration factor using 11.3 after correcting
the electrolyte to prevent titration problems due to chloride. the weight of dichromate for buoyancy (11.1.1) and for
6.2.3 The reference electrode should be covered with a oxidizing power (11.1.2).
rubber tip or submerged in a solution (saturated potassium 7.9.1.2 As a good quality practice, a check on the material
chloride solution for the calomel electrode) for overnight
handling of the K Cr O solution within laboratory accepted
2 2 7
storage. uncertaintiesmaybedonebytitrationwithaworkingreference
6.3 Magnetic Stirrer and TFE-Fluorocarbon Coated Mag-
uraniumsolution.Forguidanceinthepreparationofaworking
net. reference uranium solution, see Guide C1128. If the titrations
do not agree within laboratory accepted uncertainties, verifi-
7. Reagents
cation titrations for SRM 136e or its equivalent may be done
7.1 Purity of Reagents—Reagent grade chemicals shall be usingNewBrunswickLaboratory(NBL)CRM112-Auranium
used in all tests. Unless otherwise indicated, it is intended that metal or its equivalent, prepared in 7.12, or the K Cr O
2 2 7
all reagents conform to the specifications of the Committee on solution should be discarded.
Analytical Reagents of theAmerican Chemical Society where 7.9.2 If a reagent grade K Cr O was used, allow the
2 2 7
such specifications are available. Other grades of reagents
solutiontoequilibratetoroomtemperatureandstandardizethe
may be used, provided it is first ascertained that the reagent is K Cr O solution against CRM 112-A uranium metal or its
2 2 7
of sufficiently high purity to permit its use without lessening
equivalent prepared in 7.12 (see Appendix X3).
the accuracy of the determination. 7.9.3 StoretheK Cr O solutioninoneormoreborosilicate
2 2 7
7.2 Purity of Water— Unless otherwise indicated, refer-
glass bottles with a poly-seal top or an equivalent container to
encestowatershallbeunderstoodtomeanlaboratoryaccepted prevent concentration changes due to evaporation.
demineralized or deionized water.
7.10 NH SO H (1.5 M)—Dissolve 146 g of NH SOHin
2 3 2 3
7.3 Ferrous Sulfate Heptahydrate (FeSO ·7H O,1.0M)—
water, filter the solution, and dilute to 1 L.
4 2
Add 100 mLof sulfuric acid (H SO , sp gr 1.84) to 750 mLof
7.11 SulfuricAcid(H SO ,1M)—Add56mLofH SO (sp
2 4
2 4 2 4
waterasthesolutionisstirred.Add280gofFeSO ·7H O,and
gr 1.84) to water, while stirring, and dilute to 1 L with water.
4 2
dilutethesolutionto1Lwithwater.PreparetheFeSO ·7H O
4 2 7.12 Uranium Standard (CRM) Solution:
reagent fresh, weekly. See the note in 10.8 on combination of
7.12.1 Clean the surface of the uranium metal (CRM 112-A
this reagent with the H PO .
3 4 or its equivalent) following the instructions on the certificate.
7.4 Nitric Acid (HNO , 8 M)—Add 500 mLof HNO (sp gr
3 3 7.12.2 Obtain the weight of the metal by difference to 0.01
1.42) to <500 mL of water, and dilute to 1 L.
mg making buoyancy and purity corrections detailed in 11.1.1
7.5 HNO ,1M—Add64mLofHNO (spgr1.42)to<900
3 3
and 11.1.2, respectively.
mL of water, and dilute to 1 L.
7.12.3 Prepare the uranium standard solution. There are
7.6 HNO (8 M)—Sulfamic Acid (NH SO H, 0.15 M)—
3 2 3
manysuccessfulmethodsofuraniummetaldissolution(noneis
Ammonium Molybdate ((NH ) Mo O ·4H O, 0.4 %)—
4 6 7 24 2 specified on the CRM 112-A certificate); methods which
Dissolve4gof(NH ) Mo O ·4H O in 400 mLof water, and
4 6 7 24 2
reproduce the uranium assay value on the certificate are
add 500 mLof HNO (sp gr 1.42). Mix and add 100 mLof 1.5
3 acceptable. An example of an acceptable method is given in
M NH SO H solution (see 7.10) and mix.
2 3
Appendix X4.
7.7 Orthoph
...