ASTM C1672-07(2014)
(Test Method)Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
Standard Test Method for Determination of Uranium or Plutonium Isotopic Composition or Concentration by the Total Evaporation Method Using a Thermal Ionization Mass Spectrometer
SIGNIFICANCE AND USE
5.1 The total evaporation method is used to measure the isotopic composition of uranium and plutonium materials, and may be used to measure the elemental concentrations of the two elements when employing the IDMS technique.
5.2 Uranium and plutonium compounds are used as nuclear reactor fuels. In order to be suitable for use as a nuclear fuel the starting material must meet certain specifications, such as found in Specifications C757, C833, C753, C776, C787, C967, C996, C1008, or as specified by the purchaser. The uranium and/or plutonium concentration and isotopic abundances are measured by mass spectrometry following this method.
5.3 The total evaporation method allows for a wide range of sample loading with no loss in precision or accuracy, and is also suitable for trace-level loadings with consequent loss of precision. Typical uranium analyses are conducted using sample loadings between 10 nanograms and several micrograms. Plutonium analyses are generally conducted using between five and 200 nanograms of plutonium per filament. The total evaporation method and modern instrumentation allow for the measurement of minor isotopes using ion counting detectors, while the major isotopes are simultaneously measured using Faraday cup detectors.
5.4 New generations of miniaturized ion counters now allow extremely small samples, in the picogram to femtogram range, to be measured via total evaporation methods. The method may be employed for measuring environmental or safeguards inspection samples containing very small quantities of uranium or plutonium. Very small loadings require special sample handling and analysis techniques, and careful evaluation of measurement uncertainty contributors.
SCOPE
1.1 This method describes the determination of the isotopic composition and/or the concentration of uranium and plutonium as nitrate solutions by the thermal ionization mass spectrometric (TIMS) total evaporation method. Purified uranium or plutonium nitrate solutions are loaded onto a degassed metal filament and placed in the mass spectrometer. Under computer control, ion currents are generated by heating of the filament(s). The ion beams are continually measured until the sample is exhausted. The measured ion currents are integrated over the course of the run, and normalized to a reference isotope ion current to yield isotopic ratios.
1.2 In principle, the total evaporation method should yield isotopic ratios that do not require mass bias correction. In practice, some samples may require this bias correction. When compared to the conventional TIMS method, the total evaporation method is approximately two times faster, improves precision from two to four fold, and utilizes smaller sample sizes.
1.3 The total evaporation method may lead to biases in minor isotope ratios due to peak tailing from adjacent major isotopes, depending on sample characteristics. The use of an electron multiplier equipped with an energy filter may eliminate or diminish peak tailing effects. Measurement of instrument abundance sensitivity may be used to ensure that such biases are negligible, or may be used to bias correct minor isotope ratios.
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.
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Designation: C1672 − 07 (Reapproved 2014)
Standard Test Method for
Determination of Uranium or Plutonium Isotopic
Composition or Concentration by the Total Evaporation
Method Using a Thermal Ionization Mass Spectrometer
This standard is issued under the fixed designation C1672; 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
1.1 This method describes the determination of the isotopic 2.1 ASTM Standards:
composition and/or the concentration of uranium and pluto- C753Specification for Nuclear-Grade, Sinterable Uranium
nium as nitrate solutions by the thermal ionization mass Dioxide Powder
spectrometric (TIMS) total evaporation method. Purified ura-
C757Specification for Nuclear-Grade Plutonium Dioxide
niumorplutoniumnitratesolutionsareloadedontoadegassed
Powder, Sinterable
metal filament and placed in the mass spectrometer. Under
C776Specification for Sintered Uranium Dioxide Pellets
computer control, ion currents are generated by heating of the
C787Specification for Uranium Hexafluoride for Enrich-
filament(s). The ion beams are continually measured until the
ment
sample is exhausted. The measured ion currents are integrated
C833Specification for Sintered (Uranium-Plutonium) Diox-
over the course of the run, and normalized to a reference
ide Pellets
isotope ion current to yield isotopic ratios.
C967Specification for Uranium Ore Concentrate
C996Specification for Uranium Hexafluoride Enriched to
1.2 In principle, the total evaporation method should yield
Less Than 5 % U
isotopic ratios that do not require mass bias correction. In
C1008Specification for Sintered (Uranium-Plutonium) Di-
practice, some samples may require this bias correction.When
oxide Pellets—Fast Reactor Fuel
compared to the conventional TIMS method, the total evapo-
C1068Guide for Qualification of Measurement Methods by
ration method is approximately two times faster, improves
a Laboratory Within the Nuclear Industry
precision from two to four fold, and utilizes smaller sample
C1156Guide for Establishing Calibration for a Measure-
sizes.
ment Method Used toAnalyze Nuclear Fuel Cycle Mate-
1.3 The total evaporation method may lead to biases in
rials
minor isotope ratios due to peak tailing from adjacent major
C1168PracticeforPreparationandDissolutionofPlutonium
isotopes, depending on sample characteristics. The use of an
Materials for Analysis
electron multiplier equipped with an energy filter may elimi-
C1347Practice for Preparation and Dissolution of Uranium
nate or diminish peak tailing effects. Measurement of instru-
Materials for Analysis
ment abundance sensitivity may be used to ensure that such
C1411Practice for The Ion Exchange Separation of Ura-
biases are negligible, or may be used to bias correct minor
nium and Plutonium Prior to Isotopic Analysis
isotope ratios. 238
C1415Test Method for Pu Isotopic Abundance By Alpha
1.4 This standard does not purport to address all of the Spectrometry
D3084Practice for Alpha-Particle Spectrometry of Water
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- E137Practice for Evaluation of Mass Spectrometers for
priate safety and health practices and determine the applica- Quantitative Analysis from a Batch Inlet (Withdrawn
bility of regulatory limitations prior to use. 1992)
1 2
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 service@astm.org. For Annual Book of ASTM
Test. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2014. Published February 2014. Originally the ASTM website.
approved in 2007. Last previous edition approved in 2007 as C1672–07. DOI: The last approved version of this historical standard is referenced on
10.1520/C1672-07R14. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1672 − 07 (2014)
3. Terminology 4.2 Theisotopedilutionmassspectrometry(IDMS)method
may be used to determine the uranium or plutonium concen-
3.1 Definitions:
trations.Inthismethod,aspikeofknownisotopiccomposition
3.1.1 isotopic equilibration—chemicalstepsperformedona
and element concentration is added to a sample prior to
mixture of two samples (for example, a uranium sample and a
chemical separation. Typical spike materials include U
uranium spike) to ensure identical valency and chemical form
235 239 242 244
or U for uranium samples, and Pu, Pu or Pu for
prior to purification of the mixture. Failure to perform isotopic
plutonium samples. Samples containing both uranium and
equilibration of a sample-spike mixture may result in partial
plutonium(forexample,mixedoxidefuelsorfuelreprocessing
separation of the sample from the spike during the purification
materials) may be mixed with a combined U/Pu spike prior to
procedure,causingabiasintheresultsofisotopedilutionmass
separation. When using a spike containing significant quanti-
spectrometry measurements.
ties of one or more of the isotopes present in the sample, the
3.1.2 abundance sensitivity—the ratio of the measured in-
isotopiccompositionofthesamplemustbeknowninadvance.
tensity of an ion beam at a mass m to the measured intensity
The spike-sample mixture undergoes a valency adjustment,
from the same isotope measured at one mass difference (for
purification,andisthenloadedontoafilamentandtheisotopic
example, m 6 1). Abundance sensitivity is a measure of the
composition of the mixture is determined. Using the measured
magnitude of peak tailing. Typically measured using uranium
isotope ratios of the spike-sample mixture, the known isotopic
at masses 237 and 238.
compositionandamountofspikeaddedtothemixture,andthe
isotopic composition of the sample, the elemental concentra-
3.2 Acronyms:
tion of the sample may be calculated.
3.2.1 CRM—Certified Reference Materials
3.2.2 TIMS—Thermal Ionization Mass Spectrometry
5. Significance and Use
3.2.3 IDMS—Isotope Dilution Mass Spectrometry
5.1 The total evaporation method is used to measure the
3.2.4 IRMM—Institute for Reference Materials and isotopic composition of uranium and plutonium materials, and
may be used to measure the elemental concentrations of the
Measurements,supplierofCertifiedReferenceMaterials,Geel,
Belgium two elements when employing the IDMS technique.
3.2.5 NBL—New Brunswick Laboratory, supplier of Certi- 5.2 Uranium and plutonium compounds are used as nuclear
fied Reference Materials, Argonne, IL, USA
reactorfuels.Inordertobesuitableforuseasanuclearfuelthe
starting material must meet certain specifications, such as
4. Summary of Test Method foundinSpecificationsC757,C833,C753,C776,C787,C967,
C996, C1008, or as specified by the purchaser. The uranium
4.1 Typically, uranium and plutonium are separated from
and/or plutonium concentration and isotopic abundances are
each other and purified from other elements by selective
measured by mass spectrometry following this method.
extraction, anion exchange (such as in Practice C1411)or
5.3 Thetotalevaporationmethodallowsforawiderangeof
extractionchromatography.Thepurifieduraniumorplutonium
sample loading with no loss in precision or accuracy, and is
samples as nitrate solutions are mounted on a degassed
also suitable for trace-level loadings with consequent loss of
refractory metal filament (typically rhenium, tungsten or tan-
precision. Typical uranium analyses are conducted using
talum) and converted to a solid chemical form via controlled
sample loadings between 10 nanograms and several micro-
heating of the filament under atmospheric conditions. The
grams. Plutonium analyses are generally conducted using
filament is then mounted in the thermal ionization mass
between five and 200 nanograms of plutonium per filament.
spectrometer, in either a single filament or double filament
The total evaporation method and modern instrumentation
configuration.Thefilamentsareinitiallyheatedtoyieldasmall
allow for the measurement of minor isotopes using ion
ion beam suitable for lens focusing and peak centering.
counting detectors, while the major isotopes are simultane-
Following focusing and peak centering, the ion beam intensity
ously measured using Faraday cup detectors.
data acquisition begins, with the filaments heated under com-
puter control to yield a pre-defined major isotope ion beam or
5.4 New generations of miniaturized ion counters now
a predefined total intensity for all measured ion beams. Data
allow extremely small samples, in the picogram to femtogram
acquisition and filament heating continues until the sample is
range, to be measured via total evaporation methods. The
exhaustedortheionbeamintensityreachesapre-definedlower
method may be employed for measuring environmental or
limit. Each isotope ion beam intensity is integrated over the
safeguardsinspectionsamplescontainingverysmallquantities
course of the analysis, and the summed intensity for each
of uranium or plutonium. Very small loadings require special
isotope is divided by the summed intensity of a common
sample handling and analysis techniques, and careful evalua-
isotope (typically the most abundant isotope) to yield ratios.
tion of measurement uncertainty contributors.
Theisotopiccompositionofthesamplemaybecalculatedfrom
6. Interferences
the ratios. Additional information on the total evaporation
method may be found in Refs (1-4).
6.1 Ions with atomic masses in the uranium and plutonium
ranges cause interference if they have not been removed or if
they are generated as part of the chemical handling or analysis
238 238
of the samples. Both U and Pu interfere in the measure-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. mentofeachother,and Aminterfereswiththemeasurement
C1672 − 07 (2014)
of Pu, thereby requiring chemical separation. Removal of Practice E137.The mass spectrometer used should possess the
impurities provides uniform ionization of uranium or following characteristics:
plutonium, hence improved precision, and reduces the inter- 7.1.1 Athermal ionization source capable of analysis utiliz-
ferencefrommolecularspeciesofthesamemassnumberasthe ing single and/or double filaments of rhenium; tungsten or
uraniumorplutoniumisotopesbeingmeasured.Isotopicanaly- tantalum may be substituted with minor modifications in the
sisofPlutoniumshouldbecompletedwithinareasonabletime procedure.
period after separation from Americium to minimize interfer- 7.1.2 An analyzer radius sufficient to resolve adjacent
241 241
ence of Am in-growth from Pu. An example of a pre- masses in the mass-to-charge range being studied, that is, m/z
+ +
scribed interval limiting the time between sample purification = 233 to 238 for U or 238 to 244 for Pu . Resolution greater
and isotopic analysis is 20 days. Operators are responsible for than 360 (full width at 1% of peak height) and an abundance
-5
determining a maximum interval between purification and sensitivity of less than 10 . For measuring minor isotopes, an
mass spectrometric analysis, based on an evaluation of Am abundance sensitivity as low as achievable is recommended.
in-growth from decaying Pu and required accuracy and 7.1.3 An instrument capable of monitoring ion beam inten-
precision. Other atomic and molecular species may interfere sityandadjustingfilamentcurrentsduringionbeamintegration
with total evaporation analyses, particularly if they cause a is recommended. This eliminates the sample lost between
change in the ionization efficiency of the analyte during an integrations due to the time necessary to adjust the filament
analysis. Carbon may disturb total evaporation measurements. current.
It is recommended that operators perform validation tests on 7.1.4 A mechanism for changing samples.
unique or complex samples by mixing known pure standards 7.1.5 Multiple direct-current detectors (Faraday cups) or a
with other constituents to create a matrix-matched standard. combination of Faraday cups and electron multiplier detector
in a multi-collector design. Very small samples may be
6.2 Care must be taken to avoid contamination of the
measured utilizing a multi-ion counting array.
sample by environmental uranium or traces of plutonium. The
7.1.6 Apumpingsystemtoattainavacuumoflessthan400
level of effort needed to minimize the effect of contamination
-6
µPa (3 × 10 torr) in the source, the analyzer, and the detector
of the sample should be based upon the sample size, planned
regions. The ability to accurately measure minor isotopes is
handling and processing of the sample, and knowledge of the
directly related to analyzer pressure.Analyzer pressures below
levels of contamination present in the laboratory. For very
-8
approximately 7 µPa (5 × 10 torr) are preferable.
small uranium or plutonium samples, extreme care must be
7.1.7 Amechanism to scan masses by means of varying the
taken to ensure that the sample is not contaminated. For these
magnetic field and the accelerating voltage.
samples, residual uranium or plutonium in the mass spectrom-
7.1.8 A computer to automate instrument operation and to
eter and trace uranium in chemicals or the filaments may bias
collect and process data produced by the instrument.
measurement data.
7.2 An optical pyrometer is recommended for determining
6.3 Thetotalevaporationmethodmaygeneratebiasesinthe
filament temperatures.
minor isotopes, particularly those isotopes down mass from a
major isotope, such as trace amounts of U in a highly 7.3 Filament preheating/degassing unit for cleaning fila-
235 238 239
enriched U material, or Pu in the presence of Pu. ments.
Biasesintheminorisotopedataoccurduetopeaktailingfrom
8. Reagents and Materials
the major isotopes.The amount of peak tailing is a function of
8.1 Purity of Reagents—Reagent-grade chemicals shall be
thedesignoftheinstrumentandionbeamspreadduetosource
used in all steps. Ultra-high purity reagents may be necessary
design and particle collisions in the instrument.The amount of
forsmallsamples,thosewithextremeratios,orthoseotherwise
peak tailing may be quantified by measuring the abundance
susceptible to isotope ratio biases from cross-contamination.
sensitivity under identical experimental conditions. A bias
Distilled water is sufficient for routine analysis of large
correction may then be applie
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