1、Designation: C1832 16Standard Test Method forDetermination of Uranium Isotopic Composition by theModified Total Evaporation (MTE) Method Using a ThermalIonization Mass Spectrometer1This standard is issued under the fixed designation C1832; the number immediately following the designation indicates t
2、he year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the determination of t
3、heisotope amount ratios of uranium material as nitrate solutionsby the modified total evaporation (MTE) method using athermal ionization mass spectrometer (TIMS) instrument.1.2 The analytical performance in the determination of the235U/238U major isotope amount ratio by MTE is similar to the(“classi
4、cal”) total evaporation (TE) method as described inTestMethod C1672. However, in the MTE method, the evaporationprocess is interrupted on a regular basis to allow measurementsand subsequent corrections for background form peak tailing,perform internal calibration of a secondary electron multiplier(S
5、EM) detector versus the Faraday cups, peak centering, andion source refocusing. Performing these calibrations and cor-rections on a regular basis during the measurement, improvesprecision, and significantly reduces uncertainties for the minorisotope amount ratios234U/238U and236U/238U as compared to
6、the TE method.1.3 In principle, the MTE method yields major isotopeamount ratios without the need for mass fractionation correc-tion. However, depending on the measurement conditions,small variations are seen among sample turrets; therefore, asmall correction based on measurements of a certified ref
7、er-ence material is recommended to improve consistency. Theuncertainty around the mass fractionation correction factorusually includes unity.1.4 UnitsThe values stated in SI units are to be regardedas the standard. When non-SI units are provided, they are forinformation only.1.5 This standard does n
8、ot purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standar
9、ds:2C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC776 Specification for Sintered Uranium Dioxide PelletsC787 Specification for Uranium Hexafluoride for Enrich-mentC833 Specification for Sintered (Uranium-Plutonium) Diox-ide PelletsC859 Terminology Relating to Nuclear Materia
10、lsC967 Specification for Uranium Ore ConcentrateC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC1008 Specification for Sintered (Uranium-Plutonium)DioxidePelletsFast Reactor Fuel (Withdrawn 2014)3C1068 Guide for Qualification of Measurement Methods bya Laboratory Within the
11、Nuclear IndustryC1128 Guide for Preparation of Working Reference Materi-als for Use in Analysis of Nuclear Fuel Cycle MaterialsC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-rialsC1347 Practice for Preparation and Dissolution of UraniumMate
12、rials for AnalysisC1411 Practice for The Ion Exchange Separation of Ura-nium and Plutonium Prior to Isotopic AnalysisC1625 Test Method for Uranium and Plutonium Concentra-tions and Isotopic Abundances by Thermal IonizationMass SpectrometryC1672 Test Method for Determination of Uranium or Pluto-nium
13、Isotopic Composition or Concentration by the TotalEvaporation Method Using a Thermal Ionization MassSpectrometerD1193 Specification for Reagent Water1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Method
14、s ofTest.Current edition approved Jan. 15, 2016. Published January 2016. DOI: 10.1520/C1832-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Documen
15、t Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E2655 Guide for Reporting Uncertainty of Test Results andUse of the
16、Term Measurement Uncertainty in ASTM TestMethodsE2586 Practice for Calculating and Using Basic Statistics3. Terminology3.1 The terminology standard C859 contains terms,definitions, descriptions of terms, nomenclature, and explana-tions of acronyms and symbols specifically associated withstandards un
17、der the jurisdiction of Committee C26 on NuclearFuel Cycle.3.2 Definitions:3.2.1 abundance sensitivity, nin isotope amount ratiomeasurements, the ratio of the measured intensity of an ionbeam at a mass, m, to the measured intensity from the sameisotope measured at one mass unit difference (for examp
18、le,m 6 1).3.2.1.1 DiscussionAbundance sensitivity is a measure ofthe magnitude of the peak tailing correction. For measuringuranium on thermal ionization mass spectrometer (TIMS) andinductively coupled plasma mass spectrometry (ICP-MS)instruments, the abundance sensitivity is typically calculated as
19、the ratio of the measured signal intensities at masses 237 and238 using a suitable uranium sample.3.2.2 total evaporation, TE, nanalytical method for deter-mination of isotope amount ratios of uranium or plutonium, asdescribed in Test Method C1672, also called “classical” totalevaporation in this te
20、st method.3.2.3 turret, nholder for sample filaments.3.2.3.1 DiscussionAlternate names for turret are carousel,magazine, wheel.3.3 Acronyms:3.3.1 cpmcounts per minute3.3.2 cpscounts per second3.3.3 CRMcertified reference material3.3.4 dark noiseobserved count rate on an ion countingdetector measured
21、 without incident ion beam3.3.5 DSdouble spike3.3.6 DUdepleted uranium3.3.7 EUEuropean Union3.3.8 FARFaraday Cup3.3.9 HEUhigh enriched uranium3.3.10 IAEAInternational Atomic Energy Agency3.3.11 ICPMSinductively coupled plasma mass spectrom-etry3.3.12 IRMMInstitute for Reference Materials and Mea-sur
22、ements3.3.13 ITUInstitute for Transuranium Elements3.3.14 JRCJoint Research Centre3.3.15 LEUlow enriched uranium3.3.16 MTEmodified total evaporation3.3.17 NBLNew Brunswick Laboratory3.3.18 RSDrelative standard deviationSD (see below)divided by the mean value of the observations in repeatedsampling3.
23、3.19 RSErelative standard errorSE (see below) di-vided by the mean value of the observations in repeatedsampling.3.3.20 SDstandard deviationaccording to PracticeE2586, 3.1.30: the square root of the sum of the squareddeviations of the observed values in the sample divided by thesample size minus one
24、.3.3.21 SEstandard erroraccording to Practice E2586,3.1.29: standard deviation of the population of values of asample statistic (that is, the mean value) in repeatedmeasurements, or an estimate of it.3.3.21.1 DiscussionAccording to Practice E2586, 3.1.30:If the standard error (SE, see above) of a st
25、atistic is estimated,it will itself be a statistic with some variance that depends onthe sample size, that is, the number of observed values in thesample (Practice E2586, 3.1.26).3.3.21.2 DiscussionAccording to Guide E2655, 5.8.4.1:From statistical theory, a 95 % confidence interval for the meanof a
26、 normal distribution, given n independent observations x1,x2, ., xndrawn from the distribution is, x 6 t SD/n, wherex is the sample mean, SD is the standard deviation of theobservations (see above), and t is the 0.975 percentile of theStudents t distribution with n-1 degrees of freedom. BecauseStude
27、nts t distribution approaches the Normal as n increases,the value of t approaches 1.96 as n increases. This is the basisfor using the (coverage) factor 2 for expanded uncertainty. Thestandard error (SE) of the mean value of a series of nindependent repeated measurements can be derived from thatby us
28、ing t = 1, so the standard error (SE) is given by SD n.3.3.22 SEMsecondary electron multiplier.3.3.22.1 DiscussionIn the scientific literature the acronymSEM is also used for Scanning Electron Microscope, butwithin this test method SEM represents Secondary ElectronMultiplier.3.3.23 SGASSafeguards An
29、alytical Services Laboratoryof the IAEA3.3.24 TIMSthermal ionization mass spectrometry4. Summary of Test Method4.1 The modified total evaporation method has been devel-oped on the basis of the “classical” total evaporation technique(1-4)4, also described in Test Method C1672. By using the totalevapo
30、ration technique, the mass fractionation is minimized byevaporating the entire sample amount loaded on the filament,in contrast to the “conventional” technique as described in TestMethod C1625. The MTE method has already been describedin detail in Refs (5) and (6). If necessary, uranium is separated
31、from plutonium and other elements (to eliminate isobaricinterferences) by selective extraction, anion exchange (seePractice C1411), or extraction chromatography. The purifieduranium fraction as nitrate solution is loaded onto a degassed4The boldface numbers in parentheses refer to a list of referenc
32、es at the end ofthis standard.C1832 162filament (made of metals such as rhenium, zone-refinedrhenium, or tungsten with high evaporation temperature) andconverted to an oxide by controlled heating of the filamentunder atmospheric conditions. For the modified total evapora-tion method, the uranium loa
33、d is in the range of about 2 to 6 g,which is about one to two orders of magnitude higher than thattypically used for the “classical” total evaporation method byTIMS. The sample filament is mounted on the sample turretusing a double-filament configuration. This configuration con-sists of an evaporati
34、on filament (Re or W) on which the sampleis loaded, and an ionization filament (Re filament with nosample). For a measurement in the mass spectrometer, theionization filament is heated to a temperature of about 1800 to1900C, sufficient to generate187Re ion beam signals of 150 to400 mV (corresponding
35、 to ion currents of 1.5 to410-12Ausing an amplifier resistor of 1011). The intensity of theoptimized187Re signal depends on the Re material (zone-refined or non-zone-refined), thickness and the measurementconditions, but it is expected to be the same for all filaments onthe same sample turret. The18
36、7Re ion current is also used forthe initial ion beam focusing. The evaporation filament isheated next. After ion beam re-focusing and mass re-adjustment initially using a small sum intensity (sum of234U,235U,236U, and238U) of about 1 to 3 V, the data acquisitionbegins under computer control to yield
37、 a predefined target sumintensity of 20 to 30 V (corresponding to ion currents of 2 to 310-10A using an amplifier resistor of 1011). This targetvalue depends on the amount of uranium loaded on a filament.The MTE analysis takes between 2 and 5 h per sample filamentand is about three to ten times long
38、er than typical (“classical”)TE analyses in spite of the higher intensities at which theanalyses are performed. To ensure that the whole sample iscompletely evaporated and analyzed before the ionizationfilament breaks as a result of overheating, the MTE analysisroutine is programmed to increase the
39、target sum intensityduring the course of the analysis if necessary. The occurrencesof outliers due to technical glitches, for example, as a result oftermination before complete sample evaporation or because ofearly sample exhaustion, are minimized by a dynamic targetintensity control feature through
40、 manipulation of the target sumintensity depending on the actual measurement conditions.4.2 The sample amount to be loaded for MTE analyses islimited to a range of about 2 to 6 g to achieve ion beamsignals of about 20 to 30 V for the major isotope 238U forDU, NU, and LEU samples and235U for HEU samp
41、les cor-responding to a234U intensity of 1 to 10 mV. This causes the234U ion beam to be suitable for an internal cross calibration ofthe SEM versus the Faraday cups through the entire measure-ment time. This also allows the236U/238U isotope amount ratioto be measured in a wide dynamic range from 10-
42、2down to10-10using a Faraday cup or an SEM in combination with anenergy filter for improved abundance sensitivity. For certainDU samples, the236U ion beam is used for the cross calibrationand the234U is measured on the SEM (known as “reverse”MTE, see 13.8.8). For all samples with minor ratios234U/23
43、8Uand236U/238U higher than410-5, which also includes HEUsamples, the minor isotopes are only measured using Faradaycups with amplifier resistors of 1012 yielding a favorablesignal-to-noise ratio.4.3 Similar to the TE analysis, the isotope ion beams of themajor isotopes235U and238U are integrated ove
44、r the course ofthe analysis, and the summed intensity for235U is divided bythe summed intensity for238U to yield the major isotopeamount ratio. The result of the major isotope amount ratio iscorrected for mass fractionation using the measurement of aCRM analyzed on the same sample turret.4.4 The min
45、or isotope amount ratios are corrected for massfractionation for each integration step individually. This isaccomplished in an internal manner, the magnitude of the massfractionation for the minor ratios is calculated from themeasured mass fractionation of the major ratio. The peaktailing contributi
46、ons are determined at two positions, slightlybelow and above the isotope masses of interest. If applicable,the SEM-versus-Faraday calibration is also performed for eachintegration step individually.5. Significance and Use5.1 Uranium material is used as a fuel in certain types ofnuclear reactors. To
47、be suitable for use as nuclear fuel, thestarting material shall meet certain specifications such as thosedescribed in Specifications C753, C776, C787, C833, C967,C996, and C1008, or as specified by the purchaser. The isotopeamount ratios of uranium material can be measured by massspectrometry follow
48、ing this test method to ensure that theymeet the specification.5.2 The MTE method can be used for a wide range ofsample sizes even in samples containing as low as 50 g ofuranium. If the uranium sample is in the form of uraniumhexafluoride, it can be converted into a uranium nitrate solutionfor measu
49、rement by the MTE method. The concentration of theloading solution for MTE has to be in the range of 1 to 6 mg/gto allow a sample loading of 2 to 6 g of uranium.Aminimumloading of 3 g uranium per filament is recommended. This isneeded to have a suitable ion signal especially for the twominor isotopes (234U and236U) thus enabling the internalcalibration of SEM versus the Faraday cups during the mea-surement.5.3 Until now, the instrument capabilities for the MTEmethod have only been implemented on the TRITON TIMSinstrument.5
