1、Designation: C1672 17Standard Test Method forDetermination of Uranium or Plutonium IsotopicComposition or Concentration by the Total EvaporationMethod Using a Thermal Ionization Mass Spectrometer1This standard is issued under the fixed designation C1672; the number immediately following the designat
2、ion indicates the 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 method describes the determin
3、ation of the isotopiccomposition, or the concentration, or both, of uranium andplutonium as nitrate solutions by the total evaporation methodusing a thermal ionization mass spectrometer (TIMS) instru-ment. Purified uranium or plutonium nitrate solutions aredeposited onto a metal filament and placed
4、in the massspectrometer. Under computer control, ion currents are gener-ated by heating of the filament(s). The ion currents arecontinually measured until the whole sample is exhausted. Themeasured ion currents are integrated over the course of themeasurement and normalized to a reference isotope io
5、n currentto yield isotope ratios.1.2 In principle, the total evaporation method should yieldisotope ratios that do not require mass bias correction. Inpractice, samples may require this bias correction. Comparedto the conventional TIMS method described in Test MethodC1625, the total evaporation meth
6、od is approximately twotimes faster, improves precision of the isotope ratio measure-ments by a factor of two to four, and utilizes smaller samplesizes. Compared to the C1625 method, the total evaporationmethod provides “major” isotope ratios235U/238U and240Pu/239Pu with improved accuracy.1.3 The to
7、tal evaporation method is prone to biases in the“minor” isotope ratios (233U/238U,234U/238U, and236U/238Uratios for uranium materials and238Pu/239Pu,241Pu/239Pu,242Pu/239Pu, and244Pu/239Pu ratios for plutonium materials)due to peak tailing from adjacent major isotopes. The magni-tude of the absolute
8、 bias is dependent on measurement andinstrumental characteristics. The relative bias, however, de-pends on the relative isotopic abundances of the sample. Theuse of an electron multiplier equipped with an energy filter mayeliminate or diminish peak tailing effects. Measurement of theabundance sensit
9、ivity of the instrument may be used to ensurethat such biases are negligible, or may be used to bias correctthe minor isotope ratios.1.4 The values stated in SI units are to be regarded asstandard. When non-SI units are provided in parentheses, theyare for information only.1.5 This standard may invo
10、lve the use of hazardous mate-rials and equipment. This standard does not purport to addressall of the safety concerns, if any, associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulato
11、ry limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C753 Specification for Nuclear-Grade, Sinterable UraniumDioxide PowderC757 Specification for Nuclear-Grade Plutonium DioxidePowder for Light Water ReactorsC776 Specification for Sintered Uranium Dioxide PelletsC787 Specification
12、for Uranium Hexafluoride for Enrich-mentC833 Specification for Sintered (Uranium-Plutonium) Diox-ide Pellets for Light Water ReactorsC859 Terminology Relating to Nuclear MaterialsC967 Specification for Uranium Ore ConcentrateC996 Specification for Uranium Hexafluoride Enriched toLess Than 5 %235UC10
13、08 Specification for Sintered (Uranium-Plutonium)DioxidePelletsFast Reactor Fuel (Withdrawn 2014)3C1068 Guide for Qualification of Measurement Methods bya Laboratory Within the Nuclear IndustryC1156 Guide for Establishing Calibration for a Measure-ment Method Used to Analyze Nuclear Fuel Cycle Mate-
14、rials1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved Jan. 1, 2017. Published January 2017. Originallyapproved in 2007. Last previous edition approved in 2014 as C1
15、672 07 (2014).DOI: 10.1520/C1672-17.2For 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 Document Summary page onthe ASTM website.3The last approved versio
16、n 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization establishe
17、d in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1C1168 Practice for Preparation and Dissolution of PlutoniumMaterials for AnalysisC1347 Practice for Preparatio
18、n and Dissolution of UraniumMaterials for AnalysisC1411 Practice for The Ion Exchange Separation of Ura-nium and Plutonium Prior to Isotopic AnalysisC1415 Test Method for238Pu Isotopic Abundance By AlphaSpectrometryC1625 Test Method for Uranium and Plutonium Concentra-tions and Isotopic Abundances b
19、y Thermal IonizationMass SpectrometryC1816 Practice for The Ion Exchange Separation of SmallVolume Samples Containing Uranium, Americium, andPlutonium Prior to Isotopic Abundance and ContentAnalysisC1832 Test Method for Determination of Uranium IsotopicComposition by the Modified Total Evaporation (
20、MTE)Method Using a Thermal Ionization Mass SpectrometerD1193 Specification for Reagent WaterD3084 Practice for Alpha-Particle Spectrometry of Water3. Terminology3.1 For definitions of terms used in this test method but notdefined herein, refer to Terminology C859.3.2 Definitions of Terms Specific to
21、 This Standard:3.2.1 isotopic equilibration, nseries of chemical stepsperformed on a mixture of two samples (for example, auranium sample and a uranium spike) to ensure identicalvalency and chemical form prior to purification of the mixture.Failure to perform isotopic equilibration of a sample-spike
22、mixture may result in partial separation of the sample from thespike during the purification procedure, causing a bias in theresults of isotope dilution mass spectrometry measurements.3.2.2 major ratio, nalternate expression for235U/238U (or238U/235U) and240Pu/239Pu isotope ratios.3.2.3 minor ratios
23、, nalternate expression for233U/238U,234U/238U,236U/238U,234U/235U, and236U/235Uor238Pu/239Pu,241Pu/239Pu,242Pu/239Pu, and244Pu/239Pu isotope ratios.3.2.4 turret, nholder for sample filaments, other wordsused: wheel, magazine.3.3 Acronyms:3.3.1 CRMCertified Reference Materials3.3.2 DUDepleted Uraniu
24、m3.3.3 HEUHigh Enriched Uranium3.3.4 IDMSIsotope Dilution Mass Spectrometry3.3.5 IRMMInstitute for Reference Materials and Mea-surements (IRMM is now known as European CommissionJoint Research Center, JRC-Geel)3.3.6 LEULow Enriched Uranium3.3.7 NBLNew Brunswick Laboratory3.3.8 NUNatural Uranium3.3.9
25、 TIMSThermal Ionization Mass Spectrometry3.3.10 WRMWorking Reference Material4. Summary of Test Method4.1 Uranium and plutonium are separated from each otherand purified from other elements by selective anion exchangechromatography (such as in Practice C1411 or Test MethodC1415 or C1816). The purifi
26、ed uranium or plutonium samplesas nitrate solutions are drop-deposited or otherwise loaded ona refractory metal filament (typically rhenium, tungsten, ortantalum) and converted to a solid chemical form via controlledheating of the filament under atmospheric conditions. Thesample filament is mounted
27、on the sample turret, often in thedouble filament configuration.This configuration consists of anevaporation filament (Re or W) on which the sample is loaded,and an ionization filament (Re filament with no sample). Thefilaments are heated to yield a small ion current suitable forlens focusing and pe
28、ak centering. Following focusing and peakcentering, data acquisition begins, with the filaments heatedunder computer control to yield a pre-defined major isotope ioncurrent (235Uor238U for uranium and239Pu or240Pu forplutonium) or a predefined sum total for all measured ioncurrents. Data acquisition
29、 and filament heating continues untilthe sample is exhausted or the ion current reaches a pre-definedlower limit. Ion intensity of each isotope is integrated over thecourse of the analysis, and the summed intensity for eachisotope is divided by the summed intensity of a commonisotope (typically the
30、most abundant isotope) to yield ratios.The isotopic composition of the sample (formatted as amountfraction or mass fraction) may be calculated from the isotoperatios. Additional information on the total evaporation methodmay be found in Refs (1-5).44.2 The isotope dilution mass spectrometry (IDMS) m
31、ethodmay be used to determine the uranium or plutonium concen-trations. In this method, a spike of known isotopic compositionand element concentration is added to a sample prior tochemical separation. Typical spike materials in-clude233U,235U, or238U for uranium samples,and239Pu,242Pu, or244Pu for p
32、lutonium samples. Samplescontaining both uranium and plutonium (for example, mixedoxide fuels or fuel reprocessing materials) may be mixed witha combined U/Pu spike prior to separation. When using a spikecontaining significant quantities of one or more of the isotopespresent in the sample, the isoto
33、pic composition of the samplemust be known in advance. The spike-sample mixture under-goes a valency adjustment, purification, and is then loaded ontoa filament and the isotopic composition of the mixture isdetermined. Using the measured isotope ratios of the spike-sample mixture, the known isotopic
34、 composition and amountof spike added to the mixture, and the isotopic composition ofthe sample, the elemental concentration of the sample may becalculated. The IDMS method yield results that are directlytraceable to the SI unit of mole, provided the spike is SItraceable.5. Significance and Use5.1 T
35、he total evaporation method is used to measure theisotopic composition of uranium and plutonium materials, and4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.C1672 172may be used to measure the elemental concentrations of thetwo elements when employing
36、 the IDMS technique.5.2 Uranium and plutonium compounds are used as nuclearreactor fuels. In order to be suitable for use as a nuclear fuel thestarting material must meet certain criteria, such as found inSpecifications C757, C833, C753, C776, C787, C967, C996,C1008, or as specified by the purchaser
37、. The uraniumconcentration, plutonium concentration, or both, and isotopeabundances are measured by thermal ionization mass spec-trometry following this method.5.3 The total evaporation method allows for a wide range ofsample loading with no significant change in precision oraccuracy. The method is
38、also suitable for trace-level loadingswith some loss of precision and accuracy. The total evaporationmethod and modern instrumentation allow for the measure-ment of minor isotopes using ion counting detectors, while themajor isotope(s) is(are) simultaneously measured using Fara-day cup detectors.5.4
39、 The new generation of miniaturized ion counters allowextremely small samples, in the picogram range, to be mea-sured via the total evaporation method. The method may beemployed for measuring environmental or safeguards inspec-tion samples containing nanogram quantities of uranium orplutonium. Very
40、small loadings require special sample han-dling and careful evaluation of measurement uncertainties.5.5 Typical uranium analyses are conducted using sampleloadings between 50 nanograms and several micrograms. Foruranium isotope ratios the total evaporation method had beenused in several recent NBLis
41、otopic certified reference material(CRM) characterizations (for example (2, 3). A detailedcomparison of the total evaporation data on NBL uraniumCRMs analyzed by the MAT 261 and TRITONTMinstrumentsis provided in Ref (5). For total evaporation, plutoniumanalyses are generally conducted using sample l
42、oads in therange of 30 to 400 nanograms of plutonium.6. Interferences6.1 Ions with atomic masses in the uranium and plutoniumranges cause interference if they have not been removed or ifthey are generated as part of the chemical handling or analysisof the samples. Both238U and238Pu interfere in the
43、measure-ment of each other, and241Am interferes with the measurementof241Pu, thereby requiring chemical separation. Removal ofimpurities provides uniform ionization of uranium orplutonium, hence improved precision, and reduces the inter-ference from molecular species of the same mass number as theur
44、anium or plutonium isotopes being measured. Isotopic analy-sis of plutonium should be completed within a reasonable timeperiod after the separation of americium to minimize interfer-ence due to241Am in-growth from241Pu. An example of aprescribed interval limiting the time between sample purifica-tio
45、n and isotopic analysis is 20 days. For NBLCRMs 136, 137,and 138 the241Pu/239Pu ratio changes by about 0.092 % perweek as a result of241Pu decay. Instrument users are respon-sible for determining a maximum interval between purificationand mass spectrometric analysis, based on an evaluation of241Am i
46、n-growth from decay of241Pu and the accuracy andprecision consistent with the data quality objectives of thefacility. Other atomic and molecular species may interfere withtotal evaporation analyses, particularly if they cause a changein the ionization efficiency of the analyte during an analysis.Pre
47、sence of carbon may disturb total evaporation measure-ments. It is recommended that instrument users performvalidation tests on unique or complex samples by mixingknown pure standards with other constituents to create amatrix-matched standard.6.2 Precautionary steps must be taken to avoid contamina-
48、tion of the sample by environmental uranium or plutoniumfrom the analytical laboratory environment. The level of effortneeded to minimize the effect of contamination of the sampleshould be based upon the sample size, planned handling andprocessing of the sample, and knowledge of the levels ofcontami
49、nation present in the laboratory. For very small ura-nium or plutonium samples, extreme measures are oftenwarranted to ensure that the sample is not contaminated. Forthese samples, residual uranium or plutonium in the massspectrometer and trace uranium in chemicals or the filamentsmay bias measurement data.6.3 The total evaporation method may generate biases in theminor isotope ratios, especially when measuring trace amountsof234U in a HEU (highly enriched uranium,235U abundance 20 %) material, or trace amounts of236U in a LEU (lowenriched uranium, 1 % 1) and the min
