ASTM_C_1415_-_14.pdf

Designation:C141514Standard Test Method for238Pu Isotopic Abundance By Alpha Spectrometry1This standard is issued under the fixed designation C1415;the number immediately following the designation 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 test method covers the use of alpha spectrometryfor determining the238Pu isotopic abundance in plutoniumsamples.It is particularly useful for samples in which the238Pucontent is less than 1%of the total plutonium content.For suchsamples,mass spectrometric results are vulnerable to biasbecause of potential interference from any238U isobar remain-ing after ion exchange.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 This standard does not 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 Standards:2C697 Test Methods for Chemical,Mass Spectrometric,andSpectrochemical Analysis of Nuclear-Grade PlutoniumDioxide Powders and PelletsC859 Terminology Relating to Nuclear MaterialsC1168 Practice for Preparation and Dissolution of PlutoniumMaterials for 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 Isotopic Composition or Concentration by the TotalEvaporation Method Using a Thermal Ionization MassSpectrometerD1193 Specification for Reagent Water3.Terminology3.1 For definitions of pertinent terms not listed here,seeTerminology C859.4.Summary of Test Method4.1 This determination method involves the measurement ofthe alpha-activity ratio of238Pu and239Pu+240Pu.Theisotopic analysis of plutonium for the238Pu isotope requiresthe prior separation of potentially interfering species.Afterdissolution of the sample(see Practice C1168),the plutoniumis separated from interferences by an anion-exchange purifica-tion technique.Nitric acid(HNO3)is used to adsorb theplutonium fraction on the resin.Interfering ions,principallyuranium and americium,are not adsorbed.The plutonium isthen eluted with dilute HNO3(0.1 M).Because an alpha-activity ratio is used,quantitative recovery of the plutonium isnot required.The alpha spectrum in the 5 to 6-MeV region isobtained.The total counts in the238Pu and the239Pu+240Pupeaks are obtained and corrected for background.The238Puabundance is calculated from the ratio of the alpha activity dueto238Pu and that due to239Pu+240Pu.The abundance of239Puand240Pu is determined by mass spectrometry(see TestMethods C697,C1625,or C1672)on a separate portion of thepurified sample.5.Significance and Use5.1 This test method is used when the determination of238Pu isotopic abundance is required for plutonium samples.6.Interferences6.1 Am-241 is always present as a result of241Pu decay andis a direct interference that must be removed prior to thedetermination of238Pu.The very small amount of230Th and232Th which could be present causes insignificant interferencewith the determination of238Pu at the level of uncertainty ofthis test method.Other nuclides that could interfere,such as238U,243Am,245Cm,and249Bk,are removed by the anion-exchange separation.Any residual uranium,while it does notdirectly interfere with the alpha-pulse height determination,can raise the salt content of the sample.A high salt content candecrease the resolution of the alpha spectra,and,consequently,decrease the accuracy of the test method.1This 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 June 1,2014.Published July 2014.Originally approvedin 1999.Last previous edition approved in 2007 as C1415 01a(2007).DOI:10.1520/C1415-14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.Apparatus7.1 Counting disks of polished platinum,tantalum,or stain-less steel,sized to fit the detection chamber.A disk 25 mm indiameter and 0.5 mm thick has been found to be acceptable.7.2 Alpha spectrometer.This instrument may consist of thefollowing individual components but more typically as anintegrated system that is readily interfaced to a computer:7.2.1 Silicon surface barrier detector,with an active area ofat least 100 mm2,a depletion depth of greate