ASTM_C_1205_-_07_2012.pdf

Designation:C120507(Reapproved 2012)Standard Test Method forThe Radiochemical Determination of Americium-241 in Soilby Alpha Spectrometry1This standard is issued under the fixed designation C1205;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 method covers the determination of ameri-cium241 in soil by means of chemical separations and alphaspectrometry.It is designed to analyze up to ten grams of soilor other sample matrices that contain up to 30 mg of combinedrare earths.This method allows the determination of ameri-cium241 concentrations from ambient levels to applicablestandards.The values stated in SI units are to be regarded asstandard.1.2 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.For specificprecaution statements,see Section 10.2.Referenced Documents2.1 ASTM Standards:2C859 Terminology Relating to Nuclear MaterialsC998 Practice for Sampling Surface Soil for RadionuclidesC999 Practice for Soil Sample Preparation for the Determi-nation of RadionuclidesC1163 Practice for Mounting Actinides for Alpha Spectrom-etry Using Neodymium FluorideD1193 Specification for Reagent WaterD3084 Practice for Alpha-Particle Spectrometry of WaterD3648 Practices for the Measurement of Radioactivity3.Terminology3.1For definitions of terms in this standard,refer toTerminology C859.4.Summary of Test Method4.1 Americium241 is determined in prepared soil samplesof up to 10 g.The soil is completely dissolved by use ofpyrosulfate fusion.After an initial separation on barium sulfateand extraction with an organophosphorous compound,theamericium is separated from the other trivalent actinides andthe rare earths by oxidation of the americium and precipitationof the interferences.The americium is prepared for alphaspectrometry by coprecipitation with neodymium fluoride andthe americium241 determined by alpha spectrometry usingamericium243 as a yield monitor.4.2 Typical radiochemical recoveries of this method asdetermined by the yield monitor,are between 75 and 90%.Decontamination factors from other radionuclides that mayinterfere with the determination of americium in this energyrange are 104105.4.3 The reagent blank contains all reagents plus the ameri-cium243 tracer.Five samples and a reagent blank can becompleted and ready for alpha spectrometry in approximately6 h.The full-width at half-maximum(FWHM)detector reso-lution ranges between 43 and 65 keV.5.Significance and Use5.1 This test method provides the speed and high decon-tamination factors attainable with liquid-liquid extraction ofthe actinides and eliminates filtration techniques that are moretime consuming.5.2 This test method provides a precise determination ofamericium in concentrations normally found in environmentalsamples.6.Interferences6.1 Plutonium,if inadequately separated,may interfere withthe alpha spectrometric determination of americium241.Thorium228,identifiable by its daughter products,is a seriousinterference to the final determination of americium by alphaspectrometry if decontamination factors are not sufficientlyhigh.An inadequate separation of polonium210 may result inan inaccurate determination of the americium243 yield moni-tor but this is unlikely when using the neodymium fluoride1This test method is under the jurisdiction of ASTM CommitteeC26 on NuclearFuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods ofTest.Current edition approved June 1,2012.Published June 2012.Originallyapproved in 1991.Last previous edition approved in 2007 as C120507.DOI:10.1520/C1205-07R12.2For 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 precipitation method.If high concentrations of these radionu-clides are known to be present,a preliminary separation maybe required.7.Apparatus7.1 Alpha pulse height analysis system as in PracticeD3084.7.1.1 A system consisting of a silicon surface barrier detec-tor capable of 50 keV or better resolution on standardselectrodeposited on a flat,mirror finished disk is required.Samples prepared for alpha spectrometry using neodymiumfluoride mounting by Practice C1163 should be capable of 60to 70 keV resolution.The resolution is defined as the width ofan alpha energy peak when the counts on either side of the peakare equal to one-half of the cou