1、Designation: C 1205 07Standard Test Method forThe Radiochemical Determination of Americium-241 in Soilby Alpha Spectrometry1This standard is issued under the fixed designation C 1205; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 alpha
3、spectrometry. 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 a
4、sstandard.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
5、specificprecaution statements, see Section 10.2. Referenced Documents2.1 ASTM Standards:2C 859 Terminology Relating to Nuclear Materials3C 998 Practice for Sampling Surface Soil for RadionuclidesC 999 Practice for Soil Sample Preparation for the Deter-mination of RadionuclidesC 1163 Practice for Mou
6、nting Actinides for Alpha Spec-trometry Using Neodymium FluorideD 1193 Specification for Reagent WaterD 3084 Practice for Alpha-Particle Spectrometry of WaterD 3648 Practices for the Measurement of Radioactivity3. Terminology3.1 For definitions of terms in this standard, refer toTerminology C 859.4.
7、 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 trivalen
8、t 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 radioch
9、emical recoveries of this method asdetermined by the yield monitor, are between 75 and 90percent. Decontamination factors from other radionuclides thatmay interfere with the determination of americium in thisenergy range are 104105.4.3 The reagent blank contains all reagents plus the ameri-cium243 t
10、racer. 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 attai
11、nable 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, ma
12、y interfere withthe alpha spectrometric determination of americium241. Tho-rium228, 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 polonium21
13、0 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
14、edition approved June 1, 2007. Published July 2007. Originally approvedin 1991. Last previous edition approved in 2002 as C 1205 97(2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
15、information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.precipitation method. If high concentrations of these radionu-clides are known to be present, a p
16、reliminary separation maybe required.7. Apparatus7.1 Alpha pulse height analysis system as in PracticeD 3084.7.1.1 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 prepar
17、ed for alpha spectrometry using neodymiumfluoride mounting by Practice C 1163 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 counts at the maximum of the peak(FWHM).7.1.
18、2 The counting efficiency of the system (i.e., count/disintegration) should be greater than 20 % and the instrumentbackground in the region of each energy peak used for analysisshould be less than five counts in 60 000 s (1000 min).7.2 Membrane Filter (such as cellulose nitrate or celluloseacetate),
19、 47 mm diameter, 0.45 m pore size.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Societ
20、y,where such specifications are available. Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understoo
21、d to mean reagent water as definedin Specification D 1193, Type III or better.8.3 Americium TracerPurify the americium243 tracer.4The americium243 tracer may be available from NIST orother recognized standards laboratories.8.4 Potassium Fluoride, anhydrous.8.5 Potassium Sulfate, anhydrous.8.6 Sodium
22、 Sulfate, anhydrous.8.7 Ammonium Persulfate (ammonium peroxydisulfate).8.8 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).8.9 Hydrofluoric Acid (sp gr 1.20)Concentrated hydrof-luoric acid (HF).8.10 Sulfuric Acid (sp gr 1.84)Concentrated sulfuric acid(H2SO4).8.11 Sulfuric Acid So
23、lution 0.5 % Mix 5 mL of concen-trated sulfuric acid with water and dilute to one liter.8.12 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).8.13 Potassium Metabisulfite Solution 25 %Dissolve 25g of potassium metabisulfite in water and dilute to 100 mL.8.14 Sodium Bromate Solution 10 % Dissol
24、ve 10 g ofsodium bromate in water and dilute to 100 mL.8.15 HDEHP Solution 15 % Dissolve 150 mL ofbis(2ethylhexyl)phosphoric acid in 850 mL of nheptane.8.16 Barium Chloride Solution 0.5 % Dissolve 0.5 g ofbarium chloride in water and dilute to 100 mL.8.17 5M Nitric AcidMix 312 mL of concentrated nit
25、ricacid with water and dilute to one liter.8.18 Silver Nitrate Solution 0.5 % Dissolve 0.5 g of silvernitrate in water and dilute to 100 mL.8.19 Lanthanum Carrier (5 mg La/mL) Dissolve 1.17 g oflanthanum nitrate in 75 mL of 5M nitric acid and dilute to 100mL with water.8.20 Phosphoric Acid (sp gr 1.
26、83)Concentrated phospho-ric acid (H3PO4).8.21 0.2M Ammonium PersulfateDissolve 2.3 g of am-monium persulfate in water and dilute to 50 mL. Prepare daily.8.22 6M Ammonium FluorideDissolve 22.2 g of ammo-nium fluoride in water and dilute to 100 mL.8.23 0.10M Ammonium Persulfate3N AmmoniumFluorideMix 2
27、0 mL of 0.2M ammonium persulfate with 20mL of 6M ammonium fluoride. Prepare daily.8.24 Hydrogen Peroxide Solution 30 %.8.25 Perchloric Acid (sp gr 1.67)Concentrated perchloricacid (HClO4).8.26 Neodymium Carrier (10 mg Nd/mL) Heat 25 mL of12M hydrochloric acid and 1.17 g of neodymium oxide on ahot pl
28、ate until the neodymium oxide is in solution. Cool thesolution and dilute to 100 mL with water.8.27 Neodymium Carrier (0.5 mg Nd/mL) Dilute 5 mL ofthe 10 mg Nd/mL neodymium carrier solution to 100 mL withwater.9. Sampling9.1 Collect the sample in accordance with Practice C 998.9.2 Prepare the sample
29、 for analysis in accordance withPractice C 999.10. Hazards10.1 In addition to other precautions, adequate laboratoryfacilities, such as perchloric acid fume hoods and controlledventilation, along with safe techniques must be used in thisprocedure. Extreme care should be exercised in using hydrof-luo
30、ric acid and other hot concentrated acids, particularly hotperchloric acid. Use of safety equipment, especially safetyglasses and rubber gloves, is recommended.10.2 Hydrofluoric acid is a highly corrosive acid that canseverely burn skin, eyes, and mucous membranes. Hydrofluo-ric acid is similar to o
31、ther acids in that the initial extent of aburn depends on the concentration, the temperature, and theduration of contact with the acid. Hydrofluoric acid differsfrom other acids because the fluoride ion readily penetrates theskin, causing destruction of deep tissue layers. Unlike otheracids that are
32、 rapidly neutralized, hydrofluoric acid reactionswith tissue may continue for days if left untreated. Due to theserious consequences of hydrofluoric acid burns, prevention ofexposure or injury of personnel is the primary goal. Utilization4For a description of the process, see Sill, C. W., Anal. Chem
33、. 46, 1974, pp.14261431.C 1205 072of appropriate laboratory controls (hoods) and wearing ad-equate personel protective equipment to protect from skin andeye contact is essential.11. Calibration and Standardization11.1 If an americium243 solution traceable to a nationalstandards body is not available
34、 for use as a tracer, standardizea freshly prepared sample of americium243 using the guid-ance in Practice D 3648. These practices may also be used toestablish the counting efficiency of the alpha spectrometerwhich then can be used to calculate the chemical recovery.12. Procedure12.1 Weigh 10 g of 3
35、5 mesh soil, to 0.001 g, into a250mL platinum dish and add 30 g of anhydrous potassiumfluoride, 10 mL of water, 10 mL of concentrated hydrofluoricacid, and 2 mL of concentrated nitric acid. Slurry the contentsof the dish together and add an americium243 tracer at thelevel of approximately 0.1 Bq. Pl
36、ace the dish on a fiberglassmat-covered hot plate and evaporate the contents to dryness.Place the dish on a ring stand and heat with a high temperatureblast burner until the contents have dissolved completely. Swirlthe contents gently to dissolve any sample on the sides of thedish. When the sample h
37、as dissolved completely, carefullyremove the platinum dish from the ring stand and swirl the meltas it cools to deposit the melt evenly along the sides and thebottom of the dish.12.2 After the contents of the dish have cooled to roomtemperature, carefully add 40 mL of concentrated sulfuric acidto tr
38、anspose the fluoride cake. After the initial vigorousreaction has subsided, place the dish on a fiberglass mat-covered hot plate and heat until the fluoride cake has beencompletely transposed. Add 20 g of anhydrous sodium sulfate,place the dish on the ring stand and heat gently until theviscous solu
39、tion begins to boil. Increase the temperature fromthe blast burner until a smooth boiling mixture is obtained andcontinue heating until a clear melt results. Cool the dish tosolidify the melt and then place the dish into a cold water bathto facilitate cake removal.12.3 Bring 500 mL of water and 150
40、mL of concentratedhydrochloric acid to a boil in a 800mL beaker and carefullyadd the contents of the platinum dish to the beaker. Continueboiling until a clear solution results. Add 50 g of anhydrouspotassium sulfate and 2 mL of a 25 % potassium metabisulfitesolution to the beaker and continue boili
41、ng for two minutes.12.4 To the boiling contents of the beaker, add four 10 mLportions of a 0.5 % barium chloride solution with a 5minuteboiling interval between each addition. Stir the contents of thebeaker after each addition of barium chloride. Filter the hotsolution through a 47mm membrane filter
42、 using either a glassor polycarbonate filtering apparatus. Rinse the beaker and theprecipitate with a 0.5 % sulfuric acid solution. Place the filtercontaining the barium sulfate precipitate into a 125 mLErlenmeyer flask containing 30 mL of concentrated perchloricacid and heat the contents to fumes o
43、f perchloric acid. The useof perchloric acid during the above procedure is used todissolve the barium sulfate precipitate and the filter andpresents little or no safety hazard. The addition of nitric acidduring this step is not necessary. Cool the contents of the flaskto room temperature.12.5 Add on
44、e mL of a 10 % sodium bromate solution to theflask containing the perchloric acid and transfer the contents ofthe flask to a 60mL separatory funnel containing 10 mL of15 % HDEHP in n-heptane and shake for five minutes. Aftercomplete phase separation, draw off the lower aqueous layerand discard. Wash
45、 the organic extract twice with 5mLportions of concentrated perchloric acid for two minutes.Discard the wash solutions.12.6 Strip the trivalent actinides and lanthanides twice forfour minutes each with 10mL portions of 5M nitric acidcontaining one mL of 10 % sodium bromate solution. Transferthe solu
46、tion containing the trivalent actinides and lanthanidesto another separatory funnel containing 10 mL of 15 %HDEHP in n-heptane and extract for two minutes to removeany plutonium, thorium, or tetravalent cerium that may havestripped during the back extraction of the trivalent actinides.After complete
47、 phase separation, draw off the lower aqueouslayer into a 70 mL polycarbonate counting bottle. Any residualorganic will transfer to the sides of the counting bottle.12.7 Transfer the contents of the counting bottle to a 50mLconical polycarbonate centrifuge tube. Add 5 mg of lanthanumcarrier and 5 mL
48、 of concentrated hydrofluoric acid to thecentrifuge tube to precipitate the rare earth fluorides. Heat thecontents of the centrifuge tube in a hot water bath for tenminutes. Cool the contents to room temperature and centrifugeat 4000 rpm for five minutes. Discard the supernate, add 0.10mL of concent
49、rated phosphoric acid to the centrifuge tube, andtransfer the contents to a TFE fluorocarbon beaker with a smallvolume of water. Place the beaker on a fiberglass mat-coveredhot plate and evaporate the contents to the 0.10 mL ofconcentrated phosphoric acid previously added.12.8 Transfer the phosphoric acid to a 50mL conicalpolycarbonate centrifuge tube using 3 to 4 mL of water tocomplete the transfer. Add one drop of a 0.05 % solution ofsilver nitrate and 3 mL of 0.2M ammonium persulfate solutionand adjust the volume to 10 mL. Heat
