1、Designation: D6239 09 (Reapproved 2015)Standard Test Method forUranium in Drinking Water by High-Resolution Alpha-Liquid-Scintillation Spectrometry1This standard is issued under the fixed designation D6239; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n 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 determining the total solubleuranium activity in drinking
3、water in the range of 0.037 Bq/L(1 pCi/L) or greater by selective solvent extraction andhigh-resolution alpha-liquid-scintillation spectrometry. The en-ergy resolution obtainable with this technique also allowsestimation of the238Uto234U activity ratio.1.2 This test method was tested successfully wi
4、th reagentwater and drinking water. It is the users responsibility toensure the validity of this test method for waters of untestedmatrices.1.3 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to a
5、ddress 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 specific hazardstatements, see Section 9.2. Refer
6、enced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3648 Practices for the Measurem
7、ent of RadioactivityD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD7282 Practice for Set-up, Calibration, and Quality Controlof Instruments Used for Radioactivity Measurements3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in t
8、his test method, referto Terminology D1129. For terms not included in thisreference, refer to other published glossaries (1).34. Summary of Test Method4.1 This test method is based on solvent extraction technol-ogy to isolate and concentrate uranium in drinking water forcounting via a high-resolutio
9、n alpha-liquid-scintillation spec-trometer.4.2 To determine total uranium, as well as limited isotopicuranium (238U and234U) by activity in drinking water, a200mL acidified water sample is first spiked with232Uasanisotopic tracer, boiled briefly to remove radon, and evaporateduntil less than 50 mL r
10、emain. The solution is then madeapproximately 0.01 M in diethylenetriaminepentaacetic acid(DTPA) and the pH is adjusted to between 2.5 and 3.0. Thesample is transferred to a separatory funnel and equilibratedwith 1.50 mL of an extractive scintillator containing a dialkylphosphoric acid extracting ag
11、ent. Under these conditions onlyuranium is quantitatively transferred to the organic phase whilethe extraction of undesired ions is masked by the presence ofDTPA. Following phase separation, 1.00 mL of the organicphase is sparged with dry argon gas to remove oxygen, achemical quench agent, and count
12、ed on a high-resolutionalpha-liquid-scintillation spectrometer and multichannel ana-lyzer (MCA).4.3 The alpha spectrum of a sample that contains naturaluranium and that is analyzed with an internal232U tracer willappear similar to the spectrum in Fig. 1. An approximateresolution of 250 keV FWHM for2
13、38U (4.2 MeV) allowsresolution and analysis of the238U,234U, and232U energyspectrum peaks when their activities are of the same order ofmagnitude. Resolution of the235U (4.4 MeV) alpha peak is notpossible, but its activity, which accounts for approximately1This test method is under the jurisdiction
14、of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved Jan. 1, 2015. Published January 2015. Originallyapproved in 1998. Last previous edition approved in 2009 as D6239 09. DOI:10.1520/D6239-09R15.2For refe
15、renced 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 boldface numbers in parenthesis refer to the list of references a
16、t the end ofthe text.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 % of the total natural uranium activity, is included in thetotal uranium activity calculated when the238U and234U peaksare in the region of interest (ROI). When
17、the238U and234Upeaks are integrated separately, a portion of the235U activitywill be included in the238U activity and the rest in the234Uactivity, depending on the exact ROIs selected. Likewise, ifpresent,236U and233U will not be resolved by the spectrom-eter; however, their activity will be include
18、d in the totaluranium ROI. Fig. 2 is a flow chart that summarizes the stepsrequired in this test method.5. Significance and Use5.1 This test method is a fast, cost-effective method that canyield limited isotopic activity levels for238U and234U, as wellas total uranium activity. Although232U is incor
19、porated as atracer, uranium recoveries for this test measured during thedevelopmental work on this test method were usually between95 and 105%.5.2 The high-resolution alpha-liquid-scintillation spectrom-eter offers a constant (99.6 6 0.1) % counting efficiency andinstrument backgrounds as low as 0.0
20、01 counts per minute(min1)overa4to7MeVenergy range according toMcDowell and McDowell (2). Count rates for extractivescintillator blanks and reagent blanks usually range from 0.01min1to 0.1 min1.6. Interferences6.1 During the development work on this method, less than1% of241Am,238Pu,210Po,226Ra,222R
21、n, and230Th present inthe original sample were found to extract under the conditionsdescribed for the extraction of uranium by this procedure.Uranium extraction is quantitative at pH values from 1.0 to 5.0but extraction of230Th and238Pu increased slightly at pHvalues below 2.5 and phase separation w
22、as slower and lesscomplete at pH values above 3.5. DTPA concentration is notcritical in the range of 0.001 M to 0.1 M as long as astoichiometric excess relative to the concentration of interfer-ing ions, especially ferric ion (Fe3+), is maintained.As much as30 mg of Fe3+did not interfere with the ex
23、traction of uraniumwhen the DTPA concentration was 0.010 M, and as much as250 mg of Fe3+did not interfere when the DTPAconcentrationwas increased to 0.10 M. As much as 2000 mg of calcium ion(Ca2+) did not present an interference in a 0.010 M DTPAsolution. Sulfate ion (SO42-) did not interfere with t
24、heextraction of uranium at concentrations as high as 1 M, buthydrogen oxalate (HC2O4) concentrations greater than 0.001M and dihydrogen phosphate (H2PO4) concentrations greaterthan 0.2 M resulted in decreased uranium recovery. Theseconcentrations, however, are several orders of magnitudehigher than
25、the normal concentration of these ions in drinkingwater.6.2 Beta- and gamma-emitting radionuclide interference isminimized (typically 99.95 % rejection of beta/gamma pulses)according to McDowell and McDowell (2) by the pulse-shapediscrimination of the high-resolution alpha-liquid-scintillationspectr
26、ometer.6.3 Quenching, often a problem with liquid scintillationcounting, is significantly reduced by the use of extractivescintillator technology and will only result in a normallyinsignificant spectral energy shift with this procedure. No alphacounts will be lost due to quenching.6.4234U and238U ma
27、y exist in the232U tracer. The extent ofthe positive bias should be determined periodically.7. Apparatus7.1 Caps, vinyl or cork for culture tubes.7.2 Funnels, separatory, 125-mL, pear-shaped, polytetra-fluoroethylene or polypropylene.7.3 Meter, pH, with gel electrode or low leak-rate referenceelectr
28、ode.7.4 Multichannel Analyzer (MCA), 512 channels or more,ADC/memory or better.7.5 NIM Bin and Power Supply.7.6 Power Supply, high voltage (+1000 V at 1 mA), orintegral to the spectrometer, see item 7.10.7.7 Sample, counting reference, normal uranium.4Thiscounting reference sample is an approximatel
29、y 50/50 mix of238U and234U by activity in 1.00 mL of the extractivescintillator solution and enclosed in a 10 by 75 mm glassculture tube and is for standardization purposes only.7.8 Source,137Cs, approximately 1.85 105Bq (5 Ci).This item is for standardization purposes only.4The sole source of suppl
30、y of the238U and234U normal uranium countingreference sample known to the committee at this time is from ORDELA, Inc., 1009Alvin Weinberg Drive, Oak Ridge, TN, 37830. If you are aware of alternativesuppliers, please provide this information to ASTM Headquarters. Your commentswill receive careful con
31、sideration at a meeting of the responsible technicalcommittee that you may attend.FIG. 1 Alpha Energy Spectrum of Natural Uranium and232UTracer Measured on a High-Resolution Alpha-Liquid-ScintillationSpectrometerD6239 09 (2015)27.9 Sparging Gas Conditioner5This apparatus providesconditioned argon ga
32、s to remove oxygen, a chemical quenchagent, from the sample, thus improving pulse shape discrimi-nation and energy resolution. It consists of a specially-madeglass tube, partially filled with silicone oil, that serves as apressure-limiter, a gas drying tower filled with CaSO4(6 to 8mesh) for additio
33、nal drying of the argon gas, a gas washingbottle containing toluene and molecular sieve to saturate theargon with toluene and prevent sample evaporation whiledeoxygenating, and plastic tubing of various lengths to serve asconnections between the pieces. The inlet from the compressedargon cylinder is
34、 connected to one side arm of the pressurelimiter; the opposite side arm of the pressure limiter isconnected to the inlet (bottom) of the gas drying tower. Theoutlet (top) of the drying tower is connected to the inlet(dispersion tube) of the gas washing bottle. The outlet of thegas washing bottle is
35、 connected to a disposable Pasteur pipetthat serves as the sparging lance for the sample. For furtherinformation, consult the spectrometer (see 7.10) instructionmanual.7.10 Spectrometer, high-resolution pulse-shape discriminat-ing alpha-liquid-scintillation spectrometer. Typical perfor-mance specifi
36、cations include greater than 99 % alpha counting5The sole source of supply of the sparging gas conditioner known to thecommittee at this time is ORDELA, Inc., 1009 Alvin Weinberg Drive, Oak Ridge,TN, 37830. If you are aware of alternative suppliers, please provide this informationto ASTM Headquarter
37、s. Your comments will receive careful consideration at ameeting of the responsible technical committee that you may attend.FIG. 2 Flow Chart Summary of this Test MethodD6239 09 (2015)3efficiency, 99.95 % beta/gamma rejection, energy resolution of200 to 250 keV FWHM for the 4.78 MeV226Ra spectrum pea
38、kand instrument backgrounds of 0.001 counts per minute over a4 to 7 MeV energy range.67.11 Tubes, 10 by 75 mm borosilicate glass. These tubesserve as sample-counting cells for the spectrometer (see 7.10).8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests
39、. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society(3). Other grades may be used, provided it is first ascertainedthat the reagent is of sufficiently high purity to permit its usew
40、ithout lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type III, or better.8.3 Argon Gas, Compressed99.999 % pure, with two-stage pressure regulator.8.4 Ascorbic
41、Acid Reagent grade, solid ascorbic acid(C6H8O6).8.5 Dialkyl Phosphoric Acid Extractive ScintillatorSeeRef (4).78.6 Diethylenetriaminepentaacetic Acid (DTPA)(0.1 M)Add 3.93 g of solid DTPA (C14H23N3O10) to 50 mL of water.Adjust the pH approximately 7 by the dropwise addition of 6M sodium hydroxide (N
42、aOH) while stirring to completedissolution. Dilute to 100 mL with water.8.7 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).8.8 Molecular SieveType 4A, activated, indicating, 4-8mesh (Na12AlO2)12(SiO2)12xH2O).8.9 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).8.10 Sodium
43、Hydroxide (6 M)Slowly and with coolingadd 240 g sodium hydroxide (NaOH) pellets to 500 mL ofwater and stir to dissolve. Dilute to 1 L with water.8.11 TolueneReagent grade (C6H5CH3).8.12232U Solution, StandardNominally 0.04 Bq/mL ac-tivity and standardized as per Practice D3648.9. Hazards9.1 Use extr
44、eme caution when handling all acids and bases.They are extremely corrosive and skin contact could result insevere burns.9.2 When diluting concentrated acids, always use safetyglasses and protective clothing, and add the acid to the water.9.3 Toluene is flammable.Avoid breathing vapors. Use withadequ
45、ate ventilation and avoid open flames.10. Sampling10.1 Collect the sample in accordance with the applicablemethods as described in Practice D3370.11. Calibration and Standardization11.1 Use a normal uranium counting reference sample (thatconsists of an approximate 50/50 mixture of238U and234U, byact
46、ivity) to establish an initial region of interest (ROI) on themultichannel analyzer (MCA).NOTE 1The actual ROI for any given sample may differ slightly fromthis initial ROI setting depending on the nature of the sample and theextractive scintillator used. This reference sample may be made using thet
47、echniques cited in Burnett and Tai (5). Set the pulse shape discriminator(PSD) of the high-resolution alpha-liquid-scintillation spectrometer priorto counting each individual sample. A 1.85 105Bq (5 microcurie)137Csgamma source may be used to aid in setting the PSD by quickly inducinga beta/gamma pe
48、ak (4). For additional information, refer to the instrumentinstruction manual.NOTE 2Setting the pulse shape discriminator (PSD) is a quick, butcritical procedure. Inaccurate activity determinations will result if the PSDis set improperly.11.2 Areagent blank is prepared without tracer for use in theb
49、ackground subtraction count (BSC). The reagent blank usedfor the BSC must closely match the associated sample testsource configuration to ensure that the measurements used forbackground subtraction accurately reflect conditions whencounting sample test sources. Refer to Practice D7282, Section12.1.3.11.3 For general guidance on calibration andstandardization, refer to Practice D3648.12. ProcedureNOTE 3This procedure applies to analysis of water samples, whetherpreserved with HNO3or HCl or unpreserved.12.1 Measure 200 mL of a water sample into a 400-m
