1、Designation: D 6239 03Standard Test Method forUranium in Drinking Water by High-Resolution Alpha-Liquid-Scintillation Spectrometry1This standard is issued under the fixed designation D 6239; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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 test method covers determining the total solubleuranium activity in drinking water in the ra
3、nge 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 with reagentwater
4、 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 address all of t
5、hesafety 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. Referenced Documents
6、2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specifications for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 3648 Practices for the Measurement of Radioac
7、tivity3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminology D 1129. For terms not included in this refer-ence, refer to other published glossaries (1)34. Summary of Test Method4.1 This test method is based on solvent extraction technol-ogy to isol
8、ate and concentrate uranium in drinking water forcounting via a high-resolution 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
9、 tracer, boiled briefly to remove radon, and evaporateduntil less than 50 mL remain. 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 o
10、f an extractive scintillator containing a dialkylphosphoric acid extracting agent. 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
11、sparged with dry argon gas to remove oxygen, achemical quench agent, and counted 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 si
12、milar to the spectrum in Fig. 1. An approximateresolution of 250 keV FWHM for238U (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
13、, which accounts for approximately2.2 % of the total natural uranium activity, is included in thetotal uranium activity calculated when the238U and234U peaksare in the region of interest (ROI). When the238U and234Upeaks are integrated separately, a portion of the235U activity1This test method is und
14、er the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved June 10, 2003. Published August 2003. Originallyapproved in 1998. Last previous edition approved in 2002 as D 623902.2For reference
15、d 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 at the
16、 end ofthe text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.will 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
17、spectrometer;however, their activity will be included in the total uraniumROI.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 incorporated as atracer, uraniu
18、m 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 0.001 counts per minute(cpm) ov
19、er a 4 to 7 MeV energy range according to McDowelland McDowell (2). Count rates for extractive scintillatorblanks and reagent blanks usually range from 0.01 cpm to 0.1cpm.6. Interferences6.1 During the development work on this method, less than1% of241Am,238Pu,210Po,226Ra,222Rn, and230Th present int
20、he 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 was slower and lesscompl
21、ete 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 extraction of uraniumwhen
22、 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 the extrac-tion of urani
23、um at concentrations as high as 1 M, but hydrogenoxalate (HC2O4) concentrations greater than 0.001 M anddihydrogen phosphate (H2PO4) concentrations greater than0.2 M resulted in decreased uranium recovery. These concen-trations, however, are several orders of magnitude higher thanthe normal concentr
24、ation of these ions in drinking water.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-scintillationspectrometer.6.3 Quenchi
25、ng, 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 may exist in the232U
26、 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, polytet-rafluoroethylene or polypropylene.7.3 Meter, pH, with gel electrode or low leak-rate referenceelectrode.7.4 Multichanne
27、l Analyzer (MCA), 512 channels or more,ADC/memory or better.7.5 NIM Bin and Power Supply.7.6 Power Supply, high voltage (+1000 volt 1 ma), orintegral to the spectrometer, see item 7.10.7.7 Sample, counting reference, normal uranium.4Thiscounting reference sample is an approximately 50/50 mix of238U
28、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 3 105Bq (5 micro-curies). This item is for standardization purposes only.7.9 Sparging Gas Conditioner5Th
29、is apparatus providesconditioned argon gas 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
30、filled with CaSO4(6 to 8mesh) for additional 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 as4The sole source of supply of the238U
31、 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 consideration a
32、t a meeting of the responsible technicalcommittee that you may attend.5The 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 informat
33、ionto ASTM Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee that you may attend.FIG. 1 Alpha Energy Spectrum of Natural Uranium and232UTracer Measured on a High-Resolution Alpha-Liquid-ScintillationSpectrometerD6239032connections betwe
34、en the pieces. The inlet from the compressedargon cylinder is 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 t
35、he gas washing bottle. The outlet of thegas washing bottle is 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-li
36、quid-scintillation spectrometer. Typical perfor-mance specifications include greater than 99 % alpha countingefficiency, 99.95 % beta/gamma rejection, energy resolution of200 to 250 keV FWHM for the 4.78 MeV226Ra spectrum peakand instrument backgrounds of 0.001 counts per minute over a4 to 7 MeV ene
37、rgy 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. Unless otherwise indicated, it is intended thatall reagents shall conform
38、 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 usewithout lessening the accuracy of the determination.8.2 Purity of WaterUnles
39、s otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type III, or better.8.3 Argon Gas, Compressed99.999 % pure, with two-stage pressure regulator.8.4 Ascorbic AcidReagent grade, solid ascorbic acid(C6H8O6).8.5 Dialkyl Phosphoric Acid
40、 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 (NaOH) while stirring to completedissolution. Dilute to 100 mL with water.8.7
41、 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 Hydroxide (6 M)Slowly and with coolingadd 240 g sodium hydroxide (NaOH) pel
42、lets 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 D 3648.9. Hazards9.1 Use extreme caution when handling all acids and bases.They are extremely corrosive
43、 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 withadequate ventilation and avoid open flames.10. Sampling10.1 Collect the sample
44、in accordance with the applicablemethods as described in Practice D 3370.11. Calibration and Standardization11.1 Use a normal uranium counting reference sample (thatconsists of an approximate 50/50 mixture of238U and234U, byactivity) to establish an initial region of interest (ROI) on themultichanne
45、l 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 thetechniques cited in Burnett and Tai (5). Set the pulse shape discriminator
46、(PSD) of the high-resolution alpha-liquid-scintillation spectrometer priorto counting each individual sample.A1.85 3 105Bq (5 microcurie)137Csgamma source may be used to aid in setting the PSD by quickly inducinga beta/gamma peak (4). For additional information, refer to the instrumentinstruction ma
47、nual.NOTE 2Setting the pulse shape discriminator (PSD) is a quick, butcritical procedure. Inaccurate activity determinations will result if the PSDis set improperly.11.2 A reagent blank, without tracer, must be made inexactly the same way as the sample determination.11.3 For general guidance on cali
48、bration and standardiza-tion, refer to Practice D 3648.12. 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-mLborosilicate glass beaker.12.2 Acidify the sample with 0.5 mL of concentra
49、ted nitricacid (HNO3) and 0.5 mL of concentrated hydrochloric acid(HCl).12.3 Add an accurately measured activity (depending on theexpected uranium activity of the sample) of232U tracersolution.NOTE 4It is recommended that the tracer activity corresponds roughly(0.75 to 1.25 times the expected234U activity) to the234U activity so as tominimize uncertainties in determining the integral peak areas. If theapproximate level of uranium activity in the sample is not known it maybe estimated by the following simple screening technique: Add 40 mL ofthe water sample to
