ASTM D6239-2003e1 459 Standard Test Method for Uranium in Drinking Water by High-Resolution Alpha-Liquid-Scintillation Spectrometry.pdf

1、Designation: D 6239 03e1Standard 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

2、revision, 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.e1NOTEAdded research report reference to Section 14 editorially in March 2008.1. Scope1.1 This test method

3、covers determining the total solubleuranium activity in drinking 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 the238Uto23

4、4U activity ratio.1.2 This test method was tested successfully with 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 parenthese

5、s are for informationonly.1.4 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 pr

6、ior to use. For specific hazardstatements, see Section 9.2. Referenced Documents2.1 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 Sa

7、mpling Water from Closed ConduitsD 3648 Practices for the Measurement of Radioactivity3. 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 Te

8、st Method4.1 This test method is based on solvent extraction technol-ogy to isolate 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 dr

9、inking water, a200mL acidified water sample is first spiked with232Uasanisotopic 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

10、. Thesample is transferred to a separatory funnel and equilibratedwith 1.50 mL of 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

11、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 counted on a high-resolutionalpha-liquid-scintillation spectrometer and multichannel ana-lyzer (MCA).4.3 The alpha spectrum of a sample that contai

12、ns naturaluranium and that is analyzed with an internal232U tracer willappear similar 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 ofmagnit

13、ude. Resolution of the235U (4.4 MeV) alpha peak is notpossible, but its activity, 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

14、are integrated separately, a portion of the235U activity1This test method is under 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. Originallyapp

15、roved in 1998. Last previous edition approved in 2002 as D 623902.2For 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 web

16、site.3The boldface numbers in parenthesis refer to the list of references at the 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 ex

17、act ROIs selected. Likewise, ifpresent,236U and233U will not be resolved by the 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, a

18、s wellas total uranium activity. Although232U is incorporated 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 % countin

19、g efficiency andinstrument backgrounds as low as 0.001 counts per minute(cpm) over 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 o

20、n this method, less than1% of241Am,238Pu,210Po,226Ra,222Rn, 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 increa

21、sed slightly at pHvalues below 2.5 and phase separation was 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 mainta

22、ined.As much as30 mg of Fe3+did not interfere with the extraction 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 D

23、TPAsolution. Sulfate ion (SO42-) did not interfere with the extrac-tion of uranium 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-t

24、rations, however, are several orders of magnitude higher thanthe normal concentration 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-shapediscrimi

25、nation of the high-resolution alpha-liquid-scintillationspectrometer.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. N

26、o alphacounts will be lost due to quenching.6.4234U and238U may 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, polytet-rafluoroethylene or polypropylene.7.3 M

27、eter, pH, with gel electrode or low leak-rate referenceelectrode.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 volt 1 ma), orintegral to the spectrometer, see item 7.10.7.7 Sample, counting reference, nor

28、mal uranium.4Thiscounting reference sample is an approximately 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 3 105Bq (5 micro-curies)

29、. This item is for standardization purposes only.7.9 Sparging Gas Conditioner5This 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

30、 filled with silicone oil, that serves as apressure-limiter, a gas drying tower 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 pl

31、astic tubing of various lengths to serve as4The sole source of supply 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 inf

32、ormation to ASTM Headquarters. Your commentswill receive careful consideration at 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

33、, 37830. If you are aware of alternative suppliers, please provide this informationto 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

34、 High-Resolution Alpha-Liquid-ScintillationSpectrometerD623903e12connections between 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. T

35、heoutlet (top) of the drying tower is connected to the inlet(dispersion tube) of the 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) instruc

36、tionmanual.7.10 Spectrometer, high-resolution pulse-shape discriminat-ing alpha-liquid-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 spect

37、rum peakand 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 al

38、l 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 Society(3). Other grades may be used, provided it is first ascertainedthat the reagent is of sufficiently high purity to permit i

39、ts usewithout lessening the accuracy of the determination.8.2 Purity of WaterUnless 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 A

40、scorbic AcidReagent 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 hydro

41、xide (NaOH) 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

42、Sodium 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 D 3648.9. Hazards9.1

43、Use extreme 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 w

44、ithadequate ventilation and avoid open flames.10. Sampling10.1 Collect the sample 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 and23

45、4U, byactivity) 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 u

46、sing thetechniques 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.A1.85 3 105Bq (5 microcurie)137Csgamma source may be used to aid in setting the PSD by quickly inducinga beta

47、/gamma peak (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 A reagent blank, without tracer, must be made in

48、exactly the same way as the sample determination.11.3 For general guidance on calibration 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

49、a 400-mLborosilicate glass beaker.12.2 Acidify the sample with 0.5 mL of concentrated 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 esti