1、Designation: D1943 05 (Reapproved 2012)Standard Test Method forAlpha Particle Radioactivity of Water1This standard is issued under the fixed designation D1943; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers the measurement of alpha
3、particle activity of water. It is applicable to nuclides that emitalpha particles with energies above 3.9 MeV and at activitylevels above 0.02 Bq/mL (540 pCi/L) of radioactive homoge-neous water. This test method is not applicable to samplescontaining alpha-emitting radionuclides that are volatile u
4、nderconditions of the analysis.1.2 This test method can be used for either absolute orrelative determinations. In tracer work, the results may beexpressed by comparison with a standard that is defined to be100 %. For radioassay, data may be expressed in terms of alphadisintegration rates after calib
5、ration with a suitable standard.General information on radioactivity and measurement ofradiation has been published2and summarized in PracticeD3648.1.3 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 st
6、andard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bi
7、as ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3648 Practices for the Measurement of Radioactivity3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129. For terms not defined inthis tes
8、t method or in Terminology D1129, reference may bemade to other published glossaries.44. Summary of Test Method4.1 The test sample is reduced by evaporation or a suitablechemical method to the minimum weight of material havingmeasurable alpha activity. Alpha radioactivity is measured byan instrument
9、 composed of a detecting device, amplifier, powersupply, and scalerthe most widely used being proportionaland scintillation counters. In the proportional counter, whichmay be of the windowless or thin window type, alpha particlesentering the sensitive region of the detector produce ionizationof the
10、counting gas. The negative ion of the original ion pair isaccelerated towards the anode, producing additional ionizationof the counting gas and developing a voltage pulse at theanode. In the scintillation detector, alpha particles interact withthe material of the phosphor, transferring some of their
11、 energyto electrons. These electrons subsequently lose part of theirenergy by excitation rather than ionization of atoms, and theexcited atoms revert to the ground state by re-emitting energyin the form of light quanta. A suitable light-sensitive device,usually a multiplier phototube, transforms the
12、 resulting flashesof light into voltage impulses. By use of suitable electronicapparatus, the pulse is amplified to a voltage sufficient foroperation of the counting scaler. The number of pulses per unittime is related to the disintegration rate of the test sample. Theefficiency of the system can be
13、 determined by use of a suitablealpha standard having equivalent residual plated solids.5. Significance and Use5.1 This test method was developed for the purpose ofmeasuring gross alpha radioactivity in water. It is used for the1This test method is under the jurisdiction of ASTM Committee D19 on Wat
14、erand is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved June 1, 2012. Published August 2012. Originallyapproved in 1996. Last previous edition approved in 2005 as D1943 05. DOI:10.1520/D1943-05R12.2Friedlander, G., et al., Nuclear and
15、Radiochemistry, 3rd Ed., John Wiley andSons, Inc., New York, NY, 1981.Price, W. J., Nuclear Radiation Detection, 2nd Ed., McGraw-Hill Book Co., Inc.,New York, NY, 1964.Lapp, R. E., and Andrews, H. L., Nuclear Radiation Physics, 4th Ed.,Prentice-Hall Inc., New York, NY, 1972.Overman, R. T., and Clark
16、, H. M., Radioisotope Techniques, McGraw-Hill BookCo., Inc., New York, NY, 1960.3For 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
17、onthe ASTM website.4American National Standard Glossary of Terms in Nuclear Science andTechnology (ANSI N1.1) available from theAmerican National Standards Institute,1430 Broadway, New York, NY 10018.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
18、 United States.analysis of both process and environmental water to determinegross alpha activity which is often a result of natural radioac-tivity present in minerals.6. Measurement Variables6.1 The relatively high absorption of alpha particles in thesample media affects the counting rate of the mea
19、surement.Effects of geometry, back-scatter, source diameter, as well asthe purity, pressure variation, and type of counting gas usedshall also be considered. Thus, for reliable relative measure-ments, the variables shall be held constant while counting alltest samples and standards. For absolute mea
20、surements, appro-priate efficiency factors shall be applied. If a windowlessproportional counter is employed, the sample mount shall beelectrically conducting.6.1.1 In tracer studies or tests requiring only relative mea-surements, in which the data are expressed as being equivalentto a defined stand
21、ard, the above correction factors can besimply combined into a counting efficiency factor. The use ofa counting efficiency factor requires that sample mounting,material of mounting dish, and weight of residue (milligramsper square centimetre), in addition to conditions affecting theabove described f
22、actors, remain constant throughout the dura-tion of the test and that the comparative standard be preparedfor counting in the same manner as the test samples. The datafrom comparative studies between independent laboratorieswhen not expressed in absolute units are more meaningfulwhen expressed as pe
23、rcentage relationships or as equivalent ofa defined standard.6.2 The limit of sensitivity for both scintillation and propor-tional counters is a function of the background counting ratewhich should be as low as is feasible. Massive shielding is notused for alpha counters. The maximum activity for th
24、is testmethod is 1600 Bq.7. Interferences7.1 Solids content in the sample containing the alpha emitterproduces significant losses in sample counting rates of about 10to 15 % loss at 1 mg/cm2. Liquid samples shall be evaporatedto dryness onto dishes that allow the sample to be counteddirectly by the
25、detector. Solids on the dish shall remainconstant in amount between related test samples, and shouldduplicate the density of the solids of the plated standard.7.2 Most alpha counters are insensitive to beta, gamma, andX radiations.28. Apparatus8.1 Alpha Particle Counter, consisting of either a propo
26、r-tional detector or a scintillation detector, and a scaler conform-ing to the following requirements:8.1.1 Proportional DetectorThis may be one of severaltypes commercially available. The material used in the con-struction of the detector should contain a minimal amount ofdetectable radioactivity.
27、To establish freedom from undesirablecharacteristics, the manufacturer shall supply voltage plateauand background counting rate data. Voltage plateau data shallshow the threshold voltage, slope, and length of plateau for aparticular input sensitivity.8.1.2 Scintillation DetectorThis may be one of se
28、veraltypes commercially available. It shall consist of an “activated”zinc sulfide phosphor having a minimum effective diameter of36.5 mm and a superficial density of 10 to 15 mg/cm2. Thephosphor shall be mounted so that it can be attached andoptically coupled to a multiplier phototube. Extraneous li
29、ghtshall be excluded from the phosphor either by its being coveredwith a thin (less than 1 mg/cm2) opaque window or byenclosing the assembly in a lightproof sample changer. Thematerial used in the construction of the detector shall be freefrom detectable radioactivity. To establish freedom from unde
30、-sirable characteristics, the manufacturer shall supply voltageplateau and background counting rate data. Voltage plateaudata shall show the threshold voltage, slope, and length of aplateau for a specified scaler sensitivity.8.1.3 ScalerOften the scaler, mechanical register, powersupply, and amplifi
31、er are contained in a single chassis, gener-ally termed the scaler. The power supply and amplifier sectionsshall be matched with the type of detector to produce satisfac-tory operating characteristics and to provide sufficient range inadjustments to maintain controlled conditions. The manufac-turer
32、shall provide resolving time information for the countingsystem. The scaler shall have capacity for storing and visuallydisplaying at least 106counts with a resolving time no greaterthan 5 s. The instrument shall have an adjustable inputsensitivity that can be matched to the detector and a variableh
33、igh voltage power supply with indicating meter.8.2 Sample Mounting DishDishes having a flat bottom ofa diameter slightly less than the inside diameter of the detector.Flat dishes are preferred, but dishes may be used that have3.2-mm high side walls with the angle between dish bottomand side equal to
34、 or greater than 120. Dishes shall be of amaterial that will not corrode under the plating conditions andshall be of uniform surface density; platinum and stainless steelhave been used for this purpose.9. Reagents9.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwi
35、se indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purit
36、y and free from radioactivity to precludedetrimental effects. Some chemicals, even of high purity,contain naturally occurring radioactive elements, for example,uranium, actinium, and thorium. Consequently, when carrierchemicals are used in the analysis of low-radioactivitysamples, the radioactivity
37、of the carriers shall be determinedunder identical analytical conditions of the sample includingresidual dish solids. The radioactivity of the reagents shall beconsidered as background and subtracted from the test samplecounting rate.5Reagent Chemicals, American Chemical Society Specifications, Amer
38、icanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (US
39、PC), Rockville,MD.D1943 05 (2012)29.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type HI.9.3 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).9.4 Nitric Acid (1 + 30)Mix 1 volume of concentratedHNO3(
40、sp gr 1.42) with 30 volumes of water.9.5 Alpha-Emitting Radioactive Standard Solution (;200Bq/mL), traceable to the National Institute of Standards andTechnology (NIST).10. Sampling10.1 Collect the sample in accordance with PracticesD3370.10.2 Preserve the sample in a radioactive homogeneousstate. A
41、 sample shall be made radioactive homogeneous byaddition of a reagent in which the radionuclides or compoundsof the radionuclides present would be soluble in large concen-trations. Addition of acids, complexing agents, or stablechemically similar carriers may be used to obtain homogeneity.Considerat
42、ion of the chemical nature of the radionuclides andcompounds present and the subsequent chemistry of themethod shall indicate the action to be taken.11. Establishing Gas Proportional Counter OperatingPlateau11.1 Put the instrument into operation according to themanufacturers instructions. Place a qu
43、ality control (QC)source in the detector, set the sensitivity control near itsmaximum and turn the “count” switch to “count” position.Slowly increase the high voltage until the first counts areobserved and record the “threshold” voltage. Advance thevoltage in increments of convenient magnitude (appr
44、oximately25 V) and determine the counting rate at four or more settingsof the sensitivity control at each voltage setting. Measure thebackground counting rate at each of the settings using an emptysample mounting dish in place of the standard.11.1.1 The QC source may be any available alpha-emittingr
45、adionuclide having a half life sufficiently long to eliminatedecay corrections. Knowledge of its true disintegration rate isnot essential. The radionuclide shall be permanently fixed tothe dish and uniformly distributed over an area preferablysmaller than the dish bottom; electro-deposition and flam
46、ing ofa salt-flee solution are the two methods most generally used.Quality control sources are commercially available.11.2 Plot the gross counting rate of the standard against thevoltage. The counting rate should rise initially as the voltage isincreased, then, for at least some of the settings of t
47、hesensitivity control, reach an approximate constant value, andfinally rise again. The“ plateau” of the curve should be at least100Vin length and have a slope less than 2 %/100V; however,shorter plateaus or one with greater slope shall be acceptable ifa well regulated high voltage power supply is av
48、ailable.11.3 Plot the ratio of the square of the net counting rate ofthe standard to the background counting rate against thevoltage for each of the settings of the sensitivity control.11.4 Determine the optimum conditions for operation of theinstrument by selecting values for the high-voltage and s
49、ensi-tivity adjustments that correspond to some point lying on theplateau of the counting-rate-versus-voltage plot and near themaximum value of the ratio of the sample-squared-to-background counting rates.12. Control of Instrument Operation12.1 Tolerance or statistical control charts are used to assurethat the instrument is operating to within pre-specified limits ofthe initial calibration. Repetitive measurements of a qualitycontrol source are taken to develop the tolerance or statisticalcontrol chart. The QC source is then used on a daily orprior-to-use basis to ensur
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