1、Designation: D 1943 05Standard Test Method forAlpha Particle Radioactivity of Water1This standard is issued under the fixed designation D 1943; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 alphaparticle activi
3、ty 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 underconditions
4、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 calibration with a s
5、uitable standard.General information on radioactivity and measurement ofradiation has been published2and summarized in PracticeD 3648.1.3 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 standard to esta
6、blish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplic
7、able Methods of Committee D-19 on WaterD 3370 Practices for Sampling Water from Closed Con-duitsD 3648 Practice for the Measurement of Radioactivity3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129. For terms not defined inthis test method or
8、in Terminology D 1129, 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 composed o
9、f 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 counting ga
10、s. 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 energyto e
11、lectrons. 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 resulting
12、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 determined
13、 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 Waterand is th
14、e direct responsibility of Subcommittee D19.04 on Methods of Radiochemi-cal Analysis.Current edition approved Dec. 1, 2005. Published December 2005. Originallyapproved in 1996. Last previous edition approved in 1996 as D 1943 96.2Friedlander, G., et al., Nuclear and Radiochemistry, 3rd Ed., John Wil
15、ey 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, H. M., Radioisotope Techniques,
16、 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 onthe ASTM website.4American Nati
17、onal 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, United States.analysis of both p
18、rocess 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 measurement.Effects of geometry, bac
19、k-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 measurements, appro-priate efficienc
20、y 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 standard, the above correction factors
21、 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 factors, remain constant throughou
22、t 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 percentage relationships or as equi
23、valent 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 this testmethod is 1600 Bq.7. Inter
24、ferences7.1 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 detector. Solids on the dish shal
25、l 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 propor-tional detector or a scintillat
26、ion 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. To establish freedom from undesir
27、ablecharacteristics, 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 severaltypes commercially available
28、. 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 lightshall be excluded from the pho
29、sphor 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-sirable characteristics, the man
30、ufacturer 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 amplifier are contained in a single chas
31、sis, 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 shall provide resolving time info
32、rmation 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 variablehigh voltage power supply with ind
33、icating 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 or greater than 120. Dishes shal
34、l 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 otherwise indicated, it is intended that
35、all 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 purity and free from radioactivity to
36、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 of the carriers shall be determin
37、edunder identical analytical conditions of the sample including5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals,
38、BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D 1943 052residual dish solids. The radioactivity of the reagents shall beconsidered as background and subtracted from the test samplecounting rate.9.2 P
39、urity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, 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(sp gr 1.42) with 30 volumes of water.9
40、.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 PracticesD 3370.10.2 Preserve the sample in a radioactive homogeneousstate. A sample shall be made radioactive hom
41、ogeneous 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.Consideration of the chemical nature of the rad
42、ionuclides 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 quality control (QC)source in the detec
43、tor, 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 (approximately25 V) and determine the coun
44、ting 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-emittingradionuclide having a half life suffic
45、iently 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 flaming ofa salt-flee solution are the tw
46、o 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 thesensitivity control, reach an appro
47、ximate 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 available.11.3 Plot the ratio of the sq
48、uare 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 sensi-tivity adjustments that correspo
49、nd 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 ensure proper operation. Refer to PracticeD
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