ASTM D1890-2005(2012) Standard Test Method for Beta Particle Radioactivity of Water&thinsp 《水的β粒子放射性的标准试验方法》.pdf

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1、Designation: D1890 05 (Reapproved 2012)Standard Test Method forBeta Particle Radioactivity of Water1This standard is issued under the fixed designation D1890; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio

2、n. 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 beta p

3、ar-ticle activity of water. It is applicable to beta emitters havingmaximum energies above 0.1 MeV and at activity levels above0.02 Bq/mL(540 pCi/L) of radioactive homogeneous water formost counting systems. This test method is not applicable tosamples containing radionuclides that are volatile unde

4、r con-ditions 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 which is defined to be100 %. For radioassay, data may be expressed in terms of aknown radionuclide standard if the r

5、adionuclides of concernare known and no fractionation occurred during processing, ormay be expressed arbitrarily in terms of some other standardsuch as137Cs. General information on radioactivity and mea-surement of radiation may be found in the literature2andPractice D3648.1.3 This standard does not

6、 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 prior to use.2. Referenced Documents2.1 ASTM Standards

7、:3D1129 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 Measurement of Radioactivity3. Terminolog

8、y3.1 Definitions of Terms Specific to This Standard:3.1.1 Becquerela unit of radioactivity equivalent to 1nuclear transformation per second.3.1.2 beta energy, maximumthe maximum energy of thebeta-particle energy spectrum produced during beta decay of agiven radioactive species.NOTE 1Since a given be

9、ta-particle emitter may decay to severaldifferent quantum states of the product nucleus, more than one maximumenergy may be listed for a given radioactive species.3.1.3 counter backgroundin the measurement of radioac-tivity, the counting rate resulting from factors other than theradioactivity of the

10、 sample and reagents used.NOTE 2Counter background varies with the location, shielding of thedetector, and the electronics; it includes cosmic rays, contaminatingradioactivity and electrical noise.3.1.4 counter beta-particle effciencyin the measurementof radioactivity, that fraction of beta particle

11、s emitted by asource which is detected by the counter.3.1.5 counter effciencyin the measurement of radioactiv-ity, that fraction of the disintegrations occurring in a sourcewhich is detected by the counter.3.1.6 radioactive homogeneous waterwater in which theradioactive material is uniformly dispers

12、ed throughout thevolume of water sample and remains so until the measurementis completed or until the sample is evaporated or precipitatingreagents are added to the sample.3.1.7 reagent backgroundin the measurement of radioac-tivity of water samples, the counting rate observed when asample is replac

13、ed by mock sample salts or by reagentchemicals used for chemical separations that contain noanalyte.NOTE 3Reagent background varies with the reagent chemicals andanalytical methods used and may vary with reagents from differentmanufacturers and from different processing lots.1This 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 1, 2012. Published August 2012. Originallyapproved in 1961. Last previous edition approved in 2005 as D1890 05. DOI:10.1520/D1

15、890-05R12.2Friedlander, G., et al., Nuclear and 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 In

16、c., New York, NY, 1972.Overman, R. T., and Clark, 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 informatio

17、n, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 DefinitionsFor terms not defined in this test method orin Terminology D1129, reference may be made to otherpublish

18、ed glossaries.44. Summary of Test Method4.1 Beta radioactivity may be measured by one of severaltypes of instruments composed of a detecting device andcombined amplifier, power supply, and scalerthe mostwidely used being proportional or Geiger-Mller counters.Where a wide range of counting rates is e

19、ncountered (0.1 to1300 counts per seconds), the proportional-type counter ispreferable due to a shorter resolving time and greater stabilityof the instrument. The test sample is reduced to the minimumweight of solid material having measurable beta activity byprecipitation, ion exchange resin, or eva

20、poration techniques.Beta particles entering the sensitive region of the detectorproduce ionization of the counting gas. The negative ion of theoriginal ion pair is accelerated towards the anode, producingadditional ionization of the counting gas and developing avoltage pulse at the anode. By use of

21、suitable electronicapparatus, the pulse is amplified to a voltage sufficient foroperation of the counter scaler. The number of pulses per unitof time is related to the disintegration rate of the test sample.The beta-particle efficiency of the system can be determined byuse of prepared standards havi

22、ng the same radionuclide com-position as the test specimen and equivalent residual platedsolids. An arbitrary efficiency factor can be defined in terms ofsome other standard such as cesium-137.5. Significance and Use5.1 This test method was developed for the purpose ofmeasuring the gross beta radioa

23、ctivity in water. It is used forthe analysis of both process and environmental water todetermine gross beta activity.6. Measurement Variables6.1 The relatively high absorption of beta particles in thesample media and any material interposed between source andsensitive volume of the counter results i

24、n an interplay of manyvariables which affect the counting rate of the measurement.Thus, for reliable relative measurements, hold all variablesconstant while counting all test samples and standards. Forabsolute measurements, appropriate correction factors are ap-plied. The effects of geometry, backsc

25、atter radiation, sourcediameter, self-scatter and self-absorption, absorption in air anddetector window for external counters, and counting coinci-dence losses have been discussed2and may be described bythe following relation:cps 5 BqbGp!fbs!faw!fd!fssa!fc! (1)where:cps = recorded counts per second

26、corrected for back-ground,Bqb= disintegrations per second yielding beta particles,Gp= point source geometry (defined by the solid anglesubtended by the sensitive area of the detector),fbs= backscatter factor or ratio of cps with backing to cpswithout backing,faw= factor to correct for losses due to

27、absorption in theair and window of external detectors. It is equal tothe ratio of the actual counting rate to that whichwould be obtained if there were no absorption by theair and window between the source and sensitivevolume of the detector. Expressed in terms ofabsorption coefficient and density o

28、f absorber,faw= ex, where = absorption coefficient, insquare centimetres per milligram, and x = absorberdensity in milligrams per square centimetre.fd= factor to correct a spread source counting rate to thecounting rate of the same activity as a point sourceon the same axis of the system,fssa= facto

29、r to correct for the absorption and scatter of betaparticles within the material accompanying the ra-dioactive element, andfc= factor for coincident events to correct the countingrate for instrument resolving time losses and definedby the simplified equation, fc=1nr, where,n = the observed counts pe

30、r second, and r = instru-ment resolving time in seconds. Generally, thesample size or source to detector distance is varied toobtain a counting rate that precludes coincidentlosses. Information on the effect of random disinte-gration and instrument resolving time on the samplecount rate as well as m

31、ethods for determining theresolving time of the counting system may be foundin the literature.For most applications, a detector system is calibrated using asingle beta emitting radionuclide and an efficiency of detection,fo, response curve generated for various sample residueweights. The efficiency

32、of detection for each sample residualweight incorporates all the factors mentioned above so that:fo5 cps/Bq 5 Gp!fbs!faw!fd!fssa!fc! (2)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 correctio

33、n factors can besimply combined into a counting efficiency factor. The use ofa counting efficiency factor requires that sample mounting,density of mounting dish, weight of residue in milligrams persquare centimetre, and radionuclide composition, in addition toconditions affecting the above described

34、 factors, remain con-stant throughout the duration of the test and that the compara-tive standard be prepared for counting in the same manner asthe test samples. The data from comparative studies betweenindependent laboratories, when not expressed in absolute units,are more meaningful when expressed

35、 as percentage relation-ships or as the equivalent of a defined standard. Expressing thedata in either of these two ways minimizes the differences incounters and other equipment and in techniques used by thelaboratories conducting the tests.6.2 The limit of sensitivity for both Geiger-Muller andprop

36、ortional counters is a function of the background countingrate. Massive shielding or anti-coincidence detectors and4American National Standard Glossary of Terms in Nuclear Science andTechnology (ANSI N1.1).D1890 05 (2012)2circuitry, or both, are generally used to reduce the backgroundcounting rate t

37、o increase the sensitivity.7. Interferences7.1 Material interposed between the test sample and theinstrument detector, as well as increasing density in the samplecontaining the beta emitter, produces significant losses insample counting rates. Liquid samples are evaporated todryness in dishes that a

38、llow the sample to be counted directlyby the detector. Since the absorption of beta particles in thesample solids increases with increasing density and variesinversely with the maximum beta energy, plated solids shallremain constant between related test samples and shouldduplicate the density of the

39、 solids of the plated standard.7.2 Most beta radiation counters are sensitive to alpha,gamma, and X-ray radiations, with the degree of efficiencydependent upon the type of detector.2The effect of interferingradiations on the beta counting rate is more easily evaluatedwith external-type counters wher

40、e appropriate absorbers can beused to evaluate the effects of interfering radiation.8. Apparatus8.1 Beta Particle Counter, consisting of the followingcomponents:8.1.1 DetectorThe end-window Geiger-Muller tube andthe internal or external sample gas-flow proportional chambersare the two most prevalent

41、 commercially available detectortypes. The material used in the construction of the detectorshould be free from detectable radioactivity. When detectorscontain windows, the manufacturer shall supply the windowdensity expressed in milligrams per square centimetre. Toestablish freedom from undesirable

42、 characteristics, the manu-facturer shall supply voltage plateau and background countingrate data. Voltage plateau data shall show the threshold voltage,slope, and length of plateau. Detectors requiring externalpositioning of the test sample are mounted on a tube support oflow-density material (alum

43、inum or plastic) and positioned sothe center of the window is directly above the center of the testsample. The distance between the detector window and testsample plays an important part in determining the geometry ofthe system and can be varied for external counters to corre-spond more favorably wi

44、th such factors as activity level,source size, sensitivity requirements, energy of beta particles,etc. A convenient arrangement is to combine the tube mountwith a sample holder containing slots for positioning thesample at three or four distances from the detector window,varying from approximately 5

45、 to 100 mm from tube flange.8.1.2 Detector ShieldThe detector assembly is sur-rounded by an external radiation shield of massive metalequivalent to approximately 51 mm of lead and lined with3.2-mm thick aluminum. The material of construction shouldbe free from detectable radioactivity. The shield ha

46、s a door orport for inserting or removing specimens. Detectors havingother than completely opaque windows are light sensitive. Thedesign of the shield and its openings shall eliminate direct lightpaths to the detector window; beveling of door and opening isgenerally satisfactory. The percentage of t

47、he beta particlesscattered from the walls of the shield into the detector can bereduced by increasing the internal diameter of the shield. Theuse of a detector without a shield will significantly increase thebackground and the detection capability.8.1.3 ScalerNormally the scaler, mechanical register

48、,power supply, and amplifier are contained in a single chassis,generally termed the scaler. The power supply and amplifiersections are matched by the manufacturer with the type ofdetector to produce satisfactory operating characteristics and toprovide sufficient range in adjustments to maintain cont

49、rolledconditions. The manufacturer shall provide resolving timeinformation for the counting system. The scaler shall havecapacity for storing and visually displaying at least 106countsand with a resolving time no greater than 250 s for use withGeiger Muller detectors or 5 s for use with proportionaldetectors. The instrument shall have an adjustable input sensi-tivity matched and set by the manufacturer to that of thedetector, and a variable high-voltage power supply with indi-cating meter.8.2 Sample MountingSample mounting shall utilizedishes ha