1、Designation: D 1890 05Standard Test Method forBeta Particle Radioactivity of Water1This standard is issued under the fixed designation D 1890; 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 p
2、arentheses 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 beta par-ticle activi
3、ty 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 under con-ditions o
4、f 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 radionuclides of
5、 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 D 3648.1.3 This standard does not purport to ad
6、dress 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:3D 1129 Termi
7、nology Relating to WaterD 1193 Specification 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 Con-duitsD 3648 Practice for the Measurement of Radioactivity3. Terminology3.1 Definitio
8、ns 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 beta-particle em
9、itter 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 sample and re
10、agents 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 particles emitted by a
11、source 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 dispersed throughout
12、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 replaced by mock sam
13、ple salts or by reagentchemicals used for chemical separations that contain noanalyte.1This 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 Jan. 1, 2005. Publish
14、ed January 2005. Originallyapproved in 1961. Last previous edition approved in 1996 as D 1890 96.2Friedlander, 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, 19
15、64.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, McGraw-Hill BookCo., Inc., New York, NY, 1960.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
16、Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, 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.NOTE 3Reagent background varies
17、 with the reagent chemicals andanalytical methods used and may vary with reagents from differentmanufacturers and from different processing lots.3.2 DefinitionsFor terms not defined in this test method orin Terminology D 1129, reference may be made to otherpublished glossaries.44. Summary of Test Me
18、thod4.1 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 encountered (0.1 to1300 counts per se
19、conds), 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 evaporation techniques.Beta particles e
20、ntering 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 suitable electronicapparatus, the pu
21、lse 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 having the same radionuclide com-positio
22、n 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 radioactivity in water. It is used forthe
23、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 in an interplay of manyvariables whic
24、h 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, backscatter radiation, sourcediameter, sel
25、f-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 corrected for back-ground,Bqb= disin
26、tegrations 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 absorption in theair and window of e
27、xternal 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 of absorber,faw= ex, where = absorpti
28、on 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= factor to correct for the absorption and
29、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 per second, andr = instrument resolvin
30、g time in seconds. Generally,the sample size or source to detector distance isvaried to obtain a counting rate that precludescoincident losses. Information on the effect of ran-dom disintegration and instrument resolving time onthe sample count rate as well as methods fordetermining the resolving ti
31、me of the countingsystem may be found in 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 of detection for each sample residualw
32、eight 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 correction factors can besimply combined into a
33、 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 factors, remain con-stant throughout
34、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 as percentage relation-ships or as th
35、e 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.4American National Standard Glossary of Terms in Nuclear Science andTechnology (ANSI N1.1).D 1890
36、 0526.2 The limit of sensitivity for both Geiger-Muller andproportional counters is a function of the background countingrate. Massive shielding or anti-coincidence detectors andcircuitry, or both, are generally used to reduce the backgroundcounting rate to increase the sensitivity.7. Interferences7
37、.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 allow the sample to be counted directlyby the
38、 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 solids of the plated standard.7.2 Most beta
39、 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 where appropriate absorbers can beused to evalua
40、te 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 commercially available detectortypes. The m
41、aterial 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 characteristics, the manu-facturer shall su
42、pply 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 (aluminum or plastic) and positioned sothe center
43、 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 with such factors as activity level,source siz
44、e, 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 to 100 mm from tube flange.8.1.2 Detector S
45、hieldThe 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 has a door orport for inserting or removing sp
46、ecimens. 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 the beta particlesscattered from the walls of
47、 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,power supply, and amplifier are contained i
48、n 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 controlledconditions. The manufacturer shall pro
49、vide 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 having a flat bottom of a diameter no greater t
