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2、n American National StandardStandard Test Method forAlpha-Particle-Emitting Isotopes of Radium in Water1This standard is issued under the fixed designation D 2460; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
3、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the separation of dissolved radium from water for the purpose of measuring its radioac- tivity. Alth
4、ough all radium isotopes are separated, the test method is limited to alpha-particle-emitting isotopes by choice of radiation detector. The most important of these radioisotopes are radium-223, radium-224, and radium-226. The lower limit of concentration to which this test method is applicable is 3.
5、73 102 Bq/L (1 pCi/L).1.2 This test method may be used for absolute measure- ments by calibrating with a suitable alpha-emitting radioiso- tope such as radium-226, or for relative methods by comparing measurements with each other. Mixtures of radium isotopes may be reported as equivalent radium-226.
6、 Information is also provided from which the relative contributions of radium isotopes may be calculated.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety
7、and health practices and determine the applica- bility of regulatory limitations prior to use. For a specific precautionary statement, see Section 9.2. Referenced Documents2.1 ASTM Standards:C 859 Terminology Relating to Nuclear Materials2D 1129 Terminology Relating to Water3D 1193 Specification for
8、 Reagent Water3D 1943 Test Method for Alpha Particle Radioactivity ofWater4D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D-19 on Water3D 3370 Practices for Sampling Water3D 3454 Test Method for Radium-226 in Water4D 3648 Practices for the Measurement of Ra
9、dioactivity41 This test method is under the jurisdiction of ASTM Committee D-19 on Water and is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemi- cal Analysis.Current edition approved Aug 10, 1997. Published October 1997. Originally issued 1966. Replaces D 246066 T. Last pre
10、vious edition D 246090.2 Annual Book of ASTM Standards, Vol 12.01.3 Annual Book of ASTM Standards, Vol 11.01.4 Annual Book of ASTM Standards, Vol 11.02.3. Terminology3.1 Definition:3.1.1 For definitions of terms used in this standard, see Terminology C 859 and D 1129. For terms not included in these
11、, reference may be made to other published glossaries (1,2).54. Summary of Test Method4.1 Radium is collected from the water by coprecipitation with mixed barium and lead sulfates. The barium and lead carriers are added to a solution containing alkaline citrate ion which prevents precipitation until
12、 interchange has taken place. Sulfuric acid is then used to precipitate the sulfates, which are purified by nitric acid washes. The precipitate is dissolved in ammoniacal EDTA. The barium and radium sulfates are reprecipitated by the addition of acetic acid, thereby separating them from lead and oth
13、er radionuclides. The precipitate is dried on a planchet weighed to determine the chemical yield, and alpha-counted to determine the total disintegration rate of alpha-particle-emitting radium isotopes. This procedure is based upon published ones (3, 4).5. Significance and Use5.1 Radium is one of th
14、e most radiotoxic elements. Its isotope of mass 226 is the most hazardous because of its long half-life. The isotopes 223 and 224, although not as hazardous, are of some concern in appraising the quality of water.5.2 The alpha-particle-emitting isotopes of radium other than that of mass 226 may be d
15、etermined by difference if radium-226 is measured separately, such as by Test Method D 3454. Note that one finds radium-226 and -223 together in variable proportions (5, 6), but radium-224 does not normally occur with them. Thus, radium-223 often may be determined by simply subtracting the radium-22
16、6 content from the total: and if radium-226 and -223 are low, radium-224 may be determined directly. The determination of a single isotope in a mixture is less precise than if it occurred alone.5 The boldface numbers in parentheses refer to a list of references at the end of this standard.Copyright
17、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1D 2460 97 6. Interferences6.1 A barium content in the sample exceeding 0.2 mg will cause a falsely high chemical yield.7. Apparatus7.1 For suitable gas-flow proportional or alpha-scintillation co
18、unting equipment, refer to Test Method D 1943.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Commit- tee on Analytical Reagents of the American Chemical Socie
19、ty, where such specifications are available.6 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the precision, or increasing the bias, of the determination.8.2 Purity of WaterUnless otherwise indicated, refe
20、rences to water shall be understood to mean reagent water conforming to Specification D 1193, Type III.8.3 Radioactivity Purity Of Reagentsshall be such that the measured results of blank samples do not exceed the calculated probable error of the measurement or are within the desired precision.8.4 A
21、cetic Acid, Glacial (sp gr 1.05).8.5 Ammonium Hydroxide (sp gr 0.90)Concentrated am- monium hydroxide (NH4OH).8.6 Ammonium Hydroxide (1+1) Mix 1 volume of concen- trated ammonium hydroxide (NH4OH, sp gr 0.90) with 1 volume of water.8.7 Barium Nitrate Carrier Solution (10 mg Ba/mL) Dissolve 1.90 g of
22、 barium nitrate (Ba(NO3)2) in water and dilute to 100 mL.8.8 Citric Acid Solution (350 g/L)Dissolve 350 g of citric acid (anhydrous) in water and dilute to 1 L.8.9 Disodium Ethylendiamine Tetraacetate Solution (93 g/L)Dissolve 93 g of disodium ethylenediamine tetraacetate dihydrate in water and dilu
23、te to 1 L.8.10 Lead Nitrate Carrier Solution (104 mg Pb/mL) Dissolve 33.2 g of lead nitrate (Pb(NO3)2) in water and dilute to 200 mL.8.11 Methyl Orange Indicator SolutionDissolve 1.0 g of methyl orange in water and dilute to 1 L.8.12 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).8.13 Sulfur
24、ic Acid (1 + 1)Cautiously add with stirring 1volume of concentrated sulfuric acid (H2SO4, sp gr 1.84) to 1volume of water.9. Safety Precautions9.1 When diluting concentrated acids, always use safety glasses and protective clothing, and add the acid to the water.6 Reagent Chemicals, American Chemical
25、 Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of Reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDN Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Ph
26、armacuetical Convention, Inc. (USPC), Rockville, MD.TABLE 1 Growth of Alpha Activity into Initially Pure Radium-226Time, hCorrection, F01.000011.016021.036331.058041.079851.102161.1238241.4892481.9054722.252510. Sampling10.1 Collect the sample in accordance with PracticesD 3370 as applicable.10.2 Sa
27、mple 1 L, or a smaller volume, provided that it is estimated to contain from 3.7 to 370 Bq (100 to 10 00 pCi) of radium. Add 10 mL of HNO3/L of sample.11. Calibration and Standardization11.1 For absolute counting, the alpha-particle detector must be calibrated to obtain the ratio of count rate to di
28、sintegration rate. Use NIST traceable radium-226 standards. Analyze two or more portions of such solution, containing known disintegra- tion rates, in accordance with Section 12. After counting, correct the measured activity for chemical yield, and calculate the efficiency, E (see Section 13), as th
29、e ratio of the observed counting rate to the known disintegration rate.12. Procedure12.1 Add to a measured volume of sample 5 mL of citric acid and make alkaline (pH 7.0) with NH4OH. Confirm the alkalinity with pH-indicating paper or strip. Add 2 mL of lead carrier and 1.00 mL of barium carrier, and
30、 mix.12.2 Heat to boiling and add 10 drops of methyl orange pH-indicator solution. With stirring, add H2SO4 (1 + 1) until the solution becomes pink, then add 5 drops more.12.3 Digest the precipitate with continued heating for 10 min. Let cool and collect the precipitate in a centrifuge tube. When la
31、rge volumes are handled, collection will be facilitated by first letting the precipitate settle, and then decanting most of the clear liquid. Centrifuge then discard the supernatant liquid.12.4 Wash the precipitate with 10 mL of HNO3, centrifuge, and discard the washings. Repeat this wash the precip
32、itate.12.5 Dissolve the precipitate in 10 mL of water, 10 mL of EDTA solution, and 4 mL of NH4OH (1 + 1). Warm if necessary to effect dissolution.12.6 Reprecipitate barium sulfate (BaSO4) by the dropwise addition of acetic acid, then add 3 drops more. Record the time. Centrifuge, then discard the su
33、pernatant liquid. Add 10 mL of water, mix well, centrifuge, and discard the supernatant liquid.12.7 Clean, flame, cool, and weigh a stainless steel planchet that fits the alpha-particle counter being used. Transfer the precipitate to the planchet with a minimum of water. Dry, flame, and weigh the pr
34、ecipitate to determine the chemical yield.12.8 Promptly count the planchet in an appropriate alpha- particle counter, recording the time. Reserve the planchet for additional measurements, if desired (see 13.4).2D 2460 97 where:C = alpha counting rate, net counts/s, (sample counts/sminus background c
35、ounts/s)E = detection efficiency of the counter for alpha particles,counts/disintegration,V = sample volume, LY = fractional chemical yield for the separation, andF = correction for the ingrowth of descendents between thetime of separation (see 12.6 and Table 1) and the time of counting.13.3 See sec
36、tion 10 of Practices D 3648 concerning the overall uncertainty in a measurement.13.4 The total propagated uncertainty (1 s) for the concen- tration of alpha-emitting radium isotopes is calculated as follows:22sD Bq!/L 5 DBq/L! * sN/N! 1 sE/E! 122 1 / 2where:sv/V! 1 sy/Y! #(3)NOTE 1Vertical scale is
37、ratio of radioactivity, a, at later time, t, toradioactivity at initial time of separation. T is half-life.sN = one sigma uncertainty of the net sample countingrate,sE = one sigma uncertainty of the detection efficiency of the alpha counter,sV = one sigma uncertainty of the sample volume, andsY= one
38、 sigma uncertainty in the fractional radium recov-ery.13.4.1 The one sigma uncertainty (sN) in the net sample counting rate is calculated from:FIG. 1 Growth and Decay of Alpha Activity into Initially Pure22 1 / 2Radium Isotopeswhere:sN 5 G/TG 1 B/tB !1(4)12.9 Measure the background count rate of the
39、 detector byG = the sample gross counting rate, (s1) (5 )B= the background counting rate, (s1) (5 ),counting an empty, cleaned and flamed planchet for at least aslong as the precipitate was counted.13. Calculation13.1 Calculate the fractional radium recovery (chemicaltG = the sample counting time, s
40、, andtB = the background counting time, s.13.5 The a priori minimum detectable concentration(MDC) is calculated as follows:1 / 2yield of the carrier) as follows:Y 5 MB MP! / 0.01699(1)where:2.71 1 4.65 * tG * B!MDC Bq/L! 5 t * E * Y * V * I(5)where:MB= mass of planchet with the dried barium sulfate
41、precipitate, g,MP= mass of planchet only, g, and0.01699 = mass of barium sulfate precipitate if all of theadded barium carrier were recovered, g.13.2 Calculate the concentration D of alpha-emitting radium radionuclides as radium-226 in becquerels (Bq) of radium per litre as follows:D 5 C/EVYF(2)tG =
42、 the counting duration, s, and other terms are as definedearlier.13.6 The relative contribution of various radium isotopes, if desired, may be obtained by alpha-particle spectroscopy (7). Otherwise, repeated measurements of the activity permit esti- mation of the isotopic composition. Table 2 lists
43、radioactive properties of radium-226, radium-224, radium-223, and their descendents (8). Fig. 1 shows characteristic growth and decay curves for the three important isotopes, and equations and tables have been published (9).3D 2460 97 TABLE 2 Important Alpha-Particle-Emitting Isotopes of Radium and
44、their DescendentsANuclideRadiationParentDescendentsTypeBEnergy, MeVC226Raa4.784 (94.5 %)1.60 3 103 years4.601 (5.5 %)222Rna5.490 (99.9 %)3.83 days218Poa6.003 (100.0 %)3.11 min214Pbb (g)27 min214Bib (g)19.9 min214Po7.687 (99.9 %)1.64 3 104 s224Raa5.686 (95.1 %)3.66 days5.449 (4.9 %)220Rna6.288 (99.9
45、%)55.6 s216Poa6.779 (100.0 %)0.15 s212Pob (g)10.6 h212Bib (64.1 %) (g)1.01 ha (35.9 %)6.090 (9.6 %)6.051 (25.2 %)others212Poa8.7840.30 s208Tib (g)3.05 min223Raa (g)5.716 (52.5 %)11.4 days5.607 (24.2 %)5.747 (9.5 %)5.540 (9.2 %)others219Rna (g)6.819 (81 %)3.96 s6.553 (12 %)6.425 (7.5 %)215Poa7.386 (100.0 %)1.8 ms211Pbb (g)36.1 min211Bia (g)6.623 (83.8 %)2.14 min6.279 (16.0 % )207Tib4.77 minADescendents with half-lives of less than 30 days.BGamma ray indicated only when emission probability per decay is more than 5 % and energy is greater than 0.1 MeV.C
