1、Designation: D 7362 07Standard Guide forRapid Screening of Vegetation for Radioactive StrontiumAerial Deposition1This standard is issued under the fixed designation D 7362; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. 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 guide provides a rapid procedure by which vegeta-tion samples may be screened for surface contamination ofradi
3、oactive strontium (89Sr and90Sr, collectively referred to asradiostrontium) following an airborne radioactive dispersalevent. It provides a conservative estimate of radiostrontiumdeposition that can be used by decision makers for immediateactions prior to obtaining definitive results from a fixedlab
4、oratory asset.1.2 Insoluble forms of radiostrontium, such as the strontium(90Sr) titanate (SrTiO3) used in radio-isotope thermal-electricgenerators (RTGs), will not be measured by this method.1.3 Non-SI units are used in the calculations of this guidefor ease of use during the emergency phase of an
5、event. Theinstrumentation used typically provides count rates in countsper minute (cpm) rather than per second (s1, the SI unit), thusactivity is expressed in dpm (decays per minute) rather thanBq. Additionally, US EPA protective guidelines for surfacecontamination are expressed in dpm/100 cm2.1.4 T
6、his 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Docume
7、nts2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 3648 Practices for the Measurement of Radioactivity2.2 Other Documents:EPA Protective Action Guidelines33. Terminology3.1 Definitions:3.1.1 ROIregion of interest; the span of channels, orregion, in the spectrum in which the counts due to
8、 a specificradioisotope appear on a functioning, calibrated liquid scintil-lation spectrometry system.4. Summary of Guide4.1 Vegetation is collected from an area equivalent to 100cm2. The leafy material is shaken with pH = 2 water tosolubilize radiostrontium deposited on the vegetation. Theradiostro
9、ntium is then extracted onto a solid phase extraction(SPE) disk for counting and quantification.4.2 Testing has shown that chemical recoveries for90Srunder these extraction conditions average 3050 %, withsimilar recoveries expected for89Sr.4.3 A counting efficiency of 8085 % can be achieved usingliq
10、uid scintillation spectrometry.4.4 Quantification may also be accomplished using a simplegas-filled count rate meter (a “pancake probe”); however thepresence of other beta-emitting radionuclides can not bediscerned when using such a non-discriminatory detector.5. Significance and Use5.1 Strontium-90
11、 is a major component of nuclear waste andis also a potential radioisotope for use as a weapon of massdestruction in a radiological dispersal device. It is a beta-emitting radioisotope with moderate half-life (30 years).Strontium-89 is also a beta emitting radionuclide, but with ahalf-life of only 5
12、0 days it is not usually present in significantquantities. If ingested the radiostrontium may deposit in thebone of an individual and thus can contribute a significantradiological dose to an affected person.1This guide is under the jurisdiction of ASTM Committee D19 on Water and isthe direct respons
13、ibility of Subcommittee D19.04 on Methods of RadiochemicalAnalysis.Current edition approved June 15, 2007. Published August 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informati
14、on, refer to the standards Document Summary page onthe ASTM website.3Available from United States Environmental Protection Agency (EPA), ArielRios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, http:/www.epa.gov.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consho
15、hocken, PA 19428-2959, United States.5.2 Following an explosion in which radioactive materialwas present, the potential exists for the material to becomeairborne. It will quickly attach to atmospheric particles and bedeposited on surfaces as the plume passes. This guide providesa rapid procedure by
16、which vegetation can be screened todetermine if radiostrontium is present and to provide a conser-vative estimate of its deposition on vegetation.5.3 This guide is intended to be used in a field portable lab,or if needed, can be performed completely in the field;therefore no hazardous chemicals are
17、required to complete theanalysis. However, an option for the use of acid in certain stepsis documented in this guide.5.4 This guide is not intended to be used for screening foodproducts or animal feed following an accident or incident.6. Interferences6.1 Liquid scintillation (LS) counting is the pre
18、ferredmethod of counting. Because this is a screening method,chemical decontamination from other beta-emitting isotopes isnot as rigorous as found in traditional laboratory methods.Careful evaluation of the liquid scintillation spectrum mayprovide indications of the presence of contaminants.6.2 Lead
19、 and radium are known to also be retained by theSPE disk under these extraction conditions and do occurnaturally as part of fallout deposition, although at low concen-trations compared to the radiostrontium surface contaminationof concern. Careful evaluation of the liquid scintillation spec-trum may
20、 provide indications of the presence of alpha peaks(Ra isotopes) or other beta continuums (Pb or other isotopes).6.3 Yttrium-90, the daughter of90Sr and also a beta emitter,will be partially retained by the SPE disk using this method. Ifpermissible, and with appropriate personal protective equip-men
21、t and engineering controls, the SPE disk can be washedwith 1520 mL of 2-3 M nitric acid. Note the time the washfinished going through the SPE disk as the start time for90Yingrowth.6.4 Particles containing90Sr (such as from an RTG explo-sion), as opposed to particles with radiostrontium adsorbed onth
22、e surface, may not be sufficiently attacked by the weak acidsolution and so will not be detected by this procedure.However, particles containing90Sr would only be expected tobe encountered very close to the site of the initial explosion.7. InstrumentationNOTE 1See D 3648 for a description of these d
23、etector systems.7.1 Liquid Scintillation SpectrometerCommercial sys-tems are available that are reasonably portable, but may requiremanual sample changing. The system should have a stablebackground in the counting region of interest and reproducibledetection efficiency for90Sr on the SPE disk. The s
24、pectrometershould allow the option of looking at the entire countingspectrum so that evaluation of other interferences may becompleted. Automatic discrimination of alpha and beta par-ticles is desirable but not required.7.2 Gas Filled Count Rate MeterA non-discriminatingbeta/gamma radiation detector
25、, often called a “pancake probe,”consisting of a gas-filled detector coupled to an electronicspackage that provides count rate information.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents sha
26、ll conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.48.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type I water as defined inSpecification D 1193.8.3 Solid P
27、hase Extraction (SPE) Disk47 mm in diam-eter, impregnated with strontium selective resin,5supplied aseither loose SPE disks or in the Rapid Liquid Sampler (RLS)housing.8.4 pH = 2 WaterWater acidified to a pH of 2 with nitricacid. Concentrated nitric acid may be added dropwise, mixingand monitoring t
28、he pH of the water until it begins to approach24, then carefully add a more dilute nitric solution (12 M)until a pH of 2 is obtained. If the pH is overshot, add a diluteNa2CO3, NaHCO3or NaOH solution to a final pH of 2.8.5 Nitric Acid(HNO3) concentrated and diluted solution.8.6 Liquid Scintillation
29、(LS) CocktailAny commercialcocktail that provides acceptable counting efficiency and back-grounds in the ROI for89+90Sr, many are deemed environmen-tally friendly thus do not require disposal as a mixed waste.8.7 Strontium-90 Calibration SolutionA solution whoseactivity is traceable to a national st
30、andards body, such as NISTor NPL, in dilute nitric acid. Alternatively,89Sr may be usedbut the known activity must be decay corrected to the time ofuse.9. Apparatus9.1 Wide mouth plastic bottle, 12 L preferred or 12 qtresealable plastic bags (that is, bags with a zipper-locking seal).9.2 Device for
31、measuring or delivering approximately50-mL aliquots of acidified water.9.3 60-mL syringe, disposable, plastic.9.4 47-mm filter holder with Leur-Lock fitting (not requiredif the SPE disks are packaged in the RLS housing).9.5 Tin snips or wire cutters used to open the RLS housingof the SPE disk (not r
32、equired if using disks in the 47-mm filterholder).9.6 Liquid scintillation counting vials (glass or plastic),20-mL, or as appropriate for the detector to be used.9.7 Sample holder for the SPE disks for counting bygas-filled detector: small plastic bags with a zip-lock seal orpouches made from thin a
33、luminum foil to prevent the spread ofcontamination when counting the SPE disks.4Reagent 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 Labo
34、ratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5The sole source of supply of the apparatus known to the committee at this timeis trademark Strontium Empore solid phase extraction disk
35、or equivalent, 3MCompany, St. Paul, MN, http:/. If you are aware of alternativesuppliers, please provide this information to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.D73620729.8 pH-indica
36、ting test strips (to include a range of 18) orcalibrated pH meter.10. Calibration and Standardization10.1 Detector Effciency:10.1.1 The liquid scintillation (LS) spectrometry systemshould be calibrated for background and detection efficiency.Typical ROIs for the determination of90Sr are 2500 keV and
37、5002000 keV. The90Sr will be in the lower window; indica-tions of90Y will be seen as counts in the higher energywindow.10.1.1.1 The background count rate is determined by plac-ing a blank Strontium SPE disk in a LS counting vial withcocktail and counted using the appropriate ROIs.10.1.1.2 To determi
38、ne the counting efficiency for90Sr on theSPE disk a known amount of90Sr, in equilibrium with90Y, isadded to 50 mL of DI water and the pH adjusted to 2 asdescribed in 8.4. The solution is poured through a SPE disk (forcalibration the syringe method may be used or a vacuumfiltration apparatus may be u
39、sed). The disk is placed in a LScounting vial with cocktail and counted using the preset ROIs.NOTE 2The waste solution can be saved, reduced in volume andcounted by LSC to confirm quantitative recovery of the90Sr on thecalibration disk.10.1.1.3 The ratio of the net counts per minute (cpm) inthe90Sr
40、ROI to the known activity added (in decays perminute, dpm) is the fractional detection efficiency (e):e5Rs RbAse(1)where:Rs= gross count rate in90Sr ROI (in cpm),Rb= background count rate in90Sr ROI (in cpm),Ase= spike activity added (in dpm).10.1.1.4 Prepare at least three calibration disks and use
41、 theaverage in all subsequent calculations.10.1.2 If a gas-filled detector is to be used for the fieldscreening analyses, the counting efficiency may be determinedby counting the disk prepared above with the appropriatedetector. The ratio of the net count rate (in cpm) to the knownspike addition (in
42、 dpm) is an indication of counting efficiency(see Eq 1).610.2 Chemical Recovery:10.2.1 Because the samples are analyzed with no yieldmonitor, an average chemical recovery is determined in the laband applied to the rapid field analyses.10.2.2 Leafy vegetation should be collected from an areaknown to
43、contain no radioactive contamination. It should be acommon variety so that it will be applicable to emergencyresponse actions.10.2.3 An amount of vegetation equivalent to 100 cm2collection area is placed in a plastic bottle or bag.10.2.4 A known amount of90Sr spike solution is dispenseddirectly onto
44、 the vegetation in the bottle and then the extractionprocedure, below, is followed.10.2.5 The samples are counted on either the LS system orusing the gas-filled detector. The ratio of the measured netcount rate (in cpm), corrected for counting efficiency, to theknown spike addition (in dpm) is an in
45、dication of the fractionalchemical recovery (Y).Y 5Rs Rbe3AsY(2)where:Rs= gross count rate in90Sr ROI (in cpm),Rb= background count rate in90Sr ROI (in cpm),e = counting efficiency (calculated in Eq 1),AsY= spike activity added (in dpm).10.2.6 Several spiked samples should be completed in thelaborat
46、ory to obtain an average chemical yield for fieldanalyses.11. Procedure11.1 Collect vegetation from an area of concern, preferablyleafy material out in the open. Vegetation should be collectedfrom an area roughly equivalent to 100 cm2. Use gloves; trynot to dislodge any dust off the leaves while col
47、lecting as muchof the vegetation as possible from the sampling area. Stems andother material close to the ground that may not have depositiondo not need to be collected. A pair of grass clippers may beuseful to aid in collecting the sample.11.2 Place the vegetation in a wide-mouth 12 L plasticbottle
48、. The bottle should be no more than about 1025 % full.Alternatively, the sample could be placed ina1or2-qtresealable plastic bag (that is, a bag with zipper-lockingclosure).11.3 Add approximately 50 mL of pH = 2 water.11.4 Cap and shake the bottle. Make sure the acidic solutioncomes in contact with
49、as much of the leafy material as possible.Shake for at least 3 min.11.5 Place a 60-mL syringe on a SPE disk holder (either theRLS format or 47-mm filter holder with Luer-Lock fittingscontaining the disk). Pull the plunger out of the syringe.11.6 Decant the water from the sample bottle into thesyringe. Replace the plunger and push the solution through theSPE disk. Collect the waste in a container designated for waste.11.7 Remove the syringe from the SPE disk holder and pullthe plunger out then reattach the syringe to the SPE disk holderwithout t
