1、Designation: D7362 14Standard Guide forRapid Screening of Vegetation for Radioactive StrontiumAerial Deposition1This standard is issued under the fixed designation D7362; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 ofradioac
3、tive 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 fixedlabora
4、tory 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 eve
5、nt. 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 This
6、 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 Documents
7、2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD3648 Practices for the Measurement of Radioactivity2.2 Other Documents:EPA Protective Action Guidelines33. Terminology3.1 DefinitionsSee Terminology D1129 for terms relatedto water.3.2 Definitions of Terms S
8、pecific to This Standard:3.2.1 ROI, nregion of interest; the span of channels, orregion, in the spectrum in which the counts due to a specificradioisotope appear on a functioning, calibrated liquid scintil-lation spectrometry system.3.3 Acronyms:3.3.1 RLS, nrapid liquid sampler3.3.2 SPE, nsolid phas
9、e extraction4. 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. Theradiostrontium is then extracted onto a solid phase extraction(SPE) disk for counting and quantific
10、ation.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 usingliquid scintillation spectrometry.4.4 Quantification may also be accomplished using a simpleg
11、as-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 is a major component of nuclear waste andis also a potential radioisotope for use as a we
12、apon of massdestruction in a radiological dispersal device. It is a beta-emitting radioisotope with moderate half-life (30 years).1This guide is under the jurisdiction of ASTM Committee D19 on Water and isthe direct responsibility of Subcommittee D19.04 on Methods of RadiochemicalAnalysis.Current ed
13、ition approved Nov. 1, 2014. Published November 2014. Originallyapproved in 2007. Last previous edition approved in 2007 as D7362 07. DOI:10.1520/D7362-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
14、Standards volume information, 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.Copyright ASTM International, 100 Barr Harbor Drive,
15、 PO Box C700, West Conshohocken, PA 19428-2959. United States1Strontium-89 is also a beta emitting radionuclide, but with ahalf-life of only 50 days it is not usually present in significantquantities. If ingested the radiostrontium may deposit in thebone of an individual and thus can contribute a si
16、gnificantradiological dose to an affected person.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 p
17、rocedure by 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 ch
18、emicals are 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) countin
19、g is the preferredmethod 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 contamina
20、nts.6.2 Lead 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 s
21、pec-trum may 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 protecti
22、ve equip-ment 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 RTGexplosion), as opposed to particles with radiostrontium ad-
23、sorbed on the surface, may not be sufficiently attacked by theweak acid solution and so will not be detected by thisprocedure. However, particles containing90Sr would only beexpected to be encountered very close to the site of the initialexplosion.7. InstrumentationNOTE 1See Practices D3648 for a de
24、scription of these detectorsystems.7.1 Liquid Scintillation SpectrometerCommercial systemsare 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 th
25、e SPE disk. The spectrometershould 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 r
26、adiation detector, 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 tha
27、tall reagents shall 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
28、1193.8.3 Solid Phase Extraction (SPE) Disk47 mm in diameter,impregnated with strontium selective resin,5supplied as eitherloose 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, mixingan
29、d monitoring the 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
30、Scintillation (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
31、 a national standards 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
32、.2 Device for measuring or delivering approximately50-mL aliquots of acidified water.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
33、 LaboratoryChemicals, 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
34、disk 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.D7362 1429.3 60-
35、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 required if using disks in the 47-mm filterholder).9.6 Liquid scintillation cou
36、nting 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 resealable plastic bags (that is, bagswith a zipper-locking seal) or pouches made from thin alumi-num foil to prevent the spread of contam
37、ination when countingthe SPE disks.9.8 pH-indicating 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 RO
38、Is for the determination of90Sr are 2500 keV and5002000 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 counte
39、d using the appropriate ROIs.10.1.1.2 To determine the counting efficiency for90Sr onthe SPE disk a known amount of90Sr, in equilibrium with90Y,is added 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
40、be used or a vacuumfiltration apparatus may be used). 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 rat
41、io of the net counts per minute (cpm) inthe90Sr ROI to the known activity added (in decays perminute, dpm) is the fractional detection efficiency (): 5Rs2 RbAs(1)where:Rs= gross count rate in90Sr ROI (in cpm),Rb= background count rate in90Sr ROI (in cpm), andAs= spike activity added (in dpm).10.1.1.
42、4 Prepare at least three calibration disks and use 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
43、count rate (in cpm) to the knownspike addition (in 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 ve
44、getation should be collected from an areaknown to 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 amou
45、nt of90Sr spike solution is dispenseddirectly onto 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 effici
46、ency, to theknown spike addition (in dpm) is an indication of the fractionalchemical recovery (Y):Y 5Rs2 Rb 3AsY(2)where:Rs= gross count rate in90Sr ROI (in cpm),Rb= background count rate in90Sr ROI (in cpm), = counting efficiency (calculated in Eq 1), andAsY= spike activity added (in dpm).10.2.6 Se
47、veral spiked samples should be completed in thelaboratory 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
48、; trynot to dislodge any dust off the leaves while collecting 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 P
49、lace the vegetation in a wide-mouth 12 L plasticbottle. 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 as much of the leafy material as possible.Shake for at least 3 min.6Beals, D.M., Hofstetter, K.J., Johnson, V.G., Patton, G.W., Seely, D.C.,“Development of field portable sampling and an
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