1、ISO/ASTM 51956:2013(E)An American National StandardStandard Practice forUse of a Thermoluminescence-Dosimetry System (TLDSystem) for Radiation Processing1This standard is issued under the fixed designation ISO/ASTM 51956; the number immediately following the designation indicates theyear of original
2、 adoption or, in the case of revision, the year of last revision.1. Scope1.1 This practice covers procedures for the use of thermolu-minescence dosimeters (TLDs) to measure the absorbed dosein materials irradiated by photons or electrons in terms ofabsorbed dose to water. Thermoluminescence-dosimetr
3、y sys-tems (TLD systems) are generally used as routine dosimetrysystems.1.2 The thermoluminescence dosimeter (TLD) is classifiedas a type II dosimeter on the basis of the complex effect ofinfluence quantities on the dosimeter response. See ISO/ASTMPractice 52628.1.3 This document is one of a set of
4、standards that providesrecommendations for properly implementing dosimetry inradiation processing, and describes a means of achievingcompliance with the requirements of ISO/ASTM 52628 “Prac-tice for Dosimetry in Radiation Processing” for a TLD system.It is intended to be read in conjunction with ISO
5、/ASTM 52628.1.4 This practice covers the use of TLD systems under thefollowing conditions:1.4.1 The absorbed-dose range is from 1 Gy to 10 kGy.1.4.2 The absorbed-dose rate is between110-2and11010Gy s-1.1.4.3 The radiation-energy range for photons and electronsis from 0.1 to 50 MeV.1.5 This practice
6、does not cover measurements of absorbeddose in materials subjected to neutron irradiation.1.6 This practice does not cover procedures for the use ofTLDs for determining absorbed dose in radiation-hardnesstesting of electronic devices. Procedures for the use of TLDsfor radiation-hardness testing are
7、given in ASTM PracticeE668.1.7 This 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 p
8、rior to use.2. Referenced documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE666 Practice for Calculating Absorbed Dose From Gammaor X RadiationE668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining AbsorbedDose in Radia
9、tion-Hardness Testing of Electronic Devices2.2 ISO/ASTM Standards:251261 Practice for Calibration of Routine Dosimetry Sys-tems for Radiation Processing51608 Practice for Dosimetry in an X-Ray (Bremsstrahlung)Facility for Radiation Processing51649 Practice for Dosimetry in an Electron-Beam Facilityf
10、or Radiation Processing at Energies Between 300 keVand 25 MeV51702 Practice for Dosimetry in Gamma Irradiation Facili-ties for Radiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing51939 Practice for Blood Irradiation Dosimetry51940 Guide for Dosimetry for
11、Sterile Insect Release Pro-grams52628 Practice for Dosimetry in Radiation Processing52701 Guide for Performance Characterization of Dosim-eters and Dosimetry Systems for Use in Radiation Pro-cessing2.3 Joint Committee for Guides in Metrology (JCGM)Reports:JCGM 100:2008, GUM 1995, with minor correcti
12、ons,Evaluation of measurement dataGuide to the Expres-sion of Uncertainty in Measurement31This practice is under the jurisdiction of ASTM Committee E61 on RadiationProcessing and is the direct responsibility of Subcommittee E61.02 on DosimetrySystems, and is also under the jurisdiction of ISO/TC 85/
13、WG 3.Current edition approved Aug. 1, 2013. Published November 2013. Originallypublished as ASTM E 195698. The present International Standard ISO/ASTM51956:2013(E) is a major revision of the last previous edition ISO/ASTM51956:2005(E).2For referenced ASTM and ISO/ASTM standards, visit the ASTM websi
14、te,www.astm.org, or contact ASTM Customer Service at serviceastm.org. ForAnnual Book of ASTM Standards volume information, refer to the standardsDocument Summary page on the ASTM website.3Document produced by Working Group 1 of the Joint Committee for Guides inMetrology (JCGM/WG 1). Available free o
15、f charge at the BIPM website (http:/www.bipm.org. ISO/ASTM International 2013 All rights reserved1JCGM 200:2008, VIM, International Vocabulary ofMetrologyBasis and general concepts and associatedterms42.4 ISO Standard:ISO 10012 Measurement Management SystemsRequirements for Measurement Processes and
16、 MeasuringEquipment52.5 International Commission on Radiation Units and Mea-surements (ICRU) Report:ICRU Report 85a Fundamental Quantities and Units forIonizing Radiation63. Terminology3.1 Definitions:3.1.1 annealingthermal treatment of a TLD prior to irra-diation or prior to readout.3.1.1.1 Discuss
17、ionPre-irradiation annealing of TLDs isusually done to erase the effects of previous irradiation and toreadjust the sensitivity of the phosphor; pre-readout annealingusually is done to reduce low-temperature TLD response.3.1.2 calibrationset of operations that establish, underspecified conditions, t
18、he relationship between values of quan-tities indicated by a measuring instrument or measuringsystem, or values represented by a material measure or areference material, and the corresponding values realized bystandards.3.1.2.1 DiscussionCalibration conditions include environ-mental and irradiation
19、conditions present during irradiation,storage and measurement of the dosimeters that are used for thegeneration of a calibration curve. To achieve stable environ-mental conditions, it may be necessary to condition thedosimeters before performing the calibration procedure.3.1.3 calibration curveexpre
20、ssion of the relation betweenindication and corresponding measured quantity value. (VIM)3.1.4 charged-particle equilibriumcondition in which thekinetic energy of charged particles (or electrons), excludingrest mass, entering an infinitesimal volume of the irradiatedmaterial equals the kinetic energy
21、 of charge particles (orelectrons) emerging from it.3.1.4.1 DiscussionWhen electrons are the predominantcharged particles, the term “electron equilibrium” is often usedto describe charged-particle equilibrium.3.1.5 dosimeter batchquantity of dosimeters made from aspecific mass of material with unifo
22、rm composition, fabricatedin a single production run under controlled, consistentconditions, and having a unique identification code.3.1.6 dosimeter stockpart of a dosimeter batch held by theuser.3.1.7 dosimetry systemsystem used for measuring ab-sorbed dose, consisting of dosimeters, measurement in
23、stru-ments and their associated reference standards, and proceduresfor the systems use.3.1.8 electron equilibriumcharged-particle equilibriumfor electrons. See charged-particle equilibrium.3.1.9 measurement management systemset of interrelatedor interacting elements necessary to achieve metrological
24、confirmation and continual control of measurement processes.(ISO 10012)3.1.10 quality assuranceall systematic actions necessaryto provide adequate confidence that a calibration,measurement, or process is performed to a predefined level ofquality.3.1.11 reference standard dosimetry systemdosimetrysys
25、tem, generally having the highest metrological qualityavailable at a given location or in a given organization, fromwhich measurements made there are derived.3.1.12 routine dosimetry systemdosimetry system cali-brated against a reference standard dosimetry system and usedfor routine absorbed dose me
26、asurements, including dose map-ping and process monitoring.3.1.13 thermoluminescence dosimeter (TLD)TLphosphor, alone or incorporated in a material, used for deter-mining the absorbed dose to materials.3.1.13.1 DiscussionFor example, the TL phosphor issometimes incorporated in a TFE-fluorocarbon mat
27、rix.3.1.14 thermoluminescence dosimeter reader (TLDreader)instrument used to measure the light emitted from aTLD consisting essentially of a heating element, a light-measuring device, and appropriate electronics.3.1.15 thermoluminescence dosimeter response (TLDresponse)light emitted by the TLD and r
28、ead out during itsheating cycle consisting of one of the following: (a) the totallight output over the entire heating cycle, (b) a part of that totallight output, or (c) the peak amplitude of the light output.3.1.16 thermoluminescence phosphor (TL phosphor)material that stores, upon irradiation, a f
29、raction of its absorbeddose in various excited energy states and when thermallystimulated, it emits this stored energy as ultraviolet, visible,and infrared lights.3.1.17 TLD preparationprocedure of cleaning, annealing,and encapsulating the TL phosphor prior to irradiation.3.2 Definitions of other te
30、rms used in this standard thatpertain to radiation measurement and dosimetry may be foundin ASTM Terminology E170. Definitions in ASTM Terminol-ogy E170 are compatible with ICRU Report 85a; thatdocument, therefore, may be used as an alternative reference.4. Significance and use4.1 In radiation proce
31、ssing, TLDs are mainly used in theirradiation of blood products (see ISO/ASTM Practice 51939)and insects for sterile insect release programs (see ISO/ASTMGuide 51940). TLDs may also be used in other radiationprocessing applications such as the sterilization of medical4Document produced by Working Gr
32、oup 2 of the Joint Committee for Guides inMetrology (JCGM/WG 2). Available free of charge at the BIPM website (http:/www.bipm.org.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.6Available from International Commission on
33、 Radiation Units andMeasurements, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA.ISO/ASTM 51956:2013(E)2 ISO/ASTM International 2013 All rights reservedproducts, food irradiation, modification of polymers, irradia-tion of electronic devices, and curing of inks, coatings andadhesives. (See IS
34、O/ASTM Practices 51608, 51649, and51702.)4.2 For radiation processing, the absorbed-dose range ofinterest is from 1 Gy to 100 kGy. Some TLDs can be used inapplications requiring much lower absorbed doses (forexample, for personnel dosimetry), but such applications areoutside the scope of this practi
35、ce. Examples of TLDs andapplicable dose ranges are given in Table 1. Information onvarious types of TLDs and their applications can be found inRefs (1-10).75. Overview5.1 During the irradiation of certain crystalline materials,for example, LiF, CaF2, CaSO4,Li2B4O7, andAl2O3, the fillingof electron a
36、nd hole traps between the ground state and theconduction band results in stored energy that can be released asluminescence during subsequent heating.TLD systems providea means of determining absorbed dose to materials by measur-ing this luminescence by the controlled heating of the irradi-ated cryst
37、alline material. The amount of luminescence emittedby the TL phosphor upon heating can be directly related toabsorbed dose by a calibration.5.2 TLDs can be reused by subjecting the irradiated TLDsto an annealing process at a higher temperature to release allthe electron and hole traps.6. Influence q
38、uantities6.1 Factors other than absorbed dose which influence thedosimeter response are referred to as influence quantities andare discussed in the following sections. Examples of suchfactors are temperature, relative humidity, light and dose rate(see ISO/ASTM Guide 52701). See Refs (1-10) for examp
39、lesof the types and magnitudes of the effects for different TLDs.6.2 Pre-Irradiation Conditions:6.2.1 Dosimeter PackagingThe TLD response is not usu-ally influenced by the water content, so the TLDs are notusually supplied in vapor tight pouches. They may be suppliedin light tight pouches to minimiz
40、e the effect of light.6.2.2 Time Since ManufactureThere is no known influ-ence of time since manufacture on TLDs when stored underrecommended conditions. However, it is recommended thatusers carry out periodic performance verification of responseover the time the dosimeter batch is used.6.2.3 Temper
41、atureExposure to extreme temperature dur-ing shipment and storage at the users facility might affect theTLD response. Manufacturer should be consulted for specificrecommendation for dosimeter shipment and storage.6.2.4 Relative HumidityThe TLD response is not usuallyaffected by environmental changes
42、 in humidity.6.2.5 Exposure to LightTLDs with high sensitivity shouldbe packaged to protect them from light such as sunlight orfluorescent light which have an appreciable ultraviolet compo-nent. Prolonged exposure to ultraviolet light before irradiationcan cause spurious TLD response or enhanced pos
43、t-irradiationfading. Incandescent lighting should be used for the TLDpreparation and readout areas. However, brief exposures of afew minutes to normal room fluorescent lighting is not likely tosignificantly affect the TLD response except for low dosemeasurements (102Gy) recalibration may be required
44、 after eachanneal-irradiation cycle because of possible changes inabsorbed-dose sensitivity (7). If the TLD system being used issubject to this effect, it is recommended that each TLD in thebatch be irradiated only once until the entire batch has beenused after which the entire batch can be annealed
45、 and a newcalibration performed. In addition, because of possible changesin batch response uniformity due to high absorbed-doseirradiations, periodically repeat the tests.10. Routine use10.1 Before Irradiation:10.1.1 TLDs may be used either as reusable or as single-usedosimeters. Single-use dosimete
46、rs are irradiated once, read out,and then discarded; they are generally used as received fromthe manufacturer. Dosimeters that are reused are cycled repeat-edly through an anneal-irradiation-readout procedure.ISO/ASTM 51956:2013(E)4 ISO/ASTM International 2013 All rights reserved10.1.2 Preparation o
47、f the TLDs for irradiation may requirecleaning, annealing, or encapsulation, or combinations thereof,depending on the type and form of the TL phosphor.10.1.3 Reusable TLDs require careful treatment duringannealing in order to obtain reliable results in dose measure-ments. The annealing procedure sho
48、uld include a reproducibletemperature cycle of the annealing oven, accurate timing of theannealing period, and a reproducible cooling rate.10.1.4 Ensure that the dosimeters are selected from anapproved batch stored according to users procedures. Theseprocedures should be based on manufacturers writt
49、en recom-mendations or user specific performance characterization re-sults.10.1.5 Use only dosimeters that are within shelf life andcalibration expiration dates.10.1.6 Inspect each dosimeter and discard any dosimetersthat indicate possible damage.10.1.7 Bare TLDs should not be handled with the barefingers; dirt or grease on their surfaces can affect their responseand can contaminate the heating chamber of the TLD reader.Avacuum pen or tweezers coated with TFE-fluorocarbon shouldbe used in handling. If required, the TLDs can be cleaned byusing p
