1、ISO/ASTM 51631:2013(E)Standard Practice forUse of Calorimetric Dosimetry Systems for Electron BeamDose Measurements and Routine Dosimetry SystemCalibration1This standard is issued under the fixed designation ISO/ASTM 51631; the number immediately following the designation indicates theyear of origin
2、al adoption or, in the case of revision, the year of last revision.1. Scope1.1 This practice covers the preparation and use of semi-adiabatic calorimetric dosimetry systems for measurement ofabsorbed dose and for calibration of routine dosimetry systemswhen irradiated with electrons for radiation pr
3、ocessing appli-cations. The calorimeters are either transported by a conveyorpast a scanned electron beam or are stationary in a broadenedbeam.1.2 This document is one of a set of standards that providesrecommendations for properly implementing dosimetry inradiation processing, and describes a means
4、 of achievingcompliance with the requirements ofASTM Practice E2628 fora calorimetric dosimetry system. It is intended to be read inconjunction with ASTM Practice E2628.1.3 The calorimeters described in this practice are classifiedas Type II dosimeters on the basis of the complex effect ofinfluence
5、quantities. See ASTM Practice E2628.1.4 This practice applies to electron beams in the energyrange from 1.5 to 12 MeV.1.5 The absorbed dose range depends on the absorbingmaterial and the irradiation and measurement conditions.Minimum dose is approximately 100 Gy and maximum dose isapproximately 50 k
6、Gy.1.6 The average absorbed-dose rate range shall generally begreater than 10 Gys-1.1.7 The temperature range for use of these calorimetricdosimetry systems depends on the thermal resistance of thematerials, on the calibrated range of the temperature sensor,and on the sensitivity of the measurement
7、device.1.8 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 prior to use.2. Refer
8、enced 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 Radiation-Hardness Testin
9、g of Electronic DevicesE2628 Practice for Dosimetry in Radiation ProcessingE2701 Guide for Performance Characterization of Dosim-eters and Dosimetry Systems for Use in Radiation Pro-cessing2.2 ISO/ASTM Standards:251261 Practice for Calibration of Routine Dosimetry Sys-tems for Radiation Processing51
10、431 Practice for Dosimetry in Electron and X-Ray(Bremsstrahlung) Irradiation Facilities for Food Process-ing51649 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies Between 300 keVand 25 MeV51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Proces
11、sing2.3 International Commission on Radiation Units and Mea-surements (ICRU) Reports:3ICRU Report 34 The Dosimetry of Pulsed RadiationICRU Report 35 Radiation Dosimetry: Electron Beams withEnergies Between 1 and 50 MeVICRU Report 37 Stopping Powers for Electrons and Posi-trons1This practice is under
12、 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/WG 3.Current edition approved Aug. 16, 2012. Published April 2013. Originallypublished as E 1631 94. ASTM E 1631
13、 961was adopted by ISO in 1998 withthe intermediate designation ISO 15568:1998(E).The present International StandardISO/ASTM 51631:2013(E) replaces ISO 15568 and is a major revision of the lastprevious edition ISO/ASTM 516312003(E).2For referenced ASTM and ISO/ASTM standards, visit the ASTM website,
14、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.3Available from the Commission on Radiation Units and Measurements, 7910Woodmont Ave., Suite 800, Bethesda, MD 20814
15、, U.S.A. ISO/ASTM International 2017 All rights reservedThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by
16、the World Trade Organization Technical Barriers to Trade (TBT) Committee.1ICRU Report 44 Tissue Substitutes in Radiation Dosimetryand MeasurementsICRU Report 80 Dosimetry Systems for use in RadiationProcessingICRU Report 85a Fundamental Quantities and Units forIonizing Radiation2.4 Joint Committee f
17、or Guides in Metrology (JCGM)Reports:4JCGM 100:2008, GUM 1995, with minor corrections,Evaluation of measurement data Guide to the Expres-sion of Uncertainty in Measurement3. Terminology3.1 Definitions:3.1.1 primary-standard dosimetry systemdosimetry sys-tem that is designated or widely acknowledged
18、as having thehighest metrological qualities and whose value is acceptedwithout reference to other standards of the same quantity.3.1.2 reference standard dosimetry systemdosimetrysystem, generally having the highest metrological qualityavailable at a given location or in a given organization, fromwh
19、ich measurements made there are derived.3.1.3 transfer standard dosimetry systemdosimetry sys-tem used as an intermediary to calibrate other dosimetrysystems.3.1.4 type II dosimeterdosimeter, the response of which isaffected by influence quantities in a complex way that cannotpractically be expresse
20、d in terms of independent correctionfactors.3.2 Definitions of Terms Specific to This Standard:3.2.1 adiabaticno heat exchange with the surroundings.3.2.2 calorimeterassembly consisting of calorimetricbody (absorber), thermal insulation, and temperature sensorwith wiring.3.2.3 calorimetric bodymass
21、of material absorbing radia-tion energy and whose temperature is measured.3.2.4 calorimetric dosimetry systemdosimetry systemconsisting of calorimeter, measurement instruments and theirassociated reference standards, and procedures for the systemsuse.3.2.5 endothermic reactionchemical reaction that
22、con-sumes energy.3.2.6 exothermic reactionchemical reaction that releasesenergy.3.2.7 heat defect (thermal defect)amount of energy re-leased or consumed by chemical reactions caused by theabsorption of radiation energy.3.2.8 specific heat capacityamount of energy required toraise 1 kg of material by
23、 the temperature of 1 K.3.2.9 thermistorelectrical resistor with a well-defined re-lationship between resistance and temperature.3.2.10 thermocouplejunction of two metals producing anelectrical voltage with a well-defined relationship to junctiontemperature.3.3 Definitions of other terms used in thi
24、s standard thatpertain to radiation measurement and dosimetry may be foundin ASTM Terminology E170. Definitions in E170 are compat-ible with ICRU Report 85a; that document, therefore, may beused as an alternative reference.4. Significance and use4.1 This practice is applicable to the use of calorime
25、tricdosimetry systems for the measurement of absorbed dose inelectron beams, the qualification of electron irradiationfacilities, periodic checks of operating parameters of electronirradiation facilities, and calibration of other dosimetry systemsin electron beams. Calorimetric dosimetry systems are
26、 mostsuitable for dose measurement at electron accelerators utilizingconveyor systems for transport of product during irradiation.NOTE 1For additional information on calorimetric dosimetry systemoperation and use, see ICRU Report 80. For additional information on theuse of dosimetry in electron acce
27、lerator facilities, see ISO/ASTM Prac-tices 51431 and 51649, and ICRU Reports 34 and 35, and Refs (1-3).54.2 The calorimetric dosimetry systems described in thispractice are not primary standard dosimetry systems. Thecalorimeters are classified as Type II dosimeters (ASTME2628). They may be used as
28、internal standards at an electronbeam irradiation facility, including being used as transferstandard dosimetry systems for calibration of other dosimetrysystems, or they may be used as routine dosimeters. Thecalorimetric dosimetry systems are calibrated by comparisonwith transfer-standard dosimeters
29、.4.3 The dose measurement is based on the measurement ofthe temperature rise in an absorber (calorimetric body) irradi-ated by an electron beam. Different absorbing materials areused, but the response is usually defined in terms of dose towater.NOTE 2The calorimetric bodies of the calorimeters descr
30、ibed in thispractice are made from low atomic number materials. The electronfluences within these calorimetric bodies are almost independent of energywhen irradiated with electron beams of 1.5 MeV or higher, and the masscollision stopping powers are approximately the same for these materials.4.4 The
31、 absorbed dose in other materials irradiated underequivalent conditions may be calculated. Procedures for mak-ing such calculations are given in ASTM Practices E666 andE668, and Ref (1).4.4.1 Calorimeters for use at industrial electron acceleratorshave been constructed using graphite, polystyrene or
32、 a Petridish filled with water as the calorimetric body (4-10). Thethickness of the calorimetric body shall be less than the rangeof the electrons.4.4.2 Polymeric materials other than polystyrene may alsobe used for calorimetric measurements. Polystyrene is usedbecause it is known to be resistant to
33、 radiation (11) and becausealmost no exo- or endothermic reactions take place (12).4Document produced by Working Group 1 of the Joint Committee for Guides inMetrology (JCGM/WG 1). Available free of charge at the BIPM website (http:/www.bipm.org).5The boldface numbers in parentheses refer to the bibl
34、iography at the end of thispractice.ISO/ASTM 51631:2013(E)2 ISO/ASTM International 2017 All rights reserved 5. Interferences5.1 ExtrapolationThe calorimetric dosimetry systems de-scribed in this practice are not adiabatic, because of theexchange of heat with the surroundings or within the calorim-et
35、er assembly. The maximum temperature reached by thecalorimetric body is different from the temperature that wouldhave been reached in the absence of that heat exchange. Thetemperature drifts before and after irradiation are extrapolatedto the midpoint of the irradiation period in order to determinet
36、he true temperature increase due to the absorbed dose.5.2 Heat DefectChemical reactions in irradiated material(resulting in what is called the heat defect or thermal defect)may be endo- or exothermic and may lead to measurabletemperature changes (3).5.3 Specific Heat CapacityThe specific heat capaci
37、ty ofsome materials used as a calorimetric body may change withaccumulated absorbed dose, thereby affecting the response ofthe calorimeters. This is notably the case for polymers, such aspolystyrene, and it will therefore be necessary to recalibratecalorimetric dosimetry systems at intervals that wi
38、ll depend onthe total accumulated dose.5.4 Influence QuantitiesThe response of the calorimetricdosimetry systems to absorbed dose does not depend onenvironmental relative humidity and temperature.5.5 Temperature Effects from Accelerator StructureThecalorimeters are often irradiated on a conveyor use
39、d for passingproducts and samples through the irradiation zone. Radiatedheat from the mechanical structures of the irradiation facilityand from the conveyor may contribute to the measuredtemperature increase in the calorimeters.5.6 Thermal EquilibriumThe most reproducible resultsare obtained when th
40、e calorimeters are in thermal equilibriumwith their surroundings before irradiation.5.7 Other MaterialsThe temperature sensors, wires, etc.of the calorimeter represent foreign materials, which mayinfluence the temperature rise of the calorimetric body. Thesecomponents should be as small as possible.
41、5.8 Dose GradientsDose gradients will exist within thecalorimetric body when it is irradiated with electrons. Thesegradients must be taken into account, for example, when otherdosimeters are calibrated by comparison with calorimetricdosimetry systems.6. Apparatus6.1 A Typical Graphite Calorimeter is
42、 a disc of graphiteplaced in a thermally-insulating material such as foamedplastic (4-6). A calibrated thermistor or thermocouple is em-bedded inside the disc. Some typical examples of graphite discthicknesses and masses are listed in Table 1 (2).6.2 A Typical Water Calorimeter is a sealed polystyre
43、nePetri dish filled with water and placed in thermally-insulatingfoamed plastic (4). A calibrated temperature sensor (thermis-tor) is placed through the side of the dish into the water. Theshape and size of the water calorimeter can be similar to theshape and size of the polystyrene calorimeter (see
44、 6.3).6.3 A Typical Polystyrene Calorimeter is a polystyrene discplaced in thermally-insulating foamed plastic. A calibratedthermistor or thermocouple is imbedded inside the disc. Thedimension of the polystyrene disc may be similar to that of thegraphite and water calorimeters (9). See Fig. 1 as an
45、exampleof a 10 MeV-calorimeter. Fig. 2 shows an example of apolystyrene calorimeter designed for use at 1.5 to 4 MeVelectron accelerators.6.4 The thickness of the calorimetric body should be lessthan the range of the irradiating electrons, typically notexceeding13 of the range of the electrons. That
46、 will limit thevariation of the dose gradients within the calorimetric body.6.5 Radiation-resistant components should be used for theparts of the calorimeter that are exposed to the electron beam.This also applies to insulation of electrical wires.6.6 Good thermal contact must exist between the temp
47、era-ture sensor and the calorimetric body. For graphite andpolystyrene calorimeters, this can be assured by adding a smallamount of heat-conducting compound when mounting thetemperature sensor.TABLE 1 Thickness and size of several graphite calorimetric bodies designed at NIST for use at specific ele
48、ctron energiesElectronEnergyMeVElectron Rangein GraphiteAdensity: 1.7 g cm-3Calorimeter Disc (30 mm diameter)ThicknessBMass, ggcm-2cm g cm-2cm4 2.32 1.36 0.84 0.49 5.95 2.91 1.71 1.05 0.62 7.56 3.48 2.05 1.25 0.74 8.98 4.59 2.70 1.65 0.97 11.710 5.66 3.33 2.04 1.20 14.411 6.17 3.63 2.22 1.31 15.712
49、6.68 3.93 2.40 1.41 16.9AThis is the continuous-slowing-down approximation (CSDA) range roof electrons for a broad beam incident on a semi-infinite absorber. It is calculated from:r05 e0Es0ds1/sS/dtotd dEwhere:E0= the primary electron energy, and(S/)tot= the total mass stopping power at a given electron energy (1).BThe thicknesses specified are equal to 0.36 ro.ISO/ASTM 51631:2013(E)3 ISO/ASTM International 2017 All rights reserved
