1、ISO/ASTM 51649:2015(E)An American National StandardStandard Practice forDosimetry in an Electron Beam Facility for RadiationProcessing at Energies Between 300 keV and 25 MeV1This standard is issued under the fixed designation ISO/ASTM 51649; the number immediately following the designation indicates
2、 theyear of original adoption or, in the case of revision, the year of last revision.1. Scope1.1 This practice outlines dosimetric procedures to be fol-lowed in installation qualification (IQ), operational qualifica-tion (OQ) and performance qualifications (PQ), and routineprocessing at electron bea
3、m facilities.1.2 The electron beam energy range covered in this practiceis between 300 keV and 25 MeV, although there are somediscussions for other energies.1.3 Dosimetry is only one component of a total qualityassurance program for adherence to good manufacturing prac-tices used in radiation proces
4、sing applications. Other measuresbesides dosimetry may be required for specific applicationssuch as health care product sterilization and food preservation.1.4 Specific standards exist for the radiation sterilization ofhealth care products and the irradiation of food. For theradiation sterilization
5、of health care products, see ISO 11137-1(Requirements) and ISO 11137-3 (Guidance on dosimetricaspects). For irradiation of food, see ISO 14470. In those areascovered by these standards, they take precedence. Informationabout effective or regulatory dose limits for food products isnot within the scop
6、e of this practice (seeASTM Guides F1355,F1356, F1736, and F1885).1.5 This document is one of a set of standards that providesrecommendations for properly implementing and utilizingdosimetry in radiation processing. It is intended to be read inconjunction with ISO/ASTM 52628, “Practice for Dosimetry
7、in Radiation Processing”.NOTE 1For guidance in the calibration of routine dosimetry systems,see ISO/ASTM Practice 51261. For further guidance in the use of specificdosimetry systems, see relevant ISO/ASTM Practices. For discussion ofradiation dosimetry for pulsed radiation, see ICRU Report 34.1.6 Th
8、is 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 requirements prior to use.2. Referenced docume
9、nts2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE2232 Guide for Selection and Use of Mathematical Meth-ods for Calculating Absorbed Dose in Radiation Process-ing ApplicationsE2303 Guide for Absorbed-Dose Mapping in RadiationProcessing FacilitiesF1355 Guide for
10、Irradiation of FreshAgricultural Produce asa Phytosanitary TreatmentF1356 Practice for Irradiation of Fresh and Frozen Red Meatand Poultry to Control Pathogens and Other Microorgan-ismsF1736 Guide for Irradiation of Finfish and Aquatic Inverte-brates Used as Food to Control Pathogens and SpoilageMic
11、roorganismsF1885 Guide for Irradiation of Dried Spices, Herbs, andVegetable Seasonings to Control Pathogens and OtherMicroorganisms2.2 ISO/ASTM Standards:251261 Practice for Calibration of Routine Dosimetry Sys-tems for Radiation Processing51275 Practice for Use of a Radiochromic Film DosimetrySyste
12、m51539 Guide for the Use of Radiation-Sensitive Indicators51608 Practice for Dosimetry in an X-Ray (Bremsstrahlung)Facility for Radiation Processing51702 Practice for Dosimetry in a Gamma Facility forRadiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing518
13、18 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies Between 80 and 300keV52628 Practice for Dosimetry in Radiation Processing1This practice is under the jurisdiction of ASTM Committee E61 on RadiationProcessing and is the direct responsibility of Subcommittee E
14、61.03 on DosimetryApplication, and is also under the jurisdiction of ISO/TC 85/WG 3.Current edition approved Sept. 8, 2014. Published February 2015. Originallypublished as E 164994. Last previous ASTM edition E 164900. ASTME 1649941was adopted by ISO in 1998 with the intermediate designation ISO1556
15、9:1998(E). The present International Standard ISO/ASTM 51649:2015(E) is amajor revision of the last previous edition ISO/ASTM 51649:2005(E), whichreplaced ISO/ASTM 51649:2002(E).2For referenced ASTM and ISO/ASTM standards, visit the ASTM website,www.astm.org, or contact ASTM Customer Service at serv
16、iceastm.org. ForAnnual Book of ASTM Standards volume information, refer to the standardsDocument Summary page on the ASTM website. ISO/ASTM International 2015 All rights reserved152701 Guide for Performance Characterization of Dosim-eters and Dosimetry Systems for Use in Radiation Pro-cessing2.3 ISO
17、 Standards:3ISO 11137-1 Sterilization of Health Care ProductsRadia-tion Part 1: Requirements for development, validation,and routine control of a sterilization process for medicaldevicesISO 11137-3 Sterilization of Health Care ProductsRadia-tion Part 3: Guidance on dosimetric aspectsISO 14470 Food I
18、rradiation Requirements for thedevelopment, validation and routine control of the processof irradiation using ionizing radiation for the treatment offoodISO 10012 Measurement Management Systems Require-ments for Measurement Processes and Measuring Equip-mentISO/IEC 17025 General Requirements for the
19、 Competenceof Calibration and Testing Laboratories2.4 International Commission on Radiation Units and Mea-surements (ICRU) Reports:4ICRU Report 34 The Dosimetry of Pulsed RadiationICRU Report 35 Radiation Dosimetry: Electron Beams withEnergies Between 1 and 50 MeVICRU Report 37 Stopping Powers for E
20、lectrons and Posi-tronsICRU Report 80 Dosimetry for Use in Radiation ProcessingICRU Report 85a Fundamental Quantities and Units forIonizing Radiation2.5 Joint Committee for Guides in Metrology (JCGM)Reports:5JCGM 100:2008, GUM 1995 , with minor corrections,Evaluation of measurement data Guide to the
21、 expressionof uncertainty in measurement3. Terminology3.1 Definitions:3.1.1 absorbed dose (D)quantity of ionizing radiationenergy imparted per unit mass of a specified material.3.1.1.1 Discussion(1) The SI unit of absorbed dose is thegray (Gy), where 1 gray is equivalent to the absorption of 1joule
22、per kilogram in the specified material (1 Gy = 1 J/kg).The mathematical relationship is the quotient of d by dm,where d is the mean incremental energy imparted by ionizingradiation to matter of incremental mass dm. (See ICRU Report85a.)D 5 dH/dm3.1.1.2 Discussion(2) Absorbed dose is sometimes re-fer
23、red to simply as dose.3.1.2 approved laboratorylaboratory that is a recognizednational metrology institute; or has been formally accredited toISO/IEC 17025, or has a quality system consistent with therequirements of ISO/IEC 17025.3.1.2.1 DiscussionA recognized national metrology insti-tute or other
24、calibration laboratory accredited to ISO/IEC17025 or its equivalent should be used for issue of referencestandard dosimeters or irradiation of dosimeters in order toensure traceability to a national or international standard. Acalibration certificate provided by a laboratory not havingformal recogni
25、tion or accreditation will not necessarily beproof of traceability to a national or international standard.3.1.3 average beam currenttime-averaged electron beamcurrent; for a pulsed accelerator, the averaging shall be doneover a large number of pulses (see Fig. 1).3.1.4 beam lengthdimension of the i
26、rradiation zone alongthe direction of product movement at a specified distance fromthe accelerator window (see Fig. 2).3.1.4.1 DiscussionBeam length is therefore perpendicularto beam width and to the electron beam axis. In case of productthat is stationary during irradiation, beam length and beamwid
27、th may be interchangeable.3.1.5 beam width (Wb)dimension of the irradiation zoneperpendicular to the direction of product movement at aspecified distance from the accelerator window (see Fig. 2).3.1.5.1 DiscussionFor a radiation processing facility witha conveyor system, the beam width is usually pe
28、rpendicular tothe direction of motion of the conveyor (see Fig. 2). Beamwidth is the distance between two points along the dose profile,which are at a defined level from the maximum dose region inthe profile (see Fig. 3). Various techniques may be employed toproduce an electron beam width adequate t
29、o cover the process-ing zone, for example, use of electromagnetic scanning of apencil beam (in which case beam width is also referred to asscan width), defocussing elements, and scattering foils.3.1.6 compensating dummysee simulated product.3.1.7 depth-dose distributionvariation of absorbed dosewith
30、 depth from the incident surface of a material exposed toa given radiation.3.1.7.1 DiscussionTypical distributions along the beamaxis in homogeneous materials produced by a normally inci-dent monoenergetic electron beam are shown in Annex A2.3.1.8 dose uniformity ratio (DUR)ratio of the maximumto th
31、e minimum absorbed dose within the irradiated product.3.1.8.1 DiscussionThe concept is also referred to as themax/min dose ratio.3.1.9 dosimetry systemsystem used for measuring ab-sorbed dose, consisting of dosimeters, measurement instru-ments and their associated reference standards, and procedures
32、for the systems use.3.1.10 electron beam energykinetic energy of the acceler-ated electrons in the beam. Unit: J3.1.10.1 DiscussionElectron volt (eV) is often used as theunit for electron beam energy where 1 eV = 1.60210-19J. Inradiation processing, where beams with a broad electronenergy spectrum a
33、re frequently used, the terms most probableenergy (Ep) and average energy (Ea) are common. They are3Available from International Organization for Standardization, 1 Rue deVaremb, Case Postale 56, CH-1211 Geneva 20, Switzerland.4Available from the International Commission on Radiation Units andMeasur
34、ements, 7910 Woodmont Ave., Suite 800, Bethesda MD 20814, U.S.A.5Document 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).ISO/ASTM 51649:2015(E)2 ISO/ASTM International 2015 All rights reservedli
35、nked to the practical electron range Rpand half-valuedepth R50by empirical equations (see Fig. 4 and Annex A4).3.1.11 electron beam facilityestablishment that uses ener-getic electrons produced by particle accelerators to irradiateproduct.3.1.12 electron energy spectrumparticle fluence distribu-tion
36、 of electrons as a function of energy.3.1.13 installation qualification (IQ)process of obtainingand documenting evidence that equipment has been providedand installed in accordance with its specification.3.1.14 operational qualification (OQ)process of obtainingand documenting evidence that installed
37、 equipment operateswithin predetermined limits when used in accordance with itsoperational procedures.3.1.15 performance qualification (PQ)process of obtain-ing and documenting evidence that the equipment, as installedand operated in accordance with operational procedures, con-sistently performs in
38、accordance with predetermined criteriaand thereby yields product meeting its specification.3.1.16 process loadvolume of material with a specifiedproduct loading configuration irradiated as a single entity.3.1.17 production runseries of process loads consisting ofmaterials or products having similar
39、radiation-absorptioncharacteristics, that are irradiated sequentially to a specifiedrange of absorbed dose.3.1.18 reference materialhomogeneous material of knownradiation absorption and scattering properties used to establishcharacteristics of the irradiation process, such as scanuniformity, depth-d
40、ose distribution, and reproducibility of dosedelivery.3.1.19 reference planeselected plane in the radiation zonethat is perpendicular to the electron beam axis.FIG. 1 Example showing pulse beam current (Ipulse), average beam current (Iavg), (pulse width (W) and repetition rate (f) for a pulsedaccele
41、ratorFIG. 2 Diagram showing beam length and beam width for ascanned beam using a conveyor systemISO/ASTM 51649:2015(E)3 ISO/ASTM International 2015 All rights reserved3.1.20 routine monitoring positionposition where ab-sorbed dose is monitored during routine processing to ensurethat the product is r
42、eceiving the absorbed dose specified for theprocess.3.1.20.1 DiscussionThis position may be a location ofminimum or maximum dose in the process load or it may be analternate convenient location in, on or near the process loadwhere the relationship of the dose at this position with theminimum and max
43、imum dose has been established.3.1.21 simulated productmaterial with radiation absorp-tion and scattering properties similar to those of the product,material or substance to be irradiated.3.1.21.1 DiscussionSimulated product is used during irra-diator characterization as a substitute for the actual
44、product,material or substance to be irradiated. When used in routineproduction runs in order to compensate for the absence ofproduct, simulated product is sometimes referred to as com-pensating dummy. When used for absorbed-dose mapping,simulated product is sometimes referred to as phantom mate-rial
45、.3.1.22 standardized depth (z)thickness of the absorbingmaterial expressed as the mass per unit area, which is equal tothe product of depth in the material t and density .3.1.22.1 DiscussionIf m is the mass of the materialbeneath area A of the material through which the beam passes,then:z 5 m/A 5 tT
46、he SI unit of z is in kg/m2, however, it is common practiceto express t in centimetres and in grams per cm3, then z isin grams per square centimetre. Standardized depth may alsobe referred to as surface density, area density, mass-depth ormass-thickness.3.2 Definitions of Terms Specific to This Stan
47、dard:3.2.1 beam powerproduct of the average electron beamenergy and the average beam current.3.2.2 beam spotshape of the unscanned electron beamincident on the reference plane.3.2.3 continuous-slowing-down-approximation (CSDA)range (r0)average pathlength traveled by a charged particleFIG. 3 Example
48、of electron-beam dose distribution along the scan direction, where the beam width is specified at a defined fractionallevel f of the average maximum dose DmaxDe: Dose at entrance surfaceRopt: Depth at which dose at descending part of curve equals DeR50: Depth at which dose has decreased to 50 % of i
49、ts maximumvalueR50e: Depth at which dose has decreased to 50 % of DeRp: Depth where extrapolated straight line of descending curvemeets depth axisFIG. 4 A typical depth-dose distribution for an electron beam ina homogeneous materialISO/ASTM 51649:2015(E)4 ISO/ASTM International 2015 All rights reservedas it slows down to rest, calculated in the continuous-slowing-down-approximation method.3.2.3.1 DiscussionIn this approximation, the rate of en-ergy loss at every point along the track is assumed to be equalto t
