1、Designation: E 2381 04An American National StandardStandard Guide forDosimetry In Radiation Processing of Fluidized Beds andFluid Streams1This standard is issued under the fixed designation E 2381; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of 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 describes several dosimetry systems andmethods suitable for the documentation o
3、f the irradiation ofproduct transported as fluid or in a fluidized bed.1.2 The sources of penetrating ionizing radiation included inthis guide are electron beams, x-rays (bremsstrahlung) andgamma rays.1.3 Absorbed doses from 10 to 100,000 gray are considered,including applications such as disinfesta
4、tion, disinfection,bioburden reduction, sterilization, crosslinking and graft modi-fication of products, particularly powders and aggregates.1.4 This guide does not purport to address the safetyconcerns, if any, associated with the use of fluidized beds andstreams incorporating sources of ionizing r
5、adiation. It is theresponsibility of the user of this guide to establish appropriatesafety and health practices and to determine compliance withregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 170 Terminology Relating to Radiation Measurementsand DosimetryE 666 Practi
6、ce for CalculatingAbsorbed Dose from Gammaor X-RadiationE 1026 Practice for Using the Fricke Reference StandardDosimetry SystemE 2232 Standard Guide for Selection and Use of Math-ematical Methods for Calculating Absorbed Dose in Ra-diation Processing ApplicationsF 1355 Standard Guide for Irradiation
7、 of Fresh Fruits forInsect Disinfestation and as a Quarantine TreatmentF 1885 Guide for the Irradiation of Dried Spices, Herbs andVegetable Seasonings to Control Pathogens and OtherMicroorganisms2.2 ISO/ASTM Standards:51204 Standard Practice for Dosimetry in Gamma Irradia-tion Facilities for Food Pr
8、ocessing51261 Guide for Selection and Calibration of DosimetrySystems for Radiation Processing51275 Practice for Use of a Radiochromic Film DosimetrySystem51310 Practice for the Use of a Radiochromic OpticalWaveguide Dosimetry Systems51400 Practice for Characterization and Performance of aHigh-Dose
9、Radiation Dosimetry Calibration Laboratory51431 Practice for Dosimetry in Electron and X-Ray(Bremsstrahlung) Irradiation Facilities for Food Process-ing51538 Practice for Use of the Ethanol-Chlorobenzene Do-simetry System51540 Practice for Use of a Radiochromic Liquid Dosim-etry System51607 Practice
10、 for Use of the Alanine-EPR DosimetrySystem51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-ung) Facility for Radiation Processing51649 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies between 300 keV and25 MeV51702 Practice for Dosimetry in a Gamma Irradi
11、ation Fa-cility for Radiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing51818 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies Between 80 and 300keV51956 Practice forApplication of Thermoluminescence Do-simetry (TLD)
12、 Systems for Radiation Processing2.3 International Commission on Radiation Units andMeasurements Reports3ICRU Report 14 Radiation Dosimetry: X-Rays and GammaRays with Maximum Photon Energies Between 0.6 and 50MeVICRU Report 17 Radiation Dosimetry: X-Rays Generatedat Potentials of 5 to 150 kV1This gu
13、ide is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.01 on Dosimetry for Radiation Processing.Current edition approved June 1, 2004. Published July 2004.2For referenced ASTM standards, visit the ASTM website, ww
14、w.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from the International Commission on Radiation Units and Measure-ments, 7910 Woodmont Avenue, Suite 800, Bet
15、hesda, MD, 20814,USA1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ICRU Report 30 International Comparison of RadiologicalUnits and Measurements: Quantitative Concepts and Do-simetry in RadiobiologyICRU Report 34 The Dosimetry of Pu
16、lsed RadiationICRU Report 35 Radiation Dosimetry: Electron Beamswith Energies Between 1 and 50 MeVICRU Report 37 Stopping Powers for Electrons andPositronsICRU Report 60 Fundamental Quantities and Units forIonizing Radiation2.4 National Committee for Radiation ProtectionNCRP Report 69 Dosimetry of X
17、-Ray and Gamma-RayBeams for Radiation Therapy in the Energy Range 10 keVto 50 MeV3. Terminology3.1 Definitions:3.1.1 Absorbed dose Dquantity of ionizing radiation en-ergy imparted per unit mass of a specified material. The SI unitof absorbed dose is the gray (Gy), where 1 gray is equivalentto the ab
18、sorption of 1 joule per kilogram of the specifiedmaterial (1 Gy=1Jkg-1). The mathematical relationship fordose is the quotient of de by dm, where de is the meanincremental energy imparted by ionizing radiation to matter ofincremental mass dm (see ICRU 60).3.1.1.1 Discussiondiscontinued unit for abso
19、rbed dose isthe rad (1 rad = 0.01 Gy).Absorbed dose is sometimes referredto simply as dose.3.1.2 Absorbed dose mappingmeasurement of absorbeddose within a process stream using dosimeters transported atspecified locations to produce a one or two-dimensionaldistribution of absorbed dose, thus renderin
20、g a map ofabsorbed-dose values.3.1.3 Absorbed dose rateabsorbed dose in a material perincremental time interval, i.e. the quotient of dD by dt (seeICRU 60) Unit: Gy s-13.1.3.1 Discussionabsorbed dose rate can be specified interms of the average value of dD by dt over long-time intervals,for example,
21、 in units of Gy min-1or Gy h-13.1.4 Areal densitythickness of an object normalized bydensity. The SI unit is kg m-2.3.1.4.1 Discussionthe abbreviation gsm is also used inreferring to areal density in grams per square meter in sometechnical literature.3.1.5 Bed controltechnique used for determining t
22、he flu-idized bed thickness and maintaining it between the limitsrequired for controlled application of the process.3.1.6 Bed thicknesstotal thickness of the fluidized bed,which includes the product being processed and the carriermedium, both normalized by density. The SI unit is kg. m-2.3.1.6.1 Dis
23、cussionthickness is typically quoted in g. m-2due to its numerical equivalence to thickness in micrometersfor unit density matter.3.1.7 Bremsstrahlungbroad-spectrum electromagnetic ra-diation (X-rays) emitted when an energetic electron is influ-enced by strong electric field or magnetic field such a
24、s that inthe vicinity of an atomic nucleus.3.1.7.1 Discussionbremsstrahlung is produced when anelectron beam strikes any material (converter). Thebremsstrahlung spectrum depends on the electron energy, theconverter material and its thickness, and contains energies upto the maximum kinetic energy of
25、the incident electrons (seeISO/ASTM Practice 51608).3.1.8 Calibration curvegraphical representation of thedosimetry systems response function.3.1.9 Depth-dose distributionvariation of absorbed dosewith depth from the incident surface of a material exposed toa given radiation.3.1.10 Dose uniformity r
26、atioratio of the maximum to theminimum absorbed dose within the irradiated object or processstream.3.1.10.1 Discussionthe concept is also referred to as themax/min dose ratio and is significantly influenced by theturbulence of the product flow.3.1.11 Dosimeterdevice that, when irradiated, exhibits a
27、quantifiable change in some property of the device which canbe related to absorbed dose in a given material using appro-priate analytical instrumentation and techniques.3.1.12 Dosimeter responsereproducible, quantifiable ra-diation effect on a dosimeter produced by a given absorbeddose.3.1.13 Dosime
28、try systemsystem used for determining ab-sorbed dose, consisting of dosimeters, measurement instru-ments and their associated reference standards, and proceduresfor the systems use.3.1.14 Electron energykinetic energy of the acceleratedelectrons. The electron energy at the product is equal to itsacc
29、elerated energy in vacuum less its energy losses in theaccelerators window and the air gap separating the productand the window.3.1.15 Electron fluenceamount of electronic charge tra-versing a unit area of the target, usually expressed in micro-coulombs per square centimeter. It is the integral of f
30、lux overtotal exposure time3.1.16 Fluidized bed or streammeans by which the prod-uct is transported and presented to the radiation source. Thecarrier medium may be gaseous or liquid. The product distri-bution within the carrier medium may not be uniform.3.1.17 Primary-standard dosimeterdosimeter of
31、the high-est metrological quality, established and maintained as anabsorbed dose standard by a national or international standardsorganization.3.1.18 Quality assuranceall systematic actions necessaryto provide adequate confidence that a calibration, measure-ment, or process is performed to a predefi
32、ned level of quality.3.1.19 Real time dose monitorinstrument capable of con-tinuously providing measured data on dose delivered duringprocessing.3.1.20 Reference-standard dosimeterdosimeter of highmetrological quality, used as a standard to provide measure-ments traceable to and consistent with meas
33、urements madeusing primary standard dosimeters.3.1.21 Response functionmathematical representation ofthe relationship between dosimeter response and absorbed dosefor a given dosimetry system.E23810423.1.22 Routine dosimeterdosimeter calibrated against aprimary, reference, or transfer standard dosime
34、ter and used forroutine absorbed dose measurement.3.1.23 Self-shielded systemproduct transport-irradiationunit with integral shielding.3.1.23.1 Discussionthis type of conformal shielding istypically used at lower radiation energies where rather thinlayers of lead can protect the surrounding environm
35、ent fromvirtually all of the radiation generated by the irradiator.3.1.24 Simulated productmass of material with attenua-tion and scattering properties similar to those of the product,material or substance to be irradiated, sometimes called adummy product.3.1.25 Surface doseabsorbed dose at the surf
36、ace of theproduct.3.1.25.1 DiscussionThis definition becomes particularlyimportant where low energy radiation is used to treat only thesurface of particulates.3.1.26 Target doseabsorbed dose delivered to the surfaceof the bed which will produce the required absorbed dosedistribution within the remai
37、nder of the product irradiated inthe fluidized bed.3.1.27 Traceabilityability to demonstrate by means of anunbroken chain of comparisons that a measurement is inagreement within acceptable limits of uncertainty with compa-rable nationally or internationally recognized standards.3.1.28 Transfer-stand
38、ard dosimeterdosimeter, often a ref-erence standard dosimeter, suitable for transport betweendifferent locations, used to compare absorbed-dose measure-ments.3.1.29 Uncertaintyparameter associated with the result ofany measurement that characterizes the dispersion of the valuesthat could reasonably
39、be attributed to the measured or derivedquantity.3.1.30 Validationestablishment of documented evidence,which provides a high degree of assurance that a specifiedprocess will consistently produce a product meeting its prede-termined specifications and quality attributes.3.2 Definitions of other terms
40、 used in this standard thatpertain to radiation measurement and dosimetry may be foundin ASTM Terminology E 170. Definitions in E 170 are com-patible with ICRU 60; that document, therefore, may be usedas an alternative reference.4. Significance and Use4.1 Dosimetric TechniquesThe processes addressed
41、 hereutilize a variety of techniques for the dynamic presentation ofthe product to the radiation source. This may involve gravita-tional flow or simple pneumatic transport about or past theradiation source. In the case of fluidized beds, the product maybe presented to the radiation source while supp
42、orted in agaseous or liquid stream moving at relatively high velocities.This document provides a guide to the dosimetric techniquessuitable for these processes.4.2 Food ProductsFood products may be treated withionizing radiation, such as energetic electrons from accelera-tors or gamma rays from60Co
43、or137Cs sources, or X-rays, fornumerous purposes, including control of parasites and patho-genic microorganisms, insect disinfestation, growth and matu-ration inhibition, and shelf-life extension.NOTE 1Food irradiation specifications usually include upper andlower limits of absorbed dose: a minimum
44、to ensure the intendedbeneficial effect and a maximum to avoid product degradation. For a givenapplication, one or both of these values may be prescribed by regulationsthat have been established on the basis of available scientific data.Therefore, it is necessary to determine the capability of an ir
45、radiationfacility to process within these absorbed-dose limits prior to the irradiationof the food product. Once this capability is established, it may benecessary to monitor and record the dose range delivered to the productduring each production run to verify compliance with the processspecificati
46、ons within a predetermined level of confidence.4.3 Randomized FlowIn a stream of randomized flow; i.e.turbulent instead of laminar, variations occur which lead to adose distribution for the particles entrained in the stream. The“idealized” maximum and minimum doses possible can becalculated based up
47、on knowledge of the applied dose rate, theproduct dwell time in the irradiation cell and the product or bedthickness. The experimentally determined maximum and mini-mum doses delivered to each particle, should not be confusedwith these idealized dose limits.4.4 Treatment rangeThe location of the pro
48、duct (or of thedosimeter) in the fluidized bed or stream will determine itsabsorbed dose during passage through the radiation field. Theexperimental dose measurements in the fluidized bed or streamwill define the range of product dose. The desired effectimparted to the product by irradiation will th
49、en be based uponthis range of product dose and not upon maximum or minimumdose.NOTE 2In situations where a randomized mixing within the fluidizedbed occurs with the intention that the particles or fluid elements passthrough several radiation zones and accumulate a total dose with differentdose rates, maximum and minimum dose values are difficult to determineand must be based on the results for the experimental dosimetry irradiatedwith the product . In the case of fluids, stirring after processing results onlyin effective treatment at a mean
