ASTM E2381-04

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An American National Standard
Designation:E2381–04
Standard Guide for
Dosimetry In Radiation Processing of Fluidized Beds and
Fluid Streams
This standard is issued under the fixed designation E2381; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ISO/ASTM Standards:
51204 Standard Practice for Dosimetry in Gamma Irradia-
1.1 This guide describes several dosimetry systems and
tion Facilities for Food Processing
methods suitable for the documentation of the irradiation of
51261 Guide for Selection and Calibration of Dosimetry
product transported as fluid or in a fluidized bed.
Systems for Radiation Processing
1.2 Thesourcesofpenetratingionizingradiationincludedin
51275 Practice for Use of a Radiochromic Film Dosimetry
this guide are electron beams, x-rays (bremsstrahlung) and
System
gamma rays.
51310 Practice for the Use of a Radiochromic Optical
1.3 Absorbeddosesfrom10to100,000grayareconsidered,
Waveguide Dosimetry Systems
including applications such as disinfestation, disinfection,
51400 Practice for Characterization and Performance of a
bioburden reduction, sterilization, crosslinking and graft modi-
High-Dose Radiation Dosimetry Calibration Laboratory
fication of products, particularly powders and aggregates.
51431 Practice for Dosimetry in Electron and X-Ray
1.4 This guide does not purport to address the safety
(Bremsstrahlung) Irradiation Facilities for Food Process-
concerns, if any, associated with the use of fluidized beds and
ing
streams incorporating sources of ionizing radiation. It is the
51538 Practice for Use of the Ethanol-Chlorobenzene Do-
responsibility of the user of this guide to establish appropriate
simetry System
safety and health practices and to determine compliance with
51540 Practice for Use of a Radiochromic Liquid Dosim-
regulatory limitations prior to use.
etry System
2. Referenced Documents
51607 Practice for Use of the Alanine-EPR Dosimetry
System
2.1 ASTM Standards:
51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-
E170 TerminologyRelatingtoRadiationMeasurementsand
ung) Facility for Radiation Processing
Dosimetry
51649 Practice for Dosimetry in an Electron Beam Facility
E666 PracticeforCalculatingAbsorbedDoseFromGamma
forRadiationProcessingatEnergiesbetween300keVand
or X Radiation
25 MeV
E1026 Practice for Using the Fricke Reference-Standard
51702 Practice for Dosimetry in a Gamma Irradiation Fa-
Dosimetry System
cility for Radiation Processing
E2232 Guide for Selection and Use of Mathematical Meth-
51707 Guide for Estimating Uncertainties in Dosimetry for
odsforCalculatingAbsorbedDoseinRadiationProcessing
Radiation Processing
Applications
51818 Practice for Dosimetry in an Electron Beam Facility
F1355 Guide for Irradiation of Fresh Agricultural Produce
for Radiation Processing at Energies Between 80 and 300
as a Phytosanitary Treatment
keV
F1885 Guide for Irradiation of Dried Spices, Herbs, and
51956 Practice forApplication ofThermoluminescence Do-
Vegetable Seasonings to Control Pathogens and Other
simetry (TLD) Systems for Radiation Processing
Microorganisms
2.3 International Commission on Radiation Units and
Measurements Reports
ICRUReport14 RadiationDosimetry:X-RaysandGamma
This guide is under the jurisdiction of ASTM Committee E10 on Nuclear
RayswithMaximumPhotonEnergiesBetween0.6and50
Technology and Applications and is the direct responsibility of Subcommittee
E10.01 on Dosimetry for Radiation Processing.
MeV
Current edition approved June 1, 2004. Published July 2004. DOI: 10.1520/
ICRU Report 17 Radiation Dosimetry: X-Rays Generated
E2381-04.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from the International Commission on Radiation Units and Measure-
the ASTM website. ments, 7910 Woodmont Avenue, Suite 800, Bethesda, MD, 20814,USA
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2381–04
at Potentials of 5 to 150 kV 3.1.7.1 Discussion—bremsstrahlung is produced when an
electron beam strikes any material (converter). The
ICRU Report 30 International Comparison of Radiological
bremsstrahlung spectrum depends on the electron energy, the
Units and Measurements: Quantitative Concepts and Do-
converter material and its thickness, and contains energies up
simetry in Radiobiology
to the maximum kinetic energy of the incident electrons (see
ICRU Report 34 The Dosimetry of Pulsed Radiation
ISO/ASTM Practice 51608).
ICRU Report 35 Radiation Dosimetry: Electron Beams
3.1.8 Calibration curve—graphical representation of the
with Energies Between 1 and 50 MeV
dosimetry system’s response function.
ICRU Report 37 Stopping Powers for Electrons and
3.1.9 Depth-dose distribution—variation of absorbed dose
Positrons
with depth from the incident surface of a material exposed to
ICRU Report 60 Fundamental Quantities and Units for
a given radiation.
Ionizing Radiation
3.1.10 Dose uniformity ratio—ratio of the maximum to the
2.4 National Committee for Radiation Protection
minimum absorbed dose within the irradiated object or process
NCRP Report 69 Dosimetry of X-Ray and Gamma-Ray
stream.
BeamsforRadiationTherapyintheEnergyRange10keV
3.1.10.1 Discussion—the concept is also referred to as the
to 50 MeV
max/min dose ratio and is significantly influenced by the
turbulence of the product flow.
3. Terminology
3.1.11 Dosimeter—device that, when irradiated, exhibits a
3.1 Definitions:
quantifiable change in some property of the device which can
3.1.1 Absorbed dose D—quantity of ionizing radiation en-
be related to absorbed dose in a given material using appro-
ergy imparted per unit mass of a specified material.The SI unit
priate analytical instrumentation and techniques.
of absorbed dose is the gray (Gy), where 1 gray is equivalent
3.1.12 Dosimeter response—reproducible, quantifiable ra-
to the absorption of 1 joule per kilogram of the specified
diation effect on a dosimeter produced by a given absorbed
-1
material (1 Gy=1Jkg ). The mathematical relationship for
dose.
dose is the quotient of d´ by dm, where d´ is the mean
3.1.13 Dosimetry system—system used for determining ab-
incremental energy imparted by ionizing radiation to matter of
sorbed dose, consisting of dosimeters, measurement instru-
incremental mass dm (see ICRU 60).
ments and their associated reference standards, and procedures
3.1.1.1 Discussion—discontinued unit for absorbed dose is
for the system’s use.
the rad (1 rad = 0.01 Gy).Absorbed dose is sometimes referred
3.1.14 Electron energy—kinetic energy of the accelerated
to simply as dose.
electrons. The electron energy at the product is equal to its
3.1.2 Absorbed dose mapping—measurement of absorbed
accelerated energy in vacuum less its energy losses in the
dose within a process stream using dosimeters transported at
accelerator’s window and the air gap separating the product
specified locations to produce a one or two-dimensional
and the window.
distribution of absorbed dose, thus rendering a map of
3.1.15 Electron fluence—amount of electronic charge tra-
absorbed-dose values.
versing a unit area of the target, usually expressed in micro-
3.1.3 Absorbed dose rate—absorbed dose in a material per
coulombs per square centimeter. It is the integral of flux over
incremental time interval, i.e. the quotient of dD by dt (see
-1 total exposure time
ICRU 60) Unit: Gy s
3.1.16 Fluidized bed or stream—means by which the prod-
3.1.3.1 Discussion—absorbed dose rate can be specified in
uct is transported and presented to the radiation source. The
termsoftheaveragevalueofdDbydtoverlong-timeintervals,
-1 -1
carrier medium may be gaseous or liquid. The product distri-
for example, in units of Gy min or Gy h
bution within the carrier medium may not be uniform.
3.1.4 Areal density—thickness of an object normalized by
-2
3.1.17 Primary-standard dosimeter—dosimeter of the high-
density. The SI unit is kg m .
est metrological quality, established and maintained as an
3.1.4.1 Discussion—the abbreviation gsm is also used in
absorbed dose standard by a national or international standards
referring to areal density in grams per square meter in some
organization.
technical literature.
3.1.18 Quality assurance—all systematic actions necessary
3.1.5 Bed control—technique used for determining the flu-
to provide adequate confidence that a calibration, measure-
idized bed thickness and maintaining it between the limits
ment, or process is performed to a predefined level of quality.
required for controlled application of the process.
3.1.19 Real time dose monitor—instrument capable of con-
3.1.6 Bed thickness—total thickness of the fluidized bed,
tinuously providing measured data on dose delivered during
which includes the product being processed and the carrier
-2
processing.
medium, both normalized by density. The SI unit is kg. m .
-2
3.1.6.1 Discussion—thickness is typically quoted in g. m 3.1.20 Reference-standard dosimeter—dosimeter of high
metrological quality, used as a standard to provide measure-
due to its numerical equivalence to thickness in micrometers
for unit density matter. ments traceable to and consistent with measurements made
using primary standard dosimeters.
3.1.7 Bremsstrahlung—broad-spectrum electromagnetic ra-
diation (X-rays) emitted when an energetic electron is influ- 3.1.21 Response function—mathematical representation of
enced by strong electric field or magnetic field such as that in therelationshipbetweendosimeterresponseandabsorbeddose
the vicinity of an atomic nucleus. for a given dosimetry system.
E2381–04
3.1.22 Routine dosimeter—dosimeter calibrated against a genic microorganisms, insect disinfestation, growth and matu-
primary, reference, or transfer standard dosimeter and used for ration inhibition, and shelf-life extension.
routine absorbed dose measurement.
NOTE 1—Food irradiation specifications usually include upper and
3.1.23 Self-shielded system—product transport-irradiation
lower limits of absorbed dose: a minimum to ensure the intended
unit with integral shielding.
beneficialeffectandamaximumtoavoidproductdegradation.Foragiven
application, one or both of these values may be prescribed by regulations
3.1.23.1 Discussion—this type of conformal shielding is
that have been established on the basis of available scientific data.
typically used at lower radiation energies where rather thin
Therefore, it is necessary to determine the capability of an irradiation
layers of lead can protect the surrounding environment from
facilitytoprocesswithintheseabsorbed-doselimitspriortotheirradiation
virtually all of the radiation generated by the irradiator.
of the food product. Once this capability is established, it may be
3.1.24 Simulated product—mass of material with attenua-
necessary to monitor and record the dose range delivered to the product
tion and scattering properties similar to those of the product,
during each production run to verify compliance with the process
material or substance to be irradiated, sometimes called a specifications within a predetermined level of confidence.
dummy product.
4.3 Randomized Flow—In a stream of randomized flow; i.e.
3.1.25 Surface dose—absorbed dose at the surface of the
turbulent instead of laminar, variations occur which lead to a
product.
dose distribution for the particles entrained in the stream. The
3.1.25.1 Discussion—This definition becomes particularly
“idealized” maximum and minimum doses possible can be
important where low energy radiation is used to treat only the
calculated based upon knowledge of the applied dose rate, the
surface of particulates.
productdwelltimeintheirradiationcellandtheproductorbed
3.1.26 Target dose—absorbed dose delivered to the surface
thickness.The experimentally determined maximum and mini-
of the bed which will produce the required absorbed dose
mum doses delivered to each particle, should not be confused
distribution within the remainder of the product irradiated in
with these idealized dose limits.
the fluidized bed.
4.4 Treatment range—The location of the product (or of the
3.1.27 Traceability—ability to demonstrate by means of an
dosimeter) in the fluidized bed or stream will determine its
unbroken chain of comparisons that a measurement is in
absorbed dose during passage through the radiation field. The
agreement within acceptable limits of uncertainty with compa-
experimental dose measurements in the fluidized bed or stream
rable nationally or internationally recognized standards.
will define the range of product dose. The desired effect
3.1.28 Transfer-standard dosimeter—dosimeter, often a ref-
imparted to the product by irradiation will then be based upon
erence standard dosimeter, suitable for transport between
thisrangeofproductdoseandnotuponmaximumorminimum
different locations, used to compare absorbed-dose measure-
dose.
ments.
NOTE 2—In situations where a randomized mixing within the fluidized
3.1.29 Uncertainty—parameter associated with the result of
bed occurs with the intention that the particles or fluid elements pass
anymeasurementthatcharacterizesthedispersionofthevalues
through several radiation zones and accumulate a total dose with different
that could reasonably be attributed to the measured or derived
dose rates, maximum and minimum dose values are difficult to determine
quantity. and must be based on the results for the experimental dosimetry irradiated
withtheproduct.Inthecaseoffluids,stirringafterprocessingresultsonly
3.1.30 Validation—establishment of documented evidence,
in effective treatment at a mean dose; no max and min dose measurement.
which provides a high degree of assurance that a specified
For example, lethality curves will be determined as a function of this
process will consistently produce a product meeting its prede-
range of product treatment to the product in the fluidized bed or stream as
termined specifications and quality attributes.
determined by dosimetric techniques.
3.2 Definitions of other terms used in this standard that
pertain to radiation measurement and dosimetry may be found 5. Types of Facilities, Source Characteristics and
Fluidized Bed Parameters
inASTM Terminology E170. Definitions in E170 are compat-
60 137
iblewithICRU60;thatdocument,therefore,maybeusedasan
5.1 Conventional gamma-ray sources ( Co or Cs), due
alternative reference.
to their low intrinsic dose rates, are
...