ISO/ASTM 51940:2013

INTERNATIONAL ISO/ASTM
STANDARD 51940
Third edition
2013-04-15
Guide for dosimetry for sterile insects
release programs
Guide de la dosimétrie pour des programmes de lâchers
d’insectes stériles
Reference number
© ISO/ASTM International 2013
ISO/ASTM51940:2013(E)
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ii © ISO/ASTM International 2013 – All rights reserved

ISO/ASTM51940:2013(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 3
5 Types of facilities and modes of operation . 4
6 Radiation source characteristics . 5
7 Dosimetry systems . 5
8 Installation and operational qualification . 6
9 Performance qualification . 7
10 Routine product processing . 8
11 Measurement uncertainty . 9
12 Keywords . 9
Annexes . 9
Bibliography . 11
Table A2.1 Recommended Procedures . 11
© ISO/ASTM International 2013 – All rights reserved iii

ISO/ASTM51940:2013(E)
Foreword
ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for
voting. Publication as an International Standard requires approval by at least 75% of the member bodies
casting a vote.
ASTM International is one of the world’s largest voluntary standards development organizations with global
participation from affected stakeholders. ASTM technical committees follow rigorous due process balloting
procedures.
A pilot project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this pilot project, ASTM Committee E61,
Radiation Processing, is responsible for the development and maintenance of these dosimetry standards with
unrestricted participation and input from appropriate ISO member bodies.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. Neither ISO nor ASTM International shall be held responsible for identifying any or all such patent
rights.
International Standard ISO/ASTM 51940 was developed by ASTM Committee E61, Radiation Processing,
through Subcommittee E61.04, Specialty Application, and by Technical Committee ISO/TC 85, Nuclear
energy, nuclear technologies and radiological protection.
iv © ISO/ASTM International 2013 – All rights reserved

An American National Standard
Standard Guide for
Dosimetry for Sterile Insects Release Programs
This standard is issued under the fixed designation ISO/ASTM 51940; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision.
1. Scope 1.5 This guide also covers the use of radiation-sensitive
indicators for the visual and qualitative indication that the
1.1 This guide outlines dosimetric procedures to be fol-
insects have been irradiated.
lowed for the radiation-induced reproductive sterilization of
1.6 This document is one of a set of standards that provides
liveinsectsforuseinpestmanagementprograms.Theprimary
recommendations for properly implementing and utilizing
use of such insects is in the Sterile Insect Technique, where
dosimetry in radiation processing and describes a means of
largenumbersofreproductivelysterileinsectsarereleasedinto
achievingcompliancewiththerequirementsofASTMPractice
the field to mate with and thus control pest populations of the
E2628. It is intended to be read in conjunction with ASTM
same species. A secondary use of sterile insects is as benign
E2628.
hosts for rearing insect parasitoids. The procedures outlined in
1.7 This standard does not purport to address all of the
this guide will help ensure that insects processed with ionizing
safety concerns, if any, associated with its use. It is the
radiation from gamma, electron, or X-ray sources receive
responsibility of the user of this standard to establish appro-
absorbed doses within a predetermined range. Information on
priate safety and health practices and determine the applica-
effective dose ranges for specific applications of insect steril-
bility of regulatory limitations prior to use.
ization, or on methodology for determining effective dose
ranges, is not within the scope of this guide.
2. Referenced documents
NOTE 1—Dosimetry is only one component of a total quality assurance 3
2.1 ASTM Standards:
programtoensurethatirradiatedinsectsareadequatelysterilizedandfully
E170 TerminologyRelatingtoRadiationMeasurementsand
competitive or otherwise suitable for their intended purpose.
Dosimetry
1.2 This guide provides information on dosimetry for the
E2303 Guide for Absorbed-Dose Mapping in Radiation
irradiation of insects for these types of irradiators: self-
Processing Facilities
137 60
contained dry-storage Cs or Co irradiators, self-contained
E2628 Practice for Dosimetry in Radiation Processing
low-energy X-ray irradiators (maximum processing energies
E2701 Guide for Performance Characterization of Dosim-
from 150 to 300 keV), large-scale gamma irradiators, and
etersandDosimetrySystemsforUseinRadiationProcess-
electron accelerators (electron and X-ray modes).
ing
2.2 ISO/ASTM Standards:
NOTE 2—Additional, detailed information on dosimetric procedures to
51261 Practice for Calibration of Routine Dosimetry Sys-
be followed in installation qualification, operational qualification, perfor-
mance qualification, and routine product processing can be found in
tems for Radiation Processing
ISO/ASTM Practices 51608 (X-ray [bremsstrahlung] facilities processing
51275 Practice for Use of a Radiochromic Film Dosimetry
at energies over 300 keV), 51649 (electron beam facilities), 51702
System
(large-scale gamma facilities), and 52116 (self-contained dry-storage
51310 Practice for Use of a Radiochromic Optical Wave-
gamma facilities), and in Ref (1) (self-contained X-ray facilities).
guide Dosimetry System
1.3 The absorbed dose for insect sterilization is typically
51539 Guide for the Use of Radiation-Sensitive Indicators
within the range of 20 to 600 Gy.
51607 Practice for Use of an Alanine-EPR Dosimetry Sys-
1.4 This guide refers, throughout the text, specifically to
tem
reproductive sterilization of insects. It is equally applicable to
51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-
radiation sterilization of invertebrates from other taxa (for
ung) Facility for Radiation Processing
example,Acarina,Gastropoda)andtoirradiationofliveinsects
51649 Practice for Dosimetry in an Electron Beam Facility
or other invertebrates for other purposes (for example, induc-
for Radiation Processing at Energies Between 300 keV
ing mutations), provided the absorbed dose is within the range
and 25 MeV
specified in 1.3.
51702 Practice for Dosimetry in a Gamma Facility for
Radiation Processing
51707 Guide for Estimating Uncertainties in Dosimetry for
This guide is under the jurisdiction of ASTM Committee E61 on Radiation
Processing and is the direct responsibility of Subcommittee E61.04 on Specialty Radiation Processing
Application, and is also under the jurisdiction of ISO/TC 85/WG 3.
51956 Practice for Use of Thermoluminescence-Dosimetry
Current edition approved Dec. 26, 2012. Published April 2013. Originally
published as ASTM E 1940–98. Last previous ASTM edition E 1940–98. The
present International Standard ISO/ASTM 51940:2013(E) replaces ASTM E
1940–98 and is a major revision of the last previous edition ISO/ASTM For referenced ASTM and ISO/ASTM standards, visit the ASTM website,
51940:2004(E). www.astm.org, or contact ASTM Customer Service at service@astm.org. For
Theboldfacenumbersinparenthesesrefertothebibliographyattheendofthis Annual Book of ASTM Standards volume information, refer to the standard’s
standard. Document Summary page on the ASTM website.
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
(TLD) Systems for Radiation Processing 3.1.4.1 Discussion—Arecognized national metrology insti-
52116 Practice for Dosimetry for a Self-Contained Dry- tute or other calibration laboratory accredited to ISO/IEC
Storage Gamma-Ray Irradiator 17025 should be used in order to ensure traceability to a
2.3 International Commission on Radiation Units and national or international standard. A calibration certificate
Measurements (ICRU) Reports: provided by a laboratory not having formal recognition or
ICRU 85a Fundamental Units and Quantities for Ionizing accreditation will not necessarily be proof of traceability to a
Radiation national or international standard.
2.4 ISO Standards:
3.1.5 calibration [VIM, 6.11]—set of operations that estab-
ISO/IEC 17025 General Requirements for the Competence
lish, under specified conditions, the relationship between
of Testing and Calibration Laboratories values of quantities indicated by a measuring instrument or
2.5 Joint Committee for Guides in Metrology (JCGM)
measuringsystem,orvaluesrepresentedbyamaterialmeasure
Reports: or a reference material, and the corresponding values realized
JCGM100:2008,GUM, withminorcorrections,Evaluation
by standards.
of measurement data – Guide to the Expression of
3.1.5.1 Discussion—Calibration conditions include envi-
Uncertainty in Measurement
ronmentalandirradiationconditionspresentduringirradiation,
JCGM 100:2008, VIM International vocabulary of metrol-
storageandmeasurementofthedosimetersthatareusedforthe
ogy – Basis and general concepts and associated terms
generation of a calibration curve. To achieve stable environ-
mental conditions, it may be necessary to condition the
3. Terminology
dosimeters before performing the calibration procedure.
3.1 Definitions:
3.1.6 dose uniformity ratio—ratioofmaximumtominimum
3.1.1 absorbed dose (D)—quantity of ionizing radiation
absorbed dose within the irradiated product.
energy imparted per unit mass of a specified material. The SI
3.1.6.1 Discussion—The concept is also referred to as the
unit of absorbed dose is the gray (Gy), where 1 gray is
max/min dose ratio.
equivalent to the absorption of 1 joule per kilogram of the
3.1.7 dosimeter—device that, when irradiated, exhibits a
specified material (1 Gy = 1 J/kg). The mathematical relation-
quantifiable change that can be related to absorbed dose in a
ship is the quotient of dϵ by dm, where dϵ is the mean
givenmaterialusingappropriatemeasurementinstrumentsand
incremental energy imparted by ionizing radiation to matter of
procedures.
incremental mass dm (see ICRU85a).
3.1.8 dosimeter batch—quantity of dosimeters made from a
D 5d´¯/dm
specific mass of material with uniform composition, fabricated
in a single production run under controlled, consistent condi-
3.1.1.1 Discussion—The discontinued unit for absorbed
tions and having a unique identification code.
dose is the rad (1 rad = 100 erg/g = 0.01 Gy). Absorbed dose
is sometimes referred to simply as dose. 3.1.9 dosimeter set—one or more dosimeters used to mea-
3.1.2 absorbed-dose mapping—measurement of absorbed- suretheabsorbeddoseatalocationandwhoseaveragereading
dose within an irradiated product to produce a one-, two- or is used to determine absorbed dose at that location.
three-dimensionaldistributionofabsorbeddose,thusrendering 3.1.10 dosimetry system—system used for measuring ab-
a map of absorbed-dose values.
sorbed dose, consisting of dosimeters, measurement instru-
˙
3.1.3 absorbed-dose rate, D—absorbed dose in a material ments and their associated reference standards, and procedures
per incremental time interval, that is, the quotient of dD by dt. for the system’s use.
−1
Also see ASTM E170. The SI unit is Gy·s
3.1.11 influence quantity—quantity that is not the mea-
surand but that affects the result of the measurement.
˙
D 5dD/dt
3.1.11.1 Discussion—In radiation processing dosimetry,
3.1.3.1 Discussion—The absorbed-dose rate can be speci-
this term includes temperature, relative humidity, time inter-
fied in terms of its average value over long-time intervals, for
vals, light, radiation energy, absorbed-dose rate, and other
−1 −1
example in units of Gy·min or Gy·h
factors that might affect dosimeter response, as well as quan-
3.1.4 approved laboratory—laboratory that is a recognized
tities associated with the measurement instrument.
nationalmetrologyinstitute,orhasbeenformallyaccreditedto
3.1.12 in-situ/in-plant calibration—calibration where the
ISO/IEC 17025, or has a quality system consistent with the
dosimeter irradiation is performed in the place of use of the
requirements of ISO/IEC 17025.
routine dosimeters.
3.1.12.1 Discussion—In-situ/in-plant calibration of dosim-
etry systems refers to irradiation of dosimeters along with
AvailablefromtheInternationalCommissiononRadiationUnitsandMeasure-
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA.
reference or transfer dosimeters, under operating conditions
Available from International Organization for Standardization (ISO), 1 Rue de
that are representative of the routine processing environment,
Varembé, Case Postale 56, CH-1211, Geneva 20, Switzerland.
forthepurposeofdevelopingacalibrationcurvefortheroutine
DocumentproducedbyWorkingGroup1oftheJointCommitteeforGuidesin
Metrology (JCGM/WG 1). Available free of charge at the BIPM website (http://
dosimetry systems.
www.bipm.org).
3.1.13 installation qualification—process of obtaining and
DocumentproducedbyWorkingGroup2oftheJointCommitteeforGuidesin
documenting evidence that equipment has been provided and
Metrology (JCGM/WG 2). Available free of charge at the BIPM website (http://
www.bipm.org). installed in accordance with its specification.
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
3.1.14 irradiation container—holder in which product is product, it is sometimes referred to as compensating dummy.
placed during the irradiation process. When used for absorbed-dose mapping, simulated product is
sometimes referred to as a phantom material.
3.1.14.1 Discussion—For insect irradiation, the configura-
3.1.22 traceability—propertyoftheresultofameasurement
tionofirradiationcontainersvarieswidelywithsuchfactorsas
type and energy of radiation, irradiator design, insect species, or the value of a standard whereby it can be related to stated
references, usually national or international standards, through
insect stage being irradiated, and other process specifications
(for example, some insects are irradiated in reduced-oxygen an unbroken chain of comparisons all having stated uncertain-
ties.
atmospheres, requiring air-tight containers). Irradiation con-
tainers for insects range from single-use items such as paper 3.1.22.1 Discussion—The unbroken chain of comparisons
cylinders or plastic bags to reusable canisters of stainless steel is called a “traceability chain.”
or other durable material. When canisters are used, insects are
3.1.23 transfer standard dosimetry system—dosimetry sys-
often held secondarily within the canister in a plastic bag or tem used as an intermediary to calibrate other dosimetry
other disposable container.
systems.
3.1.15 irradiator turntable—device used to rotate the
3.1.24 transit dose—absorbed dose delivered to a product
sample during the irradiation process so as to improve dose (or a dosimeter) while it travels between the non-irradiation
uniformity.
position and the irradiation position, or in the case of a
3.1.15.1 Discussion—An irradiator turntable is often re- movable source while the source moves into and out of its
ferred to as a turntable. Some irradiator geometries, for irradiation position.
example, with an annular array of radiation sources surround-
3.1.25 type I dosimeter—dosimeter of high metrological
ing the product, may not need a turntable. quality, the response of which is affected by individual influ-
3.1.16 operational qualification (OQ)—process of obtain- ence quantities in a well-defined way that can be expressed in
terms of independent correction factors.
ing and documenting evidence that installed equipment oper-
ateswithinpredeterminedlimitswhenusedinaccordancewith 3.1.26 type II dosimeter—dosimeter, the response of which
its operational procedures. isaffectedbyinfluencequantitiesinacomplexwaythatcannot
practically be expressed in terms of independent correction
3.1.17 performance qualification (PQ)—process of obtain-
ing and documenting evidence that the equipment, as installed factors.
and operated in accordance with operation procedures, consis- 3.2 Definitions of Terms Specific to This Standard:
tently performs in accordance with predetermined criteria and
3.2.1 factory-reared insects—insects that are reared in large
thereby yields product meeting its specification. quantity in a laboratory or factory setting for use, following
3.1.18 radiation-sensitive indicator—material such as a reproductivesterilizationthroughirradiation,asliveanimalsin
coated or impregnated adhesive-backed substrate, ink, coating pest management programs.
or other materials which may be affixed to or printed on the 3.3 Definitions of other terms used in this standard that
product or irradiation container and which undergoes a visual
pertain to radiation measurement and dosimetry may be found
change when exposed to ionizing radiation (see ISO/ASTM inASTM Terminology E170. Definitions in E170 are compat-
Guide 51539).
ible with ICRU85a; that document, therefore, may be used as
an alternative reference.
3.1.18.1 Discussion—Radiation-sensitive indicators are of-
ten referred to as “indicators.” Indicators may be used to show
that products have been exposed to ionizing radiation. They 4. Significance and use
can be used to provide a visual and qualitative indication of
4.1 The major use of factory-reared insects is in sterile
radiation exposure and can be used to distinguish between
insectreleaseprograms(forexample,SterileInsectTechnique,
irradiated and unirradiated samples. Indicators cannot be used
or SIT) for suppressing or eradicating pest populations (2,3).
as a substitute for proper dosimetry.
Large numbers of reproductively sterile (irradiated) insects are
3.1.19 reference standard dosimetry system—dosimetry
released into an area where a wild “target population” of the
system, generally having the highest metrological quality
same species exists. The wild population is reduced to the
available at a given location or in a given organization, from
extent that the sterile males are successful in mating with wild
which measurements made there are derived.
females. The radiation dose absorbed by the factory-reared
3.1.20 routine dosimetry system—dosimetry system cali-
insects should be within a range that induces the desired level
brated against a reference standard dosimetry system and used
ofsterilitywithoutsubstantiallyreducingtheabilityoffactory-
for routine absorbed-dose measurements, including dose map-
reared males to compete with wild males for mates. Species
ping and process monitoring.
targeted by SIT programs are typically major pests affecting
3.1.21 simulated product—massofmaterialwithabsorption agriculture or human health, so the assurance by standardized
and scattering properties similar to those of the product,
dosimetry that insects have been properly irradiated is of
material or substance to be irradiated.
crucial importance to agriculture growers, agricultural regula-
3.1.21.1 Discussion—Simulated product is used during ir- tors, public health officials, and the public (3). The irradiator
radiator characterization as a substitute for the actual product, operatormustdemonstratebymeansofaccurateabsorbed-dose
material, or substance to be irradiated. When used in routine measurements that all insects have received absorbed dose
production runs in order to compensate for the absence of within the specified range.
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
4.2 Another use of factory-reared insects is in the produc- rotate the irradiation container from a load position to the
tion of parasitoids for release against populations of insect irradiation position and then to a separate unload position.
pests (4). Parasitoids are insects that spend the larval stage
5.1.1.1 Inatypicalconfiguration,theradionuclideishoused
feeding within or on the body of a “host” species, typically
inrodsor“pencils”(see6.1.1)thataredistributedinanannular
killing the host. In some parasitoid programs, factory-reared
array around the irradiation chamber. For processing, the
host insects are irradiated before being offered to parasitoids.
irradiation container is located at the center of the array, where
This eliminates the need to separate unparasitized hosts from
the absorbed-dose rate is relatively uniform.
parasitoids so that fertile, unparasitized host insects are not
5.1.1.2 In an alternative configuration, the radionuclide is
inadvertently released into the field.
contained in a single rod. In this case, the irradiation container
4.3 Factory-reared insects may be treated with ionizing is rotated on an irradiator turntable within the irradiation
137 60
radiation,suchasgammaradiationfrom Csor Cosources,
chamber to achieve an acceptably uniform dose. The axis of
or X-radiation or electrons from accelerators. Gamma irradia- rotation is parallel to the source rod, which is vertical.
tion of insects is often carried out in small, fixed-geometry,
5.1.2 Low-energy X-ray irradiators—Low-energy X-ray ir-
dry-storage irradiators (5). Dosimetry methods for gamma and
radiators utilize X-ray tubes that consist of an electron source
X-ray irradiation of insects have been demonstrated and
(generally a heated wire, a filament which emits electrons), an
include useful procedures for measuring the absorbed dose
electrostatic field to accelerate these electrons and a converter
distribution throughout the volume of the irradiation contain-
to generate X-radiation. In the currently available irradiators,
er(s)inthesesmallirradiators(ASTMPractice52116andRefs
the converter is present throughout the curved surface of the
(1,6)) as well as large-scale gamma irradiators (ISO/ASTM
tube, and hence the X-radiation is emitted in all directions.
Practice 51702 and Ref (7)).
5.1.2.1 One method is to operate the irradiator in a batch
4.4 Specifications for irradiation of factory-reared insects
mode where several canisters of insects are placed around and
include a lower limit of absorbed dose and may include a
parallel to the X-ray tube, and revolve around the tube during
central target dose and an upper limit. These values are based
irradiation while maintaining their orientation (much like
on program requirements and on scientific data on effects of
chairs on a Ferris wheel), achieving acceptable dose unifor-
absorbeddoseonthesterility,viability,andcompetitivenessof
mity.
the factory-reared insects.
5.1.2.2 An alternate method is to continuously pass trays
4.5 To demonstrate control of the radiation process, the
with insects between two X-ray tubes, providing irradiation
absorbed dose must be measured using a calibrated dosimetry
from two sides.
system. Regulations or policies under which the facility oper-
5.2 Large-Scale Panoramic Gamma Irradiators—Gamma
ates may require the calibration to be traceable to appropriate
irradiation of insects is also carried out in large-scale irradia-
national or international standards. The radiation-induced
tors, either wet-storage or dry-storage. In these facilities, the
change in the dosimeter is evaluated and related to absorbed
source typically consists of either a single rod or a series of
dose through calibration (ISO/ASTM Practice 51261).
rods (pencils) that contain Co and can be raised or lowered
4.6 For each irradiator, absorbed-dose rate at a reference
into a large irradiation room. When retracted from the irradia-
position within the irradiated volume of insects or simulated
tion room, the source is shielded by water (wet-storage; IAEA
product is measured using a transfer or reference standard
Category IV (10), or lead or other appropriate high atomic
dosimetry system. That measurement provides a basis for
number material (dry-storage; IAEACategory II (10), or both.
calculatingthedurationofirradiation,conveyorspeed,orother
5.2.1 Continuous Operation—A common method of use is
parameterrequiredtodeliverthespecifiedabsorbeddosetothe
for irradiation containers to be carried on a conveyor in one or
insects.
more revolutions around a central source, resulting in a
4.7 Absorbed-dose mapping for establishing magnitudes
relatively uniform absorbed dose. The source is retracted from
and locations of minimum dose (D ) and maximum dose
min the irradiation room only when the irradiator is not in use.
(D ) is performed using actual product or simulated product
max 5.2.2 Batch Operation—An alternative method of use is to
(5).
place irradiation container(s) of insects into the irradiation
room while the source is shielded, and then raise or lower the
5. Types of facilities and modes of operation
source into the irradiation room for the length of time required
to achieve the desired absorbed dose. For this mode of
5.1 Self-Contained Irradiators —These devices house the
operation,eachirradiationcontaineristypicallyrotatedaround
radiation source in a protective shield of lead (or other
its own axis to improve dose uniformity.
appropriate high atomic number material), and require no
5.3 Electron Accelerator—Accelerator-generated high en-
additionalorexternalshieldingagainstradiation.Theradiation
ergy (3-10 MeV) electrons can also be used for insect irradia-
source could be either a radionuclide or an X-ray tube.
tion. Such irradiators are housed in heavily shielded rooms.
5.1.1 Gamma Irradiators (IAEA Category I, Ref (8,9)—
5.3.1 Typically, accelerators produce a narrow electron
Currently, most reproductive sterilization of insects is accom-
137 60
beamthatisscannedtocoverthelengthandwidthoftheinsect
plished by using gamma radiation from either Cs or Co in
container, generally a tray.
dry-storage, self-contained irradiators. These irradiators often
have a mechanism to move the irradiation container from the 5.3.2 X-radiation (bremsstrahlung) produced by striking an
load/unload position to the irradiation position and back, or to X-ray target with an electron beam can also be used for this
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
purpose. The target is made of tungsten, tantalum, or other absorbed dose with depth in a given material, and the average
metal with a high atomic number, high melting temperature, beam current affects the absorbed-dose rate. Because of low
and high thermal conductivity. penetration of electrons, electron energy of at least 3 MeV is
5.3.3 For processing, insects are typically carried on a necessary to achieve useful dose uniformity.
movingconveyorthroughtheelectronorX-raybeam.Because
6.3.1.1 Direct-actionelectronacceleratorsthatemploydcor
of the narrow angular distribution of the radiation, use of
pulsed high-voltage generators typically produce electron en-
continuously moving conveyors (rather than static-irradiation
ergies up to 5 MeV.
or shuffle-dwell systems) enhances dose uniformity.
6.3.1.2 Indirect-action electron accelerators use microwave
5.3.4 Additional information on electron and X-ray facili-
or very high frequency (VHF) ac power to produce electron
ties and their modes of operation may be found in ISO/ASTM
energies typically from 5 to 15 MeV.
Practices 51649 (electrons) and 51608 (X-radiation).
6.3.2 For an X-ray (bremsstrahlung) facility, besides beam
characteristics noted in 6.3.1, X-ray target design is a critical
6. Radiation source characteristics
parameter. X-radiation is similar to gamma radiation from
6.1 Gamma Irradiators:
radioactive isotopic sources. Although their effects on materi-
6.1.1 The radiation source used in the gamma facilities
als are generally similar, these kinds of radiation differ in their
considered in this guide consists of sealed elements of Co
energy spectra, angular distributions, and absorbed-dose rates.
or Cs which are typically linear rods or “pencils” arranged
The continuous energy spectrum of the X-radiation
in one or more planar or cylindrical arrays.
(bremsstrahlung)extendsfromapproximately35keVuptothe
6.1.2 Cobalt-60 emits photons with energies of approxi-
maximum energy of the electrons incident on the X-ray target
mately 1.17 and 1.33 MeV in nearly equal proportions.
(see ISO/ASTM Practice 51608). In some X-ray facilities,
Cesium-137 emits photons with energies of approximately
spectrumfiltrationisusedtoreducethelowenergycomponent
0.662 MeV (11).
60 137
of the radiation, thus improving dose uniformity.
6.1.3 The radioactive decay half-lives for Co and Cs
are regularly reviewed and updated. The most recent publica-
7. Dosimetry systems
tionbytheNationalInstituteofStandardsandTechnology(12)
gave values of 1925.20 (60.25) days for Co and 11018.3
7.1 Description of Dosimeters and Dosimetry Systems—
137 137
(69.5) days for Cs. In addition, the Cs radiation source
Classificationofdosimetersanddosimetrysystemsisbasedon
may contain radioimpurities which should be quantified by the
the inherent metrological dosimeter properties and the field of
source manufacturer.
application of the dosimetry system (see ASTM Practice
6.1.4 For gamma sources, the only variation in the source
E2628). These classifications influence both the selection and
output is the known reduction in the activity caused by
calibration of dosimetry systems.
radioactive decay. The reduction in the activity (source
7.1.1 Classification of Dosimeters—Classification of do-
strength), and the corresponding required increase in the
simetersisbasedontheirinherentmetrologicalproperties.The
irradiationtime,maybecalculated(see8.2.3)orobtainedfrom
method of measurement may be important in the classification
tables provided by the irradiator manufacturer.
(see below), but the classification does not include consider-
6.2 Self-Contained Low-Energy X-ray Irradiators—The
ation of the actual instrumentation used, or the quality of
electrons that generate X-radiation (bremsstrahlung) are elec-
preparation (manufacture) of the dosimeter.
trostatically accelerated through a small potential difference to
7.1.1.1 Type I Dosimeters—In order for a dosimeter to be
energies in the range of a few hundred keV (13,14).
classified as a type I dosimeter, it must be possible to apply
6.2.1 Currently, available low-energy X-ray irradiators use
accurate,independentcorrectionstoitsresponsetoaccountfor
tubesthatgenerateX-radiationwithamaximumenergyof150
theeffectsofinfluencequantities,suchastemperatureanddose
keV. The continuous energy spectrum of the X-radiation
rate. In classifying a dosimeter as a type I dosimeter, it may be
extends from approximately 35 keV up to the energy of the
necessarytospecifythemethodofmeasurement.Forexample,
electrons (1).
freeradicalsproducedinirradiatedalaninecan,inprinciple,be
NOTE 3—Because of the low photon energy, some dosimetry systems
measured by a number of different techniques; however, only
that are commonly used with gamma irradiators and accelerators are not
the EPR technique has been shown to provide the high
applicable to low-energy X-ray irradiators (see Annex A1 and Refs
metrological quality necessary to classify alanine as a type I
(1,13)). For example, Farmer-type ionization chambers are appropriate as
dosimeter. Refer to ASTM Practice E2628 for a list of type I
reference standard dosimetry systems for low-energy X-ray irradiators
dosimeters.
(1,13,15).
7.1.1.2 Type II Dosimeters—The classification of a dosim-
6.2.2 Energy of the X-radiation influences the size and
eter as a type II dosimeter is based on the complexity of
shapeoftheirradiationcontainerneededtoachievethedesired
interaction between influence quantities, such as temperature
level of dose uniformity. The tube current influences the
anddoserate,whichmakesitimpracticaltoapplyindependent
absorbed-dose rate and thus time of irradiation.
correction factors to the dosimeter response. Refer to ASTM
6.3 Electron Accelerator (Electron and X-ray Modes):
Practice E2628 for a list of type II dosimeters.
6.3.1 For an electron accelerator, the two principal beam
7.1.2 Classification of Dosimetry Systems:
characteristics are the energy spectrum and the average beam
current. The electron energy spectrum affects the variation of 7.1.2.1 Reference Standard Dosimetry Systems:
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
(1) The classification of a dosimetry system as a reference
7.2.2.1 Calibration irradiations performed at an approved
standard dosimetry system is based on its application. Refer- laboratory followed by a calibration verification exercise for
ence standard dosimetry systems are used as standards to the actual conditions of use (see ISO/ASTM 51261), and
calibrate other dosimetry systems that are used for routine 7.2.2.2 In-situ/in-plant calibration irradiations of routine
measurements. In addition, the reference standard dosimetry
dosimeters along with transfer standard dosimeters issued and
systemsareusedtocertifytheabsorbed-doserateatareference analyzed by an approved laboratory.
position within the irradiator. The uncertainty of the reference
7.2.3 Calibration of a dosimetry system is most commonly
standard dosimetry system will affect the uncertainty of the
made in terms of absorbed dose to water, but absorbed dose to
system being calibrated and thus the uncertainty in the ab-
other materials might be used.
sorbed dose value for the product being irradiated.
8. Installation and operational qualification
(2) Reference standard dosimetry systems may take the
form of systems held at a given location or they may take the
8.1 Installation qualification is performed to obtain and
form of transfer standard dosimetry systems operated by a
document evidence that the irradiator and measurement instru-
national standards laboratory or an accredited dosimetry cali-
ments have been delivered and installed in accordance with
bration laboratory. In the case of transfer standard dosimetry
their specifications. Installation qualification includes docu-
systems, dosimeters are sent to a facility for irradiation and
mentation of the irradiator equipment and measurement instru-
then returned to the issuing laboratory for measurement. The
ments; establishment of testing, operation and calibration
requirement that dosimeters be transported without unduly
procedures for their use; and verification that the installed
increasing the measurement uncertainty restricts the type of
irradiator equipment and measurement instruments operate
dosimeter that can be used. Alanine/EPR, dichromate and
according to specification. Specific information on installation
Ceric-Cerous dosimetry systems are commonly used in this
qualification for various types of facilities can be found in
way.
ISO/ASTM Practices 52116 (self-contained dry-storage
gamma facilities), 51608 (X-ray [bremsstrahlung] facilities),
(3) The dosimeter used in a reference standard dosimetry
51649 (electron beam facilities), and 51702 (large-scale
system is generally a type I dosimeter. The expanded uncer-
gamma facilities).
tainty achievable with measurements made using a reference
standard dosimetry system is typically of the order of 63% (at
NOTE 4—Table A2.1 gives some recommended steps in the following
the 95 % confidence level).
areas for insect irradiation: installation qualification, operational qualifi-
cation, performance qualification, and routine product processing. The
7.1.2.2 Routine Dosimetry Systems—The classification of a
recommended steps in Table A2.1 are not meant to be exhaustive.
dosimetry system as a routine dosimetry system is based on its
application, i.e. routine absorbed-dose measurements, includ-
8.2 Operational qualification of an irradiation facility is
ing dose mapping and process monitoring.The dosimeter used
performed to establish baseline data for characterizing facility
in a routine dosimetry system is generally a type II dosimeter,
effectiveness, predictability, and reproducibility for the range
although there may be exceptions, for example the use of type
of conditions of operation for key process parameters that
I alanine dosimeters. The expanded uncertainty achievable
affect absorbed dose in the product. As part of this process,
with measurements made using a routine dosimetry system is
dosimetry may, for example, be performed to: (1) establish
typically of the order of 66 % (at the 95 % confidence level).
relationships between the absorbed dose for a reference geom-
7.2 Dosimetry System Calibration: etry and the operating parameters of the irradiator, (2) measure
absorbed-dosedistributionsinirradiationcontainerscontaining
7.2.1 Dosimetry systems consist of dosimeters, measure-
homogeneous simulated product (dose mapping), (3) charac-
ment instruments and their associated reference standards, and
terize absorbed-dose variations when a facility and process
proceduresforthesystem’suse.Priortouse,routinedosimetry
parametersfluctuatestatisticallyduringnormaloperations,and
systems shall be calibrated in accordance with documented
(4) measure the absorbed-dose rate at a reference position
proceduresthatspecifydetailsofthecalibrationprocessandbe
within the irradiation container filled with insects or simulated
in compliance with ISO/ASTM 51261. Calibration shall be
product.
repeated at regular intervals to ensure that the accuracy of the
absorbed-dose measurement is maintained within required
NOTE 5—Specificinformationonoperationalqualificationcanbefound
limits. Detailed calibration procedures are provided in ISO/
in ISO/ASTM Practices 52116 (for self-contained dry-storage gamma
ASTM 51261. All dosimetry equipment requires either cali-
facilities), 51608 (for X-ray facilities), 51649 (for electron beam facili-
ties), and 51702 (for large-scale gamma facilities), and in Ref (1) (for
bration traceable to appropriate standards or performance
self-contained low-energy X-ray facilities).
checks to verify its operation. Similarly, each dosimeter batch
that a facility uses requires calibration. If required by regula-
8.2.1 Irradiator Characterization—The absorbed dose re-
tion or policy, it is necessary to demonstrate that dose mea-
ceivedbyinsectsdependsontheoperatingparameters(suchas
surements are traceable to recognized national or international
the source activity or power at the time of irradiation, the
standards.
geometry of the source, the source-to-product distance, the
7.2.2 Irradiationisacriticalcomponentofthecalibrationof irradiationgeometry)andotherprocessparameters(suchasthe
the dosimetry system. There are two methods for irradiating irradiation time, the product composition and density, and the
dosimeters for calibration: loading configuration).
© ISO/ASTM International 2013 – All rights reserved
ISO/ASTM51940:2013(E)
8.2.1.1 Absorbed-Dose Rate—A reference or transfer stan- system (see 8.2.1.1) provides the value at t = 0. The absorbed-
dard dosimetry system, traceable to nationally or internation- dose rate at t days later can then be computed from Eq 1 using
ally recognized standards, shall be used to measure the λ for the appropriate radionuclide from Eq 2 or Eq 3.
absorbed-doserateatareferenceposition,suchasthecenterof
9. Performance qualification
the irradiation container filled with insects or simulated prod-
uct. This measurement of absorbed-dose rate at a reference
9.1 Objective—The purpose of dosimetry in performance
position provides a basis for calculating the value of param-
qualification is to ensure that the absorbed-dose requirements
eter(s) (e.g., duration of irradiation or conveyor speed) neces-
for a particular product and process can be satisfied. In sterile
sary to deliver the specified absorbed dose to the insects (see
insect release programs, the end user or a regulatory agency
9.4). The measurement should be repeated periodically (for
typically specifies the minimum absorbed dose necessary to
example,everythreeyearsforagammafacility)andfollowing
produce the desired level of reproductive sterility. Although a
any changes to the source, geometry, or other irradiator
maximum absorbed dose is not usually specified, the ability of
parameters that could affect dose rate.
sterile insects to successfully compete for mates will decline
with increased dose. Knowledge of the dose distribution
NOTE 6—When the irradiator absorbed-dose rate is measured per
throughout the irradiation container is critical for ensuring
8.2.1.1,itisconvenienttocalibratethefacility‘sroutinedosimetrysystem
program security and sterile insect quality. This is accom-
concurrently per 7.2.2.2. ISO/ASTM 51261 provides guidelines on
calibration proce
...