ISO/ASTM 51940:2002

Guide for dosimetry for irradiation of insects for sterile release programs

ISO/ASTM 51940 outlines dosimetric procedures to be followed for the radiation sterilization of live insects for use in pest management programmes. The primary use of irradiated, reproductively sterile insects is in the Sterile Insect Technique, where large numbers of sterile insects are released into the field to mate with and thus control pest populations of the same species. A secondary use of irradiated insects is as benign hosts for rearing insect parasitoids. If followed, the procedures outlined in this International Standard will help to ensure that insects processed with ionizing radiation from gamma, electron or X-ray sources receive absorbed doses within a predetermined range. ISO/ASTM 51940 covers dosimetry in the irradiation of insects for these types of irradiators: self-contained dry-storage 137Cs or 60Co irradiators, larger-scale gamma irradiators and electron accelerators. The absorbed dose for insect sterilization is typically within the range of 20 Gy to 600 Gy. This International Standard specifically refers, throughout the text, to reproductive sterilization of insects. It is equally applicable to radiation sterilization of invertebrates from other taxa (for example, Acarina, Gastropoda) and to irradiation of live insects or other invertebrates for other purposes (e.g., inducing mutations), presuming the absorbed dose is within the range specified above. It also covers the use of radiation-sensitive indicators for the visual and qualitative indication that the insects have been irradiated.

Guide de la dosimétrie pour les programmes de stérilisation des insectes

General Information

• Status: Withdrawn
• Publication Date: 17-Apr-2002
• Withdrawal Date: 17-Apr-2002
• ICS: 07.080 - Biology. Botany. Zoology
• ICS: 17.240 - Radiation measurements
• Technical Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Drafting Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 25-Oct-2004

Relations

• Revised: ISO/ASTM 51940:2004 - Guide for dosimetry for sterile insects release programs
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO/ASTM
STANDARD 51940
First edition
2002-03-15
Guide for dosimetry for irradiation of
insects for sterile release programs
Guide de la dosimétrie pour l’irradiation d’insectes pour des
programmes de lâchers d’insectes stériles
Reference number
ISO/ASTM 51940:2002(E)
© ISO/ASTM International 2002

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ISO/ASTM 51940:2002(E)
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ii © ISO/ASTM International 2002 – All rights reserved

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ISO/ASTM 51940:2002(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 . 3
6 Radiation source characteristics . 4
7 Dosimetry systems . 4
8 Radiation-sensitive indicators . 5
9 Installation qualification . 5
10 Process qualification . 6
11 Routine product processing . 7
12 Measurement uncertainty . 8
13 Keywords . 8
Annexes . 9
Bibliography . 10
Table A2.1 Recommended quality assurance procedures for insect irradiation . 10
© ISO/ASTM International 2002 – All rights reserved iii

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ISO/ASTM 51940:2002(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(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 Subcommittee E10.01,
Dosimetry for 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 International Standard 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 E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear Energy.
Annexes A1 and A2 of this International Standard are for information only.
iv © ISO/ASTM International 2002 – All rights reserved

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ISO/ASTM 51940:2002(E)
Standard Guide for
1
Irradiation of Insects for Sterile 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 priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This guide outlines dosimetric procedures to be fol-
lowed for the radiation sterilization of live insects for use in
2. Referenced Documents
pest management programs. The primary use of irradiated,
2.1 ASTM Standards:
reproductively sterile insects is in the Sterile Insect Technique,
E 170 Terminology Relating to Radiation Measurements
where large numbers of sterile insects are released into the field
2
and Dosimetry
to mate with and thus control pest populations of the same
E 177 Practice for Use of the Terms Precision and Bias in
species. A secondary use of irradiated insects is as benign
3
ASTM Test Methods
“hosts” for rearing insect parasitoids. If followed, the proce-
3
E 456 Terminology Relating to Quality and Statistics
dures outlined in this guide will help to ensure that insects
E 668 Practice for Application of Thermoluminescence-
processed with ionizing radiation from gamma, electron, or
Dosimetry (TLD) Systems for Determining Absorbed Dose
X-ray sources receive absorbed doses within a predetermined
2
in Radiation-Hardness Testing of Electronic Devices
range. Information on effective dose ranges for specific appli-
E 1026 Practice for Using the Fricke Reference Standard
cations of insect sterilization, or on methodology for determin-
2
Dosimetry System
ing effective dose ranges, is not within the scope of this guide.
2.2 ISO/ASTM Standards:
NOTE 1—Dosimetry is only one component of a total quality control
51261 Guide for Selection and Calibration of Dosimetry
program to ensure that irradiated insects are adequately sterilized and fully 2
Systems for Radiation Processing
competitive or otherwise suitable for their intended purpose.
51275 Practice for Use of a Radiochromic Film Dosimetry
2
1.2 This guide covers dosimetry in the irradiation of insects
System
137
for these types of irradiators: self-contained dry-storage Cs
51538 Practice for Use of the Ethanol-Chlorobenzene Do-
60
2
or Co irradiators, larger-scale gamma irradiators, and elec-
simetry System
2
tron accelerators. Additional, detailed information on dosimet-
51539 Guide for the Use of Radiation-Sensitive Indicators
ric procedures to be followed in installation qualification,
51540 Practice for Use of a Radiochromic Liquid Dosim-
2
process qualification, and routine product processing can be
etry System
found in ISO/ASTM Practices 51608 (X-ray, bremsstrahlung
51607 Practice for Use of the Alanine-EPR Dosimetry
2
facilities), 51649 (electron beam facilities), and 51702 (large-
System
scale gamma facilities).
51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-
2
1.3 The absorbed dose for insect sterilization is typically
ung) Facility for Radiation Processing
within the range of 20 Gy to 600 Gy.
51649 Practice for Dosimetry in an Electron Beam Facility
1.4 This guide refers, throughout the text, specifically to
for Radiation Processing at Energies Between 300 keV
2
reproductive sterilization of insects. It is equally applicable to
and 25 MeV
radiation sterilization of invertebrates from other taxa (for
51702 Practice for Dosimetry in a Gamma Irradiation Fa-
2
example, Acarina, Gastropoda) and to irradiation of live insects
cility for Radiation Processing
or other invertebrates for other purposes (for example, induc-
51707 Guide for Estimating Uncertainties in Dosimetry for
2
ing mutations), presuming the absorbed dose is within range
Radiation Processing
specified in 1.3.
51956 Practice for Use of Thermoluminescence-Dosimetry
1.5 This guide also covers the use of radiation-sensitive
(TLD) Systems for Radiation Processing
indicators for the visual and qualitative indication that the
2.3 International Commission on Radiation Units and
4
insects have been irradiated.
Measurements (ICRU) Reports:
1.6 This standard does not purport to address all of the
ICRU 14 Radiation Dosimetry: X-rays and Gamma Rays
safety concerns, if any, associated with its use. It is the
with Maximum Photon Energies Between 0.6 and 50 MeV
responsibility of the user of this standard to establish appro-
ICRU 17 Radiation Dosimetry: X-rays Generated at Poten-
tials of 5 to 150 kV
1
This guide is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee
2
Annual Book of ASTM Standards, Vol 12.02.
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
3
Annual Book of ASTM Standards, Vol 14.02.
ISO/TC 85/WG 3.
4
Available from the International Commission on Radiation Units and Measure-
Current edition approved Jan. 22, 2002. Published March 15, 2002. Originally
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA.
published as ASTM E 1940–98. Last previous ASTM edition E 1940–98.
© ISO/ASTM International 2002 – All rights reserved
1

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ISO/ASTM 51940:2002(E)
ICRU 34 The Dosimetry of Pulsed Radiation be related to absorbed dose in a given material using appro-
ICRU 35 Radiation Dosimetry: Electron Beams with Ener- priate analytical instrumentation and techniques.
gies Between 1 and 50 MeV 3.1.7.1 Discussion—A dosimeter shall exhibit the reproduc-
ICRU 60 Radiation Quantities and Units
ible and quantifiable properties that allow it to be calibrated
5
2.4 NCRP Publications: and compared to national standards.
NCRP Report No. 69, Dosimetry of X-Ray and Gamma-
3.1.8 dosimetry system—a system used for determining
Ray Beams for Radiation Therapy in the Energy Range 10
absorbed dose, consisting of dosimeters, measurement instru-
keV to 50 MeV, December 1981.
ments and their associated reference standards, and procedures
for the system’s use.
3. Terminology
3.1.9 factory-reared insects—insects that are reared en
3.1 Definitions:
masse in a laboratory or factory setting for use, following
3.1.1 absorbed dose (D)—quantity of ionizing radiation
reproductive sterilization through irradiation, as live animals in
energy imparted per unit mass of a specified material. The SI
pest management programs.
unit of absorbed dose is the gray (Gy), where 1 gray is
3.1.10 irradiator turntable—device used to rotate the can-
equivalent to the absorption of 1 joule per kilogram of the
ister during the radiation process so as to improve the dose
-1
specified material (1 Gy=1J·kg , which is equivalent to 100
uniformity ratio.
rad). The mathematical relationship is the quotient of de¯ by dm,
3.1.10.1 Discussion—An irradiator turntable is often re-
where de¯ is the mean incremental energy imparted by ionizing
ferred to as a turntable. Some irradiator geometries, for
radiation to matter of incremental mass dm (see ICRU 60).
example, with an annular array of radiation sources surround-
D 5 de¯/dm
ing the product, may not need a turntable.
3.1.11 measurement quality assurance plan—a documented
3.1.1.1 Discussion—The discontinued unit for absorbed
program for the measurement process that ensures on a
dose is the rad (1 rad = 1 cGy = 100 erg per gram). Absorbed
continuing basis that the overall uncertainty meets the require-
dose is sometimes referred to simply as dose.
ments of the specified application. This plan requires traceabil-
3.1.2 absorbed-dose mapping—measurement of absorbed-
ity to, and consistency with, nationally or internationally
dose within process load using dosimeters placed at specified
recognized standards.
locations to produce a one-, two- or three-dimensional distri-
3.1.12 measurement traceability—the ability to demonstrate
bution of absorbed dose, thus rendering a map of absorbed-
dose values. by means of an unbroken chain of comparisons that a mea-
surement is in agreement within acceptable limits of uncer-
3.1.3 absorbed-dose rate—the absorbed dose in a material
per incremental time interval, that is, the quotient of dD by dt tainty with comparable nationally or internationally recognized
standards.
(see ICRU 60).
3.1.13 packaging container—a container such as a paper
21
˙
D 5 dD/dt ~SI unit: Gy · s !
cup with lid, plastic bag, or plastic bottle that is used to hold
3.1.3.1 Discussion—The absorbed-dose rate can be speci-
factory-reared insects during irradiation and, typically, during
˙
fied in terms of average value of D over long-time intervals,
subsequent shipment from the irradiation facility to the release
-1 -1
for example, in units of Gy · min or Gy · h .
site.
3.1.4 calibration—the comparison of a measurement sys-
3.1.14 process load—volume of material with a specified
tem or device of known accuracy that is traceable to national
loading configuration irradiated as a single entity.
standards to detect, correlate, report, or eliminate by adjust-
3.1.15 radiation-sensitive indicator—material such as a
ment any variation from the required performance limits of the
coated or impregnated adhesive-back (or adhesive-front) sub-
unverified measurement system or device.
strate, ink, or coating which may be affixed to or printed on the
3.1.5 canister—a durable, reusable container, usually an
irradiated sample and which undergoes a visual change when
aluminum or steel cylinder, used to house factory-reared
exposed to ionizing radiation (see ISO/ASTM Guide 51539).
insects (in packaging containers) during the radiation process.
3.1.15.1 Discussion—Radiation-sensitive indicators are of-
3.1.5.1 Discussion—Canisters are not used in some appli-
ten referred to as “indicators.” Radiation-sensitive indicators
cations in which the packaging container is sufficiently rigid
cannot be classified as a “label” under certain trade association
and the design of irradiator is appropriate.
guidelines. Indicators may be used to show that products have
3.1.6 dose uniformity ratio—ratio of maximum to minimum
been exposed to ionizing radiation. They can be used to
absorbed dose within the irradiated factory-reared insects. This
provide a visual and qualitative indication of radiation expo-
concept is also referred to as the “max/min ratio.”
sure and can be used to distinguish between irradiated and
3.1.6.1 Discussion—The central plane/minimum dose ratio
unirradiated samples. Indicators cannot be used as a substitute
is not used in this guide.
for proper dosimetry.
3.1.7 dosimeter—a device that, when irradiated, exhibits a
3.1.16 reference–standard dosimeter—a dosimeter of high
quantifiable change in some property of the device which can
metrological quality, used as a standard to provide measure-
ments traceable to and consistent with measurements made
5 with primary–standard dosimeters (see ISO/ASTM Guide
Available from the National Council on Radiation Protection and Measure-
51261).
ments, 7910 Woodmont Ave., Bethesda, MD 20814, USA.
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2

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ISO/ASTM 51940:2002(E)
3.1.17 routine dosimeter—dosimeter calibrated against a insects are irradiated before being offered to parasitoids. This
primary-, reference-, or transfer-standard dosimeter and used eliminates the need to separate unparasitized hosts from
for routine absorbed-dose measurement (see ISO/ASTM Guide parasitoids so that fertile, unparasitized host insects are not
51261). inadvertently released into the field.
3.1.18 simulated product—a mass of material with attenu- 4.3 Factory-reared insects may be treated with ionizing
137 60
ation and scattering properties similar to those of the product, radiation, such as gamma rays from Cs or Co sources,
material or substance to be irradiated. X-rays, and in electron accelerators. Gamma irradiation of
3.1.18.1 Discussion—Simulated product is used during ir- insects is usually carried out in small, fixed-geometry, dry-
radiator characterization as a substitute for the actual product, storage irradiators (6, 7, and 8). Dosimetry methods for gamma
material, or substance to be irradiated. When used in routine irradiation of insects have been demonstrated and include
production runs, it is sometimes referred to as compensating useful procedures for mapping the absorbed dose throughout
dummy. When used for absorbed-dose mapping, simulated the volume of the insect canister in these small irradiators (9)
product is sometimes referred to as a phantom material. as well as larger gamma units (10).
3.1.19 traceability—see measurement traceability. 4.4 Specifications for irradiation of factory-reared insects
3.1.20 transfer–standard dosimeter—a dosimeter, often a include a lower limit of absorbed dose and may include a
reference–standard dosimeter, suitable for transport between central target dose and an upper limit. These values are based
different locations, used to compare absorbed-dose measure- on program requirements and on scientific data on effects of
ments (see ISO/ASTM Guide 51261). absorbed dose on the sterility, viability, and competitiveness of
3.1.21 transit dose—absorbed dose delivered to product the factory-reared insects.
while the product moves from the load position to the irradiate 4.5 For each irradiator, and absorbed-dose rate at a refer-
position, and immediately back to the unload position. ence dose position within the irradiated volume of insects or
3.2 Definitions of other terms used in this standard that simulated product is measured using a reference-standard
pertain to radiation measurement and dosimetry may be found dosimetry system. That reference-standard measurement must
in ASTM Terminology E 170. Definitions in ASTM Terminol- be used to calculate the timer setting, conveyor speed, or other
ogy E 170 are compatible with ICRU 60; that document, parameter required to deliver the specified absorbed dose to the
therefore, may be used as an alternative reference. center of the irradiated sample or other reference position
within the sample. Either relative or absolute absorbed-dose
4. Significance and Use
measurements are performed within the irradiated sample of
4.1 The major use of factory-reared insects is in sterile insects or insect-equivalent material for determining the
absorbed-dose distribution (9). Accurate radiation dosimetry at
release programs (for example, Sterile Insect Technique, or
6
SIT) for suppressing or eradicating pest populations (1) . Large a reference position which could be the position of the
minimum absorbed dose (D ) or maximum absorbed dose
numbers of reproductively sterile (irradiated) insects are re-
min
leased into an area where a wild “target population” of the (D ) offers a quantitative, independent method of process
max
control.
same species exists. The wild population is reduced to the
extent that the sterile males are successful in mating with wild 4.6 Dosimetry is part of a measurement quality assurance
plan that is applied to ensure that the radiation process meets
females. The irradiation dose absorbed by the factory-reared
insects should be with a range that induces the desired level of predetermined specifications (11, 12).
4.7 Absorbed-dose mapping for establishing locations of
sterility without substantially reducing the ability of factory-
reared males to compete with wild males for mates. Species D and D , is often performed using simulated product (9).
min max
targeted by SIT programs are typically major pests affecting
5. Types of Facilities and Modes of Operation
agriculture or human health, so the assurance by standardized
5.1 Self-Contained Dry-Source Irradiators (see Ref (13))—
dosimetry that insects have been properly irradiated is of
Most insect sterilization is accomplished by using gamma rays
crucial importance to agriculture growers, agricultural regula-
137 60
from either Cs or Co self-contained irradiators. These
tors, public health officials, the public or a combination of these
devices house the radiation source in a protective lead shield
(1, 2, 3, and 4). The irradiator operator must demonstrate by
(or other appropriate high atomic number material), and
means of accurate absorbed-dose measurements within the
usually have a mechanism to rotate or lower the canister from
volume of irradiated insects, or in simulated product, that all
the load position to the irradiation position.
insects will receive an absorbed dose that produces an accept-
5.1.1 A common method of use is to distribute the source in
able level of sterility.
an annular array. The factory-reared insects are located at the
4.2 Another use of factory-reared insects is in the produc-
center of the array, resulting in a relatively uniform absorbed-
tion of parasitoids for release against populations of insect
dose distribution. In this design, irradiator turntables would not
pests (5). Parasitoids are insects that spend the larval stage
normally be necessary.
feeding within the body of a “host” species, typically killing
5.1.2 A second method is to rotate the canister holding the
the host. In some parasitoid programs, factory-reared host
insects on an irradiator turntable in front of the source such that
the only points that remain a fixed distance from the source are
6
along an axis of rotation.
The boldface numbers in parentheses refer to the bibliography at the end of this
standard.
5.2 Large-Scale Gamma Irradiators—Gamma irradiation
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ISO/ASTM 51940:2002(E)
of insects is also carried out in pool-type irradiators, and 6.2 Electron Accelerator (Electron and Bremmstrahlung
larger-scale dry-storage irradiators could also be used. In these X-ray Modes):
facilities, the source typically consists of a series of rods 6.2.1 Direct-action electron accelerators that employ dc or
60 137
(pencils) containing Co or Cs which can be raised or pulsed high-voltage generators typically produce electron en-
lowered into a large irradiation chamber. When retracted from ergies up to 5 MeV. Indirect-action electron accelerators use
the chamber, the source is shielded by water (pool-type) or microwave or very high frequency (VHF) ac power to produce
lead, or both, or other appropriate high atomic number mate- electron energies typically from 5 MeV to 15 MeV.
rial. 6.2.2 The continuous energy spectrum of the X-rays
5.2.1 For pool irradiators, a common method of use is for (bremsstrahlung) varies from approximately 35 keV up to the
samples of insects to be carried on a conveyor in one or more maximum energy of the electrons incident on the X-ray target
revolutions around a central source, resulting in a relatively (see ISO/ASTM Practice 51608).
uniform absorbed-dose distribution. The source is lowered into
7. Dosimetry Systems
the pool only when the irradiator is not in use or the conveyors
7.1 Dosimetry systems used to determine the absorbed dose
require service.
or dose rate shall cover the absorbed dose range of interest and
5.2.2 An alternative method of use is to distribute the source
shall be calibrated before use.
in an annular array. After the irradiated sample is placed in the
7.2 Description of Dosimeter Classes:
center of the irradiation chamber, the source is raised or
7.2.1 Dosimetry systems are used to determine absorbed
lowered around it for the length of time required to achieve the
dose. They consist of dosimeters, measurements instruments,
desired absorbed dose.
and their associated reference standards, and procedures for the
5.3 Electron Accelerator (Electron and bremsstrahlung
system’s use.
X-ray modes)—Accelerator-generated radiation is in the form
7.2.2 Dosimeters may be divided into four basic classes
of electrons or bremsstrahlung X-rays.
according to their accuracy and areas of application: primary
5.3.1 For an electron accelerator, the two principal beam
standard, reference standard, transfer standard, and routine
characteristics are the energy spectrum and the average beam
dosimeters. ISO/ASTM Guide 51261 provides detailed infor-
current. The electron energy spectrum affects the variation of
mation about the selection of dosimetry systems for different
absorbed dose with depth in a given material, and the average
applications.
beam current affects the absorbed-dose rate.
7.2.2.1 Primary–Standard Dosimeters—Primary–standard
5.3.2 A bremsstrahlung X-ray accelerator emits short-
dosimeters are established and maintained by national stan-
wavelength electromagnetic radiation, similar in energy to
dards laboratories for calibration of radiation environments
nuclear gamma radiation. Although their effects on materials
(fields) and other dosimeters. The two most commonly used
are generally similar, these kinds of radiation differ in their
primary standard dosimeters are ionization chambers and
energy spectra, angular distributions, and absorbed-dose rates.
calorimeters (see ISO/ASTM Guide 51261, ICRU Reports 14,
5.3.3 Insects could be irradiated using a self-contained
17, 34 and 35 and NCRP Report 69).
portable bremsstrahlung X-ray irradiator. The bremsstrahlung
7.2.2.2 Reference–Standard Dosimeters—
X-rays are produced in a conventional manner, but the unit is
Reference–standard dosimeters are used to calibrate radiation
totally self-contained (free standing). Spectrum filtration would
environments and routine dosimeters. Reference–standard do-
be used to reduce the low energy component of the radiation,
simeters may also be used as routine dosimeters. Examples of
thus improving the dose uniformity ratio.
reference–standard dosimeters along with their useful dose
6. Radiation Source Characteristics
ranges are given in a table in ISO/ASTM Guide 51261. For
6.1 Self-Contained Dry-Storage and Large-Scale Gamma insect irradiators, the following reference–standard dosimeters
Irradiators: may be suitable; ferrous sulfate (Fricke) aqueous solution
6.1.1 The radiation source used in the facilities considered (ASTM Practice E 1026), alanine dosimeters (ISO/ASTM
60 137
in this guide consist of sealed elements of Co or Cs which Practice 51607), radiochromic solutions (ISO/ASTM Practice
are typically linear rods or “pencils” arranged in one or more 51540 and Refs (11) and (16)), and ethanol-chlorobenzene
planar or cylindrical arrays. solution (ISO/ASTM Practice 51538).
6.1.2 Cobalt-60 emits photons with energies of approxi- 7.2.2.3 Transfer–Standard Dosimeters—Transfer–standard
mately 1.17 and 1.33 MeV in nearly equal proportions. dosimeters are specially selected dosimeters used for transfer-
Cesium-137 produces photons with energies of approximately ring absorbed-dose information from an accredited or national
0.662 MeV (11). standards laboratory to an irradiation facility in order to
60 137
6.1.3 The half-lives for Co and Cs are approximately establish traceability for the facility. These dosimeters should
5.27 years (14) and 30.1 years, respectively (15). be used under conditions that are carefully controlled by the
6.1.4 For gamma-ray sources, the only variation in the issuing laboratory. Transfer–standard dosimeters may be se-
source output is the known reduction in the activity caused by lected from either reference–standard dosimeters or routine
radioactive decay. Th
...