ASTM ISO/ASTM52116-13(2020)

Standard Practice for Dosimetry for a Self-Contained Dry-Storage Gamma Irradiator

SIGNIFICANCE AND USE
4.1 The design and operation of a self-contained irradiator should ensure that reproducible absorbed doses are obtained when the same irradiation parameters are used. Dosimetry is performed to determine the relationship between the irradiation parameters and the absorbed dose.  
4.1.1 For most applications, the absorbed dose is expressed as absorbed dose to water (see ISO/ASTM Practice 51261). For conversion of absorbed dose to water to that to other materials, for example, silicon, see Annex A1 of ISO/ASTM Practice 51261.  
4.2 Self-contained dry-storage gamma irradiators contain properly shielded radioactive sources, namely  137Cs or  60Co, that emit ionizing electromagnetic radiation (gamma radiation). These irradiators have an enclosed, accessible irradiator sample chamber connected with a sample positioning system, for example, irradiator drawer, rotor, or irradiator turntable, as part of the irradiation device.  
4.3 Self-contained dry-storage gamma irradiators can be used for many radiation processing applications, including the calibration irradiation of dosimeters; studies of dosimeter influence quantities; radiation effects studies, and irradiation of materials or biological samples for process compatibility studies; batch irradiations of microbiological, botanical, or in-vitro samples; irradiation of small animals; radiation “hardness” testing of electronics components and other materials; and batch radiation processing of containers of samples.
Note 1: Self-contained dry-storage gamma irradiators contain a sealed radiation source, or an array of sealed radiation sources securely held in a dry container constructed of solid materials. The sealed radiation sources are shielded at all times, and human access to the chamber undergoing irradiation is not physically possible due to the irradiator’s design configuration (see ANSI/HPS N43.7).
Note 2: For reference–standard dosimetry, the absorbed dose and absorbed-dose rate can be expressed in water or o...
SCOPE
1.1 This practice outlines dosimetric procedures to be followed with self-contained dry-storage gamma irradiators. For irradiators used for routine processing, procedures are given to ensure that product processed will receive absorbed doses within prescribed limits.  
1.2 This practice covers dosimetry in the use of dry-storage gamma irradiators, namely self-contained dry-storage 137Cs or  60Co irradiators (shielded freestanding irradiators). It does not cover underwater pool sources, panoramic gamma sources, nor does it cover self-contained bremsstrahlung X-ray units.  
1.3 The absorbed-dose range for the use of the dry-storage self-contained gamma irradiators covered by this practice is typically 1 to 105 Gy, depending on the application. The absorbed-dose rate range typically is from 10–2 to 103 Gy/min.  
1.4 For irradiators supplied for specific applications, specific ISO/ASTM or ASTM practices and guides provide dosimetric procedures for the application. For procedures specific to dosimetry in blood irradiation, see ISO/ASTM Practice 51939. For procedures specific to dosimetry in radiation research on food and agricultural products, see ISO/ASTM Practice 51900 . For procedures specific to radiation hardness testing, see ASTM Practice E1249. For procedures specific to the dosimetry in the irradiation of insects for sterile release programs, see ISO/ASTM Guide 51940. In those cases covered by ISO/ASTM 51939, 51900 , 51940, or ASTM E1249, those standards take precedence.  
1.5 This document is one of a set of standards that provides recommendations for properly implementing and utilizing dosimetry in radiation processing. It is intended to be read in conjunction with ASTM E2628, “Practice for Dosimetry in Radiation Processing”.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate ...

General Information

• Status: Published
• Publication Date: 30-Jun-2020
• ICS: 17.240 - Radiation measurements
• Technical Committee: E61 - Radiation Processing
• Drafting Committee: E61.04 - Specialty Application

Relations

• Refers: ASTM E170-17 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2017
• Refers: ASTM E170-16a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Oct-2016
• Refers: ASTM E170-16 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Feb-2016
• Refers: ASTM E170-15a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2015
• Refers: ASTM E170-15 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Mar-2015
• Refers: ASTM E170-14a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Oct-2014
• Refers: ASTM E170-14 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2014
• Refers: ASTM E1249-10 - Standard Practice for Minimizing Dosimetry Errors in Radiation Hardness Testing of Silicon Electronic Devices Using Co-60 Sources
• Effective Date: 01-Dec-2010
• Refers: ASTM E170-10 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2010
• Refers: ASTM E2628-09 - Standard Practice for Dosimetry for Radiation Processing
• Effective Date: 15-Aug-2009
• Refers: ASTM E170-09a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Aug-2009
• Refers: ASTM E170-09 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Jun-2009
• Refers: ASTM E170-08d - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Nov-2008
• Refers: ASTM E170-08c - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2008
• Refers: ASTM E170-08b - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-May-2008

Overview

ASTM ISO/ASTM52116-13(2020) - Standard Practice for Dosimetry for a Self-Contained Dry-Storage Gamma Irradiator - provides comprehensive guidance for establishing and controlling dosimetry procedures in self-contained dry-storage gamma irradiators, typically using ^137Cs (cesium-137) or ^60Co (cobalt-60) radioactive sources. This internationally recognized standard ensures reproducible and reliable absorbed dose delivery for a wide range of radiation processing applications, emphasizing quality assurance and regulatory compliance in the use of gamma irradiators.

Key Topics

• Dosimetric Procedures: The standard outlines detailed processes for measuring and mapping the absorbed dose within irradiated products or samples, ensuring doses remain within prescribed limits for routine processing.
• Absorbed Dose Ranges: Typical operation includes absorbed-dose ranges from 1 to 10^5 Gy and dose rates of 10^-2 to 10^3 Gy/min, suitable for various applications.
• Types of Irradiators: Focuses on shielded, freestanding ^137Cs or ^60Co units with sample positioning mechanisms (e.g., drawers, rotors, or turntables) and excludes underwater, panoramic, or X-ray sources.
• Quality Assurance: Covers installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ) to validate equipment performance and dosimetric accuracy.
• Routine Monitoring: Provides guidelines for ongoing process control, environmental influence management, and proper documentation to ensure consistent irradiation results.
• Safety and Compliance: Users are responsible for implementing safe operational and environmental practices and for complying with regulatory limitations.

Applications

• Calibration of Dosimeters: Used extensively for the controlled irradiation of dosimeters to ensure their accuracy and reliability.
• Radiation Research: Facilitates studies on radiation effects in materials, electronics reliability, radiation “hardness” testing, and biological research, including research on microbiological, botanical, and in-vitro samples.
• Sterilization and Compatibility Testing: Supports process compatibility studies and batch irradiation of medical, agricultural, or packaging products.
• Blood and Food Irradiation: While this practice is foundational, specific applications such as blood irradiation, food, and agricultural products have dedicated referenced standards.
• Irradiation of Small Animals and Insects: Used in research and sterile release programs, supporting agricultural and pest control initiatives.
• Radiation Hardness Testing: Provides consistent dose environments for electronic components and materials used in radiation-prone environments.

Related Standards

• ISO/ASTM 51261: Calibration of routine dosimetry systems for radiation processing.
• ISO/ASTM 51939: Dosimetry practice specific to blood irradiation.
• ISO/ASTM 51900: Dosimetry for radiation research on food and agricultural products.
• ISO/ASTM 51940: Sterile insect release programs.
• ASTM E1249: Minimizing dosimetry errors in radiation hardness testing of silicon electronic devices.
• ASTM E2628: Dosimetry in radiation processing (companion standard for broader implementation).
• ASTM E170, E2701: Terminology and characterization guides related to radiation measurement and dosimetry.
• ANSI/HPS N43.7: Safe design and use of self-contained, dry source storage gamma irradiators.

Practical Value

Implementing ASTM ISO/ASTM52116-13(2020) enables facilities to:

• Ensure accurate, consistent, and reproducible absorbed-dose delivery.
• Meet regulatory and process validation requirements for gamma irradiation.
• Optimize product quality and safety in various industrial, research, and medical applications.
• Maintain reliable records through rigorous documentation and equipment qualification.
• Integrate with other international standards for comprehensive dosimetry system management.

Keywords

gamma irradiation dosimetry, self-contained dry-storage gamma irradiator, cobalt-60, cesium-137, absorbed dose mapping, radiation processing, dosimeter calibration, quality assurance, radiation safety, ISO/ASTM standards

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
ISO/ASTM 52116:2013 (Reapproved 2020)(E)
Standard Practice for
Dosimetry for a Self-Contained Dry-Storage Gamma
Irradiator
This standard is issued under the fixed designation ISO/ASTM 52116; 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 responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This practice outlines dosimetric procedures to be fol-
mine the applicability of regulatory limitations prior to use.
lowed with self-contained dry-storage gamma irradiators. For
1.7 This international standard was developed in accor-
irradiators used for routine processing, procedures are given to
dance with internationally recognized principles on standard-
ensure that product processed will receive absorbed doses
ization established in the Decision on Principles for the
within prescribed limits.
Development of International Standards, Guides and Recom-
1.2 This practice covers dosimetry in the use of dry-storage
mendations issued by the World Trade Organization Technical
gamma irradiators, namely self-contained dry-storage Cs or
Barriers to Trade (TBT) Committee.
Co irradiators (shielded freestanding irradiators). It does not
cover underwater pool sources, panoramic gamma sources, nor
2. Referenced documents
does it cover self-contained bremsstrahlung X-ray units.
2.1 ASTM Standards:
1.3 The absorbed-dose range for the use of the dry-storage
E170 Terminology Relating to Radiation Measurements and
self-contained gamma irradiators covered by this practice is
Dosimetry
typically 1 to 10 Gy, depending on the application. The
E1249 Practice for Minimizing Dosimetry Errors in Radia-
–2 3
absorbed-dose rate range typically is from 10 to 10 Gy/min.
tion HardnessTesting of Silicon Electronic Devices Using
Co-60 Sources
1.4 For irradiators supplied for specific applications, spe-
E2628 Practice for Dosimetry in Radiation Processing
cific ISO/ASTM or ASTM practices and guides provide
E2701 Guide for Performance Characterization of Dosim-
dosimetric procedures for the application. For procedures
eters and Dosimetry Systems for Use in Radiation Pro-
specific to dosimetry in blood irradiation, see ISO/ASTM
cessing
Practice 51939. For procedures specific to dosimetry in radia-
tionresearchonfoodandagriculturalproducts,seeISO/ASTM
2.2 ISO/ASTM Standards:
Practice 51900 . For procedures specific to radiation hardness
51261 Practice for Calibration of Routine Dosimetry Sys-
testing, see ASTM Practice E1249. For procedures specific to
tems for Radiation Processing
the dosimetry in the irradiation of insects for sterile release
51539 Guide for Use of Radiation-Sensitive Indicators
programs,seeISO/ASTMGuide51940.Inthosecasescovered
51707 Guide for Estimating Uncertainties in Dosimetry for
by ISO/ASTM 51939, 51900 , 51940, or ASTM E1249, those
Radiation Processing
standards take precedence.
51900 Guide for Dosimetry in Radiation Research on Food
and Agricultural Products
1.5 This document is one of a set of standards that provides
51939 Practice for Blood Irradiation Dosimetry
recommendations for properly implementing and utilizing
51940 Guide for Dosimetry for Sterile Insects Release Pro-
dosimetry in radiation processing. It is intended to be read in
grams
conjunction with ASTM E2628, “Practice for Dosimetry in
Radiation Processing”.
2.3 International Commission on Radiation Units and Mea-
surements (ICRU) Reports:
1.6 This standard does not purport to address all of the
ICRU 85a Fundamental Quantities and Units for Ionizing
safety concerns, if any, associated with its use. It is the
Radiation
This practice is under the jurisdiction of ASTM Committee E61 on Radiation
Processing and is the direct responsibility of Subcommittee E61.04 on Specialty For referenced ASTM and ISO/ASTM standards, visit the ASTM website,
Application, and is also under the jurisdiction of ISO/TC 85/WG 3. www.astm.org, or contact ASTM Customer Service at [e-mail]. For
Current edition approved July 1, 2020. Published September 2020. Originally Annual Book of ASTM Standards volume information, refer to the standard’s
published as ASTM E 2116–00. Last previous ASTM edition E 2116–00. The Document Summary page on the ASTM website.
present International Standard ISO/ASTM 52116:2013(20)(E) replaces E 2116-00 International Commission on Radiation Units and Measurements (ICRU), 7910
and is a reapproval of the last previous edition ISO/ASTM 52116:2013(E). Woodmont Ave., Suite 800, Bethesda, MD 20810, U.S.A.
© ISO/ASTM International 2020 – All rights reserved
ISO/ASTM 52116:2013 (2020)(E)
2.4 ANSI Standards: performedtodeterminetherelationshipbetweentheirradiation
ANSI/HPS N43.7 Safe Design and Use of Self-Contained, parameters and the absorbed dose.
Dry Source Storage Gamma Irradiators (Category I)
4.1.1 For most applications, the absorbed dose is expressed
as absorbed dose to water (see ISO/ASTM Practice 51261).
2.5 Joint Committee for Guides in Metrology (JCGM)
For conversion of absorbed dose to water to that to other
Reports:
materials, for example, silicon, see Annex A1 of ISO/ASTM
JCGM 100:2008, GUM 1995 with minor corrections, Evalu-
Practice 51261.
ation of measurement data – Guide to the Expression of
Uncertainty in Measurement
4.2 Self-contained dry-storage gamma irradiators contain
137 60
JCGM 100:2008, VIM International vocabulary of metrol-
properly shielded radioactive sources, namely Cs or Co,
ogy – Basis and general concepts and associated terms
that emit ionizing electromagnetic radiation (gamma radia-
tion). These irradiators have an enclosed, accessible irradiator
3. Terminology
sample chamber connected with a sample positioning system,
3.1 Definitions: for example, irradiator drawer, rotor, or irradiator turntable, as
3.1.1 absorbed-dose mapping—measurement of absorbed part of the irradiation device.
dose within an irradiated product to produce a one-, two-, or
4.3 Self-contained dry-storage gamma irradiators can be
three-dimensionaldistributionofabsorbeddose,thusrendering
used for many radiation processing applications, including the
a map of absorbed-dose values.
calibration irradiation of dosimeters; studies of dosimeter
3.1.2 calibration—[VIM, 6.11] set of operations under
influence quantities; radiation effects studies, and irradiation of
specified conditions, which establishes the relationship be-
materials or biological samples for process compatibility
tween values indicated by a measuring instrument or measur-
studies; batch irradiations of microbiological, botanical, or
ing system, and the corresponding values realised by standards
in-vitro samples; irradiation of small animals; radiation “hard-
traceable to a nationally or internationally recognised labora-
ness” testing of electronics components and other materials;
tory.
and batch radiation processing of containers of samples.
3.1.2.1 Discussion—Calibration conditions include environ-
NOTE 1—Self-contained dry-storage gamma irradiators contain a sealed
mental and irradiation conditions present during irradiation,
radiation source, or an array of sealed radiation sources securely held in a
storageandmeasurementofthedosimetersthatareusedforthe
dry container constructed of solid materials. The sealed radiation sources
generation of a calibration curve. To achieve stable environ-
are shielded at all times, and human access to the chamber undergoing
irradiation is not physically possible due to the irradiator’s design
mental conditions, it may be necessary to condition the
configuration (see ANSI/HPS N43.7).
dosimeters before performing the calibration procedure.
NOTE 2—For reference–standard dosimetry, the absorbed dose and
3.1.3 dose uniformity ratio—ratio of the maximum to the
absorbed-dose rate can be expressed in water or other material which has
minimum absorbed dose within the irradiated product.
similarradiationabsorptionpropertiestothatofthesamplesordosimeters
being irradiated. In some cases, the reference-standard dosimetry may be
3.1.4 measurement management system—set of interrelated
performed using ionization chambers, and may be calibrated in terms of
–1
or interacting elements necessary to achieve metrological
exposure (C kg ), or absorbed dose to air, water or tissue (Gy).
confirmation and continual control of measurement processes.
Measurements performed in terms of exposure apply to ionization in air,
and care should be taken to apply that measurement to the sample being
3.1.5 transit dose—absorbed dose delivered to a product (or
irradiated.
a dosimeter) while it travels between the non-irradiation
position and the irradiation position, or in the case of a
5. Types of facilities and modes of operation
movable source while the source moves into and out of its
5.1 Facility Types—Typical self-contained dry-storage
irradiation position.
gamma irradiators are illustrated in Annex A1. These irradia-
3.2 Definitions of other terms used in this standard that
tors house the radiation source(s) in a protective lead shield (or
pertain to radiation measurement and dosimetry may be found
other appropriate material), and usually have a sample posi-
in ASTM Terminology E170. Definitions in ASTM Terminol-
tioning mechanism tied to an accurate calibrated reset timer to
ogy E170 are compatible with ICRU 85a; that document,
lowerorrotatethesampleholderfromtheload/unloadposition
therefore, may be used as an alternative reference.
to the irradiation position and back to the load/unload position.
Details on the calibration of dosimetry systems and dose
4. Significance and use
mapping in such irradiators may be found, respectively in
4.1 The design and operation of a self-contained irradiator
ISO/ASTM Guide 51261 and in this practice. Details on the
should ensure that reproducible absorbed doses are obtained
designs of such irradiators and on safety considerations in the
when the same irradiation parameters are used. Dosimetry is
use of such irradiators may be found in ANSI/HPS N43.7.
5.2 Modes of Operation—Three common modes of opera-
tion are described. This does not purport to include all modes
Available from the Health Physics Society, http://hps.org.
of operation.
Document produced by Working Group 1 of the Joint Committee for Guides in
Metrology (JCGM/WG 1). Available free of charge at the BIPM website (http://
5.2.1 One method of use is to rotate the sample holder on an
www.bipm.org).
irradiator turntable in front of the source such that the only
Document produced by Working Group 2 of the Joint Committee for Guides in
pointsthatremainafixeddistancefromthesourcearealongan
Metrology (JCGM/WG 2). Available free of charge at the BIPM website (http://
www.bipm.org). axis of rotation (ANSI/HPS N43.7).
© ISO/ASTM International 2020 – All rights reserved
ISO/ASTM 52116:2013 (2020)(E)
NOTE 4—Table A2.1 gives some recommended steps in the following
5.2.2 A second method is to distribute the source in an
areas: installation qualification, operational qualification, performance
annular array, resulting in a relatively uniform absorbed-dose
qualification, and routine product processing.
distribution. In this design, the irradiator turntable normally
8.2 Equipment Documentation—Establish and document an
would not be necessary.
IQ program that includes descriptions of the instrumentation
5.2.3 A third method is to use opposed sources with
and equipment installed at the facility. This documentation
appropriate beam flattening to obtain a uniform dose through-
shall be retained for the life of the facility. At a minimum, it
out the sample.
shall include:
6. Radiation source characteristics 8.2.1 A description of the irradiator’s specifications, char-
acteristics and parameters, including any modifications made
6.1 The radiation sources used in the irradiation devices
60 during or after installation,
considered in this practice consist of sealed elements of Co
8.2.2 A description of the location of the irradiator within
or Cs, which are typically linear rods or pencils arranged
the operator’s premises,
singly or in a planar array or cylindrical array.
8.2.3 Operating instructions and standard operating proce-
6.2 Cobalt-60 emits photons with energies of approximately
dures for the irradiator and associated measurement
1.17 and 1.33 MeV in nearly equal proportions; cesium-137
instruments,
emits photons with energies of approximately 0.662 MeV.
8.2.4 Licensing and safety documents and procedures, in-
60 137
cluding those required by regulatory and occupational health
6.3 The radioactive decay half-lives for Co and Cs are
regularly reviewed and updated. The most recent publication and safety agencies,
8.2.5 A description of a calibration program to ensure that
by the National Institute of Standards and Technology gave
values of 1925.20 (6 0.25) days for Co and 11018.3 (6 9.5) all processing equipment that may influence absorbed-dose
137 137
delivery is calibrated periodically (for example, the timer
days for Cs. In addition, the Cs radiation source may
containradioimpuritieswhichshouldbequalifiedbythesource mechanism),
manufacturer. 8.2.6 Operating procedures and calibration procedures for
60 137 associated measurement instruments or systems.
6.4 For pure Co and Cs gamma sources, the only
variation in the source strength is the known reduction in the 8.3 Equipment Testing and Calibration—Test all processing
activity caused by radioactive decay. The reduction in the equipment and instrumentation that may influence absorbed
source strength and the required increase in the irradiation time dose in order to verify satisfactory operation of the irradiator
to deliver the same dose may be calculated or obtained from within the design specifications.
tables provided by the irradiator manufacturer. 8.3.1 Implement a documented calibration program to en-
sure that all processing equipment and instrumentation that
7. Dosimetry systems
may influence absorbed-dose delivery are calibrated periodi-
cally.
7.1 The basic requirements that apply when making ab-
8.3.2 If any modification or change is made to the irradiator
sorbed dose measurements are given in ASTM E2628. ASTM
equipment or measurement instruments during the installation
E2628 also provides guidance on the selection of dosimetry
qualification phase, they shall be re-tested.
systems and describes the classification of dosimeters based on
two criteria. Users are directed to other standards that provide
8.4 For self-contained irradiators, some IQ may begin prior
specific information on individual dosimetry systems, calibra-
to the shipment of the irradiator to the customer’s site.
tion methods, and uncertainty estimation.
NOTE 3—The operation of a self-contained dry-storage irradiator,
9. Operational qualification (OQ)
absorbed-dose measurements made in the sample under controlled envi-
9.1 Objective—The purpose of operational qualification
ronmentalandgeometricalconditionsofcalibration,testing,orprocessing
provide an independent quality control record.
(OQ) of an irradiation facility is to establish baseline data for
evaluating irradiator effectiveness, predictability, and repro-
8. Installation qualification (IQ)
ducibility for the range of conditions of operation for key
8.1 Objective—The purpose of an installation qualification
processing parameters that affect absorbed dose in the product.
(IQ) program is to obtain and document evidence that the As part of this process, dosimetry may be performed to: (1)
irradiator and measurement instruments have been delivered
establish relationships between the absorbed dose for a repro-
and installed in accordance with their specifications. IQ in- ducible geometry and the process parameters of the irradiator,
cludesdocumentationoftheirradiatorequipmentandmeasure-
(2) measure absorbed-dose distributions in product (dose
ment instruments; establishment of testing, operation and mapping), (3) characterize absorbed dose variations when
calibration procedures for their use; and verification that the
irradiator and processing parameters fluctuate statistically
installed irradiator equipment and measurement instruments through normal operations, and (4) measure the absorbed-dose
operate according to specification.
rate at a reference position within the holder filled with
product.
9.1.1 For self-contained irradiators, OQ may begin prior to
Unterweger, M. P., Hoppes, D. D., Schima, F. J., and Coursey, J. S.,
the shipment of the irradiator to the customer’s site.As part of
“Radionuclide Half-Life Measurements,” National Institute of Standards and
release-for-shipment criteria, the irradiator manufacturer may
Technology, available online at http://physics.nist.gov/Halflife (updated October 5,
2010). perform absorbed-dose mapping to establish baseline data.
© ISO/ASTM International 2020 – All rights reserved
ISO/ASTM 52116:2013 (2020)(E)
After the unit is installed at the user’s site, OQ is performed as 9.3.3.1 Dosimetry performed at the same dose level as used
part of the user’s quality assurance plan. for product irradiation includes the transit dose contribution.
Therefore, it is usually unnecessary to measure the transit dose
9.2 Dosimetry Systems—Calibrate the routine dosimetry
separately.
system to be used at the facility.
9.3.3.2 Procedures for measuring and correcting for transit
9.3 Irradiator Characterization—The absorbed dose re-
dose in terms of transit time are given in Annex A3.
ceived by any portion of product depends on the irradiator
9.3.3.3 In self-contained gamma irradiators, the transit dose
parameters (such as the source activity at the time of
should be small relative to the total dose delivered (for
irradiation, the geometry of the source, the source-to-product
example, less than 1 %).
distance and the irradiation geometry) and the processing
9.3.3.4 The absorbed-dose range of the dosimetry system
parameters (such as the irradiation time, the product composi-
used for mapping the dose distribution may not be suitable for
tion and density and the loading configuration).
measuring the transit dose. Thus, it may be necessary to utilize
9.3.1 Absorbed-Dose Rate—A reference- or transfer-
a different dosimetry system for measuring the transit dose.
standard dosimetry system, traceable to nationally or interna-
9.3.4 Timer Setting Calculation—An important calculation
tionally recognized standards, shall be used to measure the
in the use of gamma sources is the correction for radioactive
absorbed-dose rate within product or simulated product at a
decay. For a pure radionuclide source, the reduction in activity
reference position (such as the center of the product or
with time is exponential. For an initial activity ofA (at time =
simulated product volume). For a defined irradiation geometry,
0 which is usually specified as the date of the last reference
the absorbed-dose rate at the reference position should have a
dose-rate measurement), the activity at some later time, t,is
reproducibleanddocumentedrelationshiptotheabsorbed-dose
given by:
rate at locations of maximum (D ) and minimum (D ) dose
max min
2λt
A 5 A ·e (1)
t 0
rate.
where A is the source activity at time t, and the decay
t
9.3.1.1 Most manufacturers of irradiators use a reference-
constant, λ, for a given radionuclide, is defined as:
standard dosimetry system to measure absorbed-dose rate at a
ln 2
~ !
reference position within simulated product following installa- λ 5 (2)
t
1/2
tion of (or, in the case of some self-contained units, before
where:
shipping) the irradiator.
t is the half-life for a given radionuclide. The half-lives
1/2
used in these examples for gamma emission by Co and
9.3.1.2 Reference- or transfer-standard dosimeter measure-
Cs are 1925.20 (60.25) days and 11018.3 (69.5) days,
ment of absorbed-dose rate at a reference position should be
respectively (see 6.3). The values for λ in Eq 2 for Co
repeated periodically (for example, every two years for a
and Cs are as follows:
gamma facility) and following any changes to the source,
60 24 21
For Co, λ 5 3.60076 310 day (3)
geometry, or other irradiator parameter that could affect
137 25 21
absorbed-dose rate.
For Cs, λ 5 6.29087 310 day (4)
where no round-off occurs until the final answer. The decay
9.3.2 Dose Mapping—Ideally, the irradiation process is
factor is defined as follows:
designed to irradiate product uniformly throughout the irradi-
ated volume; in reality, a certain variation in absorbed-dose A
t
2λt
Decay Factor 5 5 e (5)
through the product will exist. The OQ process includes A
mapping the absorbed-dose distributions for product (or simu- NOTE 6—Examples of using these equations to obtain decay factors are
given as follows: for an elapsed time period of 500 days and using the
lated product), and identifying the magnitudes and locations
decay constants according to Eq 3 and Eq 4, Eq 5 gives decay factors for
D and D within the product.
60 137
max min
Coand Csof0.835238and0.969035,respectively.Thedecayfactor
9.3.2.1 Map the absorbed-dose distribution by placing do-
can be used to correct a known dose rate or source activity for time. Refer
to http://physics.nist.gov/Halflife for up-to-date radionuclide half lives.
simeters throughout the actual or simulated product. Select
placement patterns that can identify the locations of D and
max Since the absorbed-dose rate due to a radionuclide source
D . Dosimetry data from previously characterized irradiators
min also varies expon
...