ISO/ASTM 51649:2002
(Main)Practice for dosimetry in an electron-beam facility for radiation processing at energies between 300 keV and 25 MeV
Practice for dosimetry in an electron-beam facility for radiation processing at energies between 300 keV and 25 MeV
ISO/ASTM 51649 covers dosimetric procedures to be followed in facility characterization, process qualification and routine processing using electron beam radiation in order to ensure that the entire product has been treated with an acceptable range of absorbed doses. Other procedures related to facility characterization (including equipment documentation), process qualification and routine product processing that may influence and may be used to monitor absorbed dose in the product are also discussed. The electron energy range covered by this International Standard is between 300 keV and 25 MeV, although other energy levels are discussed. Dosimetry is only one component of a total quality assurance programme for an irradiation facility. Other controls besides dosimetry may be required for specific applications such as medical device sterilization and food preservation.
Pratique de la dosimétrie dans une installation de traitement par irradiation utilisant un faisceau d'électrons d'énergies comprises entre 300 keV et 25 MeV
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Standards Content (Sample)
INTERNATIONAL ISO/ASTM
STANDARD 51649
First edition
2002-03-15
Practice for dosimetry in an electron
beam facility for radiation processing at
energies between 300 keV and 25 MeV
Pratique de la dosimétrie dans une installation de traitement par
irradiation utilisant un faisceau d’électrons d’énergies comprises
entre 300 keV et 25 MeV
Reference number
ISO/ASTM 51649:2002(E)
© ISO/ASTM International 2002
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ISO/ASTM 51649:2002(E)
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ISO/ASTM 51649:2002(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 4
5 Radiation source characteristics . 4
6 Types of irradiation facility . 4
7 Dosimetry systems . 5
8 Irradiation facility qualification . 5
9 Process qualification . 6
10 Routine product processing . 7
11 Certification . 8
12 Measurement uncertainty . 8
13 Keywords . 8
Annexes . 9
Bibliography . 20
Figure 1 Diagram showing beam length and width for a scanned beam using a conveyor material
handling system . 2
Figure 2 Example of electron-beam dose distribution along the beam width . 3
Figure 3 A typical depth-dose distribution for an electron beam . 3
Figure 4 Typical pulse current waveform . 3
Figure A1.1 Calculated depth-dose distribution curves in various homogeneous materials for
normally incident monoenergetic electrons at 5.0 MeV . 9
Figure A1.2 Calculated depth-dose distribution curves in polystyrene for normally incident, plane
parallel incident electrons at monoenergetic energies from 400 to 1000 keV . 10
Figure A1.3 Calculated depth-dose distribution curves in polystyrene for normally incident, plane
parallel incident electrons at monoenergetic energies from 1.0 to 5.0 MeV . 11
Figure A1.4 Calculated depth-dose distribution curves in polystyrene for normally incident, plane
parallel incident electrons at monoenergetic energies from 3.0 to 12.0 MeV . 11
Figure A1.5 Superposition of theoretically calculated depth-dose distribution curves for aluminum
irradiated with 5 MeV monoenergetic electrons . 12
Figure A1.6 Calculated correlations between optimum electron range, half-value depth, half-
entrance depth, and practical range, and incident electron energy for polystyrene . 12
Figure A1.7 Measured depth-dose distribution curves for nominal 10 MeV energy electron beams
incident to polystyrene . 13
Figure A1.8 Depth-dose distribution curves in stacks of cellulose acetate films backed with wood,
aluminum, and iron for incident electrons with 400 keV energy . 14
Figure A1.9 Depth-dose distributions with 2 MeV electrons incident on polystyrene absorbers . 14
Figure A1.10 Area processing coefficient at the entrance surface of the material as a function of
incident electron energy from 400 keV to 12 MeV . 14
Figure A3.1 Stack energy measurement device . 18
Figure A3.2 Wedge energy measurement device . 18
Table A1.1 Key parameters for measured depth-dose distribution curves . 13
Table A3.1 Some relevant properties of common reference materials . 16
Table A3.2 Practical range and half-value depth in aluminum for monoenergetic electron energies
from 0.2 to 50 MeV . 17
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ISO/ASTM 51649:2002(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 51649 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, A2, A3 and A4 of this International Standard are for information only.
iv © ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51649:2002(E)
Standard Practice for
Dosimetry in an Electron Beam Facility for Radiation
1
Processing at Energies Between 300 keV and 25 MeV
This standard is issued under the fixed designation ISO/ASTM 51649; 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 2. Referenced Documents
1.1 This practice covers dosimetric procedures to be fol- 2.1 ASTM Standards:
lowed in facility characterization, process qualification, and E 170 Terminology Relating to Radiation Measurements
2
routine processing using electron beam radiation to ensure that and Dosimetry
the entire product has been treated with an acceptable range of E 668 Practice for the Application of Thermoluminescence-
absorbed doses. Other procedures related to facility character- Dosimetry (TLD) Systems for Determining Absorbed Dose
2
ization (including equipment documentation), process qualifi- in Radiation-Hardness Testing of Electronic Devices
cation, and routine product processing that may influence and E 1026 Practice for Using the Fricke Reference Standard
2
may be used to monitor absorbed dose in the product are also Dosimetry System
discussed. 2.2 ISO/ASTM Standards:
51205 Practice for Use of a Ceric-Cerous Sulfate Dosimetry
NOTE 1—For guidance in the selection and calibration of dosimeters,
2
System
see ISO/ASTM Guide 51261. For further guidance in the selection,
51261 Guide for Selection and Calibration of Dosimetry
calibration, and use of specific dosimeters, and interpretation of absorbed
2
dose in the product from dosimetry, also see ASTM Practice E 668 and Systems for Radiation Processing
ISO/ASTM Practices 51275, 51276, 51431, 51607, 51631, and 51650. For
51275 Practice for Use of a Radiochromic Film Dosimetry
2
use with electron energies above 5 MeV, see ASTM Practice E 1026, and
System
ISO/ASTM Practices 51205, 51401, 51538, and 51540 for discussions of
51276 Practice for Use of a Polymethylmethacrylate Do-
specific large volume dosimeters. For discussion of radiation dosimetry
2
simetry System
for pulsed radiation, see ICRU Report 34. When considering a dosimeter
2
51401 Practice for Use of a Dichromate Dosimetry System
type, be cautious of influences from dose rates and accelerator pulse rates
51431 Practice for Dosimetry in Electron and Bremsstrahl-
and widths (if applicable).
2
ung Irradiation Facilities for Food Processing
1.2 The electron energy range covered in this practice is
51538 Practice for Use of an Ethanol-Chlorobenzene Do-
between 300 keV and 25 MeV, although there are some
2
simetry System
discussions for other energies.
2
51539 Guide for the Use of Radiation-Sensitive Indicators
1.3 Dosimetry is only one component of a total quality
51540 Practice for Use of a Radiochromic Liquid Solution
assurance program for an irradiation facility. Other controls
2
Dosimetry System
besides dosimetry may be required for specific applications
51607 Practice for Use of the Alanine–EPR Dosimetry
such as medical device sterilization and food preservation.
2
System
1.4 For the irradiation of food and the radiation sterilization
51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-
of health care products, other specific ISO standards exist. For
2
ung) Irradiation Facility for Radiation Processing
food irradiation, see ISO/ASTM Practice 51431. For the
51631 Practice for Use of Calorimetric Dosimetry Systems
radiation sterilization of health care products, see ISO 11137.
for Electron Beam Measurements and Dosimeter Calibra-
In those areas covered by ISO 11137, that standard takes
2
tions
precedence.
51650 Practice for Use of a Cellulose Acetate Dosimetry
1.5 This standard does not purport to address all of the
2
System
safety concerns, if any, associated with its use. It is the
2.3 ISO Standard:
responsibility of the user of this standard to establish appro-
ISO 11137 Sterilization of Health Care Products–Require-
priate safety and health practices and determine the applica-
ments for Validation and Routine Control–Radiation Ster-
bility of regulatory limitations prior to use.
3
ilization
2.4 International Commission on Radiation Units and
Measurements (ICRU) Reports:
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
ISO/TC 85/WG 3.
2
Current edition approved Jan. 22, 2002. Published March 15, 2002. Originally Annual Book of ASTM Standards, Vol 12.02.
3
published as E 1649–94. Last previous ASTM edition E 1649–00. ASTM E
Available from International Organization for Standardization, 1 Rue de
e1
1649–94 was adopted by ISO in 1998 with the intermediate designation ISO
Varembé, Case Postale 56, CH-1211 Geneva 20, Switzerland.
15569:1998(E). The present International Standard ISO/ASTM 51649:2002(E) is a
revision of ISO 15569.
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ISO/ASTM 51649:2002(E)
4
ICRU Report 34 The Dosimetry of Pulsed Radiation
ICRU Report 35 Radiation Dosimetry: Electron Beams with
4
Energies Between 1 and 50 MeV
ICRU Report 37 Stopping Powers for Electrons and
4
Positrons
4
ICRU Report 60 Radiation Quantities and Units
3. Terminology
3.1 Definitions—Other terms used in this practice may be
found in ASTM Terminology E 170 and ICRU Report 60.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbed dose, D—the quotient of de¯ by dm, where de¯
is the mean energy imparted by ionizing radiation to the matter
of mass dm (see ICRU Report 60).
de¯
D 5 (1)
dm
The special name of the unit for absorbed dose is the gray
(Gy):
FIG. 1 Diagram Showing Beam Length and Width for a Scanned
Beam Using a Conveyor Material Handling System
21
1 Gy 5 1 J ·kg (2)
Formerly, the special unit for absorbed dose was the rad:
22 21 22
3.2.7 depth-dose distribution—variation of absorbed dose
1 rad 5 10 J ·kg 5 10 Gy (3)
with depth from the incident surface of a material exposed to
radiation.
and:
3.2.7.1 Discussion—A typical distribution in homogeneous
1 Mrad 5 10 kGy (4)
material produced by an electron beam along the beam axis is
3.2.2 average beam current—time-averaged electron beam
shown in Fig. 3. See Annex A1.
current; for a pulsed machine, the averaging shall be done over
3.2.8 dose uniformity ratio—ratio of the maximum to the
a large number of pulses.
minimum absorbed dose within the irradiation unit; it is a
3.2.3 beam length—dimension of the irradiation zone per-
measure of the degree of uniformity of the absorbed dose; the
pendicular to the beam width and direction of the electron
concept is also referred to as the max/min dose ratio.
beam specified at a specified distance from the accelerator
3.2.9 dosimetry system—a system used for determining
window.
absorbed dose, consisting of dosimeters, measurement instru-
3.2.3.1 Discussion—See Fig. 1.
ments and their associated reference standards, and procedures
3.2.4 beam power—product of the average electron energy
for the system’s use.
and the average beam current.
3.2.10 duty cycle—for a pulsed accelerator, the fraction of
3.2.5 beam width—dimension of the irradiation zone per-
time the beam is effectively on; it is the product of the pulse
pendicular to the beam length and direction of the electron
width in seconds and the pulse rate in pulses per second.
beam specified at a specific distance from where the beam exits
3.2.11 electron beam facility—an establishment that uses
the accelerator.
energetic electrons produced by particle accelerators to irradi-
3.2.5.1 Discussion—For a radiation processing facility with
ate product.
a conveyor system, the beam width is usually perpendicular to
3.2.12 electron energy—kinetic energy of electron (unit:
the flow of motion of the conveyor (see Fig. 1). Beam width is
electron volt (eV))
the distance between the points along the dose profile which
3.2.13 electron energy spectrum—frequency or energy dis-
are at a defined level from the maximum dose region in the
tribution of electrons as a function of energy; the energy
profile (see Fig. 2). Various techniques may be employed to
spectrum of the electron beam impinging on the product
produce an electron beam width adequate to cover the process-
depends on the type of the accelerator and the conditions of the
ing zone, for example, use of electromagnetic scanning of
irradiation process.
pencil beam (in which case beam width is also referred to as
3.2.14 electron range—penetration distance along the beam
scan width), defocussing elements, and scattering foils.
axis of electrons within homogeneous material.
3.2.6 compensating dummy—simulated product used during
3.2.14.1 Discussion—Several range parameters may be de-
routine production runs with irradiation units containing less
fined to describe the characteristics of the electron beam. For
product than specified in the product loading configuration or
more information, refer to ICRU Report 35.
at the beginning and end of a production run to compensate for
3.2.15 half-entrance depth (R )—depth in homogeneous
50e
the absence of product.
material at which the absorbed dose has decreased 50 % of the
absorbed dose at the surface of the material.
4
Available from International Commission on Radiation Units and Measure-
3.2.15.1 Discussion—See Fig. 3.
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A.
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ISO/ASTM 51649:2002(E)
4
FIG. 2 Example of Electron-beam Dose Distribution Along the Beam Width with the Width Noted at Some Defined Fractional Level f of
the Average Maximum Dose D
max
point) on the almost straight descending portion of the depth-
dose distribution curve meets the depth axis.
3.2.19.1 Discussion—See Fig. 3.
3.2.20 production run—series of irradiation units contain-
ing the same product, and irradiated sequentially to the same
absorbed dose.
3.2.21 pulse beam current—for a pulsed accelerator, the
beam current averaged over the top ripples (aberrations) of the
pulse current waveform; this is equal to I /wf, where I is
avg avg
the average beam current, w is the pulse width, and f is the
pulse rate.
3.2.21.1 Discussion—See Fig. 4.
3.2.22 pulse rate—for a pulsed accelerator, the pulse current
repetition frequency in hertz, or pulses per second; this is also
referred to as the repetition (rep) rate.
3.2.23 pulse width—for a pulsed accelerator, the time inter-
val between the half peak beam current amplitude points on the
FIG. 3 A Typical Depth-Dose Distribution for an Electron Beam
3.2.16 half-value depth (R )—depth in homogeneous ma-
50
terial at which the absorbed dose has decreased 50 % of its
maximum value.
3.2.16.1 Discussion—See Fig. 3.
3.2.17 irradiation unit—a volume of product with a speci-
fied loading configuration processed as a single entity; this
term is not relevant to bulk-flow processing.
3.2.18 optimum thickness (R )—depth in homogeneous
opt
material at which the absorbed dose equals the absorbed dose
at the surface where the electron beam enters.
3.2.18.1 Discussion—See Fig. 3.
3.2.19 practical range (R )—distance from the surface of
p
homogeneous material where the electron beam enters to the
FIG. 4 Typical Pulse Current Waveform with Pulse Current and
point where the tangent at the steepest point (the inflection Pulse Width Noted
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ISO/ASTM 51649:2002(E)
leading and falling edges of the pulse beam current waveform. tion to the absorbed dose in the material or product being
3.2.23.1 Discussion—See Fig. 4. irradiated.
3.2.24 reference material—homogeneous material of
NOTE 3—Measured dose is often characterized as absorbed dose in
known radiation absorption and scattering properties used to
water because materials commonly found in disposable medical devices
establish characteristics of the irradiation process, such as scan
and food are approximately equivalent to water in the absorption of
uniformity, depth-dose distribution, throughput rate, and repro-
ionizing radiation. Absorbed dose in materials other than water may be
determined by applying conversion factors in accordance with ISO/ASTM
ducibility.
Guide 51261.
3.2.25 reference plane—a selected plane in the radiation
zone that is perpendicular to the electron beam axis.
4.3 A beneficial irradiation process is usually specified by a
3.2.26 scanned beam—an electron beam which is swept
minimum absorbed dose to achieve the desired effect and a
back and forth with a varying magnetic field.
maximum dose limit that the product can tolerate and still be
3.2.26.1 Discussion—This is most commonly done along
functional. Since it is used to determine these limits, dosimetry
one dimension (beam width), although two dimensional scan-
is essential in the evaluation and control of the radiation
ning (beam width and length) may be used with high-current
process.
electron beams to avoid overheating the beam exit window of
4.4 The dose distribution within the product depends on
the accelerator.
irradiation unit characteristics, irradiation conditions, and op-
3.2.27 scan uniformity—the degree of uniformity of the
erating parameters. The operating parameters consist of beam
dose measured along the scan direction.
characteristics (such as energy and beam current), beam
3.2.28 simulated product—a mass of material with attenu-
dispersion parameters, and product material handling. These
ation and scattering properties similar to those of a particular
critical parameters must be controlled to obtain reproducible
material or combination of materials; this material is some-
results.
times referred to as dummy product or phantom.
4.5 Before a radiation process can be used, the facility must
be qualified to demonstrate its ability to deliver known,
4. Significance and Use
controllable doses in a reproducible manner. This involves
4.1 Various products and materials are routinely irradiated
testing the process equipment, calibrating the equipment and
at pre-determined doses at electron beam facilities to preserve
dosimetry system, and characterizing the magnitude, distribu-
or modify their characteristics. Dosimetry requirements may
tion, and reproducibility of the dose absorbed by a reference
vary depending upon the radiation process and end use of the
material.
product. For example, a partial list of processes where dosim-
4.6 To ensure that products are irradiated with reproducible
etry may be used is:
doses, routine process control requires documented product
4.1.1 Cross-linking or degradation of polymers and elas-
handling procedures before, during, and after the irradiation,
tomers,
consistent orientation of the products during irradiation, moni-
4.1.2 Polymerization of monomers and grafting of mono-
toring of critical process parameters, routine product dosim-
mers onto polymers,
etry, and documentation of the required activities and func-
4.1.3 Sterilization of medical devices,
tions.
4.1.4 Disinfection of consumer products,
5. Radiation Source Characteristics
4.1.5 Food irradiation (parasite and pathogen control, insect
disinfestation, and shelf-life extension),
5.1 Radiation sources for electrons with energies greater
4.1.6 Control of pathogens in liquid or solid waste, than 300 keV considered in this practice are either direct-action
4.1.7 Modification of characteristics of semiconductor de-
(potential-drop) or indirect-action (microwave-powered) accel-
vices, erators. These are further discussed in Annex A2.
4.1.8 Color enhancement of gemstones and other materials,
6. Types of Irradiation Facility
and
6.1 An electron beam facility includes the electron beam
4.1.9 Research on materials effects.
accelerator system; material handling systems; a radiation
NOTE 2—Dosimetry is required for regulated radiation processes such
shield with personnel safety system; product staging, loading,
5,6
as the sterilization of medical devices (1, 2, 3) and the preservation of
and storage areas; auxiliary equipment for power, cooling,
food. It may be less important for other processes, such as polymer
ventilation, etc.; equipment control room; a laboratory for
modification, which may be evaluated by changes in the physical and
chemical properties of the irradiated materials. Nevertheless, routine dosimetry and product testing; and personnel offices. The
dosimetry may be used to monitor the reproducibility of the treatment
electron beam accelerator system consists of the radiation
process.
source (see Annex A2), equipment to disperse the beam on
4.2 As a means of (quality) control of the radiation process, product, and associated equipment (4).
6.2 Process Parameters:
dosimeters are used to relate the calibrated response to radia-
6.2.1 There are various process parameters that play essen-
tial roles in determining and controlling the absorbed dose in
5
McKeown, J., AECL Accelerators, private communication, 1993. Example of a
radiation processing at an irradiation facility. They should,
beam width profile of an AECL Impela accelerator.
6 therefore, be considered when performing the absorbed-dose
The boldface numbers in parentheses refer to the bibliography at the end of this
practice. measurements required in Sections 8, 9, and 10.
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ISO/ASTM 51649:2002(E)
6.2.2 Process parameters include irradiation unit character- 7.2 It is important that the dosimeter be evaluated for those
istics (for example, size, bulk density, and heterogeneity), parameters which may influence the dosimeter’s response; for
irradiation conditions (for example, processing geometry, example, electron energy, average and peak absorbed dose rate
multi-sided exposure, and number of passes through the beam), (particularly for pulsed accelerators), and environmental con-
and operating parameters. ditions (for example, temperature, humidity, and light). Guid-
6.2.3 Operating parameters include beam characteristics ance as to desirable characteristics and selection criteria for
(controlled by accelerator parameters: for example, energy, dosimetry systems can be found in ISO/ASTM Guide 51261,
average beam current, and pulse rate), performance character- ASTM Practice E 1026, and ISO/ASTM Practices 51205,
istics of material handling (see 6.3), and beam dispersion 51275, 51276, 51401, 51538, 51540, 51607, 51631, and
parameters (for example, beam width and frequency at which 51650.
scanned beam is swept across product). Operating parameters 7.3 The dosimetry system should be properly calibrated
are measurable, and their values depend on the facility con- using a calibration service traceable to national standards.
trolling parameters. During irradiation facility qualification Guidance for calibration can be found in ISO/ASTM Guide
(see Section 8), absorbed dose characteristics over the expected 51261.
range of the operating parameters are established for a refer-
8. Irradiation Facility Qualification
ence material.
8.1 Objective—The purpose of qualifying an electron beam
6.2.4 Process parameters for a radiation process are estab-
facility is to establish baseline data for evaluating the ability of
lished during process qualification (see Section 9) to achieve
the facility to accurately and reproducibly deliver doses over
the absorbed dose within the specified limits.
the range of conditions at which the facility will operate (4).
6.2.5 During routine product processing (see Section 10),
For example, dosimetry can be used (1) to establish relation-
the facility operating parameters are controlled and monitored
ships between measured absorbed dose distributions in refer-
to maintain all values that were set during process qualifica-
ence materials in given geometries and operating parameters of
...
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