ISO/ASTM 51608:2002

INTERNATIONAL ISO/ASTM
STANDARD 51608
First edition
2002-03-15
Practice for dosimetry in an X-ray
(bremsstrahlung) facility for radiation
processing
Pratique de la dosimétrie dans une installation de traitement par
des rayons X (bremsstrahlung)
Reference number
ISO/ASTM 51608:2002(E)
© ISO/ASTM International 2002

---------------------- Page: 1 ----------------------
ISO/ASTM 51608:2002(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe’s licensing policy, this file may be printed or viewed but shall
not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe’s licensing policy. Neither the ISO Central
Secretariat nor ASTM International accepts any liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies
and ASTM members. In the unlikely event that a problem relating to it is found, please inform the ISO Central Secretariat or ASTM
International at the addresses given below.
© ISO/ASTM International 2002
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s member body in the country of the
requester. In the United States, such requests should be sent to ASTM International.
ISO copyright office ASTM International, 100 Barr Harbor Drive, PO Box C700,
Case postale 56 • CH-1211 Geneva 20 West Conshohocken, PA 19428-2959, USA
Tel. +41 22 749 01 11 Tel. +610 832 9634
Fax +41 22 749 09 47 Fax +610 832 9635
E-mail copyright@iso.ch E-mail khooper@astm.org
Web www.iso.ch Web www.astm.org
Printed in the United States
ii © ISO/ASTM International 2002 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/ASTM 51608:2002(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 2
5 Radiation source characteristics . 3
6 Irradiation facilities . 3
7 Dosimetry systems . 3
8 Installation qualification . 4
9 Process qualification . 5
10 Routine processing . 5
11 Certification . 5
12 Measurement uncertainty . 5
13 Keywords . 5
Annex . 6
Bibliography . 9
Figure A1.1 Beam Current Density Distributions in the X and Y Directions of No. 1 Accelerator
of JAERI Takasaki . 6
Figure A1.2 X-ray Intensity per Incident 2 MeV Electron Incident Perpendicularly on a Tantalum
Target . 7
Figure A1.3 X-ray Intensity per Incident 5 MeV Electron Incident Perpendicularly on a Tantalum
Target . 7
Figure A1.4 X-Ray Emission Rates from High-Z Targets . 7
Figure A1.5 Spectrum of Transmitted Photons . 8
Figure A1.6 Spectrum of Reflected Photons . 8
Figure A1.7 Depth Dose Distribution . 8
Figure A1.8 Dose Contour Map, Moving Exposure . 8
Figure A1.9 Attenuation Curve for 5 MeV X-Rays in Absorbers of Various Densities . 9
Figure A1.10 A High-Resolution Attenuation Curve for 5 MeV X-Rays in the Heaviest Absorber
.................................................................................................................................................. 9
© ISO/ASTM International 2002 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO/ASTM 51608:2002(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 51608 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear Energy.
Annex A1 of this International Standard is for information only.
iv © ISO/ASTM International 2002 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/ASTM 51608:2002(E)
Standard Practice for
Dosimetry in an X-Ray (Bremsstrahlung) Facility for
1
Radiation Processing
This standard is issued under the fixed designation ISO/ASTM 51608; 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 X rays (bremsstrahlung) to ensure that and Dosimetry
the entire product has been treated within an acceptable range E 177 Practice for Use of the Terms Precision and Bias in
3
of absorbed doses. Other procedures related to facility charac- ASTM Test Methods
terization, process qualification, and routine processing that E 275 Practice for Describing and Measuring Performance
may influence absorbed dose in the product are also discussed. of Ultraviolet, Visible, and Near Infrared Spectrophotom-
4
The establishment of effective or regulatory dose and X-ray eters
3
energy limits are not within the scope of this practice. E 456 Terminology Relating to Quality and Statistics
1.2 In contrast to monoenergetic gamma rays, the E 925 Practice for the Periodic Calibration of Narrow Band-
4
bremsstrahlung energy spectrum extends from low values up to Pass Spectrophotometers
the maximum energy of the electrons incident on the X-ray E 958 Practice for Measuring Practical Spectral Bandwidth
4
target (see Section 5 and Annex A1). of Ultraviolet-Visible Spectrophotometers
1.3 Dosimetry is only one component of a total quality E 1026 Practice for Using the Fricke Reference Standard
2
assurance program for an irradiation facility. Other controls Dosimetry System
besides dosimetry may be required for specific applications 2.2 ISO/ASTM Standards:
such as medical device sterilization and food preservation. 51204 Practice for Dosimetry in Gamma Irradiation Facili-
2
1.4 For the irradiation of food and the radiation sterilization ties for Food Processing
of health care products, other specific ISO standards exist. For 51205 Practice for Use of a Ceric-Cerous Sulfate Dosimetry
2
food irradiation, see ISO/ASTM Practice 51431. For the System
radiation sterilization of health care products, see ISO 51261 Guide for Selection and Calibration of Dosimetry
2
11137:1995. In those areas covered by ISO 11137, that Systems for Radiation Processing
standard takes precedence. 51275 Practice for Use of a Radiochromic Film Dosimetry
2
System
NOTE 1—For guidance in the selection, calibration, and use of specific
51276 Practice for Use of a Polymethylmethacrylate Do-
dosimeters and interpretation of absorbed dose in the product from dose
2
simetry System
measurements, see the documents listed in 2.1, 2.3 and 2.4.
51310 Practice for Use of a Radiochromic Optical
NOTE 2—Bremsstrahlung characteristics are similar to gamma rays
2
from radioactive isotopes. See ISO/ASTM Practices 51204 and 51702 for
Waveguide Dosimetry System
the applications of dosimetry in the characterization and operation of
51400 Practice for Characterization and Performance of a
gamma-ray irradiation facilities. For information concerning electron 2
High-Dose Radiation Dosimetry Calibration Laboratory
beam irradiation technology and dosimetry, see ISO/ASTM Practices
2
51401 Practice for Use of a Dichromate Dosimetry System
51431 and 51649.
51431 Practice for Dosimetry in Electron and Bremsstrahl-
2
1.5 This standard does not purport to address all of the
ung Irradiation Facilities for Food Processing
safety concerns, if any, associated with its use. It is the
51538 Practice for Use of the Ethanol-Chlorobenzene Do-
2
responsibility of the user of this standard to establish appro-
simetry System
priate safety and health practices and determine the applica- 2
51539 Guide for Use of Radiation-Sensitive Indicators
bility of regulatory limitations prior to use.
51540 Practice for Use of a Radiochromic Liquid Dosim-
2
etry System
51607 Practice for Use of the Alanine-EPR Dosimetry
2
System
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
51649 Practice for Dosimetry in an Electron Beam Facility
Technology and Applications and is the direct responsibility of Subcommittee
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of for Radiation Processing at Energies Between 300 keV
2
ISO/TC 85/WG 3.
and 25 MeV
Current edition approved Jan. 22, 2002. Published March 15, 2002. Originally
published as ASTM E 1608–94. Last previous ASTM edition E 1608–00. ASTM E
2
1608–94 was adopted by ISO in 1998 with the intermediate designation ISO
Annual Book of ASTM Standards, Vol 12.02.
3
15567:1998(E). The present International Standard ISO/ASTM 51608:2002(E) is a
Annual Book of ASTM Standards, Vol 14.02.
4
revision of ISO 15567.
Annual Book of ASTM Standards, Vol 03.06.
© ISO/ASTM International 2002 – All rights reserved
1

---------------------- Page: 5 ----------------------
ISO/ASTM 51608:2002(E)
51650 Practice for Use of Cellulose-Acetate Dosimetry bremsstrahlung spectrum depends on the electron energy,
2
Systems converter material, and its thickness.
51702 Practice for Dosimetry in a Gamma Irradiation Fa- 3.1.4 calibration curve—graphical representation of the
2
cility for Radiation Processing dosimetry system’s response function.
51707 Guide for Estimating Uncertainties in Dosimetry for 3.1.5 dose uniformity ratio—ratio of the maximum to the
2
Radiation Processing minimum absorbed dose within the process load. The concept
5
2.3 ICRU Reports: is also referred to as the max/min dose ratio.
ICRU Report 14 Radiation Dosimetry: X Rays and Gamma 3.1.6 dosimeter—a device that, when irradiated, exhibits a
Rays with Maximum Photon Energies Between 0.6 and 50 quantifiable change in some property of the device which can
MeV be related to the absorbed dose in a given material using
ICRU Report 35 Radiation Dosimetry: Electron Beams appropriate analytical instrumentation and techniques.
with Energies Between 1 and 50 MeV 3.1.7 dosimetry system—a system used for determining
ICRU Report 37 Stopping Powers for Electrons and absorbed dose, consisting of dosimeters, measurement instru-
Positrons ments and their associated reference standards, and procedures
ICRU Report 60 Radiation Quantities and Units for the system’s use.
6
2.4 ISO Standards: 3.1.8 electron energy—the kinetic energy of an electron that
ISO 11137 Sterilization of Health Care Products - Require- is usually given in units of electron volts (eV), kiloelectron
ments for Validation and Routine Control - Radiation volts (keV), or megaelectron volts (MeV).
Sterilization 3.1.9 electron energy spectrum—particle fluence distribu-
tion of electrons as a function of energy.
3. Terminology
3.1.10 equilibrium absorbed dose—the absorbed dose in a
3.1 Definitions: finite volume within the material in which the condition of
3.1.1 absorbed dose (D)—Quantity of ionizing radiation approximate electron equilibrium exists.
energy imparted per unit mass of a specified material. The SI 3.1.11 measurement quality assurance plan—a documented
unit of absorbed dose is the gray (Gy), where 1 gray is program for the measurement process that ensures on a
equivalent to the absorption of 1 joule per kilogram of the continuing basis that the overall uncertainty meets the require-
specified material (1 Gy = 1 J/kg). The mathematical relation- ments of the specific application. This plan requires traceability
to, and consistency with, nationally or internationally recog-
ship is the quotient of de by dm, where de is the mean
incremental energy imparted by ionizing radiation to matter of nized standards.
3.1.12 measurement traceability—the ability to demonstrate
incremental mass dm (see ICRU Report 60).
by means of an unbroken chain of comparisons that a mea-
D 5 de / dm (1)
surement is in agreement within acceptable limits of uncer-
3.1.1.1 Discussion—The discontinued unit for absorbed
tainty with comparable nationally or internationally recognized
dose is the rad (1 rad = 100 erg/g = 0.01 Gy).
standards.
3.1.2 absorbed dose enhancement—the increase or decrease
3.1.13 process load—a volume of material with a specified
in the absorbed dose, as compared to the equilibrium dose, at
loading configuration irradiated as a single entity.
a point in the material of interest. This will occur near an
3.1.14 X rays—the common name for the short wavelength
interface between materials with different atomic numbers.
electromagnetic radiation emitted by high-energy electrons
3.1.3 bremsstrahlung—broad-spectrum electromagnetic ra-
when they are accelerated, decelerated or deflected by strong
diation emitted when an energetic electron is influenced by a
electric and magnetic fields. The term includes both
strong magnetic or electric field, such as that in the vicinity of
bremsstrahlung from nuclear collisions and the characteristic
an atomic nucleus.
monoenergetic radiation emitted when atomic electrons make
3.1.3.1 Discussion—When a beta particle (electron) passes
transitions to more tightly bound states.
close to a nucleus, the strong attractive coulomb force causes
3.1.15 X-ray converter—a device for generating X rays
the beta particle to deviate sharply from its original path. The
(bremsstrahlung) from an electron beam, consisting of a target,
change in direction is due to radial acceleration, and in
means for cooling the target, and a supporting structure.
accordance with classical theory the beta particle loses energy
3.1.16 X-ray target—that component of the X-ray converter
by electromagnetic radiation at a rate proportional to the square
that is struck by the electron beam. It is usually made of metal
of the acceleration. This means that the bremsstrahlung pho-
with a high atomic number, high melting temperature, and high
tons have a continuous energy distribution that ranges down-
thermal conductivity.
ward from a theoretical maximum equal to the kinetic energy
3.2 Definitions of other terms used in this standard that
of the beta particle. Practically, bremsstrahlung is produced
pertain to radiation measurement and dosimetry may be found
when an electron beam strikes any material (converter). The
in ASTM Terminology E 170. Definitions in ASTM E 170 are
compatible with ICRU Report 60. That document, therefore,
may be used as an alternative reference.
5
Available from the International Commission on Radiation Units and Measure-
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A.
4. Significance and Use
6
Available from the International Organization for Standardization, 1 Rue de
Varembé, Case Postale 56, CH–1211, Geneva 20, Switzerland.
4.1 A variety of products and materials may be irradiated
© ISO/ASTM International 2002 – All rights reserved
2

---------------------- Page: 6 ----------------------
ISO/ASTM 51608:2002(E)
with X rays to modify their characteristics and improve the 5.3 These aspects of an X-ray source and its suitability for
economic value or for health-related purposes. Examples are radiation processing are reviewed in more detail in Annex A1.
single-use medical devices (sterilization), agricultural com-
6. Irradiation Facilities
modities (preservation), and various polymeric products (ma-
terial modification). Dosimetry requirements for X-ray pro- 6.1 Facility Components—An X-ray irradiation facility in-
cessing may vary depending on the type and end use of the cludes a high-energy, high-power electron accelerator with
product. X-ray converter, product conveyor, radiation shield with per-
sonnel safety system, product staging, loading and storage
NOTE 3—Dosimetry is required for regulated irradiation processes,
areas, auxiliary equipment for power, cooling, ventilation, etc.,
such as the sterilization of medical devices and the preservation of food,
an equipment room, laboratory for dosimetry and product
because the results may affect the health of the consumer. It is less
important for other industrial processes, such as polymer modification, testing, and personnel offices. The design shall conform to
which can be evaluated by changes in the physical properties of the
applicable regulations and guidelines. For information on some
7
irradiated materials. Nevertheless, routine dosimetry may be used to
existing industrial facilities, see Refs (1) and (2) .
monitor the reproducibility of the treatment process.
6.2 Product Handling System—The penetrating quality of
4.2 As a means of (quality) control of an irradiation process,
high-energy X rays permits the treatment of large containers or
dosimeters are used to relate their calibrated response to
full pallet loads of products. The container size for optimum
radiation exposure to the absorbed dose in the material or
photon power utilization and dose uniformity depends on the
product being irradiated (see Section 7).
maximum energy and product density. The narrow angular
4.3 Radiation processing specifications usually include a
distribution of the radiation favors the use of continuously
pair of absorbed-dose limits: a minimum value to ensure the
moving conveyors rather than shuffle-dwell systems to enhance
intended beneficial effect and a maximum value to avoid
dose uniformity.
product degradation. For a given application, one or both of
6.3 Irradiation System—The configuration of the X-ray
these values may be prescribed by process specifications or
converter, the beam current distribution on the target, and the
regulations. Knowledge of the dose distribution within irradi-
penetrating quality of the radiation, and the size, shape, and
ated material is essential to meet these requirements. density of the product load affect the dose uniformity ratio (see
4.4 Several critical parameters must be controlled to obtain
Refs (3-5)).
reproducible dose distributions in the processed materials. The
7. Dosimetry Systems
processing rate and dose distribution depend on the X-ray
intensity, photon energy spectrum, spatial distribution of the
7.1 Description of Dosimeter Classes:
radiation field, conveyor speed, and product configuration (see
7.1.1 Dosimeter systems are used to measure absorbed dose.
Sections 5 and 10 and Annex A1).
They consist of the dosimeters, measurement instruments and
4.5 Before an irradiation process can be used, it must be
their associated reference standards, and procedures for the
qualified to determine its effectiveness in delivering known,
system’s use.
controllable doses. This involves testing the process equip-
7.1.2 Dosimeters may be divided into four basic classes
ment, calibrating the measuring instruments and dosimetry
according to the accuracy of the dosimetry systems and areas
system, and demonstrating the ability of the process to deliver
of application: primary standard, reference standard, transfer
dose distributions in a reliable and reproducible manner (see
standard, and routine dosimeters. ISO/ASTM Guide 51261
Sections 8 and 9).
provides detailed information about the selection of dosimetry
4.6 To ensure consistent dose delivery in a qualified irradia-
systems for different applications.
tion process, routine process control requires procedures for
7.1.2.1 Primary–Standard Dosimeters—Primary–standard
product handling before and after the treatment, prescribed
dosimeters are established and maintained by national stan-
orientation of the products during irradiation, monitoring of
dards laboratories for calibration of radiation environments
critical process parameters, routine product dosimetry, and
(fields) and other dosimeters. The two most commonly used
documentation of the required activities and functions (see
primary standard dosimeters are ionization chambers and
Sections 10 and 11).
calorimeters.
7.1.2.2 Reference–Standard Dosimeters—
5. Radiation Source Characteristics
Reference–standard dosimeters are used to calibrate radiation
5.1 A high-energy X-ray (bremsstrahlung) generator emits
environments and routine dosimeters. Reference–standard do-
short-wavelength electromagnetic radiation, which is analo-
simeters may also be used as routine dosimeters. Examples of
gous to nuclear gamma radiation. Although their effects on
reference–standard dosimeters along with their useful dose
irradiated materials are generally similar, these kinds of radia-
ranges are given in a table in ISO/ASTM Guide 51261.
tion differ in their energy spectra, angular distributions, and
7.1.2.3 Transfer–Standard Dosimeters—Transfer–standard
dose rates.
dosimeters are specially selected dosimeters used for transfer-
5.2 The physical characteristics of the X-ray field depend on
ring absorbed-dose information from an accredited or national
the design of the X-ray converter and the parameters of the
electron beam striking the target, that is, the electron energy
7
spectrum, average electron beam current, and beam current
The boldface numbers in parentheses refer to the bibliography at the end of this
practice.
distribution on the target.
© ISO/ASTM International 2002 – All rights reserved
3

---------------------- Page: 7 ----------------------
ISO/ASTM 51608:2002(E)
standards laboratory to an irradiation facility in order to traceability to nationally or internationally recognized stan-
establish traceability for that facility. These dosimeters should dards, or
be used under conditions that are carefully controlled by the 7.3.3.3 a production or research irradiation facility together
issuing laboratory. Transfer–standard dosimeters may be se- with reference or transfer–standard dosimeters that have mea-
lected from either reference–standard dosimeters or routine surement traceability to nationally or internationally recog-
dosimeters and shall have performance characteristics that nized standards.
meet the requirements listed in a table in ISO/ASTM Guide 7.3.4 When a reference of transfer–standard dosimeter is to
51261. be used as a routine dosimeter, calibration may also be
7.1.2.4 Routine Dosimeters—Routine dosimeters may be performed as stated in 7.3.3.2 or 7.3.3.3.
used for quality control and process monitoring. Proper dosi- 7.3.5 Analytical Instrument Calibration and Performance
metric techniques, including calibration, shall be employed to Verification—For the calibration of the individual instruments
ensure that measurements are reliable and accurate. Examples used in the analysis of the dosimeters, and for the verification
of routine dosimeters along with their useful dose ranges are of instrument performance between calibrations, see ISO/
given in a table in ISO/ASTM Guide 51261. ASTM Guide 51261.
7.2 Dosimeter Selection—The ASTM, ISO/ASTM and
8. Installation Qualification
ICRU documents listed in 2.1 to 2.3 provide detailed informa-
8.1 The purpose of dosimetry in qualifying an X-ray facility
tion on the selection and use of high-dose dosimeter systems
is to establish baseline data for monitoring the effectiveness,
for gamma-ray (photon) and electron-beam irradiation facili-
predictability, and reproducibility of the irradiation process
ties. Many of these dosimetry systems are also applicable for
throughout a typical range of operating parameters. Dosimetry
high-energy X rays, since their radiation responses are rela-
shall be used for the following purposes:
tively insensitive to the photon or electron energies (see ASTM
8.1.1 To establish relationships between absorbed dose in a
Practice E 1026 and ISO/ASTM Practices 51204, 51205,
reproducible geometry and operating parameters.
51275, 51276, 51310, 51400, 51401, 51431, 51538, and
8.1.2 To characterize the stability of dose when these
51540, 51607, 51649, and 51702, ISO/ASTM Guides 51261
parameters fluctuate statistically and through normal opera-
and 51539, and ICRU Reports 14, 35, 37, and 60).
tions.
NOTE 4—Dosimeters consisting mainly of water or hydrocarbon mate-
8.1.3 To measure absorbed dose distributions in reference
rials are suitable for both gamma rays and high-energy X rays. Some
materials.
exceptions are dosimeters containing substantial amounts of materials
8.2 Equipment Documentation—Documentation shall exist
with high atomic numbers. These may be especially sensitive to the
describing the equipment, any modifications, and its operation.
low-energy photons in the bremsstrahlung spectrum.
NOTE 5—The X-ray dose rate may be higher than that of gamma rays This information shall be retained for the life of the facility. It
used for radiation processing, especially in products passing near the
shall include the following:
X-ray converter. The dose-rate dependence of the dosimeters should be
8.2.1 The layout of the facility showing the locations of the
considered in their calibration procedure (see Refs (6) and (7)).
major components.
7.3 Calibration of Dosimetry Systems: 8.2.2 The descriptions, specifications, and characteristics of
7.3.1 Prior to use, dosimetry systems shall be calibrated in the electron accelerator, the X-ray converter, the product
accordance with the user’s documented procedure that speci-
conveyor, the control system, and all other auxiliary equipment
fies details of the calibration process and quality assurance and instrumentation.
requirements. This calibration procedure shall be repeated at
8.2.3 The testing, calibrating, and operating procedures for
regular intervals to ensure that the accuracy of the absorbed all of the equipment and instrumentation, including the dosim-
dose measurement is maintained within required limits. Irra- etry system.
diation is a critical component of the calibration of the 8.2.4 Identification of the instrumentation used to control,
dosimetry system. Detailed calibration procedures are provided monitor, and record the crit
...