ISO/ASTM 51608:2005

INTERNATIONAL ISO/ASTM
STANDARD 51608
Second edition
2005-05-15
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 International 2005
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ii © ISO/ASTM International 2005 – All rights reserved

Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 3
5 Radiation source characteristics . 3
6 Irradiation facilities . 3
7 Dosimetry systems . 3
8 Process parameters . 4
9 Installation qualification . 5
10 Operational qualification . 5
11 Performance qualification . 7
12 Routine product processing . 8
13 Measurement uncertainty . 9
14 Certification . 10
15 Keywords . 10
Annex . 10
Bibliography . 14
Figure A1.1 Beam current density distributions along the scan direction (wide curves) and
perpendicular to the scan direction (narrow curves) of No. 1 accelerator of JAERI Takasaki . 11
Figure A1.2 X-ray intensity per 2 MeV electron incident perpendicularly on a tantalum target
with thickness of one CSDA electron range as a function of emitting angle calculated by the
ETRAN code . 12
Figure A1.3 X-ray intensity per 5 MeV electron incident perpendicularly on a tantalum target
with thickness of one CSDA electron range as a function of emitting angle calculated by ETRAN
code . 12
Figure A1.4 X-ray emission rates from high-Z targets . 12
Figure A1.5 Spectrum of transmitted photons . 12
Figure A1.6 Spectrum of reflected photons . 13
Figure A1.7 Depth dose distributions . 13
Figure A1.8 Dose contour map, moving exposure . 13
Figure A1.9 Measured attenuation curves for 5 MeV X-Rays in absorbers of various densities,
with moving conveyor and scanning beam . 14
Figure A1.10 Measurement of a high-resolution attenuation curve for 5 MeV X-rays in the
heaviest absorber (chipboard) with moving conveyor and scanning . 14
© ISO/ASTM International 2005 – All rights reserved iii

Foreword
ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for
voting. Publication as an International Standard requires approval by at least 75% of the member bodies
casting a vote.
ASTM International is one of the world’s largest voluntary standards development organizations with global
participation from affected stakeholders. ASTM technical committees follow rigorous due process balloting
procedures.
A project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this 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 document may be the subject of patent
rights. Neither ISO nor ASTM International shall be held responsible for identifying any or all such patent
rights.
International Standard ISO/ASTM 51608 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear energy.
This second edition cancels and replaces the first edition (ISO/ASTM 51608:2002), which has been
technically revised.
iv © ISO/ASTM International 2005 – All rights reserved

Standard Practice for
Dosimetry in an X-Ray (Bremsstrahlung) Facility for
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 priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This practice outlines the installation qualification pro-
gram for an X-ray (bremsstrahlung) irradiator and the dosim-
2. Referenced documents
etric procedures to be followed during operational qualifica-
2.1 ASTM Standards:
tion, performance qualification and routine processing to
E 170 Terminology Relating to Radiation Measurements
ensure that the entire product has been treated within a
and Dosimetry
predetermined range of absorbed dose. Other procedures re-
E 2232 Guide for Selection and Use of Mathematical Meth-
lated to operational qualification, performance qualification
odsforCalculatingAbsorbedDoseinRadiationProcessing
and routine processing that may influence absorbed dose in the
Applications
product are also discussed. Information about effective or
E 2303 Guide for Absorbed Dose-Mapping in Radiation
regulatory dose limits and energy limits for X-radiation is not
Processing Facilities
within the scope of this practice.
2.2 ISO/ASTM Standards:
1.2 In contrast to monoenergetic gamma radiation, the
51204 Practice for Dosimetry in Gamma Irradiation Facili-
bremsstrahlung energy spectrum extends from low values
ties for Food Processing
(about 35 keV) up to the maximum energy of the electrons
51205 PracticeforUseofaCeric-CerousSulfateDosimetry
incident on the X-ray target (see Section 5 and Annex A1).
System
1.3 Dosimetry is only one component of a total quality
51261 Guide for Selection and Calibration of Dosimetry
assurance program for an irradiation facility. Other controls
Systems for Radiation Processing
besides dosimetry may be required for specific applications,
51275 Practice for Use of a Radiochromic Film Dosimetry
such as medical device sterilization and food preservation.
System
1.4 For the irradiation of food and the radiation sterilization
51276 Practice for Use of a Polymethylmethacrylate Do-
of health care products, other specific ISO standards exist. For
simetry System
food irradiation, see ISO/ASTM Practice 51431. For the
51310 Practice for Use of a Radiochromic Optical
radiation sterilization of health care products, see ISO 11137.
Waveguide Dosimetry System
In those areas covered by ISO/ASTM Practice 51431 or ISO
51400 Practice for Characterization and Performance of a
11137, those standards take precedence.
High-Dose Radiation Dosimetry Calibration Laboratory
NOTE 1—For guidance in the selection, calibration, and use of specific
51401 Practice for Use of a Dichromate Dosimetry System
dosimeters and interpretation of absorbed dose in the product from dose
51431 Practice for Dosimetry in Electron Beam and X-ray
measurements, see the documents listed in Section 2.
(Bremsstrahlung) Irradiation Facilities for Food Process-
NOTE 2—Bremsstrahlung characteristics are similar to those of gamma
ing
radiation from radioactive nuclides. See ISO/ASTM Practices 51204 and
51538 Practice for Use of the Ethanol-Chlorobenzene Do-
51702 for the applications of dosimetry in the characterization and
operation of gamma irradiation facilities. For information concerning simetry System
electron beam irradiation technology and dosimetry, see ISO/ASTM
51539 Guide for Use of Radiation-Sensitive Indicators
Practices 51431 and 51649.
51540 Practice for Use of a Radiochromic Liquid Dosim-
1.5 This standard does not purport to address all of the etry System
safety concerns, if any, associated with its use. It is the 51607 Practice for Use of the Alanine-EPR Dosimetry
responsibility of the user of this standard to establish appro- System
51649 Practice for Dosimetry in an Electron Beam Facility
for Radiation Processing at Energies Between 300 keV
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear and 25 MeV
Technology and Applications and is the direct responsibility of Subcommittee
51650 Practice for Use of a Cellulose Triacetate Dosimetry
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
System
ISO/TC 85/WG 3.
Current edition approved by ASTM June 1, 2004. Published May 15, 2005.
OriginallypublishedasASTME1608–94.LastpreviousASTMeditionE1608–00.
ASTM E 1608–94 was adopted by ISO in 1998 with the intermediate designation
For referenced ASTM or ISO/ASTM standards, visit the ASTM website,
ISO 15567:1998(E). The present International Standard ISO/ASTM 51608:2005(E)
www.astm.org, or contact ASTM Customer Service at service@astm.org. For
is a major revision of the last previous edition ISO/ASTM 51608:2002(E), which
Annual Book of ASTM Standards volume information, refer to the standard’s
replaced ISO 15567.
Document Summary page on the ASTM website.
© ISO/ASTM International 2005 – All rights reserved
51702 Practice for Dosimetry in a Gamma Irradiation Fa- the electron energy, the composition and thickness of the
cility for Radiation Processing converter, and the angle of emission with respect to the
51707 Guide for Estimating Uncertainties in Dosimetry for incident electron.
Radiation Processing
3.1.4 calibration facility—combinationofanionizingradia-
2.3 ISO Standard: tion source and its associated instrumentation that provides, at
ISO 11137 Sterilization of Health Care Products - Require-
a specified location and within a specified material, a uniform
ments for Validation and Routine Control - Radiation and reproducible absorbed dose, or absorbed dose rate, trace-
Sterilization
able to national or international standards, and that may be
2.4 ICRU Reports:
used to derive the dosimetry system’s response function or
ICRU Report 14 Radiation Dosimetry: X Rays and Gamma
calibration curve.
RayswithMaximumPhotonEnergiesBetween0.6and50
3.1.5 dose uniformity ratio—ratio of the maximum to the
MeV
minimum absorbed dose within the process load. The concept
ICRU Report 34 Dosimetry of Pulsed Radiation
is also referred to as the max/min dose ratio.
ICRUReport35 RadiationDosimetry:ElectronBeamswith
3.1.6 dosimeter—device that, when irradiated, exhibits a
Energies Between 1 and 50 MeV
quantifiable change in some property of the device, which can
ICRU Report 37 Stopping Powers for Electrons and
be related to the absorbed dose in a given material using
Positrons
appropriate analytical instrumentation and techniques.
ICRU Report 60 Fundamental Quantities and Units for
3.1.7 dosimetry system—system used for determining ab-
Ionizing Radiation
sorbed dose, consisting of dosimeters, measurement instru-
ments and their associated reference standards, and procedures
3. Terminology
for the system’s use.
3.1 Definitions:
3.1.8 electron energy—kinetic energy of an electron that is
3.1.1 absorbed dose (D)—quantity of ionizing radiation
usually given in units of electron volts (eV), kiloelectron volts
energy imparted per unit mass of a specified material. The SI
(keV), or megaelectron volts (MeV).
unit of absorbed dose is the gray (Gy), where 1 gray is
3.1.9 electron energy spectrum—particle fluence distribu-
equivalent to the absorption of 1 joule per kilogram of the
tion of electrons as a function of energy.
specified material (1 Gy = 1 J/kg). The mathematical relation-
3.1.10 equilibrium absorbed dose—absorbed dose in a fi-
ship is the quotient of de by dm, where de is the mean
nite volume within the material in which the condition of
incremental energy imparted by ionizing radiation to matter of
approximate electron equilibrium exists.
incremental mass dm (see ICRU Report 60).
3.1.11 measurement quality assurance plan—documented
D 5 de/dm (1)
program for the measurement process that ensures on a
continuing basis that the overall uncertainty meets the require-
3.1.1.1 Discussion—The discontinued unit for absorbed
mentsofthespecificapplication.Thisplanrequirestraceability
dose is the rad (1 rad = 100 erg/g = 0.01 Gy).
to, and consistency with, nationally or internationally recog-
3.1.2 absorbed dose enhancement—increase or decrease in
nized standards.
the absorbed dose, as compared to the equilibrium dose, at a
3.1.12 measurement traceability—ability to demonstrate by
point in the material of interest. This will occur near an
interface between materials with different atomic numbers. means of an unbroken chain of comparisons that a measure-
ment is in agreement within acceptable limits of uncertainty
3.1.3 bremsstrahlung—broad-spectrum electromagnetic ra-
with comparable nationally or internationally recognized stan-
diation emitted when an energetic electron is influenced by a
dards.
strong electric or magnetic field, such as that in the vicinity of
an atomic nucleus (see 3.1.14). 3.1.13 process load—volume of material with a specified
3.1.3.1 Discussion—When an electron passes close to a loading configuration irradiated as a single entity.
nucleus,thestrongcoulombfieldcausestheelectrontodeviate
3.1.14 X-radiation—short wave-length electromagnetic ra-
sharply from its original path.The change in direction is due to diation emitted by high-energy electrons when they are accel-
radial acceleration, and in accordance with classical theory, the
erated, decelerated or deflected by strong electric or magnetic
electron loses energy by electromagnetic radiation at a rate fields. The term includes both bremsstrahlung from nuclear
proportional to the square of the acceleration. This means that
interactions and the characteristic monoenergetic radiation
the bremsstrahlung photons have a continuous energy distri- emittedwhenatomicelectronsmaketransitionstomoretightly
bution that ranges downward from a theoretical maximum
bound states (see 3.1.3).
equal to the kinetic energy of the incident electron.
3.1.15 X-ray—common term used for X-radiation.
Bremsstrahlungisproducedwhenanelectronbeamstrikesany
3.1.16 X-ray converter—device for generating X-rays
material (converter). The bremsstrahlung spectrum depends on
(bremsstrahlung) from an electron beam, consisting of a target,
means for cooling the target, and a supporting structure.
3.1.17 X-ray target—component of the X-ray converter that
Available from the International Organization for Standardization, 1 Rue de
is struck by the electron beam. It is usually made of metal with
Varembé, Case Postale 56, CH–1211, Geneva 20, Switzerland.
a high atomic number, high melting temperature, and high
Available from the International Commission on Radiation Units and Measure-
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A. thermal conductivity.
© ISO/ASTM International 2005 – All rights reserved
3.2 Definitions of other terms used in this standard that 5. Radiation source characteristics
pertain to radiation measurement and dosimetry may be found
5.1 A high-energy X-ray (bremsstrahlung) generator emits
in ASTM Terminology E 170. Definitions in E 170 are com-
short-wavelength electromagnetic radiation, which is analo-
patible with ICRU Report 60, which may be used as an
gous to nuclear gamma radiation. Although their effects on
alternative reference.
irradiated materials are generally similar, these kinds of radia-
tion differ in their energy spectra, angular distributions, and
4. Significance and use
dose rates.
5.2 ThephysicalcharacteristicsoftheX-rayfielddependon
4.1 A variety of products and materials may be irradiated
the design of the X-ray converter and the parameters of the
with X-radiation to modify their characteristics and improve
electron beam striking the target, that is, the electron energy
the economic value or for health-related purposes. Examples
spectrum, average electron beam current, and beam current
are single-use medical devices (sterilization), agricultural com-
distribution on the target.
modities (preservation), and various polymeric products (ma-
5.3 These aspects of an X-ray source and its suitability for
terial modification). Dosimetry requirements for X-ray pro-
radiation processing are reviewed in more detail inAnnexA1.
cessing may vary depending on the type and end use of the
product.
6. Irradiation facilities
4.2 Dosimeters are used as means of monitoring the radia-
6.1 Facility Components—An X-ray irradiation facility
tion process.
typically includes a high-energy electron accelerator with
NOTE 3—Dosimetry is required for regulated irradiation processes,
X-ray converter, product conveyor, radiation shield with per-
such as the sterilization of medical devices and the preservation of food,
sonnel safety system, product staging, loading and storage
because the results may affect the health of the consumer. It is less
areas, auxiliary equipment for power, cooling, ventilation, etc.,
important for other industrial processes, such as polymer modification,
which can be evaluated by changes in the physical properties of the
an equipment room, laboratory for dosimetry and product
irradiated materials. Nevertheless, routine dosimetry may be used to
testing, and personnel offices. The design shall conform to
monitor the reproducibility of the treatment process.
applicableregulationsandguidelines.Forinformationonsome
NOTE 4—It is necessary to specify the material in which radiation is
industrial facilities, see Refs (1-5).
absorbed. Frequently, water is selected as the reference material for this
6.2 Product Handling System—The penetrating quality of
purpose. Water is a convenient medium to use because its radiation
high-energyX-radiationpermitsthetreatmentoflargecontain-
absorption and scattering properties are close to those of tissue and it is
ers or full pallet loads of products. The container size for
universally available and understood. The requirement of tissue-
optimum photon power utilization and dose uniformity de-
equivalency historically originated from radiation therapy applications.
Absorbed dose in materials other than water may be determined by pends on the maximum energy and product density. The
applying conversion factors in accordance with ISO/ASTM Guide 51261.
narrow angular distribution of the radiation favors the use of
continuously moving conveyors rather than shuffle-dwell sys-
4.3 Radiation processing specifications usually include a
tems to enhance dose uniformity.
pair of absorbed-dose limits: a minimum value to ensure the
6.3 Irradiation System—The configuration of the X-ray
intended beneficial effect and a maximum value to avoid
converter, the beam current distribution on the X-ray target,
product degradation. For a given application, one or both of
andthepenetratingqualityoftheradiation,andthesize,shape,
these values may be prescribed by process specifications or
and density of the process load affect the dose uniformity ratio
regulations. Knowledge of the dose distribution within irradi-
(see Refs 1, 2, 6-8). In some cases, the dose uniformity ratio
ated material is essential to meet these requirements.
may be improved by the use of collimators between the X-ray
4.4 Several critical parameters must be controlled to obtain
target and the product (9).
reproducible dose distributions in the processed materials. The
processing rate and dose distribution depend on the X-ray
7. Dosimetry systems
intensity, photon energy spectrum, spatial distribution of the
7.1 Dosimetry systems are used to measure absorbed dose.
radiation field, conveyor speed, and product configuration (see
Theyconsistofdosimeters,measurementinstrumentsandtheir
Sections 5, 8, and Annex A1).
associatedreferencestandards,andproceduresforthesystem’s
4.5 The irradiation process must be qualified to determine
use.
its effectiveness in delivering known, controllable doses. This
involves testing the process equipment, calibrating the measur-
NOTE 5—For a comprehensive discussion of various dosimetry meth-
ods applicable to the radiation types and energies discussed in this
ing instruments and dosimetry system, and demonstrating the
practice, see ICRU Reports 14, 34 and 35, and Ref (10).
ability of the process to deliver dose distributions in a reliable
and reproducible manner (see Sections 9 and 10).
7.2 Description of Dosimeter Classes—Dosimeters may be
4.6 To ensure consistent dose delivery in a qualified irradia-
divided into four basic classes according to their relative
tion process, routine process control requires procedures for
quality and areas of application: primary-standard, reference-
routine product dosimetry, product handling before and after
standard, transfer-standard, and routine dosimeters. ISO/
the treatment, prescribed orientation of the products during
irradiation, monitoring of critical process parameters, and
documentation of the required activities and functions (see
TheboldfacenumbersinparenthesesrefertotheBibliographyattheendofthis
Sections 11 and 12). standard.
© ISO/ASTM International 2005 – All rights reserved
ASTM Guide 51261 provides information about the selection mented procedure that specifies details of the calibration
of dosimetry systems for different applications. All classes of process and quality assurance requirements. Calibration re-
dosimeters, except the primary standards, require calibration quirements are given in ISO/ASTM Guide 51261.
before their use. 7.4.2 Calibration Irradiation—Irradiation is a critical com-
7.2.1 Primary-Standard Dosimeters—Primary-standard do- ponent of the calibration of the dosimetry system. Acceptable
simeters are established and maintained by national standards ways of performing the calibration irradiation depend on
laboratories for calibration of radiation environments (fields) whether the dosimeter is used as a reference-standard, transfer-
and other classes of dosimeters. The two most commonly used standard or routine dosimeter.
primary-standard dosimeters are ionization chambers and calo- 7.4.2.1 Reference- or Transfer-Standard Dosimeters—
rimeters. Calibration irradiation shall be performed at a national or
7.2.2 Reference-Standard Dosimeters—Reference-standard accredited laboratory using criteria specified in ISO/ASTM
dosimeters are used to calibrate radiation environments and Practice 51400.
routinedosimeters.Reference-standarddosimetersmayalsobe 7.4.2.2 Routine Dosimeters—The calibration irradiation
used as routine dosimeters. Examples of reference-standard may be performed by irradiating the dosimeters at (a) a
dosimeters, along with their useful absorbed-dose ranges, are national or accredited laboratory using criteria specified in
given in ISO/ASTM Guide 51261. ISO/ASTM Practice 51400, (b) an in-house calibration facility
7.2.3 Transfer-Standard Dosimeters—Transfer-standarddo- that provides an absorbed dose (or an absorbed-dose rate)
simeters are specially selected dosimeters used for transferring having measurement traceability to nationally or internation-
absorbed-dose information from an accredited or national ally recognized standards, or (c) a production irradiator under
standards laboratory to an irradiation facility in order to actual production irradiation conditions, together with
establish traceability for that facility. These dosimeters should reference- or transfer-standard dosimeters that have measure-
be carefully used under conditions that are specified by the ment traceability to nationally or internationally recognized
issuing laboratory. Transfer-standard dosimeters may be se- standards. In case of option (a) or (b), the resulting calibration
lected from either reference-standard dosimeters or routine curve shall be verified for the actual conditions of use.
dosimeters, taking into consideration the criteria listed in 7.4.3 Measurement Instrument Calibration and Perfor-
ISO/ASTM Guide 51261. mance Verification—Forthecalibrationoftheinstruments,and
7.2.4 Routine Dosimeters—Routine dosimeters may be for the verification of instrument performances between cali-
brations, see ISO/ASTM Guide 51261, the corresponding
usedforradiationprocessqualitycontrol,absorbed-dosemoni-
toring, and absorbed-dose mapping. Proper dosimetric tech- ISO/ASTM or ASTM standard for the dosimetry system,
niques, including calibration, shall be employed to ensure that and/or instrument-specific operating manuals.
measurements are reliable and accurate. Examples of routine
8. Process parameters
dosimeters, along with their useful absorbed-dose ranges, are
8.1 Absorbeddoseinaproductisdeterminedandcontrolled
given in ISO/ASTM Guide 51261.
by several components of the irradiation facility as well as the
7.3 Selection of Dosimetry Systems—Select dosimetry sys-
product. Thus, all parameters characterizing the facility com-
temssuitablefortheexpectedradiationprocessingapplications
ponents, process load and the irradiation conditions are re-
at the facility using the selection criteria listed in ISO/ASTM
ferred to as ‘process parameters’. They should, therefore, be
Guide 51261. During the selection process, for each dosimetry
considered when performing the absorbed-dose measurements
system, take into consideration its performance behavior with
required in Sections 10-12.
respect to relevant influence quantities and the uncertainty
8.2 For accelerator-generated radiation (electrons and
associated with it. For accelerator applications, it is also
X-radiation) facilities, process parameters include:
essential to consider the influences of dose rate (average and
8.2.1 Beam characteristics (for example, electron beam
peak absorbed dose rate for pulsed accelerators), pulse rate and
energy, beam current, pulse frequency, bremsstrahlung con-
pulse width (if applicable) on dosimeter performance. Some of
verter design),
the dosimetry systems that are suitable for gamma radiation
8.2.2 Beam dispersion (for example, scan width, scan fre-
from radionuclides (such as those from Co) may also be
quency, collimator aperture),
suitable for X-rays (1, 11).
8.2.3 Product handling characteristics (for example, con-
NOTE 6—Dosimeters consisting mainly of water or hydrocarbon mate-
veyor speed),
rials are suitable for both gamma radiation from radionuclides and
8.2.4 Product loading characteristics (for example, size of
X-radiation. Some exceptions are dosimeters containing substantial
the process load, bulk density, orientation of product), and
amounts of material with high atomic numbers, which are highly sensitive
8.2.5 Irradiation geometry (for example, 1- or 2-sided irra-
to the low-energy photons in the X-ray spectrum.
NOTE 7—X-ray dose rate may be higher than that for gamma radiation diation, multiple passes, reflectors).
used for radiation processing, especially in products passing near the
8.3 The first three sets of parameters (8.2.1, 8.2.2 and 8.2.3)
converter. The dose-rate dependence of the dosimeters should be consid-
characterise the irradiation facility without reference to the
ered in their calibration procedure (11, 12).
productortheprocess.Thesesubsetsofparametersarereferred
7.4 Calibration of Dosimetry Systems:
to as “operating parameters.”
7.4.1 Adosimetrysystemshallbecalibratedpriortouseand 8.4 Procedures during operational qualification (OQ) deal
at intervals thereafter in accordance with the user’s docu-
with operating parameters.
© ISO/ASTM International 2005 – All rights reserved
8.5 The objective of performance qualification (PQ) is to ment and instruments might be required to be traceable to a
establish the values of all process parameters for the radiation national or other accredited standards laboratory.
process under consideration. 9.4 Testing of Processing Equipment and Measurement
Instruments—Verify that the installed processing equipment
8.6 During routine product processing, operating param-
eters are continuously controlled and monitored for process and measurement instruments operate within their design
control. specifications by following the testing procedures noted in
9.3.1. If necessary, ensure that the equipment and instruments
have been calibrated according to the calibration procedures
9. Installation qualification
noted in 9.3.3.
9.1 Objective—The purpose of an installation qualification
9.4.1 Test all processing equipment to verify satisfactory
program is to demonstrate that the irradiator with its associated
operation of the irradiator within the design specifications.
processing equipment and measurement instruments have been
Document all testing results.
delivered and installed in accordance with their specifications.
9.4.2 Check the performance of the measurement instru-
Installationqualificationincludesdocumentationoftheirradia-
ments to ensure that they are functioning according to perfor-
tor and the associated processing equipment and measurement
mance specifications. Document all testing results.
instruments, establishment of the testing, operation and cali-
9.4.3 If any modification or change is made to the process-
bration procedures for their use, and verification that they
ing equipment or measurement instruments during installation
operate according to specifications. An effective installation
qualification, they shall be re-tested.
qualification program will help ensure correct operation of the
irradiator.
10. Operational qualification
9.2 Equipment Documentation—Document descriptions of
10.1 Objective—The objective of the operational qualifica-
the irradiator and the associated processing equipment and
tion of an irradiation facility is to obtain and document
measurement instruments installed at the facility. This docu-
evidence that installed equipment and instrumentation operate
mentation shall be retained for the life of the facility. At a
within predetermined limits when used in accordance with
minimum, it shall include:
operational procedures. This procedure establishes baseline
9.2.1 Description of the location of the irradiator (accelera-
data for evaluating facility effectiveness, predictability, and
tor) within the operator’s premises in relation to the areas
reproducibility for the range of conditions of operation for the
assigned and the means established for ensuring the segrega-
key operating parameters that affect absorbed dose in the
tion of un-irradiated products from irradiated products,
product (13). This can be accomplished through dosimetry.
9.2.2 Accelerator specifications and characteristics,
Thus, dosimetry is used:
9.2.3 Description of the operating procedure of the irradia-
10.1.1 To measure absorbed-dose distributions in reference
tor,
material(s); this process is sometimes referred to as “dose
9.2.4 Description of the construction and operation of the
mapping” (see 10.3),
product handling equipment,
10.1.2 To measure absorbed-dose characteristics over the
9.2.5 Description of the materials and construction of any
expected operational range of the operating parameters for
containers used to hold products during irradiation,
reference conditions (see 10.4),
9.2.6 Description of the process control system, and
10.1.3 To characterize absorbed-dose variations when oper-
9.2.7 Description of any modifications made during and
ating parameters fluctuate statistically during normal opera-
after the irradiator installation.
tions (see 10.5), and
9.3 Testing, Operation and Calibration Procedures—
10.1.4 To establish the effect of a process interruption/
Establish and implement standard operating procedures for the
restart (see 10.6).
testing, operation and calibration (if necessary) of the installed
10.2 Dosimetry Systems—Calibrate the dosimetry systems
irradiator and its associated processing equipment and mea-
to be used at the facility as discussed in Section 7.
surement instruments.
10.3 Dose Mapping:
9.3.1 Testing Procedures—These procedures describe the
10.3.1 Map the absorbed-dose distribution by a three-
testing methods used to ensure that the installed irradiator and
dimensional placement of dosimeter sets in the process loads
its associated processing equipment and measurement instru-
containing homogeneous reference materials (such as grains,
ments operate according to specification.
cardboard, plywood or sheets of plastics) as discussed in
9.3.2 Operation Procedures—These procedures describe
ASTM Guide E 2303 (also see Refs 10, 14). The amount of
how to operate the irradiator and its associated processing
material in these process loads should be the amount expected
equipment and measurement instruments during routine opera-
during typical production runs or should be the maximum
tion.
design volume for the process loads.
9.3.3 Calibration Procedures—These procedures describe
NOTE 8—Dosimeter strips or sheets may be used to increase spatial
periodic calibration and verification methods that ensure that
resolution of the absorbed-dose map, if the use of individual dosimeters is
the installed processing equipment and measurement instru-
inadequate.
ments continue to operate within specifications. The frequency
of calibration for some equipment and instruments might be 10.3.2 The procedures for absorbed-dose mapping outlined
specified by a regulatory authority. Calibration of some equip- in this section may not be feasible for some types of bulk-flow
© ISO/ASTM International 2005 – All rights reserved
irradiators. In such cases, minimum and maximum absorbed 10.4.2.2 Establish relationship between surface dose and
doses should be estimated by using an appropriate number of conveyor speed, where all other operating parameters are held
dosimeters mixed randomly with and carried by the product constant. Generally, surface dose should be inversely propor-
through the irradiation zone. Enough dosimeters should be tional to the conveyor speed.
used to obtain statistically significant results (see 11.3.3).
NOTE 15—The conveyor speed and the beam current may be linked
NOTE 9—Theoretical calculations may be performed using the Monte during routine product processing so that a variation in one causes a
Carlo methods (15), and applied to industrial radiation processing (16). corresponding change in the other to maintain a constant value of the
The use of the point-kernel method can be considered for X-ray facilities surface (or reference plane) dose.
(17). Both of these methods require accurate radiation interaction cross-
10.4.2.3 For X-ray irradiators, absorbed dose rate also
sections for all materials between and surrounding the source point and
depends on the incident electron energy spectrum and the
dose point. General-purpose software packages are available for these
types of calculations (seeASTM Guide E 2232). Models built using these design of the X-ray converter.
codesshouldbevalidatedagainstdosimetrydatafortheirpredictionstobe
10.5 Dose Variability:
meaningful. Empirically derived models built directly from dosimetry
10.5.1 Establish the capability of the facility to deliver a
data may be satisfactory but should be confined to the boundaries of
reproducible dose in a reference geometry. Measure the fluc-
experiments at a specific facility.
tuations in the operating parameter values that may cause
NOTE 10—For an X-ray facility, the depth-dose distribution in a
homogeneous material with low atomic number is approximately expo- variation in absorbed dose. Estimate the magnitude of the
nential, and penetration for 5 MeVX-radiation is slightly greater than that
corresponding dose variations in a reference material, for
for cobalt-60 gamma radiation (see Fig. A1.7).
example, by passing dosimeters in the reference geometry
through the irradiation zone on the product conveyor at time
10.4 Absorbed Dose and Operating Parameters:
intervals appropriate to the frequency of the parameter fluc-
10.4.1 Objective—The dose in the product depends on
tuations. The irradiation geometry for the reference material
several operating parameters. Over the expected range of these
should be selected so that the placement of the dosimeters on
parameters, establish the absorbed-dose characteristics in a
and within the material will not affect the reproducibility of the
reference material using appropriate dosimetry.
measurements.
10.4.1.1 The depth-dose distribution depends on beam en-
10.5.2 Following the procedure of 10.3, map a sufficient
ergy and the reference material characteristics.
number of nominally identical process loads containing refer-
10.4.1.2 Surface dose and its uniformity depend on con-
ence material to allow the estimation of the variability of the
veyor speed, beam characteristics and beam dispersion.
magnitude and distribution of the absorbed dose. Dosimetry
NOTE 11—For X-ray irradiators, photon energy spectrum and angular
data from previously qualified irradiators of the same design
distribution depend on the design and composition of the bremsstrahlung
may provide useful information for determining the number of
converter and on the electron energy spectrum . Higher energy electrons
process loads for this qualification.
will increase forward concentration of the photon distribution and
therefore improve penetration in the product (7, 18, 19). 10.6 Process Interruption/Restart—In the case of a process
interruption, for example stoppage of the conveyor system due
10.4.2 Surface Dose—Establish the relationships between
to power failure, the implication of a restart on the process (for
surfacedose(ordoseinareferenceplane)andconveyorspeed,
example, uniformity of dose in a reference plane) shall be
beam charactristics and beam dispersion parameters over the
investigated.
expected range of operation.
10.6.1 Thiscanbeachievedbyexposingastripofdosimeter
NOTE 12—Dispersion of the electron beam to obtain an X-ray beam
film in a reference plane through a stop/start sequence of the
width adequate to cover the processing zone may be achieved by various
conveyor system.
techniques. These include electromagnetic scanning of a pencil beam or
10.6.2 Continuous (seamless) dose through the stop/start
use of defocussing elements or scattering foils.
sequence would suggest that the conveyor could be restarted
10.4.2.1 Establish the range of uniform surface dose that
after the failure to continue the process. The effect of the
can be delivered. This will set the range of operation for the
process interruption on the product itself is discussed in 12.6.
conveyor speed, pulse rate and scan frequency.
10.6.3 If the dose is found to be significantly non-uniform
NOTE 13—Electron beam and X-ray irradiators generally utilize
through the stop/start sequence, the impact to process load in
continuously-moving conveyors. Dose uniformity in a reference plane is
the radiation zone shall be evaluated.
strongly influenced by the coordination of the beam spot dimensions,
10.6.4 This procedure should be conducted for the extremes
conveyor speed and scan frequency (for those irradiators that employ
of the operating parameters.
beam scanning). For a pulsed-beam accelerator, all these parameters must
also be coordinated with the pulse width and pulse rate. Improper
10.7 Documentation and Maintenance of OQ—Operational
coordination of these parameters can cause unacceptable dose variation in
qualification procedures shall be repeated periodically as
the reference plane.
specified in the quality assurance program to update the
NOTE 14—Indirect-action accelerators may deliver higher dose rates
baseline data referred to in 10.1.
during the pulse compared to direct-action accelerators with the same
10.8 Facility Changes—If changes that could affect the
average beam current. Also, scanning of a small diameter beam can
magnitudes or locations of the absorbed-dose extremes are
producepulseddoseatpointsalongthebeamwidth.Thiscaninfluencethe
dosimeters’ performance if they are sensitive to dose rate. made to the facility (for example, accelerator, bremsstrahlung
© ISO/ASTM International 2005 – All rights reserved
converter, conveyor) or its mode of operation, repeat the 1
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