ISO/ASTM 51649:2005

INTERNATIONAL ISO/ASTM
STANDARD 51649
Second edition
2005-05-15
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 International 2005
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ii © ISO/ASTM International 2005 – All rights reserved

ISO/ASTM FDIS 51649:2005(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 5
5 Radiation source characteristics . 6
6 Types of irradiation facilities . 6
7 Dosimetry systems . 6
8 Process parameters . 7
9 Installation qualification . 7
10 Operational qualification . 8
11 Performance qualification . 9
12 Routine product processing . 11
13 Measurement uncertainty . 12
14 Certification . 12
15 Keywords . 12
Annexes . 12
Bibliography . 29
Figure 1 Example pulse current (I ), average beam current (I ), pulse width (W) and
pulse avg
repetition rate (f) for a pulsed accelerator . 2
Figure 2 Diagram showing beam length and width for a scanned beam using a conveyor
system . 3
Figure 3 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 . 3
max
Figure 4 A typical depth-dose distribution for an electron beam in a homogeneous material . 4
Figure 5 Typical pulse current waveform from an S-Band linear accelerator . 5
Figure A1.1 Calculated depth-dose distribution curves in various homogeneous polymers for
normally incident monoenergetic electrons at 5.0 MeV using the Program ITS3 . 13
Figure A1.2 Calculated depth-dose distribution curves in various homogeneous metals for
normally incident monoenergetic electrons at 5.0 MeV using the Program ITS3 . 14
Figure A1.3 Calculated depth-dose distribution curves in polystyrene for normally incident
electrons at monoenergetic energies from 300 to 1000 keV using the Program ITS3 . 15
Figure A1.4 Calculated depth-dose distribution curves in polystyrene for normally incident, plane
parallel incident electrons at monoenergetic energies from 1.0 to 5.0 MeV using the program ITS3
.................................................................................................................................................. 16
Figure A1.5 Calculated depth-dose distribution curves in polystyrene for normally incident, plane
parallel incident electrons at monoenergetic energies from 5.0 to 12.0 MeV using the program
ITS3 . 17
Figure A1.6 Calculated depth-dose distribution curves in Al and Ta for normally incident, plane
parallel incident electrons at a monoenergetic energy of 25 MeV using the program ITS3 . 18
Figure A1.7 Electron energy deposition D (0) at the entrance surface of a polystyrene absorber
e
as a function of incident electron energy from 0.3 MeV to 12 MeV corresponding to the Monte
Carlo calculated data shown in Figs. A1.3-A1.5 . 18
Figure A1.8 Electron energy deposition D (0) at the entrance surface of a polystyrene absorber
e
as a function of incident electron energy from 0.3 MeV to 2.0 MeV corresponding to the Monte
Carlo calculated data shown in Fig. A1.3 and Fig. A1.4 . 19
Figure A1.9 Superposition of theoretically calculated depth-dose distribution curves for aluminum
© ISO/ASTM International 2005 – All rights reserved iii

ISO/ASTM FDIS 51649:2005(E)
irradiated with 5 MeV monoenergetic electrons from both sides with different thicknesses (T) and
from one side using experimental data presented in Refs (12 and 25) . 19
Figure A1.10 Calculated correlations between optimum electron range R , half-value depth R ,
opt 50
half-entrance depth R , and practical range R , and incident electron energy for polystyrene
50e p
using Fig. A1.3 and Fig. A1.4 . 20
Figure A1.11 Calculated correlations between optimum electron range R , half-value depth R ,
opt 50
half-entrance depth R , and practical range R , and incident electron energy for polystyrene
50e p
using Figs. A1.4 and A1.5 . 20
Figure A1.12 Measured depth-dose distribution curves for nominal 10 MeV electron beams
,
incident on polystyrene for two electron beam facilities . 21
Figure A1.13 Depth-dose distribution curves in stacks of cellulose acetate films backed with
wood, aluminum, and iron for incident electrons with 400 keV energy . 22
Figure A1.14 Depth-dose distributions with 2 MeV electrons incident on polystyrene absorbers at
various angles from the normal direction . 22
Figure A3.1 Measured depth-dose distribution curve in aluminum for a 10 MeV electron beam in
comparison with the calculated relative depth-dose distribition using ITS3 . 25
Figure A3.2 Stack energy measurement device . 26
Figure A3.3 Wedge energy measurement device . 27
Table A1.1 Key parameters for measured depth-dose distribution curves presented in Fig. A1.12 . 21
Table A1.2 Electron energy deposition D (0) at the entrance surface of a polystyrene absorber as
e
a function of incident electron energy from 0.3 MeV to 12 MeV corresponding to the calculated
curves shown in Figs. A1.3-A1.5 . 21
Table A1.3 Compatible units for the quantities used in Eq A1.1 . 22
Table A3.1 Some relevant properties of common reference materials . 24
Table A3.2 Half-value depth R , half-entrance depth R , optimum thickness R and practical
50 50e opt
range R in polystyrene for monoenergetic electron energies E from 0.3 to 12 MeV derived from
p
Monte Carlo calculations . 24
Table A3.3 Half-value depth R , practical range R and extrapolated range R in aluminum for
50 p ex
monoenergetic electron energies E from 2.5 to 25 MeV derived from Monte Carlo calculations . 25
iv © ISO/ASTM International 2005 – All rights reserved

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 51649 was developed byASTM 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 51649:2002), which has been
technically revised.
© ISO/ASTM International 2005 – All rights reserved v

Standard Practice for
Dosimetry in an Electron Beam Facility for Radiation
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 Installation Qualification, Operational Qualification E 170 Terminology Relating to Radiation Measurements
and Performance Qualifications (IQ, OQ, PQ), and routine and Dosimetry
processing at electron beam facilities to ensure that the product E 1026 Practice for Using the Fricke Reference Standard
has been treated with an acceptable range of absorbed doses. Dosimetry System
Other procedures related to IQ, OQ, PQ, and routine product E 2232 Guide for Selection and Use of Mathematical Meth-
processing that may influence absorbed dose in the product are odsforCalculatingAbsorbedDoseinRadiationProcessing
also discussed. Applications
E 2303 Guide to Dose Mapping in Radiation Processing
NOTE 1—For guidance in the selection and calibration of dosimeters,
Facilities
see ISO/ASTM Guide 51261. For further guidance in the use of specific
2.2 ISO/ASTM Standards:
dosimetry systems, and interpretation of the measured absorbed dose in
51205 PracticeforUseofaCeric-CerousSulfateDosimetry
the product, also see ISO/ASTM Practices 51275, 51276, 51431, 51607,
51631, 51650, and 51956. For use with electron energies above 5 MeV,
System
see Practice E 1026, and ISO/ASTM Practices 51205, 51401, 51538, and
51261 Guide for Selection and Calibration of Dosimetry
51540 for discussions of specific large volume dosimeters. For discussion
Systems for Radiation Processing
of radiation dosimetry for pulsed radiation, see ICRU Report 34.
51275 Practice for Use of a Radiochromic Film Dosimetry
1.2 The electron beam energy range covered in this practice
System
is between 300 keV and 25 MeV, although there are some
51276 Practice for Use of a Polymethylmethacrylate Do-
discussions for other energies.
simetry System
1.3 Dosimetry is only one component of a total quality
51400 Practice for Characterization and Performance of a
assurance program for an irradiation facility. Other measures
High-Dose Radiation Dosimetry Calibration Laboratory
besides dosimetry may be required for specific applications
51401 Practice for Use of a Dichromate Dosimetry System
such as medical device sterilization and food preservation.
51431 Practice for Dosimetry in Electron and X-ray
1.4 Other specific ISO and ASTM standards exist for the
(Bremsstrahlung) Irradiation Facilities for Food Process-
irradiation of food and the radiation sterilization of health care
ing
products. For food irradiation, see ISO/ASTM Practice 51431.
51538 Practice for Use of an Ethanol-Chlorobenzene Do-
For the radiation sterilization of health care products, see ISO
simetry System
11137. In those areas covered by ISO 11137, that standard
51539 Guide for the Use of Radiation-Sensitive Indicators
takes precedence.
51540 Practice for Use of a Radiochromic Liquid Solution
1.5 This standard does not purport to address all of the
Dosimetry 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
priate safety and health practices and determine the applica-
51631 Practice for Use of Calorimetric Dosimetry Systems
bility of regulatory requirements prior to use.
for Electron Beam Measurements and Dosimeter Calibra-
tions
51650 Practice for Use of a Cellulose Triacetate Dosimetry
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear System
Technology and Applications and is the direct responsibility of Subcommittee
51707 Guide for Estimating Uncertainties in Dosimetry for
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
Radiation Processing
ISO/TC 85/WG 3.
Current edition approved by ASTM June 1, 2004. Published May 15, 2005.
OriginallypublishedasE 1649–94.LastpreviousASTMeditionE 1649–00.ASTM
e1 2
E 1649–94 was adopted by ISO in 1998 with the intermediate designation ISO For referenced ASTM and ISO/ASTM standards, visit the ASTM website,
15569:1998(E). The present International Standard ISO/ASTM 51649:2005(E) is a www.astm.org, or contact ASTM Customer Service at service@astm.org. For
major revision of the last previous edition ISO/ASTM 51649:2002(E), which Annual Book of ASTM Standards volume information, refer to the standard’s
replaced ISO 15569. Document Summary page on the ASTM website.
© ISO/ASTM International 2005 – All rights reserved
– –
51956 Practice for Thermoluminescence Dosimetry (TLD)
ship is the quotient of de by dm, where de is the mean
Systems for Radiation Processing
incremental energy imparted by ionizing radiation to matter of
2.3 ISO Standard:
incremental mass dm.
ISO 11137 Sterilization of Health Care Products–Require-
–
D 5 de/dm
ments for Validation and Routine Control–Radiation Ster-
ilization
3.1.1.1 Discussion—The discontinued unit for absorbed
2.4 International Commission on Radiation Units and
dose is the rad (1 rad = 100 erg/g = 0.01 Gy). Absorbed dose
Measurements (ICRU) Reports:
is sometimes referred to simply as dose.
ICRU Report 34 The Dosimetry of Pulsed Radiation
3.1.2 average beam current—time-averaged electron beam
ICRUReport35 RadiationDosimetry:ElectronBeamswith
current; for a pulsed machine, the averaging shall be done over
Energies Between 1 and 50 MeV
a large number of pulses (see Fig. 1).
ICRU Report 37 Stopping Powers for Electrons and
3.1.3 beam length—dimension of the irradiation zone, per-
Positrons
pendicular to the beam width and direction of the electron
ICRU Report 60 Fundamental Quantities and Units for
beam at a specified distance from the accelerator window (see
Ionizing Radiation
Fig. 2).
3. Terminology 3.1.4 beam power—product of the average electron beam
energy and the average beam current.
3.1 Definitions:
3.1.5 beam spot—shape of the unscanned electron beam
3.1.1 absorbed dose (D)—quantity of ionizing radiation
incident on the reference plane.
energy imparted per unit mass of a specified material. The SI
unit of absorbed dose is the gray (Gy), where 1 gray is 3.1.6 beam width—dimension of the irradiation zone in the
equivalent to the absorption of 1 joule per kilogram in the direction that the beam is scanned, perpendicular to the beam
specified material (1 Gy = 1 J/kg). The mathematical relation- lengthanddirectionoftheelectronbeamataspecifieddistance
from the accelerator window (see Fig. 2).
3.1.6.1 Discussion—For a radiation processing facility with
Available from International Organization for Standardization, 1 Rue de
a conveyor system, the beam width is usually perpendicular to
Varembé, Case Postale 56, CH-1211 Geneva 20, Switzerland.
4 the flow of motion of the conveyor (see Fig. 2). Beam width is
Available from the International Commission on Radiation Units and Measure-
ments, 7910 Woodmont Ave., Suite 800, Bethesda MD 20814, U.S.A. the distance between two points along the dose profile, which
FIG. 1 Example pulse current (I ), average beam current (I ), pulse width (W) and repetition rate (f) for a pulsed accelerator
pulse avg
© ISO/ASTM International 2005 – All rights reserved
configuration, or simulated product used at the beginning or
end of a production run, to compensate for the absence of
product.
3.1.7.1 Discussion—Simulatedproductorphantommaterial
may be used during irradiator characterization as a substitute
for the actual product, material or substance to be irradiated.
3.1.8 continuous-slowing-down-approximation (CSDA)
range (r )—average pathlength traveled by a charged particle
as it slows down to rest, calculated in the continuous-slowing-
down-aproximation method.
3.1.8.1 Discussion—In this approximation, the rate of en-
ergy loss at every point along the track is assumed to be equal
to the total stopping power. Energy-loss fluctuations are
neglected. The CSDA range is obtained by integrating the
reciprocal of the total stopping power with respect to energy.
Values of r for a wide range of electron energies and for many
materials can be obtained from ICRU Report 37.
3.1.9 depth-dose distribution—variation of absorbed dose
FIG. 2 Diagram showing beam length and width for a scanned
beam using a conveyor system
with depth from the incident surface of a material exposed to
a given radiation.
3.1.9.1 Discussion—Typical distributions in homogeneous
are at a defined level from the maximum dose region in the materials produced by an electron beam along the beam axis
are shown in Figs. A1.1 and A1.2. See Annex A1.
profile (see Fig. 3). Various techniques may be employed to
produce an electron beam width adequate to cover the process-
3.1.10 dose uniformity ratio—ratio of the maximum to the
ing zone, for example, use of electromagnetic scanning of a minimum absorbed dose within the process load. The concept
pencil beam (in which case beam width is also referred to as
is also referred to as the max/min dose ratio.
scan width), defocussing elements, and scattering foils.
3.1.11 dosimetry system—system used for determining ab-
3.1.7 compensating dummy—simulatedproductusedduring sorbed dose, consisting of dosimeters, measurement instru-
routine production runs in process loads that contain less ments and their associated reference standards, and procedures
product than specified in the documented product-loading for the system’s use.
NOTE—McKeown, J., AECL Accelerators, private communication, 1993. Example of a beam width profile of an AECL Impela accelerator.
FIG. 3 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
© ISO/ASTM International 2005 – All rights reserved
3.1.12 duty cycle—for a pulsed accelerator, the fraction of 3.1.19 optimum thickness (R )—depth in homogeneous
opt
time the beam is effectively on; it is the product of the pulse material at which the absorbed dose equals the absorbed dose
width in seconds and the pulse rate in pulses per second. at the surface where the electron beam enters (see Fig. 4).
3.1.13 electron beam energy—average kinetic energy of the 3.1.20 practical electron range (R )—depth in homoge-
p
accelerated electrons in the beam. Unit: J neous material to the point where the tangent at the steepest
3.1.13.1 Discussion—Electron volt (eV) is often used as the point (the inflection point) on the almost straight descending
-19
portion of the depth-dose distribution curve meets the extrapo-
unit for electron beam energy where 1 eV = 1.602·10 J
(approximately). In radiation processing, where beams with a latedX-raybackground(seeFig.4andFig.A1.6inAnnexA1).
broad electron energy spectrum are frequently used, the terms 3.1.21 extrapolated electron range (R )—depth in homo-
ex
most probable energy (E ) and average energy (E ) are geneous material to the point where the tangent at the steepest
p a
common. They are linked to the practical electron range R point (the inflection point) on the almost straight descending
p
and half-value depth R by empirical equations. portion of the depth-dose distribution curve meets the depth
3.1.14 electron beam facility—establishment that uses ener- axis (see Fig. A1.6 in Annex A1).
getic electrons produced by particle accelerators to irradiate 3.1.22 process load—volume of product with a specified
product. loading configuration processed as a single entity; this term is
not relevant to bulk-flow processing.
3.1.15 electron energy spectrum—particle fluence distribu-
tion of electrons as a function of energy. 3.1.23 production run—seriesofprocessloadsconsistingof
materials,orproductshavingsimilarradiation-absorptionchar-
3.1.16 electron range—penetration distance in a specific,
acteristics, that are irradiated sequentially to a specified range
totally absorbing material along the beam axis of the electrons
of absorbed dose.
incident on the material (equivalent to practical electron range,
3.1.24 pulse beam current, for a pulsed accelerator—beam
R ).
P
current averaged over the top ripples (aberrations) of the pulse
3.1.16.1 Discussion—R can be measured from experimen-
P
current waveform; this is equal to I /wf, where I is the
tal depth-dose distributions in a given material. Other forms of
avg avg
average beam current, w is the pulse width, and f is the pulse
electron range are found in the dosimetry literature, for
rate (see Fig. 5).
example, extrapolated range derived from depth-dose data and
3.1.25 pulse rate, for a pulsed accelerator—pulse repetition
the continuous-slowing-down-approximation range (the calcu-
lated pathlength traversed by an electron in a material in the frequency in hertz, or pulses per second; this is also referred to
as the repetition (rep) rate.
course of completely slowing down). Electron range is usually
-2
expressed in terms of mass per unit area (kg·m ), but some- 3.1.26 pulse width, for a pulsed accelerator—time interval
times in terms of thickness (m) for a specified material. between two points on the leading and trailing edges of the
pulse current waveform where the current is 50 % of its peak
3.1.17 half-entrance depth (R )—depth in homogeneous
50e
material at which the absorbed dose has decreased down to value (see Fig. 5).
50 % of the absorbed dose at the surface of the material (see 3.1.27 reference material—homogeneous material of
Fig. 4). known radiation absorption and scattering properties used to
establish characteristics of the irradiation process, such as scan
3.1.18 half-value depth (R )—depth in homogeneous ma-
uniformity, depth-dose distribution, throughput rate, and repro-
terial at which the absorbed dose has decreased down to 50 %
ducibility of dose delivery.
of its maximum value (see Fig. 4).
3.1.28 reference plane—selected plane in the radiation zone
that is perpendicular to the electron beam axis.
3.1.29 scannedbeam—electronbeamthatissweptbackand
forth with a varying magnetic field.
3.1.29.1 Discussion—This is most commonly done along
one dimension (beam width), although two-dimensional scan-
ning (beam width and length) may be used with high-current
electron beams to avoid overheating the beam exit window of
the accelerator or product under the scan horn.
3.1.30 scan frequency—number of complete scanning
cycles per second expressed in Hz.
3.1.31 scan uniformity—degree of uniformity of the dose
measured along the scan direction.
3.1.32 simulated product—mass of material with attenua-
tion and scattering properties similar to those of the product,
material or substance to be irradiated.
3.1.32.1 Discussion—Simulated product is used during ir-
radiator characterization as a substitute for the actual product,
material or substance to be irradiated. When used in routine
FIG. 4 A typical depth-dose distribution for an electron beam in a
homogeneous material production runs, it is sometimes referred to as compensating
© ISO/ASTM International 2005 – All rights reserved
FIG. 5 Typical pulse current waveform from an S-Band linear accelerator
dummy. When used for absorbed-dose mapping, simulated 4.1.3 Curing of composite materials,
product is sometimes referred to as phantom material. 4.1.4 Sterilization of medical devices,
3.1.33 standardized depth (z)—thickness of the absorbing 4.1.5 Disinfection of consumer products,
material expressed as the mass per unit area, which is equal to 4.1.6 Food irradiation (parasite and pathogen control, insect
the depth in the material t times the density r.If m is the mass disinfestation, and shelf-life extension),
of the material beneath that area and A is the area of the 4.1.7 Control of pathogens and toxins in drinking water,
material through which the beam passes, then: 4.1.8 Control of pathogens and toxins in liquid or solid
waste,
z 5 m/A 5 tr
4.1.9 Modification of characteristics of semiconductor de-
If t is in meters and r in kilograms per cubic meter, then z is
vices,
in kilograms per square meter.
4.1.10 Color enhancement of gemstones and other materi-
3.1.33.1 Discussion—It is common practice to express t in
als, and
centimeters and r in grams per cm , then z is in grams per
4.1.11 Research on radiation effects on materials.
square centimeter. Standardized depth may also be referred to
NOTE 2—Dosimetry is required for regulated radiation processes such
as surface density or area density.
as sterilization of medical devices (see ISO 11137 and Refs (1-4) and
3.2 Definitions—Definitions of other terms used in this
preservation of food (see ISO/ASTM 51431 and Ref (5). It may be less
standard that pertain to radiation measurement and dosimetry
important for other processes, such as polymer modification, which may
may be found in ASTM Terminology E 170. Definitions in
be evaluated by changes in the physical and chemical properties of the
E 170 are compatible with ICRU 60; that document, therefore,
irradiated materials. Nevertheless, routine dosimetry may be used to
may be used as an alternative reference.
monitor the reproducibility of the treatment process.
4.2 Dosimeters are used as a means of monitoring the
4. Significance and use
radiation process.
4.1 Various products and materials are routinely irradiated
NOTE 3—Measured dose is often characterized as absorbed dose in
at pre-determined doses at electron beam facilities to preserve
water to have a traceable standard reference. Moreover, materials com-
or modify their characteristics. Dosimetry requirements may
monly found in disposable medical devices and food are approximately
vary depending on the radiation process and end use of the
equivalent to water in the absorption of ionizing radiation.Absorbed dose
product. For example, a partial list of processes where dosim-
in materials other than water may be determined by applying conversion
etry may be used is given below.
4.1.1 Polymerization of monomers and grafting of mono-
mers onto polymers,
TheboldfacenumbersinparenthesesrefertotheBibliographyattheendofthis
4.1.2 Cross-linking or degradation of polymers, standard.
© ISO/ASTM International 2005 – All rights reserved
factors in accordance with ISO/ASTM Guide 51261.
6.2.2 Roll-to-Roll Feed System—Roll-to-roll (also referred
to as reel-to-reel) feed systems are used for tubing, wire, cable,
4.3 Abeneficial irradiation process is usually specified by a
and continuous web products. The speed of the system is
minimum absorbed dose to achieve the desired effect and a
controlled in conjunction with the electron beam current and
maximum dose limit that the product can tolerate and still be
beam width so that the required dose is applied.
functional. Dosimetry is essential, since it is used to determine
6.2.3 Bulk-flow System—For irradiation of liquids or par-
these limits, and dosimetry is essential in the evaluation and
ticulate materials like grain or plastic pellets, bulk-flow trans-
monitoring of the radiation process.
port through the irradiation zone may be used. Because the
4.4 The dose distribution within the product depends on
flow velocity of the individual pieces of the product cannot be
process load characteristics, irradiation conditions, and operat-
controlled, the average velocity of the product in conjunction
ing parameters. The operating parameters consist of beam
with the beam characteristics and beam dispersion parameters
characteristics (such as electron energy and beam current),
determines the average absorbed dose.
beam dispersion parameters, and product material handling.
6.2.4 Stationary—For high-dose processes, the material
These critical parameters must be controlled to obtain repro-
may be placed under the beam and not moved. Cooling may be
ducible results.
required to dissipate the heat accumulated by the product
4.5 Before a radiation facility is used, it must be qualified to
during processing. The irradiation time is controlled in con-
demonstrate its ability to deliver specified, controllable doses
junction with the electron beam current, beam length, and
in a reproducible manner. This involves testing the process
beam width to achieve the required dose.
equipment, calibrating the equipment and dosimetry system,
and characterizing the magnitude, distribution and reproduc-
ibility of the dose absorbed by a reference material. 7. Dosimetry systems
4.6 To ensure that products are irradiated with reproducible
7.1 Description of Dosimeter Classes:
doses, routine process control requires documented product
7.1.1 Dosimeters may be divided into four basic classes
handling procedures before, during and after the irradiation,
according to their relative quality and areas of application:
consistent orientation of the products during irradiation, moni-
primary-standard, reference-standard, transfer-standard, and
toringofcriticalprocessparameters,routineproductdosimetry
routine dosimeters. ISO/ASTM Guide 51261 provides infor-
and documentation of the required activities and functions.
mation about the selection of dosimetry systems for different
applications. All classes of dosimeters, except the primary
5. Radiation source characteristics
standards, require calibration before their use.
5.1 Electronradiationsourcesconsideredinthispracticeare
7.1.1.1 Primary-Standard Dosimeters—Primary-standard
either direct-action (potential-drop) or indirect-action (RF- or
dosimeters are established and maintained by national stan-
microwave-powered) accelerators. These are discussed in An-
dards laboratories for calibration of radiation environments
nex A4.
(fields) and other classes of dosimeters. The two most com-
monly used primary-standard dosimeters are ionization cham-
6. Types of irradiation facilities
bers and calorimeters.
7.1.1.2 Reference-Standard Dosimeters—Reference-
6.1 Irradiation Facility Design:
standard dosimeters are used to calibrate radiation environ-
6.1.1 The design of an irradiation facility affects the deliv-
ments and routine dosimeters. Reference-standard dosimeters
eryofabsorbeddosetoaproduct.Therefore,thefacilitydesign
mayalsobeusedasroutinedosimeters.Examplesofreference-
should be considered when performing the absorbed-dose
standard dosimeters, along with their useful dose ranges, are
measurements required in Sections 8 to 11.
given in ISO/ASTM Guide 51261.
6.1.2 An electron beam facility includes the electron beam
7.1.1.3 Transfer-Standard Dosimeters—Transfer-standard
accelerator system; material handling systems, a radiation
shield with personnel safety system, product staging, loading dosimeters are specially selected dosimeters used for transfer-
ring absorbed-dose information from an accredited or national
and storage areas; auxiliary equipment for power, cooling,
ventilation, etc.; equipment control room; laboratories for standards laboratory to an irradiation facility in order to
establish traceability for that facility. These dosimeters should
dosimetry and product testing; and personnel offices. The
be carefully used under conditions that are specified by the
electron beam accelerator system consists of the radiation
issuing laboratory. Transfer-standard dosimeters may be se-
source (see Annex A4), equipment to disperse the beam on
lected from either reference-standard dosimeters or routine
product, control system, and associated equipment (2).
dosimeters taking into consideration the criteria listed in
6.2 Configuration of Material Handling—The absorbed
ISO/ASTM Guide 51261.
dose distributions within product may be affected by the
material handling system. Examples of systems commonly 7.1.1.4 Routine Dosimeters—Routine dosimeters may be
used are: used for radiation process quality control, dose monitoring and
6.2.1 Conveyors or Carriers—Material is placed upon car- dose mapping. Proper dosimetric techniques, including cali-
riers or conveyors for passage through the electron beam. The bration, shall be employed to ensure that measurements are
speed of the conveyor or carriers is controlled in conjunction
reliable and accurate. Examples of routine dosimeters, along
with the electron beam current and beam width so that the with their useful dose ranges, are given in ISO/ASTM Guide
required dose is applied. 51261.
© ISO/ASTM International 2005 – All rights reserved
7.2 It is important that the dosimeter be evaluated for those 8. Process parameters
parameters which may influence the dosimeter’s response; for
8.1 There are various processing parameters that play es-
example, average and peak absorbed dose rate (particularly for
sential roles in determining and controlling the absorbed dose
pulsed accelerators), environmental conditions (for example,
in radiation processing. They should, therefore, be considered
temperature, humidity, and light) and electron energy. Guid-
when performing the absorbed-dose measurements required in
ance as to desirable characteristics and selection criteria for
Sections 8 to 11.
dosimetry systems can be found in ISO/ASTM Guide 51261,
8.2 Processing parameters include process load characteris-
Practice E 1026, and ISO/ASTM Practices 51205, 51275,
tics (for example, size, bulk density, and heterogeneity),
51276, 51401, 51538, 51540, 51607, 51631, and 51650.
irradiation conditions (for example, processing geometry,
7.3 Calibration of Dosimetry Systems:
multi-sidedexposure,andnumberofpassesthroughthebeam),
7.3.1 Adosimetrysystemshallbecalibratedpriortouseand
and operating parameters.
at intervals thereafter in accordance with the user’s docu-
8.2.1 Operating parameters include beam characteristics
mented procedure that specifies details of the calibration
(for example, energy, average beam current, and pulse rate),
process and quality assurance requirements. Calibration re-
performance characteristics of material handling (see 6.2), and
quirements are given in ISO/ASTM 51261.
beam dispersion parameters (for example, beam width and
7.3.2 Calibration Irradiation—Irradiation is a critical com-
frequency at which the beam is scanned across product).
ponent of the calibration of the dosimetry system. Acceptable
Operatingparametersaremeasurableandshouldbemonitored.
ways of performing the calibration irradiation depend on
Duringirradiationfacilityqualification(seeSections9and10),
whether the dosimeter is used as a reference-standard, transfer-
absorbed dose characteristics over the expected range of the
standard or routine dosimeter.
operating parameters are established for a reference material.
7.3.2.1 Reference- or Transfer-Standard Dosimeters—
8.2.2 Processing parameters for a radiation process are
Calibration irradiation shall be performed at a national or
established during performance qualification (see Section 11)
accredited laboratory using criteria specified in ISO/ASTM
to achieve the absorbed dose within the specified limits.
Practice 51400.
8.2.3 During routine product processing (see Section 12),
7.3.2.2 Routine Dosimeters—The calibration irradiation
the facility operating parameters are controlled and monitored
may be performed by irradiating the dosimeters at (a) a
to maintain values that were set during performance qualifica-
national or accredited laboratory using criteria specified in
tion.
ISO/ASTM Practice 51400, (b) an in-house calibration facility
8.2.4 Differentproducttypesmayrequiredifferentvaluesof
that provides an absorbed dose (or an absorbed-dose rate)
operating and processing parameters.
having measurement traceability to nationally or internation-
ally recognized standards, or (c) a production irradiator under
9. Installation qualification
actual production irradiation conditions, together with
9.1 Objective—The purpose of the electron beam facility
reference- or transfer-standard dosimeters that have measure-
ment traceability to nationally or internationally recognized installation qualification is to obtain and document evidence
that equipment has been provided and installed in accordance
standards. In case of option (a) or (b), the resulting calibration
with its specifications.
curve shall be verified for the actual conditions of use.
7.3.3 Measurement Instrument Calibration and Perfor- 9.2 Equipment Documentation—Documentation of an in-
mance Verification—Forthecalibrationoftheinstruments,and stallation qualification program shall be retained for the life of
the irradiator, and shall include:
for the verification of instrument performance between calibra-
tions, see ISO/ASTM Guide 51261, the corresponding ISO/
9.2.1 The accelerator specifications and characteristics,
ASTM or ASTM standard for the dosimetry system, and/or
9.2.2 A description of the construction and the operation of
instrument-specific operating manuals.
any associated material handling equipment,
9.2.3 A description of the process control system and
NOTE 4—For some dosimetry systems, the dosimeter response at
personnel safety system,
different absorbed-dose rates for the same given absorbed dose may differ
over portions of the system’s working range. Accelerator systems are 9.2.4 A description of the location of the irradiator within
available which operate from about 1 kW to many hundred kW average
the operator’s premises in relation to the means provided for
beam power. Some are DC, others are pulsed with low duty cycles. So,
the segregation of non-irradiated products from irradiated
dose rates (average and peak) can be very different from one system to the
products, if required,
next. Because of this, it may be difficult to match the dose rate
9.2.5 Description of the materials and the construction
characteristicsoftheprocessingplanttothatofthecalibrationfacility.For
dimensions of containers used to hold products during irradia-
this reason, calibration irradiation using the production irradiator (in-situ
calibration) should be strongly considered (see ISO/ASTM Guide 51261). tion, if used,
© ISO/ASTM International 2005 – All rights reserved
9.2.6 Adescriptionofthemannerofoperatingtheirradiator, 9.4.2 Beam Dispersion:
and
9.4.2.1 Dispersion of the electron beam to obtain a beam
9.2.7 Any modifications made during and after installation. width adequate to cover the processing zone may be achieved
Such documentation is necessary to ensure the reproducibility by various techniques.These include electromagnetic scanning
of absorbed dose in the reference material within specified of a pencil beam or use of defocussing elements or scattering
foils.
limits.
9.4.2.2 Beam dispersion measurements of importance in-
9.3 Testing, Operation and Calibration Procedures—
Establish and implement standard operating procedures for the clude:
testing, operation and calibration (if necessary) of the installed
(1) Scan width,
irradiator and its associated processing equipment and mea-
(2) Scan length,
surement instruments.
(3) Variation of dose along the scan width and length, and
9.3.1 Testing Procedures—These procedures describe the
(4) Beam centering with respect to the irradiation zone.
testing methods used to ensure that the installed irradiator and
NOTE 6—The beam width, in addition to s
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