ISO 15562:1998

IS0
INTERNATIONAL
15562
STANDARD
First edition
1998-l 2-15
Practice for dosimetry in electron and
bremsstrahlung irradiation facilities for
food processing
Pratique de la dosimktrie electrons et Bremsstrahlung dans /es insta(iations
de traitement des produits alimentaires irradi&
Reference number
IS0 15562: 1998(E)

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IS0 15562:1998(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies
(lS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 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.
International Standard IS0 15562 was prepared by the American Society for Testing and Materials (ASTM)
Subcommittee E1O.O1 (as E 1431-91) and was adopted, under a special “fast-track procedure ”, by Technical
Committee ISOnC 85, Nuclear energy, in parallel with its approval by the IS0 member bodies.
A new lSO/TC 85 Working Group WG 3, High-level dosimetry for radiation processing, was formed to review the
voting comments from the IS0 “Fast-track procedure” and to maintain these standards. The USA holds the
convenership of this working group.
International Standard IS0 15562 is one of 20 standards developed and published by ASTM. The 20 fast-tracked
standards and their associated ASTM designations are listed below:
IS0 Designation ASTM Designation Title
15554 E 1204-93 Practice for dosimetry in gamma irradiation facilities for food
processing
15555 E 1205-93 Practice for use of a ceric-cerous sulfate dosimetry system
E 1261-94 Guide for selection and calibration of dosimetry systems for
15556
radiation processing
E 1275-93 Practice for use of a radiochromic film dosimetry system
15557
15558 E 1276-96 Practice for use of a polymethylmethacrylate dosimetry system
E 1310-94 Practice for use of a radiochromic optical waveguide dosimetry
15559
system
15560 E 1400-95a Practice for characterization and performance of a high-dose
radiation dosime try calibration labora tory
15561 E 1401-96 Practice for use of a dichromate dosimetry system
0 IS0 1998
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 the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet iso @I iso.ch
Printed in Switzerland
ii

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IS0 15562: 1998(E)
@IS0
and bremss trahlung irradiation
15562 E1431-91 Practice for dosimetry in electron
facilities for food processing
15563 E 1538-93 Practice for use of the ethanol-chlorobenzene dosimetry system
15564 E 1539-93 Guide for use of radiation-sensitive indicators
E 1540-93 Practice for use of a radiochromic liquid dosimetry system
15565
15566 E 1607-94 Practice for use of the alanine-EPR dosimetry system
facility for
Practice for dosimetty in an X-ray (bremss tra hlung)
15567 E 1608-94
processing
radiation
Practice for use of calorimetric dosimetry systems for electron
15568 E 1631-96
beam dose measurements and dosimeter calibrations
Practice for dosimetry in an electron-beam facility for radiation
15569 E 1649-94
processing at energies between 300 keV and 25 MeV
Practice for use of cellulose acetate dosimetry system
15570 E 1650-94
E 1702-95 Practice for dosimetry in a gamma irradiation facility for radiation
15571
processing
E 1707-95 Guide for estimating uncertainties in dosimetry for radiation
15572
processing
E 1818-96 Practice for dosimetry in an electron-beam facility for radiation
15573
processing at energies between 80 keV and 300 keV

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IS0 15562: 1998(E)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
!Designation: E 1431 - 91
1916 Race St. Philadelphia, Pa 19103
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
If not listed in the current combined index, will appear in the next edition.
Standard Practice for
Dosimetry in Electron and Bremsstrahlung Irradiation
Facilities for Food Processing’
This standard is issued under the fixed designation E 1431; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 1205 Test Method for Using the Ceric-Cerous Sulfate
Dosimeter to Measure Absorbed Dose in Wates
1.1 This practice describes dosimetric procedures to be
E 126 1 Guide for Selection and Application of Dosimetry
followed in characterizing, qualifying, and operating electron
Systems for Radiation Processing of Food2
beam and bremsstrahlung irradiation facilities for food
E 1275 Practice for Use of a Radiochromic Film
processing. Other procedures related to facility characteriza-
Dosimetry System2
tion, product qualification, and routine processing are also
E 1276 Practice for Use of a Polymethylmethacrylate
discussed.
Dosimetry System2
1.2 The electron energy range covered in this practice is
E 13 10 Practice for Use of a Radiochromic Optical
from 0.1 MeV to 10 MeV. Such electrons can be generated
Waveguide Dosimetry System*
in continuous or pulse modes.
2.2 International Commission on Radiation Units and
1.3 The maximum photon energy covered in this practice
Measurements (KR V) Reports3
is 5 MeV. A photon beam can be generated by inserting a
ICRU Report 14 Radiation Dosimetry: X Rays and
bremsstrahlung converter in the electron beam path.
Gamma Rays with Maximum Photon Energies Between
1.4 For guidance in the selection, calibration, and use of
0.6 and 50 MeV
specific dosimeters, and interpretation of absorbed dose in
ICRU Report 17 Radiation Dosimetry: X Rays Gener-
the product from dosimetry measurements, see Guide
ated at Potentials of 5 to 150 kV
E 126 1, Method E 1026, and Test Method E 1205. For
ICRU Report 33 Radiation Quantities and Units
discussion of radiation dosimetry for X rays and gamma
ICRU Report 34 The Dosimetry of Pulsed Radiation
rays, see ICRU Reports 14 and 17, and for pulsed radiation,
ICRU Report 35 Radiation Dosimetry: Electron Beams
see ICRU Report 34. For application of dosimetry in the
with Energies Between 1 and 50 MeV
characterization and operation of a gamma irradiation
ICRU Report 37 Stopping Powers for Electrons and
facility for food processing, see Practice E 1204, which also
Positrons
contains material relevant to the operation of an accelerator
facility operated in a bremsstrahlung mode.
3. Terminology
1.5 This standard does not purport to address all of the
safety problems, tf any, associated with its use. It is the
3.1 Definitions-Other terms used in this practice may be
responsibility of the user of this standard to establish appro-
found in Terminology E 170 and ICRU Report 33.
priate safety and health practices and determine the applica-
3.2 Descriptions of Terms Specific to This Standard:
bility of regulatory limitations prior to use.
3.2.1 absorbed dose, D-quotient of&by dm, where dZ is
the mean energy imparted by ionizing radiation to matter of
mass dm (see ICRU Report 33).
2, Referenced Documents
2.1 ASTM Standards:
=-
D dz
dm
E 170 Terminology Relating to Radiation Measurements
and Dosimetry2
The special name for the unit for absorbed dose is the gray
E 668 Practice for Application of Thermoluminescence-
.
.
GY)
Dosimetry (TLD) Systems for Determining Absorbed
1 Gy= 1 J-kg-’
Dose in Radiation-Hardness Testing of Electronic
Devices2
Formerly, the special unit for absorbed dose was the rad:
E 1026 Method for Using the Fricke Dosimeter to Mea-
1 rad = 1O-2 Jekg-’ = 1O-2 Gy
sure Absorbed Dose in Wates
E 1204 Practice for Application of Dosimetry in the
3.2.2 average beam current-time-averaged electron
Characterization and Operation of a Gamma Irradiation
beam current. For a pulsed machine, the averaging shall be
Facility for Food Processing2
done over an integral number of pulses or a large number of
pulses.
3.2.3 beam width-dimension of the irradiation zone
I This practice is under the jurisdiction of ASTM Committee E- 10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee
E 10.0 1 on Dosimetry for Radiation Processing.
Current edition approved Aug. 15, 199 1. Published October 199 1.
3 Available from International Commission on Radiation Units and Measure-
2 Ann& Book o/ASTM Standards, Vol 12.02. ments, 79 10 Woodmont Ave., Suite 800, Bethesda, MD 208 14.
1

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IS0 15562:1998(E)
63 IS0
a#/9 E 1431
the electron beam (see Fig. 1). For more discussion, refer to
perpendicular to the flow of the product. Various techniques
ICRU Report 35 and. Ref 3.
may be employed to produce an electron beam width
3.2.12 half-value depth, &-depth in a.material at which
adequate to cover the processing zone, for example, use of
the absorbed dose has decreased to 50 % of its maximum
electromagnetic scanning of a pencil beam, extended emit-
value (see Fig. 1).
ting surface (cathode), defocusing elements, and scattering
3.2.13 optimum thickness, I&,-depth within a material
foils.
at which the absorbed dose equals the absorbed dose at the.
3.2.4 bremsstrahlung-broad-spectrum electromagnetic
surface where the electron beam enters (see Fig. 1).
radiation emitted when an energetic electron is influenced by
3.2.14 practical range, R,- distance from the surface of
a strong electric field such as that in the vicinity of an atomic
the material to the point where the tangent at the steepest
nucleus. Practically, bremsstrahlung is produced when an
point (the inflection point) on the almost straight descending
electron beam strikes any material (converter). The
portion of the depth dose distribution curve meets the depth
bremsstrahlung spectrum depends on the electron energy,
axis (see Fig. 1).
the converter material and its thickness, and contains
3.2.15 product unit- one or more containers of a product,
energies up to the maximum kinetic energy of the incident
collectively transported through the irradiator as a whole, for
electrons (I, 2).
example, box, tote, pallet, carrier. This term is not relevant
3.2.5 compensating dummy-a mass of material with
to bulk-flow processing.
attenuation and scattering properties similar to those of a
3.2.16 production run- series of product units containing
particular product, that may be placed adjacent to a product
the same product and irradiated sequentially to the same
unit at the beginning and end of a production run, or within
absorbed dose.
a partially filled product unit, to compensate for the absence
3.2.17 reference materi&--homogeneous material of
of product.
known radiation absorption properties used to establish
3.2.6 depth dose distribution-variation of absorbed dose
beam characteristics.
with depth from the incident surface of a material exposed to
a selected plane in the radiation
3.2.18 reference plane-
radiation. A typical distribution in homogeneous material
zone that is perpendicular to the electron beam axis.
produced by an electron beam along the beam axis perpen-
dicular to the product is shown in Fig. 1.
4. Significance and Use
3.2.7 dose uniformity ratio-ratio of the maximum to the
4.1 Food products may be processed with accelerator-
minimum absorbed dose within the product. It is a measure
generated radiation to derive public health or economic
of the degree of uniformity of the absorbed dose. This
benefits, or both. Examples include control of parasites,
concept is also referred to as the max/min dose ratio.
microorganisms, and insects, and extension of shelf-life.
3.2.8 dosimetry system- system used for determining ab-
Food irradiation specifications usually include a pair of
sorbed dose, consisting of the dosimeter, the calibration
absorbed-dose limits: a minimum necessary to ensure the
curve, appropriate instrumentation, and procedures for the
intended beneficial effect and a maximum to avoid product
system ’s use.
degradation. For a given application, one or both of these
3.2.9 electron energy--kinetic energy of an electron (unit:
values may be prescribed by regulations. Therefore, it is
electron volt (eV)).
necessary to determine the capability of an irradiation
3.2.10 electron energy spectrum-frequency distribution
facility to process within these absorbed-dose limits prior to
of electrons as a function of energy. The energy spectrum of
the irradiation of product for consumption. Once this
the electrons impinging on the product depends on the type
capability is established, it is necessary to monitor the
of the accelerator and the conditions of the radiation process.
maximum and minimum absorbed dose in the irradiated
3.2.11 electron range-penetration distance along the
product for each production run with an acceptable level of
beam axis of electrons within a material. Several range
confidence to verify compliance with the process specifica-
parameters may be defined to describe the characteristics of
tions.
4.2 Regulations in some countries limit the maximum
electron energy to 10 MeV and photon energy to 5 MeV for
the purpose of food irradiation to avoid induced radioac-
tivity in the food.
NOTE l-Electron beams from linear accelerators (linacs) may con-
tain some electrons with energies above these prescribed limits. These
higher energy electrons may be prevented from reaching the product by
using a beam stop in combination with a magnetic deflection device.
4.3 There are various types of pararneters that play
essential roles in determining and controlling the absorbed
dose in radiation processing at an irradiation facility. It is
important to understand clearly the relationships among
them. Figure 2 is a diagram of these relationships. The
operating parameters (beam characteristics, conveyor speed,
R
opt R50 Rp
and beam dispersion parameters) are measurable parameters,
Depth (arbitrary units)
and their values depend on the facility controlling parame-
A Typical Depth Dose Distribution for an Electron Beam
FIG. 1 ters (shown in row 4 of Fig. 2). During the facility character-
2
2

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@ IS0 IS0 15562: 1998(E)
Process Parameters
(1) during this phase should assist in establishing process pram-
eters during the product qualification phase.
.
5.2 Operating Parameters:
5.2.1 The absorbed dose within a product unit depends on
beam characteristics, conveyor speed, and beam dispersion
(2) Product Unit Operating Parameters irradiation
parameters. (It also depends on product unit characteristics
Characteristics A Conditions B
and irradiation conditions. See Fig. 2.) These operatipg
parameters are affected by various accelerator and other
facility parameters. The variety of accelerators, conveyors,
Beam Dispersion
(3) Beam Characteristics c Conveyor Speed
and beam dispersion systems and the possibility of new
Parameter9
designs make it inappropriate to state general relationships
between operating parameters and controlling facility pa-
rameters (see Fig. 2).
Controllied by
Controlled by Controlled by
5.2.2 Beam Characteristics:
(4)
Accelerator Parameters E Gears, etc E Ancillary
5.2.2.1 The two principal beam characteristics are the
Parameters E
electron energy spectrum and the average beam current. The
electron energy spectrum affects the depth dose distribution
A For example, sire, bulk density and heterogeneity.
within a material. The average beam current, in addition to
D For example, processing geometry, multi-sided exposure and number of
several other operating parameters, affects the dose rate.
passes.
c For example, energy, current and pulse repetition rate.
NOTE 3-If the accelerator does not have an energy analyzing system
D For example, scan width and scan frequency.
(for example, an analyzing magnet) the electron energy spectrum of the
E These parameters control various operating parameters; the nature of their
beam can be specified in a practical way by two parameters: the average
relationships depends on the type of irradiation facility.
electron energy (EJ and the most probable electron energy (E,). The
FIG. 2 A Diagram of the Parameter Relationships for an Electron values of these two parameters at the surface of water-equivalent
product are related to the electron range:
or Bremsstrahlung Facility
E, (MeV) = 0.22 + 1.98 R, + 0.0025 Rpz
for 1 MeV < Ep c 50 MeV
ization phase, absorbed dose characteristics over the ex-
and, Ea (MeV) = 2.33 R,. for 5 MeV c E, < 35 MeV
pected range of the operating parameters (row 3, Fig. 2) are
are, respectively, the practical range and the
where R, and R,.
established for a reference material. The process parameters
half-value depth in water-equivalent material in cm (see 3.2.12 and
(row 2, Fig. 2) for a radiation process are established during
3.2.14). These expressions are valid for a very small angular spread of
the product qualification phase to achieve the absorbed dose
the beam. More discussion of these parametric relationships and
within the set limits. During product processing, the facility procedures for measuring R,, and R, for water-equivalent and other
materials may be found in ICRU Reports 35 and 37, and Ref 14. For
controlling parameters (row 4, Fig. 2) are controlled and
lower energy beams (E, < 1 MeV), the electron spectrum is affected by
monitored to ma.intain the values of all the operating
the accelerator window, intervening air, and any backing materials.
parameters that were set during the product qualification
Mowever, reproducibility of the radiation process can be determined by
phase.
routine measurements of the depth dose distribution.
4.4 Accelerator-generated radiation can be in the form of
5.2.2.2 For bremsstrahlung irradiators, absorbed dose rate
electrons or photons (bremsstrahlung) produced by the
is affected by the angular distribution of the bremsstrahlung
electrons, Penetration into the product required to accom-
beam, in addition to the electron energy spectrum and
plish the intended effect is one of the factors affecting the
average beam current. Photon energy and angular distribu-
decision to use electrons or photons. For a given electron
tions depend on the design and composition of the converter,
energy, penetration of the bremsstrahlung radiation is sub-
and on the electron energy (1, 6).
stantially greater than that of the electrons. Penetration of
5.2.3 Conveyor Speed:
5-MeV bremsstrahlung radiation in water or plastic materials
5.2.3.1 For facilities utilizing continuously-moving con-
is slightly greater than that of Co-60 gamma rays (4, 5, 6, 7).
veyors to transport product through the irradiation zone,
NOTE 2-More detailed discussion of food irradiation processing
conveyor speed determines the irradiation time. Therefore,
may be found in Refs 8 to 13.
when other operating parameters are held constant, conveyor
speed controls the absorbed dose in the product.
5. Facility Characterization
5.2.3.2 For those facilities that irradiate products while
they are continuously in the irradiation zone, tiadiation
5.1 Objective--The purpose of dosimetry in commis-
sioning a new or modified electr
...