IEC 60544-1:2013

Electrical insulating materials - Determination of the effects of ionizing radiation - Part 1: Radiation interaction and dosimetry

IEC 60544-1:2013 deals broadly with the aspects to be considered in evaluating the effects of ionizing radiation on all types of organic insulating materials. It also provides, for X-rays, gamma-rays, and electrons, a guide to dosimetry terminology, methods for dose measurements, testing carried out at irradiation facilities, evaluation and testing of material characteristics and properties, documenting the irradiation process. This edition includes the following significant technical changes with respect to the previous edition:
a) recent advances in simulation methods of radiation interaction with different matter enables the prediction of the energy-deposition profile in matter and design the irradiation procedure;
b) many new dosimetry systems have become available.

Matériaux isolants électriques - Détermination des effets des rayonnements ionisants - Partie 1: Interaction des rayonnements et dosimétrie

La CEI 60544-1:2013 traite de manière générale des aspects à envisager lors de l'évaluation des effets des rayonnements ionisants sur tous les types de matériaux isolants organiques. Elle fournit également pour les rayons X, les rayonnement gamma et les électrons, un guide de terminologie en dosimétrie, des méthodes de mesure des doses, des essais réalisés au niveau des dispositifs d'irradiation, relatif à l'évaluation et aux essais des caractéristiques et propriétés des matériaux, de documentation du phénomène d'irradiation. Cette édition inclut les changements techniques majeurs suivants par rapport à l'édition précédente:
a) des avancées récentes au niveau des méthodes de simulation de l'interaction des rayonnements avec des types de matière différents permettent de prédire le profil de dépôt d'énergie dans la matière et de concevoir la procédure d'irradiation;
b) de nombreux nouveaux systèmes de dosimétrie sont actuellement disponibles.

General Information

• Status: Published
• Publication Date: 26-Jun-2013
• ICS: 17.240 - Radiation measurements
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: TC 112 - Evaluation and qualification of electrical insulating materials and systems
• Drafting Committee: WG 2 - TC 112/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 27-Jun-2013
• Completion Date: 31-Jul-2013

Overview

IEC 60544-1:2013 is an international standard published by the International Electrotechnical Commission (IEC) that addresses the evaluation of ionizing radiation effects on electrical insulating materials. This third edition provides comprehensive guidance on radiation interaction, dosimetry terminology, and methods for precise dose measurement involving X-rays, gamma-rays, and electrons. The standard is essential for understanding how ionizing radiation impacts organic insulating materials, ensuring reliable performance in environments where radiation exposure is a key concern.

Recent technical advancements integrated into this edition include improved simulation methods to predict energy deposition profiles in materials and the introduction of numerous new dosimetry systems. These updates enable more accurate irradiation procedures and testing, improving reliability across various industrial applications.

Key Topics

• Radiation Interaction with Materials: Detailed analysis of how ionizing radiation interacts with organic insulating materials, focusing on energy deposition and depth-dose distribution.
• Dosimetry Terminology and Methods: Defines precise dosimetry terms and introduces standardized methods for dose measurements using gamma rays, X-rays, and electron beams.
• Irradiation Facilities and Procedures: Guidelines for conducting tests at irradiation facilities using gamma-ray irradiators, electron-beam irradiators, and Bremsstrahlung X-ray sources.
• Evaluation of Material Properties: Methods for assessing changes in electrical and mechanical properties of insulating materials after radiation exposure, covering both permanent and temporary effects.
• Documentation and Monitoring: Best practices for documenting the irradiation process and monitoring dose uniformity through dose mapping and facility characterization.
• Technical Updates: Incorporation of advanced simulation techniques facilitates prediction of radiation energy deposition, enabling more effective design of irradiation procedures.
• Dosimetry Systems: Comprehensive overview of reference standard dosimetry systems and routine dosimeter options, including calibration and measurement uncertainty considerations.

Applications

IEC 60544-1:2013 is crucial for industries where electrical insulating materials are exposed to ionizing radiation, including:

• Nuclear Power Plants: Evaluating and ensuring the radiation resistance of cables and insulation materials to maintain safety and operational integrity under radiation stress.
• Medical Equipment Manufacturing: Quality control of insulating components in devices involving radiotherapy or imaging that use X-rays or gamma-rays.
• Aerospace and Defense: Assessing insulating materials used in spacecraft and military applications subjected to high-radiation environments.
• Radiation Processing and Sterilization: Standardizing dose measurements and material testing where polymer insulation is exposed to electron-beam or gamma irradiation.
• Research and Development: Supporting development of new organic insulating materials with enhanced radiation resistance using simulation tools and advanced dosimetry methods.

Related Standards

• IEC 60544-2: Complementary to Part 1, focusing on test procedures for determining the effects of ionizing radiation on insulating materials.
• ISO/IEC Directives, Part 2: Provides the general principles followed in drafting international standards, applicable to IEC 60544 series.
• Other Dosimetry Standards: Related IEC documents and technical reports expand on dosimetry techniques and calibration procedures, enhancing the reproducibility of test results.

---

Key benefits of applying IEC 60544-1:2013:

• Consistent evaluation methods to ensure material performance and safety under radiation stress.
• Enhanced accuracy in radiation dose measurement enabling reliable classification of materials.
• Support for lifecycle management of electrical insulating materials in radiation-exposed environments.
• Facilitation of international cooperation and harmonization through standardized terminology and testing procedures.

By adhering to IEC 60544-1, manufacturers and testing laboratories can confidently assess and validate the radiation resistance of organic insulating materials, thereby improving the durability and safety of electrical and electronic equipment used globally in radiation-prone applications.

Standards Content (Sample)

IEC 60544-1 ®
Edition 3.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulating materials – Determination of the effects of ionizing
radiation –
Part 1: Radiation interaction and dosimetry

Matériaux isolants électriques – Détermination des effets des rayonnements
ionisants –
Partie 1: Interaction des rayonnements et dosimétrie

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IEC 60544-1 ®
Edition 3.0 2013-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulating materials – Determination of the effects of ionizing

radiation –
Part 1: Radiation interaction and dosimetry

Matériaux isolants électriques – Détermination des effets des rayonnements

ionisants –
Partie 1: Interaction des rayonnements et dosimétrie

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX V
ICS 17.240; 29.035.01 ISBN 978-2-83220-894-6

– 2 – 60544-1 © IEC:2013
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Radiation-induced changes and their evaluation . 9
4.1 General . 9
4.2 Permanent changes . 9
4.3 Environmental conditions and material geometry . 9
4.4 Post-irradiation effects . 9
4.5 Temporary effects . 9
5 Facilities for irradiation of material samples for evaluation of properties . 10
5.1 General . 10
5.2 Gamma-ray irradiators . 10
5.3 Electron-beam irradiators . 10
5.4 X-ray (Bremsstrahlung) irradiators . 11
6 Dosimetry methods . 11
6.1 General . 11
6.2 Absolute dosimetry methods . 12
6.2.1 Gamma-rays . 12
6.2.2 Electron beams . 12
6.3 Dosimetry systems . 12
6.3.1 Reference standard dosimetry systems . 12
6.3.2 Routine dosimetry systems . 13
6.3.3 Measurement uncertainty . 14
6.3.4 Dosimeter calibration . 15
6.3.5 Dosimeter selection . 15
7 Characterization of irradiation facilities . 16
8 Dose mapping of samples for test . 16
8.1 Charged particle equilibrium . 16
8.2 Depth-dose distribution (limitations) . 16
9 Monitoring of the irradiation . 17
Annex A (informative) Radiation chemical aspects in interaction and dosimetry . 18
Bibliography . 31

Figure A.1 – Absorbed dose as a function of thickness . 19
Figure A.2 – Absorber thickness for charged-particle equilibrium as a function of
23 -3
energy for a material with an electron density of 3,3 × 10 cm (water). 20
Figure A.3 – Thickness of water (1 g/cm ) as a function of photon energy for a given
attenuation of unidirectional X-ray or γ-ray radiation . 21
Figure A.4 – Typical depth-dose distribution in a homogeneous material obtained with
electron accelerators for radiation processing . 25
Figure A.5 – Example of calculated results of energy deposition function, I(z′), for a
slab layer of polyethylene exposed to 1 MeV electron . 25
Figure A.6 – Example of calculated results of energy deposition function, I(z′), for
typical organic insulators exposed to 1 MeV electron . 26

60544-1 © IEC:2013 – 3 –
Figure A.7 – Two methods of arranging the irradiation samples in order to take into
account the typical depth-dose distributions . 27
Figure A.8 – Methods of arranging the irradiation samples for measuring electron
depth-dose distributions with a stack of slab insulating materials and wedge-shape
insulating materials . 28
Figure A.9 – Scheme of radiation effects of polymers. 29

Table 1 – Examples of reference standard dosimeters . 13
Table 2 – Examples of routine dosimeter systems . 14
Table A.1 – Electron mass collision stopping powers, S/ρ (MeV cm /g) . 23
Table A.2 – Photon mass energy absorption coefficients, µ /ρ (cm /g) . 24
en
– 4 – 60544-1 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS –
DETERMINATION OF THE EFFECTS OF IONIZING RADIATION –

Part 1: Radiation interaction and dosimetry

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60544-1 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This third edition cancels and replaces the second edition published in 1994 and constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) recent advances in simulation methods of radiation interaction with different matter
enables the prediction of the energy-deposition profile in matter and design the irradiation
procedure;
b) many new dosimetry systems have become available.

60544-1 © IEC:2013 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
112/254/FDIS 112/262/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60544 series, published under the general title Electrical insulating
materials – Determination of the effects of ionizing radiation, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60544-1 © IEC:2013
INTRODUCTION
The establishment of suitable criteria for the evaluation of the radiation resistance of
insulating materials is very complex, since such criteria depend upon the conditions under
which the materials are used. For instance, if an insulated cable is flexed during a refuelling
operation in a reactor, the service life will be that time during which the cable receives a
radiation dose sufficient to reduce to a specified value one or more of the relevant mechanical
properties. Temperature of operation, composition of the surrounding atmosphere and the
time interval during which the total dose is received (dose rate or flux) are important factors
which also determine the rate and mechanisms of chemical changes. In some applications,
temporary changes may be the limiting factor.
Given this, it becomes necessary to define the radiation fields in which materials are exposed
and the radiation dose subsequently absorbed by the material. It is also necessary to
establish procedures for testing the mechanical and electrical properties of materials which
will define the radiation degradation and link those properties with application requirements in
order to provide an appropriate classification system.

60544-1 © IEC:2013 – 7 –
ELECTRICAL INSULATING MATERIALS –
DETERMINATION OF THE EFFECTS OF IONIZING RADIATION –

Part 1: Radiation interaction and dosimetry

1 Scope
This part of IEC 60544 deals broadly with the aspects to be considered in evaluating the
effects of ionizing radiation on all types of organic insulating materials. It also provides, for X-
rays, γ-rays, and electrons, a guide to
– dosimetry terminology,
– methods for dose measurements,
– testing carried out at irradiation facilities,
– evaluation and testing of material characteristics and properties,
– documenting the irradiation process.
Dosimetry that might be carried out at locations of use of the material is not described in this
standard.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60544-2, Electrical insulating materials – Determination of the effects of ionizing radiation
on insulating materials – Part 2: Procedures for irradiation and test
IEC 60544-4, Electrical insulating materials – Determination of the effects of ionizing radiation
– Part 4: Classification system for service in radiation environments
3 Terms and definitions
For the purposes of this document, the terms and definitions in ICRU Report 33 [1] . as well
as the following definitions apply.
3.1
exposure
X
measure of an electromagnetic radiation field (X- or γ-radiation) to which a material is
exposed
Note 1 to entry: The exposure is the quotient obtained by dividing dQ by dm, where dQ is the absolute value of
the total charge of the ions of one sign produced in the air when all of the electrons (and positrons) liberated by
photons in air of mass dm are completely stopped in air:
—————————
References in square brackets refer to the Bibliography.

– 8 – 60544-1 © IEC:2013
dQ
X = (1)
dm
The SI unit of exposure is the coulomb (C) per kilogram: C/kg. The old unit is the roentgen R:
-4
1 R = 2,58 × 10 C/kg.
The exposure thus describes the effect of an electromagnetic field on matter in terms of the ionization that the
radiation produces in a standard reference material, air.
3.2
electron charge fluence
Q′
quotient obtained by dividing dQ by dA, where dQ is the electron charge impinging during the
time t on the area dA:
dQ
Q = (2)
′
d A
3.3
electron current density
j
quotient obtained by dividing dQ′ by dt, where dQ′ is the electron charge fluence during the
time interval dt:
dQ′ d Q
j = = (3)
dt d A dt
3.4
absorbed dose
D
measure of the energy imparted to the irradiated material, regardless of the nature of the
radiation field
Note 1 to entry: The absorbed dose D is the quotient obtained by dividing d ε by dm where d ε is the mean
energy imparted by ionizing radiation to matter of mass dm:
dε
D = (4)
dm
The SI unit is the gray (Gy). The old unit is the rad:
-1 2
1 Gy = 1 J × kg (= 10 rad).
Since this definition does not specify the absorbing material, the gray can be used only with reference to a specific
material. The absorbed dose is determined in part by the composition of the irradiated material. When exposed to
the same radiation field, therefore, different materials usually receive different absorbed doses.
Note 2 to entry: For purposes of dosimetry, it has been found convenient to specify dose in terms of dose to water.
The dose to other materials can be found by applying cavity theory.
3.5
absorbed dose rate

D
quotient obtained by dividing dD by dt, where dD is the increment of absorbed dose in the
time interval dt:
dD

D = (5)
dt
60544-1 © IEC:2013 – 9 –
The SI unit of absorbed dose rate is the gray per second:
-1 -1 2 -1 -1
1 Gy × s = 1 W × kg (= 10 rad × s = 0,36 Mrad × h )
4 Radiation-induced changes and their evaluation
4.1 General
Although the various types of radiation interact with matter in different ways, the primary
process is the production of ions and electrically excited states of molecules which, in turn,
may lead to the formation of free radicals. The technique to detect ions, excited states and
radicals (short-lived intermediate species) are briefly described in Clause A.4. Radiation-
generated mobile electrons, which become trapped at sites of low potential energy, are also
produced. The first phenomenon leads to permanent chemical, mechanical, and electrical
changes of the material; the second results in temporary electrical changes in performance [2].
4.2 Permanent changes
In polymeric materials, the formation of free radicals during irradiation leads to scission and
cross-linking processes that modify the chemical structure of the insulation, generally leading
to deterioration of the mechanical properties. This mechanical deterioration frequently gives
rise to significant electrical property changes. However, important electrical property changes
sometimes occur before mechanical degradation becomes serious. For example, a change in
dissipation factor or in permittivity might become serious for the reliable functioning of a
resonant circuit. The extent of scission and cross-linking processes depends on the absorbed
dose, the absorbed dose rate, the material geometry and the environmental conditions
present during the irradiation. Because the free radicals sometimes decay slowly, there may
also be post-irradiation effects.
4.3 Environmental conditions and material geometry
Environmental conditions and test specimen geometry shall be well controlled and
documented during the measurement of radiation effects. Important environmental parameters
include temperature, reactive medium, and mechanical and electrical stresses present during
the irradiation. If air is present, the irradiation time (flux and dose rate) has also been
demonstrated to be a very important experimental parameter because of oxygen diffusion
effects and hydroperoxide breakdown rate constants. Both factors are time dependent. The
conditions that influence oxygen diffusion and equilibrium concentrations in the polymer shall
be controlled. These include: temperature, oxygen pressure, material geometry and the time
during which the dose is applied.
If the effect of simultaneous stresses, e.g. radiation at high temperature, is simulated by
sequential stressing, other results are to be expected. Further, there can be differences in
results if the sample is first irradiated and then heat aged or vice versa.
4.4 Post-irradiation effects
In organic polymers, there may be post-irradiation effects due to the gradual decay of various
reactants, such as residual free radicals. Due allowance shall be made for this type of
behaviour in any evaluation procedure. The tests shall be made at recorded intervals after
irradiation, maintaining specimen storage in a standard laboratory atmosphere. The reaction
of oxygen with residual free radicals can cause further degradation.
4.5 Temporary effects
4.5.1 Performing measurements during irradiation is not within the scope of this part
of IEC 60544. Despite this, some basic aspects will be discussed briefly. The temporary
effects appear primarily as changes in electrical properties such as induced conductivity, both
during and for some time after irradiation. Hence, measurement of the induced conductivity

– 10 – 60544-1 © IEC:2013
could be used as an evaluation property to determine the temporary radiation effects. These
effects are primarily dose-rate dependent.
4.5.2 Experience has shown that the induced conductivity is usually not quite proportional
 
α
to the absorbed dose rate D, but varies as D , where α is smaller than unity. Hence, the
radiation sensitivity is described by the relation:
 α
σ = kD (6)
i
To determine k and α, at least two measurements are needed. A further complication
comes from the fact that k and α also depend on the integrated dose absorbed by the sample.
The measurement of the induced conductivity is actually quite delicate, since photoelectrons
and Compton electrons in the electrode materials will tend to perturb the intrinsic induced
current of the specimen. Ionic currents through the ionized atmosphere will also introduce
errors in the measurement if they are not eliminated. Experimental procedures eliminating
most of the disturbing effects, while remaining relatively simple, shall be defined.
NOTE It is convenient to use a simple figure such as the induced conductivity σ or σ /σ , its ratio to the dark
i i o
conductivity σ measured in the same experimental conditions, per unit dose rate to characterize the sensitivity of
o
the materials to temporary effects.
5 Facilities for irradiation of material samples for evaluation of properties
5.1 General
Irradiation of material samples for evaluation of properties shall be performed at irradiation
facilities that have undergone installation qualification, operational qualification and
performance qualification, see e.g. ISO 11137 [3].
Three principal types of radiation sources are used:
60 137
• gamma radiation from radionuclides such as Co (1,25 MeV) and Cs (0,66 MeV);
• electrons from accelerators;
• X-rays generated from accelerated electrons.
The design and properties of an irradiation facility have implications for absorbed dose
distribution in the samples and attainable absorbed dose range. Major considerations in the
design of an irradiation facility are the uniformity of the distribution of absorbed dose in the
given product, efficient utilization of radiation energy.
5.2 Gamma-ray irradiators
Large capacity gamma radiation facilities usually use Co as the radiation source. The
sources are often in the form of individual source capsules arranged in an array to maximize
the volume available for irradiations. The dose rates that are available will be dependent on
the distance from the sources at which the samples are placed. Typically, dose rates in the
range 10 kGy/h (2,78 Gy/s) down to 1 Gy/h (0,278 mGy/s) are possible. This covers the range
of dose rates that are of particular interest for materials degradation testing.
5.3 Electron-beam irradiators
Electron beam irradiators use accelerators that generate electron beam in the energy-range of
300 KeV – 10 MeV. At present, various types of accelerating procedures are available;
examples include electro-static type and high-frequency (radio-frequency) type. With respect
to radiation resistance testing, electro-static type of (0,5 – 3 )MeV is widely used. In an
electro-static accelerating system, thermo-electrons are emitted from a cathode and the

60544-1 © IEC:2013 – 11 –
emitted electrons are accelerated with high voltage applied between electrodes. Electron
beams are electro-magnetically scanned in a scanning horn and taken out from the window
(typically made of a thin foil of Titanium). The operation of electron accelerators is simple and
safe, i.e. there is no radiation if the power is switched off, compared to a Co gamma
irradiation facility. Depending on voltage (energy), beam current, scan width, distance
between the window and samples, static or conveyor irradiation, the dose rate may change,
but typically it is in the order of kGy/s, which is much higher compared with gamma irradiator.
Penetration of the electron beam in samples shall be taken into account (see Clause A.3).
5.4 X-ray (Bremsstrahlung) irradiators
X-rays (or Bremsstrahlung) are created when accelerated electrons are slowed down in an
absorbing material. The fraction of kinetic energy of the electrons that is converted into X-rays
(conversion efficiency) is higher for absorbers with a higher atomic number, and therefore
materials such as tungsten are used as X-ray converters. The conversion efficiency also
increases with increasing electron energy. At 5 MeV it is about 5 % in tungsten, increasing to
about 12,5 % at 10 MeV, and the low conversion efficiency at this energy has limited the use
of this type of irradiators. The advent of high-power electron accelerators in the range from
5 MeV to 10 MeV has renewed interest in the use of X-rays for irradiation of products.
In contrast to radionuclide sources, which emit nearly mono-energetic photons, X-ray sources
emit a broad spectrum of photons from the maximum energy of the electrons to zero energy.
For example, an X-ray beam generated by 5 MeV electrons has approximately the same
penetration characteristics as Co radiation. Other characteristics of the X-ray beam, such as
scanning and pulsing of the beam, are derived from the characteristics of the electron beam
that generated the X-rays.
6 Dosimetry methods
6.1 General
It is necessary to ensure that the correct absorbed dose is applied during irradiation. The
dose shall be measured, and measurement systems have been developed for this purpose.
Much of the development of these systems rests on the early development of dosimetry
systems for personnel radiation protection and for medical treatment. However, the doses
used in material testing are generally higher, ranging from a few kGy to 100 kGy or more and
new dosimetry systems have been developed for measurements of these doses. Dose shall
be measured with traceability to national standards, and the uncertainty known, including the
effect of influencing parameters.
Absolute methods of dosimetry are maintained as national standards by a number of national
laboratories. These dosimeters provide dose measurement by means of physical
measurements that do not depend on calibration of the dosimeter in a known radiation field.
Other dosimeters are calibrated against these national standard dosimeters, thereby providing
measurement traceability to the national standard dosimeters.
A number of dosimeter systems are in use at irradiation facilities and laboratories for
measurement of dose distribution for facility characterization and in products and samples to
be irradiated. These dosimeters are also used for monitoring the irradiation process. Selection
of a dosimeter system depends on the measurement task to be carried and of the properties
of the dosimeter. Dosimetry methods and dosimeter systems are described in several
ISO/ASTM standards and guides [4 – 18]. More details of several of these dosimetry systems
are found in ICRU 80 [19].
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6.2 Absolute dosimetry methods
6.2.1 Gamma-rays
Free-air ionization chambers are used to measure exposure X up to 3 MeV, i.e. they are
designed to measure the quantity of charge dQ produced in air and the mass dm of air where
the ionizing electrons are liberated. Ionization chambers can be used if the dose rate is not
too high [20].
Calorimeters operate by absorbing energy from the radiation field in which they are placed;
they retain this energy until it is converted to thermal energy and this heat quantity is
evaluated by measuring the rise in temperature of the calorimetric absorber [21].
6.2.2 Electron beams
In addition to calorimetric methods, measurement of electron current density has been used to
measure electron charge or current per unit area of radiation fields of electron accelerators.
This method is not a dosimetric method, but enables the calibration of absorbed dose if the
mean electron energy impinging on the charge absorber of the densitometer and the relative
depth-dose distribution in the same absorber material are known.
6.3 Dosimetry systems
6.3.1 Reference standard dosimetry systems
Reference standard dosimetry systems are used as standards to calibrate the dosimetry
systems that are used for routine measurements. The uncertainty of the reference standard
dosimetry system will affect the uncertainty of the system being calibrated and it is therefore
important that the reference standard dosimetry system is of high metrological quality. In this
context, the concept of high metrological quality implies a system with low uncertainty and
with traceability to appropriate national or international standards. It also implies that the
response of the reference standard dosimeter is not significantly influenced by environment.
The expanded uncertainty achievable with measurements made using a reference standard
dosimetry system is typically of the order of ± 3 % (k = 2, which corresponds approximately to
a 95 % level of confidence for normally distributed data). In certain specific applications, for
example the use of electrons of energy below 1 MeV, practical limitations of the techniques
may mean that the reference standard dosimetry systems have a larger uncertainty.
Examples of reference standard dosimetry systems are given in Table 1.
NOTE ASTM E 2628-09 “Standard practice for dosimetry for radiation processing” [22] is a valuable guideline
concerning Table 1 and Table 2.

60544-1 © IEC:2013 – 13 –
Table 1 – Examples of reference standard dosimeters
Dosimeter Description Reference Dose Dose rate Influencing
range range parameters
Gy Gy/s
Fricke solution Liquid solution of ASTM 20 to Temperature
< 10
ferrous and ferric ions E1026
4 × 10
in 0,4 M sulphuric
[23]
acid. Measured by
spectrophotometry
Alanine/EPR Pellet or film ISO/ASTM 1 to 10 Temperature
< 10
(electron containing alanine. 51607
Humidity
paramagnetic Measured by EPR
[8]
resonance) spectroscopy of
radiation induced
radical
Dichromate Liquid solution of ISO/ASTM Pulsed: Temperature
2 × 10
chromium ions in 51401
< 600 Gy/pulse
to 5 × 10
0,1 M perchloric acid. (12,5 pps)
[9]
Measured by
Continuous:
spectrophotometry.
-3
< 7,5 × 10
2 6
Ceric-cerous Liquid solution of ISO/ASTM Temperature
5 × 10 < 10
sulphate ceric and cerous ions 51205
to 10
in 0,4 M sulphuric
[10]
acid. Measured by
spectrophotometry or
potentiometry
Ethanol Liquid solutions of ISO/ASTM 10 < 10 Temperature
chlorobenzene various compositions 51538 to 2 × 10

containing
(Classification [11]
chlorobenzene in
dependent on
ethanol. Measured by
solution
titration
composition and
method of
measurement)
6.3.2 Routine dosimetry systems
The classification of a dosimetry system as a routine dosimetry system is based on its
application i.e. routine absorbed dose measurements, including dose mapping and process
monitoring. A routine dosimetry system comprises dosimeters and the associated
measurement equipment and quality system documentation necessary to ensure traceability
to appropriate national or international standards. The response of routine dosimeters is often
influenced by the environment in a complex way.
The expanded uncertainty achievable with measurements made using a routine dosimetry
system is typically of the order of ± 6 % (k = 2).
Examples of routine dosimetry systems are given in Table 2. Dosimeters in Table 1 can also
be used as routine systems.
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Table 2 – Examples of routine dosimeter systems
Dosimeter Description Reference Dose range Dose rate Influencing
Gy range parameters
Gy/s
2 5
Calorimeter Assembly consisting ISO/ASTM 10 to 10 Temperature
> ~10
of calorimetric body 51631
(absorber), thermal
[12]
insulation, and
temperature sensor
with wiring
3 -2
Cellulose Untinted cellulose ISO/ASTM 5 × 10 3 × 10 to Temperature
6 -7
triacetate triacetate (CTA) film. 51650
to 10 3 × 10
Humidity
Measured by
[13]
spectrophotometry
Ethanol Liquid solutions of ISO/ASTM 10 to < 10 Temperature
chlorobenzene various compositions 51538
2 × 10
containing
(classification [11]
chlorobenzene in
dependent on
ethanol. Measured by
solution
spectrophotometry or
composition and
oscillometry
method of
measurement)
-2
LiF photo- Lithium fluoride based ASTM 0,3 to Temperature
5 × 10
2 4
fluorescent photo-fluorescent E2304
to 3 × 10 2 × 10
Humidity
film. Measured by
[24]
photo-stimulated
Ambient light
luminescence
2 5 -2 7
PMMA Specially developed ISO/ASTM 10 to 10 10 to 10 Temperature
(polymethylmetha PMMA materials. 51276
Humidity
crylate) Measured by
[14]
spectrophotometry
Ambient light
0 5
Radiochromic film Specially prepared ISO/ASTM 10 to 10 Temperature
< 10
film containing dye 51275
Humidity
precursors. Measured
[15]
by spectrophotometry
Ambient light
-1 -2 11
Radiochromic Specially prepared ISO/ASTM 5 × 10 to <10 to 10 Temperature
liquid solution containing 51540
4 × 10
dye precursors.
[16]
Measured by
Ambient light
spectrophotometry
0 4 -3 3
Radiochromic Specially prepared ISO/ASTM 10 to 10 10 to 10 Temperature
optical waveguide optical waveguide 51310

containing dye
[17]
precursors. Measured
Ambient light
by spectrophotometry
-4 3 -2 10
TLD A phosphor, alone, ISO/ASTM 10 to 10 10 to 10 Temperature
(thermoluminesen or incorporated in a 51956
Humidity
ce detector) material. Measured
[18]
by
Ambient light
thermoluminescence
6.3.3 Measurement uncertainty
To be meaningful, a measurement of absorbed dose shall be accompanied by an estimate of
uncertainty. Components of uncertainty should be identified as belonging to one of two
categories:
Type A — those evaluated by statistical methods, or
Type B — those evaluated by other means.
Estimates of the expanded uncertainty of an absorbed dose measurement should be made
with a coverage factor k = 2.
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NOTE The identification of Type A and Type B uncertainties is based on the methodology published in 1995 by
the International Organization for Standardization (ISO) in the Guide to the Expression of Uncertainty in
Measurement [25]. The purpose of using this kind of characterization is to promote an understanding of how
uncertainty statements are arrived at and to provide a basis for the international comparison of measurement
results.
6.3.4 Dosimeter calibration
The radiation induced response of dosimeters depends to a larger or smaller extent on the
environment at which they are irradiated. For example, temperature, humidity and dose rate
may affect the response, and it is therefore needed to calibrate dosimeters using conditions
that are as close as possible to the conditions of use of the dosimeters.
Calibration of dosimeters should therefore be carried out using one of the following two
methods:
a) Irradiation of dosimeters at the irradiation facility where the dosimeters will be used (“in-
plant”) together with transfer standard dosimeters issued and analysed by a national
standards laboratory or an accredited dosimetry calibration laboratory.
b) Irradiations of dosimeters at a national standards laboratory or an accredited dosimetry
calibration laboratory. Calibration irradiations carried out in this way will results in a
calibration curve generated under a single set of influencing parameters. The user of the
dosimeter shall therefore evaluate the effect of influencing parameter values. This is most
readily done by a verification irradiation “in-plant” at selected doses.
Measurement traceability is defined in the International vocabulary of metrology [26] as
follows:
“the property of a result of a measurement whereby it can be related to appropriate standards,
generally international or national standards, through an unbroken chain of comparisons.”
Calibration is an important step in obtaining measurement traceability.
6.3.5 Dosimeter selection
The selection and use of a specific dosimetry system in a given application shall be justified
taking into account at least the following:
• dose range;
• radiation type;
• effect of influencing parameters;
• required level of uncertainty;
• required spatial resolution.
The dosimetry system shall be calibrated in accordance with 6.3.4.
The uncertainty associated with measurements made with the dosimetry system shall be
established and documented. All dose measurements shall be accompanied by an estimate of
uncertainty.
Documentation shall be established and maintained to ensure compliance with the minimum
requirements specified in standards for the dosimetry system. The user’s quality system might
be more detailed than these minimum requirements.
Tables 1 and 2 gives a non-exhaustive list of reference and routine dosimetry methods with
some of their characteristics, such as:
– range of absorbed doses and absorbed dose rates;
– influence of the radiation energy;

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– influence of temperature or humidity;
– material and thickness of dosimeter material;
– type of measurement;
– observations of practical interest;
– bibliographical references.
Clause A.2 gives an example for calculation of absorbed dose.
7 Characterization of irradiation facilities
Irradiation facilities that are to be used for evaluating the behaviour of electrical insulating
materials shall be characterized before use. The parameters that need to be determined will
be dependent on the type of facility being used.
For a gamma irradiation facility, the following parameters shall be determined:
– The dose rate distribution shall be measured within the volume of the facility that will be
used for sample exposure to radiation. This mapping shall be in sufficient detail to enable
the locations available for a specific dose rate to be determined.
– The ambient temperature within the radiation facility shall be measured while the sources
are in their normal operating position.
– The time for which samples are exposed shall be measured. T
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