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INTERNATIONAL ISO
STANDARD 6980-2
Third edition
2023-11
Nuclear energy — Reference beta-
particle radiation —
Part 2:
Calibration fundamentals related to
basic quantities characterizing the
radiation field
Énergie nucléaire — Rayonnement bêta de référence —
Partie 2: Concepts d'étalonnage en relation avec les grandeurs
fondamentales caractérisant le champ de rayonnement
Reference number
© ISO 2023
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms and reference and standard test conditions .3
5 Calibration and traceability of reference radiation fields . 6
6 General principles for calibration of beta‑particle radiation fields .6
6.1 General . 6
6.2 Scaling to derive equivalent thicknesses of various materials . 7
6.3 Characterization of the radiation field in terms of penetrability. 8
7 Calibration procedures using an extrapolation chamber . 8
7.1 General . 8
7.2 Determination of the reference beta-particle absorbed-dose rate . 9
8 Calibration with ionization chambers .10
9 Measurements at non-perpendicular incidence .10
10 Uncertainties .10
Annex A (normative) Reference conditions and standard test conditions .19
Annex B (informative) Extrapolation chamber measurements .21
Annex C (informative) Extrapolation chamber measurement correction factors .25
Annex D (informative) Example of an uncertainty analysis .37
Bibliography .41
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies,
and radiological protection, Subcommittee SC 2, Radiological protection.
This third edition of ISO 6980-2 cancels and replaces ISO 6980-2:2022, of which it constitutes a minor
revision.
The main changes are as follows:
— editorial changes throughout the document.
A list of all the parts in the ISO 6980 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
ISO 6980 series covers the production, calibration, and use of reference beta-particle radiation fields for
the calibration of dosemeters and dose-rate meters for protection purposes. This document describes
the procedures for the determination of absorbed dose rate to a reference depth of tissue from reference
beta particle radiation fields. ISO 6980-1 describes methods of production and characterization of the
reference radiation. ISO 6980-3 describes procedures for the calibration of dosemeters and dose-rate
meters and the determination of their response as a function of beta-particle energy and angle of beta-
particle incidence.
For beta particles, the calibration and the determination of the response of dosemeters and dose-rate
meters is essentially a three-step process. First, the basic field quantity, absorbed dose to tissue
at a depth of 0,07 mm (and optionally also at a depth of 3 mm) in a tissue-equivalent slab geometry
is measured at the point of test, using methods described in this document. Then, the appropriate
operational quantity is derived by the application of a conversion coefficient that relates the quantity
measured (reference absorbed dose) to the selected operational quantity for the selected irradiation
geometry. Finally, the reference point of the device under test is placed at the point of test for the
calibration and determination of the response of the dosemeter. Depending on the type of dosemeter
under test, the irradiation is either carried out on a phantom or free-in-air for personal and area
dosemeters, respectively. For individual and area monitoring, this document describes the methods and
the conversion coefficients to be used for the determination of the response of dosemeters and dose-
rate meters in terms of the ICRU operational quantities, i.e., directional dose equivalent, H′(0,07;Ω) and
H′(3;Ω), as well as personal dose equivalent, H (0,07) and H (3).
p p
v
INTERNATIONAL STANDARD ISO 6980-2:2023(E)
Nuclear energy — Reference beta-particle radiation —
Part 2:
Calibration fundamentals related to basic quantities
characterizing the radiation field
1 Scope
This document specifies methods for the measurement of the absorbed-dose rate in a tissue-equivalent
slab phantom in the ISO 6980 reference beta-particle radiation fields. The energy range of the beta-
particle-emitting isotopes covered by these reference radiations is 0,22 MeV to 3,6 MeV maximum
beta energy corresponding to 0,07 MeV to 1,2 MeV mean beta energy. Radiation energies outside
this range are beyond the scope of this document. While measurements in a reference geometry
(depth of 0,07 mm or 3 mm at perpendicular incidence in a tissue-equivalent slab phantom) with an
extrapolation chamber used as primary standard are dealt with in detail, the use of other measurement
systems and measurements in other geometries are also described, although in less detail. However,
[5]
as noted in ICRU 56 , the ambient dose equivalent, H*(10), used for area monitoring, and the personal
dose equivalent, H (10), as used for individual monitoring, of strongly penetrating radiation, are not
p
appropriate quantities for any beta radiation, even that which penetrates 10 mm of tissue (E > 2 MeV).
max
This document is intended for those organizations wishing to establish primary dosimetry capabilities
for beta particles and serves as a guide to the performance of dosimetry with an extrapolation chamber
used as primary standard for beta-particle dosimetry in other fields. Guidance is also provided on the
statement of measurement uncertainties.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 29661, Reference radiation fields for radiation protection — Definitions and fundamental concepts
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 29661, ISO/IEC Guide 99 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
extrapolation curve
curve given by a plot of the corrected ionization current versus the extrapolation chamber depth
3.2
ionization chamber
ionizing radiation detector consisting of a chamber filled with a suitable gas (almost always air), in
which an electric field, insufficient to induce gas multiplication, is provided for the collection at the
electrodes of charges associated with the ions and electrons produced in the measuring volume of the
detector by ionizing radiation
Note 1 to entry: The ionization chamber includes the measuring volume, the collecting and polarizing electrodes,
the guard electrode, if any, the chamber wall, the parts of the insulator adjacent to the sensitive volume and any
additional material placed in front of the ionization chamber to simulate measurement at depth.
3.3
extrapolation (ionization) chamber
ionization chamber (3.2) capable of having an ionization volume which is continuously variable to
a vanishingly small value by changing the separation of the electrodes and which allows the user to
extrapolate the measured ionization density to zero collecting volume
3.4
ionization density
measured ionization per unit volume of air
3.5
leakage current
Ι
B
ionization chamber (3.2) current measured at the operating bias voltage in the absence of radiation
3.6
maximum beta energy
E
max
highest value of the energy of beta particles emitted by a particular radionuclide which can emit one or
several continuous spectra of beta particles with different maximum energies
3.7
mean beta energy
E
mean
fluence averaged energy of the beta particle spectrum at the calibration distance free in air
3.8
parasitic current
Ι
p
negative current produced by beta particles stopped in the collecting portion of the collecting electrode
and diffusing to this electrode and the wire connecting this electrode to the electrometer connector
3.9
phantom
artefact constructed to simulate the scattering properties of the human body or parts of the human
body such as the extremities
Note 1 to entry: A phantom can be used for the definition of a quantity and made of artificial materi
...