Dosimetry for exposures to cosmic radiation in civilian aircraft — Part 2: Characterization of instrument response

This document specifies methods and procedures for characterizing the responses of devices used for the determination of ambient dose equivalent for the evaluation of exposure to cosmic radiation in civilian aircraft. The methods and procedures are intended to be understood as minimum requirements.

Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil — Partie 2: Caractérisation de la réponse des instruments

Le présent document spécifie les méthodes et les modes opératoires permettant de caractériser les réponses des dispositifs utilisés pour déterminer l'équivalent de dose ambiant en vue de l'évaluation de l'exposition au rayonnement cosmique à bord d'un avion. Les méthodes et les modes opératoires doivent être considérés comme des exigences minimales.

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Published
Publication Date
12-Jul-2020
Current Stage
6060 - International Standard published
Start Date
13-Jul-2020
Due Date
01-Jun-2020
Completion Date
13-Jul-2020
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06-Jun-2022

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INTERNATIONAL ISO
STANDARD 20785-2
Second edition
2020-07
Dosimetry for exposures to cosmic
radiation in civilian aircraft —
Part 2:
Characterization of instrument
response
Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un
avion civil —
Partie 2: Caractérisation de la réponse des instruments
Reference number
ISO 20785-2:2020(E)
©
ISO 2020

---------------------- Page: 1 ----------------------
ISO 20785-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

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ISO 20785-2:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General terms . 1
3.2 Terms related to quantities and units . 5
3.3 Atmospheric radiation field . 7
4 General considerations . 8
4.1 The cosmic radiation field in the atmosphere . 8
4.2 General considerations for the dosimetry of the cosmic radiation field in aircraft
and requirements for the characterization of instrument response . 9
4.3 General considerations for measurements at aviation altitudes .10
5 Calibration fields and procedures .12
5.1 General considerations .12
5.2 Characterization of an instrument .14
5.2.1 Determination of the dosimetric characteristics of an instrument .14
5.2.2 Reference radiation fields .16
5.2.3 Scattered radiation . .16
5.2.4 Effect of other types of radiation .16
5.2.5 Requirements for characterization in non-reference conditions .17
5.2.6 Use of numerical simulations .17
5.3 Instrument-related software .17
5.3.1 Software development procedures .17
5.3.2 Software testing .18
5.3.3 Data analysis using spreadsheets .18
6 Uncertainties .18
7 Remarks on performance tests .18
Annex A (informative) Representative particle fluence energy distributions for the cosmic
radiation field at flight altitudes for solar minimum and maximum conditions and
for minimum and maximum vertical cut-off rigidity .19
Annex B (informative) Radiation fields recommended for use in calibrations .25
Annex C (informative) Comparison measurements .29
Annex D (informative) Charged-particle irradiation facilities .31
Bibliography .32
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ISO 20785-2:2020(E)

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
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.
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO's adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: 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, Radiation protection.
This second edition cancels and replaces the first edition (ISO 20785-2:2011), which has been technically
revised. The main changes compared to the previous edition are as follows:
— revision of the definitions of the terms;
— updated references.
A list of all the parts in the ISO 20785 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 © ISO 2020 – All rights reserved

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ISO 20785-2:2020(E)

Introduction
Aircraft crews are exposed to elevated levels of cosmic radiation of galactic and solar origin and
secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following
[1]
recommendations of the International Commission on Radiological Protection in Publication 60 ,
[2]
confirmed by Publication 103 , the European Union (EU) introduced a revised Basic Safety Standards
[3] [4]
Directive and International Atomic Energy Agency (IAEA) issued a revised Basic Safety Standards.
Those standards included exposure to natural sources of ionizing radiation, including cosmic radiation,
as occupational exposure. The EU Directive requires account to be taken of the exposure of aircraft crew
liable to receive more than 1 mSv per year. It then identifies the following four protection measures:
a) to assess the exposure of the crew concerned;
b) to take into account the assessed exposure when organizing working schedules with a view to
reducing the doses of highly exposed crew;
c) to inform the workers concerned of the health risks their work involves; and
d) to apply the same special protection during pregnancy to female crew in respect of the “child to be
born” as to other female workers.
The EU Council Directive has already been incorporated into laws and regulations of EU member
states and is being included in the aviation safety standards and procedures of the European Air Safety
Agency. Other countries, such as Canada and Japan, have issued advisories to their airline industries to
manage aircraft crew exposure.
For regulatory and legislative purposes, the radiation protection quantities of interest are the
equivalent dose (to the foetus) and the effective dose. The cosmic radiation exposure of the body is
essentially uniform, and the maternal abdomen provides no effective shielding to the foetus. As a result,
the magnitude of equivalent dose to the foetus can be put equal to that of the effective dose received
by the mother. Doses on board aircraft are generally predictable, and events comparable to unplanned
exposure in other radiological workplaces cannot normally occur (with the rare exceptions of extremely
intense and energetic solar particle events). Personal dosimeters for routine use are not considered
necessary. The preferred approach for the assessment of doses of aircraft crew, where necessary, is to
calculate directly the effective dose per unit time, as a function of geographic location, altitude and solar
cycle phase, and to combine these values with flight and staff roster information to obtain estimates of
[5] [6]
effective doses for individuals. This approach is supported by the ICRP in Publications 75 and 132
and in guidance from the European Commission.
The role of calculations in this procedure is unique in routine radiation protection, and it is widely
[7]
accepted that the calculated doses should be validated by measurement . Effective dose is not directly
measurable. The operational quantity of interest is the ambient dose equivalent, H*(10). In order to
validate the assessed doses obtained in terms of effective dose, calculations can be made of ambient
dose equivalent rates or route doses in terms of ambient dose equivalent, and values of this quantity
determined by measurements traceable to national standards and taking instrument responses and
related uncertainties properly into account. The validation of calculations of ambient dose equivalent
for a particular calculation method may be taken as a validation of the calculation of effective dose by
the same computer code, but this step in the process might need to be confirmed. The alternative is to
establish, a priori, that the operational quantity ambient dose equivalent is a good estimator of effective
dose and equivalent dose to the foetus for the radiation fields being considered, in the same way that
the use of the operational quantity personal dose equivalent is justified for the estimation of effective
dose for ground-based radiation workers.
The radiation field in aircraft at altitude is complex, with many types of ionizing radiation present,
with energies ranging up to many GeV. The instrument response to particles and energies of the
atmospheric radiation field that are not covered by reference fields are carefully taken into account in
the evaluation of measurement results. While, in many cases, the methods used for the determination
of ambient dose equivalent in aircraft are similar to those used at high-energy accelerators in
research laboratories. Therefore, it is possible to recommend dosimetric methods and methods for
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ISO 20785-2:2020(E)

the calibration of dosimetric devices, as well as the techniques for maintaining the traceability of
dosimetric measurements to national standards. Dosimetric measurements made to evaluate ambient
dose equivalent should be performed using accurate and reliable methods that ensure the quality of
readings provided to workers and regulatory authorities. The purpose of this document is to specify
procedures for the determination of the responses of instruments in different reference radiation
fields, as a basis for proper characterization of instruments used for the determination of ambient dose
equivalent in aircraft at altitude.
Requirements for the determination and recording of the cosmic radiation exposure of aircraft crew have
been introduced into the national legislation of EU member states and other countries. Harmonization
of methods used for determining ambient dose equivalent and for calibrating instruments is desirable
to ensure the compatibility of measurements performed with such instruments.
This document is intended for the use of primary and secondary calibration laboratories for ionizing
radiation, by radiation protection personnel employed by governmental agencies, and by industrial
corporations concerned with the determination of ambient dose equivalent for aircraft crew.
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INTERNATIONAL STANDARD ISO 20785-2:2020(E)
Dosimetry for exposures to cosmic radiation in civilian
aircraft —
Part 2:
Characterization of instrument response
1 Scope
This document specifies methods and procedures for characterizing the responses of devices used
for the determination of ambient dose equivalent for the evaluation of exposure to cosmic radiation in
civilian aircraft. The methods and procedures are intended to be understood as minimum requirements.
2 Normative references
The following five 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/IEC Guide 98-1, Uncertainty of measurement — Part 1: Introduction to the expression of uncertainty
in measurement
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 General terms
3.1.1
angle of radiation incidence
α
angle between the direction of radiation incidence and the reference direction of the instrument
3.1.2
calibration
operation that, under specified conditions, establishes a relation between the conventional quantity,
H , and the indication, G
0
Note 1 to entry: A calibration can be expressed by a statement, calibration function, calibration diagram,
calibration curve or calibration table. In some cases, it can consist of an additive or multiplicative correction of
the indication with associated measurement uncertainty.
Note 2 to entry: It is important not to confuse calibration with adjustment of a measuring system, often
mistakenly called “self-calibration”, or with verification of calibration.
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ISO 20785-2:2020(E)

3.1.3
calibration coefficient
N
coeff
quotient of the conventional quantity value to be measured and the corrected indication of the
instrument
Note 1 to entry: The calibration coefficient is equivalent to the calibration factor multiplied by the instrument
constant.
Note 2 to entry: The reciprocal of the calibration coefficient, N , is the response.
coeff
Note 3 to entry: For the calibration of some instruments, e.g. ionization chambers, the instrument constant and
the calibration factor are not identified separately but are applied together as the calibration coefficient.
Note 4 to entry: It is necessary, in order to avoid confusion, to state the quantity to be measured, for example:
the calibration coefficient with respect to fluence, N , the calibration coefficient with respect to kerma, N , the
Φ K
calibration coefficient with respect to absorbed dose, N .
D
3.1.4
calibration factor
N
fact
factor by which the product of the corrected indication and the associated instrument constant of the
instrument is multiplied to obtain the conventional quantity value to be measured under reference
conditions
Note 1 to entry: The calibration factor is dimensionless.
Note 2 to entry: The corrected indication is the indication of the instrument corrected for the effect of influence
quantities, where applicable.
Note 3 to entry: The value of the calibration factor can vary with the magnitude of the quantity to be measured.
In such cases, a detector assembly is said to have a non-constant response.
3.1.5
measured quantity value
measured value of a quantity
measured value
M
quantity value representing a measurement result
Note 1 to entry: For a measurement involving replicate indications, each indication can be used to provide a
corresponding measured quantity value. This set of measured quantity values can be used to calculate a
resulting measured quantity value, such as an average or a median value, usually with a decreased associated
measurement uncertainty.
Note 2 to entry: When the range of the true quantity values believed to represent the measurand is small
compared with the measurement uncertainty, a measured quantity value can be considered to be an estimate
of an essentially unique true quantity value and is often an average or a median of individual measured quantity
values obtained through replicate measurements.
Note 3 to entry: In the case where the range of the true quantity values believed to represent the measurand is
not small compared with the measurement uncertainty, a measured value is often an estimate of an average or a
median of the set of true quantity values.
Note 4 to entry: In ISO/IEC Guide 98-3:2008, the terms “result of measurement” and “estimate of the value of the
measurand” or just “estimate of the measurand” are used for “measured quantity value”.
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ISO 20785-2:2020(E)

3.1.6
conventional quantity value
conventional value of a quantity
conventional value
H
0
quantity value attributed by agreement to a quantity for a given purpose
Note 1 to entry: The term “conventional true quantity value” is sometimes used for this concept, but its use is
discouraged.
Note 2 to entry: Sometimes, a conventional quantity value is an estimate of a true quantity value.
Note 3 to entry: A conventional quantity value is generally accepted as being associated with a suitably small
measurement uncertainty, which might be zero.
[8][9][10]
Note 4 to entry: In ISO 20785 series , the conventional quantity value is the best estimate of the value of
the quantity to be measured, determined by a primary or a secondary standard which is traceable to a primary
standard.
3.1.7
correction factor
k
factor applied to the indication (3.1.9) to correct for deviation of measurement conditions from reference
conditions
Note 1 to entry: If the correction of the effect of the deviation of an influence quantity requires a factor, the
influence quantity is of type F.
3.1.8
correction summand
G
S
summand applied to the indication (3.1.9) to correct for the zero indication or the deviation of the
measurement conditions from the reference conditions
Note 1 to entry: If the correction of the effect of the deviation of an influence quantity requires a summand, the
influence quantity is of type S.
3.1.9
indication
G
quantity value provided by a measuring instrument or a measuring system
Note 1 to entry: An indication can be presented in visual or acoustic form or can be transferred to another device.
An indication is often given by the position of a pointer on the display for analogue outputs, a displayed or printed
number for digital outputs, a code pattern for code outputs, or an assigned quantity value for material measures.
Note 2 to entry: An indication and a corresponding value of the quantity being measured are not necessarily
values of quantities of the same kind.
3.1.10
influence quantity
quantity that, in a direct measurement, does not affect the quantity that is actually measured, but
affects the relation between the indication (3.1.9) and the measurement result
Note 1 to entry: An indirect measurement involves a combination of direct measurements, each of which can be
affected by influence quantities.
Note 2 to entry: In ISO/IEC Guide 98-3:2008, the concept “influence quantity” is defined as
[11]
in ISO/IEC Guide 99:2007 , covering not only the quantities affecting the measuring system, as in the definition
above, but also those quantities that affect the quantities actually measured. Also, in ISO/IEC Guide 98-3, this
concept is not restricted to direct measurements.
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ISO 20785-2:2020(E)

Note 3 to entry: The correction of the effect of the influence quantity can require a correction factor (for an
influence quantity of type F) and/or a correction summand (for an influence quantity of type S) to be applied to
the indication of the detector assembly, e.g. in the case of microphonic or electromagnetic disturbance.
EXAMPLE The indication given by an unsealed ionization chamber is influenced by the temperature
and pressure of the surrounding atmosphere. Although needed for determining the value of the dose, the
measurement of these two quantities is not the primary objective.
3.1.11
instrument constant
c
i
quantity value by which the indication (3.1.9) of the instrument, G (or, if corrections or normalization
were carried out, G ), is multiplied to give the value of the measurand or of a quantity to be used to
corr
calculate the value of the measurand
Note 1 to entry: If the instrument's indication is already expressed in the same units as the measurand, as is
the case with area dosemeters, for instance, the instrument constant, c , is dimensionless. In such cases, the
i
calibration factor and the calibration coefficient (3.1.3) can be the same. Otherwise, if the indication of the
instrument has to be converted to the same units as the measurand, the instrument constant has a dimension.
3.1.12
measurand
quantity intended to be measured
3.1.13
primary measurement standard
primary standard
measurement standard established using a primary reference measurement procedure or created as
an artefact, chosen by convention
Note 1 to entry: A primary standard has the highest metrological quality in a given field.
3.1.14
quantity value
number and reference together expressing the magnitude of a quantity
Note 1 to entry: A quantity value is either a product of a number and a measurement unit (the unit “one” is
generally not indicated for quantities of dimension “one”) or a number and a reference to a measurement
procedure.
3.1.15
reference conditions
conditions of use prescribed for testing the performance of a detector assembly or for comparing the
results of measurements
Note 1 to entry: The reference conditions represent the values of the set of influence quantities for which the
calibration result is valid without any correction.
Note 2 to entry: The value of the measurand can be chosen freely in agreement with the properties of the
detector assembly to be calibrated. The quantity to be measured is not an influence quantity but can influence
the calibration result and the response (see also Note 1 to entry).
3.1.16
response
response characteristic
R
quotient of the indication, G, or the corrected indication, G , and the conventional quantity value to be
corr
measured
Note 1 to entry: To avoid confusion, it is necessary to specify which of the quotients given in the definition of the
response (that for the indication, G or G ) is applied. Furthermore, it is necessary, in order to avoid confusion,
corr
to state the quantity to be measured, for example the response with respect to fluence, R , the response with
Φ
respect to kerma, R or the response with respect to absorbed dose, R .
K D
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ISO 20785-2:2020(E)

Note 2 to entry: The reciprocal of the response under the specified conditions is equal to the calibration
coefficient, N .
coeff
Note 3 to entry: The value of the response can vary with the magnitude of the quantity to be measured. In such
cases, the detector assembly's response is said to be non-constant.
Note 4 to entry: The response usually varies with the energy and direction distribution of the incident radiation.
It is therefore useful to consider the response as a function, R(E,Ω), of the radiation energy, E, and the direction,

Ω , of the incident monodirectional radiation. R(E) describes the “energy dependence” and R(Ω) the “angle

dependence” of the response; for the latter, Ω may be expressed by the angle, α, between the reference direction
of the detector assembly and the direction of an external monodirectional field.
3.2 Terms related to quantities and units
[12]
Most of the definitions in this subclause have been adapted from ISO 80000-10:2019 and ICRU
[13] [14]
Reports 36 and 51 .
3.2.1
particle fluence
fluence
Φ
number, dN, at a given point in space, of particles incident on a small spherical domain, divided by the
cross-sectional area, da, of that domain:
dN
Φ=
da
−2 −2
Note 1 to entry: The unit of the fluence is m ; a frequently used unit is cm .
Note 2 to entry: The energy distribution of the particle fluence, Φ , is the quotient, dΦ, by dE, where dΦ is the
E
fluence of particles of energy between E and E+dE. There is an analogous definition for the direction distribution,
Φ , of the particle fluence. The complete representation of the double differential particle fluence can be written
Ω
(with arguments) Φ (E,Ω), where the subscripts characterize the variables (quantities) for differentiation and
E,Ω
where the symbols in the brackets describe the values of the variables. The values in the brackets are needed for
special function values, e.g. the energy distribution of the particle fluence at energy E = E is written as Φ (E ). If
0 E 0
no special values are indicated, the brackets may be omitted.
3.2.2
particle fluence rate
fluence rate

Φ
rate of the particle fluence (3.2.1) expressed as
2
dΦ d N

...

NORME ISO
INTERNATIONALE 20785-2
Deuxième édition
2020-07
Dosimétrie pour l'exposition au
rayonnement cosmique à bord d'un
avion civil —
Partie 2:
Caractérisation de la réponse des
instruments
Dosimetry for exposures to cosmic radiation in civilian aircraft —
Part 2: Characterization of instrument response
Numéro de référence
ISO 20785-2:2020(F)
©
ISO 2020

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ISO 20785-2:2020(F)

DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020
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publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
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Publié en Suisse
ii © ISO 2020 – Tous droits réservés

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ISO 20785-2:2020(F)

Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes et définitions . 1
3.1 Termes généraux . 1
3.2 Termes apparentés aux grandeurs et aux unités . 5
3.3 Champ de rayonnement atmosphérique . 7
4 Considérations générales . 8
4.1 Champ de rayonnement cosmique dans l’atmosphère . 8
4.2 Aspects généraux à considérer pour la dosimétrie du rayonnement cosmique
à bord d’un avion et exigences relatives à la caractérisation de la réponse des
instruments .10
4.3 Considérations générales concernant les mesurages aux altitudes de vol des avions .11
5 Champs et modes opératoires d’étalonnage .12
5.1 Considérations générales .12
5.2 Caractérisation d’un instrument.15
5.2.1 Détermination des caractéristiques dosimétriques d’un instrument.15
5.2.2 Champs de rayonnement de référence .16
5.2.3 Rayonnement diffusé .17
5.2.4 Effet des autres types de rayonnement .17
5.2.5 Exigences relatives à la caractérisation dans des conditions différentes
des conditions de référence .17
5.2.6 Utilisation de simulations numériques .18
5.3 Logiciels associés aux instruments .18
5.3.1 Modes opératoires de développement des logiciels .18
5.3.2 Essais logiciels .19
5.3.3 Analyse des données dans des feuilles de calcul .19
6 Incertitudes.19
7 Remarques concernant les essais de performances .19
Annexe A (informative) Distributions en énergie représentatives de la fluence de particules
pour le rayonnement cosmique à des altitudes de vol d’avion dans les conditions
de période d’activité solaire minimale et maximale et pour la coupure de rigidité
géomagnétique verticale minimale et maximale .20
Annexe B (informative) Champs de rayonnement recommandés pour les étalonnages .26
Annexe C (informative) Mesurages comparatifs .30
Annexe D (informative) Installations d’irradiation de particules chargées.32
Bibliographie .33
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ISO 20785-2:2020(F)

Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes
nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est
en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.
L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents
critères d’approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L’attention est attirée sur le fait que certains des éléments du présent document peuvent faire l’objet de
droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de
brevets reçues par l’ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion
de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir le lien suivant : www .iso .org/ iso/ fr/ avant -propos.
Le présent document a été élaboré par le comité technique ISO/TC 85, Énergie nucléaire, technologies
nucléaires, et radioprotection, sous-comité SC 2, Radioprotection.
Cette deuxième édition annule et remplace la première (ISO 20785-2:2011), qui a fait l’objet d’une
révision technique. Les principales modifications par rapport à l’édition précédente sont les suivantes :
— révision des termes et définitions ;
— mise à jour des références.
Une liste de toutes les parties de la série ISO 20785 se trouve sur le site web de l’ISO.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/ fr/ members .html.
iv © ISO 2020 – Tous droits réservés

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ISO 20785-2:2020(F)

Introduction
Le personnel navigant est exposé à des niveaux élevés de rayonnement cosmique d’origine galactique
et solaire, ainsi qu’au rayonnement secondaire produit dans l’atmosphère, dans la structure de
l’avion et son contenu. Suivant les recommandations de la Commission internationale de protection
[1] [2]
radiologique (CIPR) dans la Publication 60 , confirmées par la Publication 103 , l’Union
[3]
européenne (UE) a établi la révision d’une Directive relative aux normes de sécurité de base et
[4]
l’Agence internationale de l’énergie atomique (IAEA) a publié une version révisée des normes de
sécurité de base. Ces normes classaient parmi les expositions professionnelles le cas de l’exposition
aux sources naturelles de rayonnements ionisants, y compris le rayonnement cosmique. Cette Directive
de l’UE exige de prendre en compte l’exposition du personnel navigant susceptible de recevoir plus de
1 mSv par an. Elle identifie ensuite les quatre mesures de protection suivantes :
a) évaluer l’exposition du personnel concerné ;
b) prendre en compte l’exposition évaluée lors de l’organisation des programmes de travail, en vue de
réduire les doses du personnel navigant le plus fortement exposé ;
c) informer les travailleurs concernés sur les risques pour la santé que leur travail implique ; et
d) appliquer les mêmes règles de protection spécifiques en cas de grossesse pour le personnel navigant
féminin, eu égard à « l’enfant à naître », que pour tout autre travailleur exposé de sexe féminin.
La Directive du Conseil de l’UE a déjà été intégrée aux lois et réglementations des états membres de l’UE
ainsi que dans les normes et modes opératoires de sécurité de l’aviation de l’Agence européenne pour
la sécurité aérienne (European Air Safety Agency). D’autres pays tels que le Canada et le Japon ont émis
des règles ou des recommandations à l’attention de leurs compagnies aériennes pour gérer la question
de l’exposition du personnel navigant.
Les grandeurs de protection concernées, dans un cadre réglementaire et législatif, sont la dose
équivalente (au fœtus) et la dose efficace. L’exposition de l’organisme au rayonnement cosmique est
globalement uniforme et l’abdomen maternel ne fournit aucune protection particulière au fœtus.
Ainsi, la dose équivalente au fœtus peut être considérée comme égale à la dose efficace reçue par la
mère. Les doses liées à l’exposition à bord des avions sont généralement prévisibles, et des événements
comparables à des expositions non prévues à d’autres postes de travail sous rayonnement ne peuvent
pas habituellement se produire (à l’exception rare des éruptions solaires extrêmement intenses
produisant des particules solaires très énergétiques). Le recours à des dosimètres individuels pour un
usage de routine n’est pas considéré comme nécessaire. L’approche préférée pour l’évaluation des doses
reçues par le personnel navigant, si nécessaire, consiste à calculer directement la dose efficace par
unité de temps, en fonction des coordonnées géographiques, de l’altitude et de la phase du cycle solaire,
et à combiner ces valeurs avec les informations concernant le vol et le tableau de service du personnel,
afin d’obtenir des estimations des doses efficaces pour les individus. Cette approche est recommandée
[5] [6]
par la CIPR dans les Publications 75 et 132 et dans la directive de la Commission européenne.
Le rôle des calculs dans ce mode opératoire est unique par rapport aux méthodes d’évaluation
habituellement utilisées en radioprotection et il est largement admis qu’il convient de valider les doses
[7]
calculées par mesurage . La dose efficace n’est pas directement mesurable. La grandeur opérationnelle
utilisée est l’équivalent de dose ambiant, H*(10). Afin de valider les doses évaluées en termes de dose
efficace, il est possible de calculer les débits d’équivalent de dose ambiant ou les doses pendant le vol,
en termes d’équivalent de dose ambiant, ainsi que les valeurs de cette grandeur déterminées par des
mesurages traçables à des étalons nationaux et en prenant correctement en compte les réponses des
instruments et les incertitudes associées. La validation des calculs de l’équivalent de dose ambiant
par une méthode de calcul particulière peut être considérée comme la validation du calcul de la
dose efficace par le même code de calcul, mais cette étape du processus d’évaluation peut nécessiter
d’être confirmée. La variante consiste à établir, a priori, que l’équivalent de dose ambiant constitue
un bon estimateur de la dose efficace et de la dose équivalente destinée au fœtus pour les champs
de rayonnements considérés, de la même façon que l’utilisation de l’équivalent de dose individuel est
justifiée pour l’estimation de la dose efficace des travailleurs sous rayonnement au niveau du sol.
© ISO 2020 – Tous droits réservés v

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ISO 20785-2:2020(F)

Le champ de rayonnement auquel est soumis un avion aux altitudes de vol est complexe, avec la présence
de nombreux types de rayonnements ionisants dont les énergies peuvent atteindre plusieurs GeV. Les
réponses des instruments aux particules et aux énergies du champ de rayonnement atmosphérique
qui ne sont pas couvertes par les champs de référence sont soigneusement prises en compte lors de
l’évaluation des résultats de mesure. Dans de nombreux cas, les méthodes employées pour déterminer
l’équivalent de dose ambiant à bord d’un avion sont semblables à celles utilisées auprès d’accélérateurs
haute énergie dans les laboratoires de recherche. Des méthodes dosimétriques et des méthodes
d’étalonnage des dispositifs dosimétriques peuvent par conséquent être recommandées, ainsi que
les techniques permettant de conserver la traçabilité des mesurages dosimétriques à des étalons
nationaux. Il convient de réaliser les mesurages dosimétriques destinés à évaluer l’équivalent de
dose ambiant à l’aide de méthodes précises et fiables qui assurent la qualité des relevés fournis aux
travailleurs et aux autorités en charge de la réglementation. Le présent document a pour objectif de
spécifier les modes opératoires permettant de déterminer les réponses des instruments dans différents
champs de rayonnement de référence, lesquelles réponses serviront de base pour la caractérisation
correcte des instruments utilisés pour déterminer l’équivalent de dose ambiant à bord d’un avion aux
altitudes de vol.
Les exigences relatives à la détermination et à l’enregistrement de l’exposition au rayonnement cosmique
du personnel navigant font partie intégrante de la législation nationale des États membres de l’UE et
d’autres pays. Il est souhaitable d’harmoniser les méthodes permettant de déterminer l’équivalent de
dose ambiant et d’étalonner les instruments utilisés afin de garantir la compatibilité des mesurages
effectués avec de tels instruments.
Le présent document est destiné à être utilisé par les laboratoires d’étalonnages primaire et secondaire
dans le domaine des rayonnements ionisants, par le personnel des services de radioprotection employé
par les organismes publics et par les entreprises industrielles, intéressées par la détermination de
l’équivalent de dose ambiant du personnel navigant.
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NORME INTERNATIONALE ISO 20785-2:2020(F)
Dosimétrie pour l'exposition au rayonnement cosmique à
bord d'un avion civil —
Partie 2:
Caractérisation de la réponse des instruments
1 Domaine d’application
Le présent document spécifie les méthodes et les modes opératoires permettant de caractériser les
réponses des dispositifs utilisés pour déterminer l’équivalent de dose ambiant en vue de l’évaluation
de l’exposition au rayonnement cosmique à bord d’un avion. Les méthodes et les modes opératoires
doivent être considérés comme des exigences minimales.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique.
Pour les références non datées, la dernière édition du document de référence s’applique (y compris les
éventuels amendements).
Guide ISO/IEC 98-1, Incertitude de mesure — Partie 1 : Introduction à l’expression de l’incertitude de mesure
Guide ISO/IEC 98-3, Incertitude de mesure — Partie 3 : Guide pour l’expression de l’incertitude de mesure
(GUM: 1995)
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions suivants s’appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes :
— ISO Online browsing platform : disponible à l’adresse https:// www .iso .org/ obp ;
— IEC Electropedia : disponible à l’adresse http:// www .electropedia .org/ .
3.1 Termes généraux
3.1.1
angle d’incidence du rayonnement
α
angle entre la direction de l’incidence du rayonnement et la direction de référence de l’instrument
3.1.2
étalonnage
opération qui, dans des conditions spécifiées, établit une relation entre la grandeur conventionnelle, H ,
0
et l’indication, G
Note 1 à l'article: Un étalonnage peut être exprimé sous la forme d’un énoncé, d’une fonction d’étalonnage, d’un
diagramme d’étalonnage, d’une courbe d’étalonnage ou d’une table d’étalonnage. Dans certains cas, il peut
consister en une correction additive ou multiplicative de l’indication avec une incertitude de mesure associée.
© ISO 2020 – Tous droits réservés 1

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ISO 20785-2:2020(F)

Note 2 à l'article: Il est important de ne pas confondre l’étalonnage avec l’ajustage d’un système de mesure,
souvent appelé improprement « auto‑étalonnage », ni avec la vérification de l’étalonnage.
3.1.3
coefficient d’étalonnage
N
coeff
quotient de la valeur conventionnelle d’une grandeur à mesurer et de l’indication corrigée de
l’instrument
Note 1 à l'article: Le coefficient d’étalonnage est équivalent au facteur d’étalonnage multiplié par la constante de
l’instrument.
Note 2 à l'article: L’inverse du coefficient d’étalonnage, N , est la réponse.
coeff
Note 3 à l'article: Pour l’étalonnage de quelques instruments, par exemple les chambres d’ionisation, la constante
de l’instrument et le facteur d’étalonnage ne sont pas identifiés séparément, mais sont appliqués ensemble en
tant que coefficient d’étalonnage.
Note 4 à l'article: Il est nécessaire, pour éviter toute confusion, d’indiquer la grandeur à mesurer, par exemple
le coefficient d’étalonnage en ce qui concerne la fluence, N , le coefficient d’étalonnage en ce qui concerne le
Φ
kerma, N , ou le coefficient d’étalonnage en ce qui concerne la dose absorbée, N .
K D
3.1.4
facteur d’étalonnage
N
fact
facteur par lequel le produit de l’indication corrigée et de la constante associée de l’instrument est
multiplié afin d’obtenir la valeur conventionnelle d’une grandeur à mesurer dans les conditions de
référence
Note 1 à l'article: Le facteur d’étalonnage n’a pas de dimension.
Note 2 à l'article: L’indication corrigée est l’indication de l’instrument corrigée en fonction de l’effet des grandeurs
d’influence, le cas échéant.
Note 3 à l'article: La valeur du facteur d’étalonnage peut varier selon l’expression quantitative de la grandeur à
mesurer. Dans de tels cas, la réponse de l’ensemble de détecteur est dite non constante.
3.1.5
valeur de la grandeur mesurée
valeur mesurée
M
valeur d’une grandeur représentant un résultat de mesure
Note 1 à l'article: Pour un mesurage impliquant des indications répétées, chacune peut être utilisée pour
fournir une valeur mesurée correspondante. Cet ensemble de valeurs mesurées peut ensuite être utilisé pour
calculer une valeur mesurée résultante, telle qu’une valeur moyenne ou une valeur médiane, en général avec une
incertitude de mesure associée qui décroît.
Note 2 à l'article: Lorsque l’étendue des valeurs vraies considérées comme représentant le mesurande est petite
par rapport à l’incertitude de mesure, une valeur mesurée peut être considérée comme une estimation d’une
valeur vraie par essence unique, souvent sous la forme d’une moyenne ou d’une médiane de valeurs mesurées
individuelles obtenues par des mesurages répétés.
Note 3 à l'article: Lorsque l’étendue des valeurs vraies considérées comme représentant le mesurande n’est pas
petite par rapport à l’incertitude de mesure, une valeur mesurée est souvent une estimation d’une moyenne ou
d’une médiane de l’ensemble des valeurs vraies.
Note 4 à l'article: Dans le Guide ISO/IEC 98-3:2008, les termes « résultat de mesure » et « estimation de la valeur
du mesurande », ou simplement « estimation du mesurande », sont utilisés au sens de « valeur mesurée ».
2 © ISO 2020 – Tous droits réservés

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ISO 20785-2:2020(F)

3.1.6
valeur conventionnelle
valeur conventionnelle d’une grandeur
H
0
valeur attribuée à une grandeur par un accord pour un usage donné
Note 1 à l'article: Le terme « valeur conventionnellement vraie » est quelquefois utilisé pour ce concept, mais son
utilisation est déconseillée.
Note 2 à l'article: Une valeur conventionnelle est quelquefois une estimation d’une valeur vraie.
Note 3 à l'article: Une valeur conventionnelle est généralement considérée comme associée à une incertitude de
mesure convenablement petite, qui peut être nulle.
[8][9][10]
Note 4 à l'article: Dans la série ISO 20785 , la valeur conventionnelle est la meilleure estimation de la
valeur de la grandeur à mesurer, déterminée par un étalon primaire ou par un étalon secondaire traçable à un
étalon primaire.
3.1.7
facteur de correction
k
facteur appliqué à une indication (3.1.9) en vue de corriger l’écart existant entre les conditions de
mesure et les conditions de référence
Note 1 à l'article: Si la correction de l’effet de l’écart d’une grandeur d’influence exige un facteur, la grandeur
d’influence est de type F.
3.1.8
terme de correction
G
S
terme appliqué à une indication (3.1.9) en vue de corriger l’indication nulle ou l’écart existant entre les
conditions de mesure et les conditions de référence
Note 1 à l'article: Si la correction de l’effet de l’écart d’une grandeur d’influence exige un terme, la grandeur
d’influence est de type S.
3.1.9
indication
G
valeur fournie par un instrument de mesure ou un système de mesure
Note 1 à l'article: Une indication peut être présentée sous forme visuelle ou acoustique, ou peut être transférée
à un autre dispositif. Elle est souvent donnée par la position d’un pointeur sur un affichage pour les sorties
analogiques, par un nombre affiché ou imprimé pour les sorties numériques, par une configuration codée pour
les sorties codées, ou par la valeur assignée pour les mesures matérialisées.
Note 2 à l'article: Une indication et la valeur de la quantité mesurée correspondante ne sont pas nécessairement
des valeurs de grandeurs de même nature.
3.1.10
grandeur d’influence
grandeur qui, lors d’un mesurage direct, n’a pas d’effet sur la grandeur effectivement mesurée, mais a
un effet sur la relation entre l’indication (3.1.9) et le résultat de mesure
Note 1 à l'article: Un mesurage indirect implique une combinaison de mesurages directs, sur chacun desquels des
grandeurs d’influence peuvent avoir un effet.
Note 2 à l'article: Dans le Guide ISO/IEC 98‑3:2008, le concept « grandeur d’influence » est défini comme dans
[11]
le Guide ISO/IEC 99:2007 , de façon à comprendre non seulement les grandeurs qui ont un effet sur le système
de mesure, comme dans la définition ci‑dessus, mais aussi celles qui ont un effet sur les grandeurs effectivement
mesurées. En outre, dans le Guide ISO/IEC 98-3, ce concept n’est pas limité aux mesurages directs.
© ISO 2020 – Tous droits réservés 3

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ISO 20785-2:2020(F)

Note 3 à l'article: La correction de l’effet de la grandeur d’influence peut exiger un facteur de correction (pour
une grandeur d’influence de type F) et/ou un terme de correction (pour une grandeur d’influence de type S) à
appliquer à l’indication de l’ensemble de détecteur, par exemple dans le cas de perturbations microphoniques ou
électromagnétiques.
EXEMPLE L’indication donnée par une chambre d’ionisation non scellée est influencée par la température
et la pression de l’atmosphère environnante. Bien qu’elles soient requises pour déterminer la valeur de la dose, le
mesurage de ces deux grandeurs n’est pas l’objectif principal.
3.1.11
constante de l’instrument
c
i
valeur par laquelle l’indication (3.1.9) de l’instrument, G (ou, en cas de corrections ou de
normalisation, G ), est multipliée pour obtenir la valeur du mesurande ou d’une grandeur à utiliser
corr
pour calculer la valeur du mesurande
Note 1 à l'article: Si l’indication de l’instrument est déjà exprimée dans les mêmes unités que le mesurande, comme
c’est le cas des dosimètres de zone, par exemple, la constante de l’instrument, c , n’a pas de dimension. Dans de
i
tels cas, le facteur d’étalonnage et le coefficient d’étalonnage (3.1.3) peuvent être identiques. Sinon, si l’indication
de l’instrument doit être convertie dans les mêmes unités que le mesurande, la constante de l’instrument a une
dimension.
3.1.12
mesurande
grandeur destinée à être mesurée
3.1.13
étalon primaire
étalon établi à l’aide d’un mode opératoire de mesure primaire ou créé comme objet choisi par
convention
Note 1 à l'article: Un étalon primaire présente les plus hautes qualités métrologiques dans un domaine spécifié
de métrologie.
3.1.14
valeur d’une grandeur
ensemble d’un nombre et d’une référence constituant l’expression quantitative d’une grandeur
Note 1 à l'article: La valeur d’une grandeur est le produit soit d’un nombre et d’une unité de mesure (l’unité « un »
n’est généralement pas indiquée pour les grandeurs de dimension « un »), soit d’un nombre et d’une référence à
un mode opératoire de mesure.
3.1.15
conditions de référence
conditions d’utilisation prescrites pour contrôler les performances d’un ensemble de détecteur ou pour
comparer les résultats des mesurages
Note 1 à l'article: Les conditions de référence représentent les valeurs de l’ensemble de grandeurs d’influence
pour lesquelles le résultat d’étalonnage est valide sans aucune correction.
Note 2 à l'article: La valeur du mesurande peut être choisie librement en accord avec les propriétés de l’ensemble
de détecteur à étalonner. La grandeur à mesurer n’est pas une grandeur d’influence mais peut influer sur le
résultat d’étalonnage et la réponse (voir aussi Note 1 à l’article).
4 © ISO 2020 – Tous droits réservés

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ISO 20785-2:2020(F)

3.1.16
réponse
caractéristique de la réponse
R
quotient de l’indication, G, ou de l’indication corrigée, G , et de la valeur conventionnelle d’une
corr
grandeur à mesurer
Note 1 à l'article: Pour éviter toute confusion, il est nécessaire de spécifier lequel des quotients indiqués dans la
définition de la réponse (celui associé à l’indication G ou G ) a été utilisé. De plus, il est nécessaire, pour éviter
corr
toute confusion, d’indiquer la grandeur à mesurer, par exemple la réponse en ce qui concerne la fluence, R , la
Φ
réponse en ce qui concerne le ke
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 20785-2
ISO/TC 85/SC 2
Dosimetry for exposures to cosmic
Secretariat: AFNOR
radiation in civilian aircraft —
Voting begins on:
2020-04-03
Part 2:
Voting terminates on:
Characterization of instrument
2020-05-29
response
Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un
avion civil —
Partie 2: Caractérisation de la réponse des instruments
ISO/CEN PARALLEL PROCESSING
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 20785-2:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2020

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ISO/FDIS 20785-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

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ISO/FDIS 20785-2:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General terms . 1
3.2 Terms related to quantities and units . 5
3.3 Atmospheric radiation field . 7
4 General considerations . 8
4.1 The cosmic radiation field in the atmosphere . 8
4.2 General considerations for the dosimetry of the cosmic radiation field in aircraft
and requirements for the characterization of instrument response . 9
4.3 General considerations for measurements at aviation altitudes .10
5 Calibration fields and procedures .12
5.1 General considerations .12
5.2 Characterization of an instrument .14
5.2.1 Determination of the dosimetric characteristics of an instrument .14
5.2.2 Reference radiation fields .16
5.2.3 Scattered radiation . .16
5.2.4 Effect of other types of radiation .16
5.2.5 Requirements for characterization in non-reference conditions .17
5.2.6 Use of numerical simulations .17
5.3 Instrument-related software .17
5.3.1 Software development procedures .17
5.3.2 Software testing .18
5.3.3 Data analysis using spreadsheets .18
6 Uncertainties .18
7 Remarks on performance tests .18
Annex A (informative) Representative particle fluence energy distributions for the cosmic
radiation field at flight altitudes for solar minimum and maximum conditions and
for minimum and maximum vertical cut-off rigidity .19
Annex B (informative) Radiation fields recommended for use in calibrations .25
Annex C (informative) Comparison measurements .29
Annex D (informative) Charged-particle irradiation facilities .31
Bibliography .32
© ISO 2020 – All rights reserved iii

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ISO/FDIS 20785-2:2020(E)

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
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.
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO's adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: 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, Radiation protection.
This second edition cancels and replaces the first edition (ISO 20785-2:2011), which has been technically
revised. The main changes compared to the previous edition are as follows:
— revision of the definitions of the terms;
— updated references.
A list of all the parts in the ISO 20785 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.
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ISO/FDIS 20785-2:2020(E)

Introduction
Aircraft crews are exposed to elevated levels of cosmic radiation of galactic and solar origin and
secondary radiation produced in the atmosphere, the aircraft structure and its contents. Following
[1]
recommendations of the International Commission on Radiological Protection in Publication 60 ,
[2]
confirmed by Publication 103 , the European Union (EU) introduced a revised Basic Safety Standards
[3] [4]
Directive and International Atomic Energy Agency (IAEA) issued a revised Basic Safety Standards.
Those standards included exposure to natural sources of ionizing radiation, including cosmic radiation,
as occupational exposure. The EU Directive requires account to be taken of the exposure of aircraft crew
liable to receive more than 1 mSv per year. It then identifies the following four protection measures:
a) to assess the exposure of the crew concerned;
b) to take into account the assessed exposure when organizing working schedules with a view to
reducing the doses of highly exposed crew;
c) to inform the workers concerned of the health risks their work involves; and
d) to apply the same special protection during pregnancy to female crew in respect of the “child to be
born” as to other female workers.
The EU Council Directive has already been incorporated into laws and regulations of EU member
states and is being included in the aviation safety standards and procedures of the European Air Safety
Agency. Other countries, such as Canada and Japan, have issued advisories to their airline industries to
manage aircraft crew exposure.
For regulatory and legislative purposes, the radiation protection quantities of interest are the
equivalent dose (to the foetus) and the effective dose. The cosmic radiation exposure of the body is
essentially uniform, and the maternal abdomen provides no effective shielding to the foetus. As a result,
the magnitude of equivalent dose to the foetus can be put equal to that of the effective dose received
by the mother. Doses on board aircraft are generally predictable, and events comparable to unplanned
exposure in other radiological workplaces cannot normally occur (with the rare exceptions of extremely
intense and energetic solar particle events). Personal dosimeters for routine use are not considered
necessary. The preferred approach for the assessment of doses of aircraft crew, where necessary, is to
calculate directly the effective dose per unit time, as a function of geographic location, altitude and solar
cycle phase, and to combine these values with flight and staff roster information to obtain estimates of
[5] [6]
effective doses for individuals. This approach is supported by the ICRP in Publications 75 and 132
and in guidance from the European Commission.
The role of calculations in this procedure is unique in routine radiation protection, and it is widely
[7]
accepted that the calculated doses should be validated by measurement . Effective dose is not directly
measurable. The operational quantity of interest is the ambient dose equivalent, H*(10). In order to
validate the assessed doses obtained in terms of effective dose, calculations can be made of ambient
dose equivalent rates or route doses in terms of ambient dose equivalent, and values of this quantity
determined by measurements traceable to national standards and taking instrument responses and
related uncertainties properly into account. The validation of calculations of ambient dose equivalent
for a particular calculation method may be taken as a validation of the calculation of effective dose by
the same computer code, but this step in the process might need to be confirmed. The alternative is to
establish, a priori, that the operational quantity ambient dose equivalent is a good estimator of effective
dose and equivalent dose to the foetus for the radiation fields being considered, in the same way that
the use of the operational quantity personal dose equivalent is justified for the estimation of effective
dose for ground-based radiation workers.
The radiation field in aircraft at altitude is complex, with many types of ionizing radiation present,
with energies ranging up to many GeV. The instrument response to particles and energies of the
atmospheric radiation field that are not covered by reference fields are carefully taken into account in
the evaluation of measurement results. While, in many cases, the methods used for the determination
of ambient dose equivalent in aircraft are similar to those used at high-energy accelerators in
research laboratories. Therefore, it is possible to recommend dosimetric methods and methods for
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the calibration of dosimetric devices, as well as the techniques for maintaining the traceability of
dosimetric measurements to national standards. Dosimetric measurements made to evaluate ambient
dose equivalent should be performed using accurate and reliable methods that ensure the quality of
readings provided to workers and regulatory authorities. The purpose of this document is to specify
procedures for the determination of the responses of instruments in different reference radiation
fields, as a basis for proper characterization of instruments used for the determination of ambient dose
equivalent in aircraft at altitude.
Requirements for the determination and recording of the cosmic radiation exposure of aircraft crew have
been introduced into the national legislation of EU member states and other countries. Harmonization
of methods used for determining ambient dose equivalent and for calibrating instruments is desirable
to ensure the compatibility of measurements performed with such instruments.
This document is intended for the use of primary and secondary calibration laboratories for ionizing
radiation, by radiation protection personnel employed by governmental agencies, and by industrial
corporations concerned with the determination of ambient dose equivalent for aircraft crew.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 20785-2:2020(E)
Dosimetry for exposures to cosmic radiation in civilian
aircraft —
Part 2:
Characterization of instrument response
1 Scope
This document specifies methods and procedures for characterizing the responses of devices used
for the determination of ambient dose equivalent for the evaluation of exposure to cosmic radiation in
civilian aircraft. The methods and procedures are intended to be understood as minimum requirements.
2 Normative references
The following five 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/IEC Guide 98-1, Uncertainty of measurement — Part 1: Introduction to the expression of uncertainty
in measurement
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1 General terms
3.1.1
angle of radiation incidence
α
angle between the direction of radiation incidence and the reference direction of the instrument
3.1.2
calibration
operation that, under specified conditions, establishes a relation between the conventional quantity,
H , and the indication, G
0
Note 1 to entry: A calibration can be expressed by a statement, calibration function, calibration diagram,
calibration curve or calibration table. In some cases, it can consist of an additive or multiplicative correction of
the indication with associated measurement uncertainty.
Note 2 to entry: It is important not to confuse calibration with adjustment of a measuring system, often
mistakenly called “self-calibration”, or with verification of calibration.
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3.1.3
calibration coefficient
N
coeff
quotient of the conventional quantity value to be measured and the corrected indication of the
instrument
Note 1 to entry: The calibration coefficient is equivalent to the calibration factor multiplied by the instrument
constant.
Note 2 to entry: The reciprocal of the calibration coefficient, N , is the response.
coeff
Note 3 to entry: For the calibration of some instruments, e.g. ionization chambers, the instrument constant and
the calibration factor are not identified separately but are applied together as the calibration coefficient.
Note 4 to entry: It is necessary, in order to avoid confusion, to state the quantity to be measured, for example:
the calibration coefficient with respect to fluence, N , the calibration coefficient with respect to kerma, N , the
Φ K
calibration coefficient with respect to absorbed dose, N .
D
3.1.4
calibration factor
N
fact
factor by which the product of the corrected indication and the associated instrument constant of the
instrument is multiplied to obtain the conventional quantity value to be measured under reference
conditions
Note 1 to entry: The calibration factor is dimensionless.
Note 2 to entry: The corrected indication is the indication of the instrument corrected for the effect of influence
quantities, where applicable.
Note 3 to entry: The value of the calibration factor can vary with the magnitude of the quantity to be measured.
In such cases, a detector assembly is said to have a non-constant response.
3.1.5
measured quantity value
measured value of a quantity
measured value
M
quantity value representing a measurement result
Note 1 to entry: For a measurement involving replicate indications, each indication can be used to provide a
corresponding measured quantity value. This set of measured quantity values can be used to calculate a
resulting measured quantity value, such as an average or a median value, usually with a decreased associated
measurement uncertainty.
Note 2 to entry: When the range of the true quantity values believed to represent the measurand is small
compared with the measurement uncertainty, a measured quantity value can be considered to be an estimate
of an essentially unique true quantity value and is often an average or a median of individual measured quantity
values obtained through replicate measurements.
Note 3 to entry: In the case where the range of the true quantity values believed to represent the measurand is
not small compared with the measurement uncertainty, a measured value is often an estimate of an average or a
median of the set of true quantity values.
Note 4 to entry: In ISO/IEC Guide 98-3:2008, the terms “result of measurement” and “estimate of the value of the
measurand” or just “estimate of the measurand” are used for “measured quantity value”.
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3.1.6
conventional quantity value
conventional value of a quantity
conventional value
H
0
quantity value attributed by agreement to a quantity for a given purpose
Note 1 to entry: The term “conventional true quantity value” is sometimes used for this concept, but its use is
discouraged.
Note 2 to entry: Sometimes, a conventional quantity value is an estimate of a true quantity value.
Note 3 to entry: A conventional quantity value is generally accepted as being associated with a suitably small
measurement uncertainty, which might be zero.
[8][9][10]
Note 4 to entry: In ISO 20785 series , the conventional quantity value is the best estimate of the value of
the quantity to be measured, determined by a primary or a secondary standard which is traceable to a primary
standard.
3.1.7
correction factor
k
factor applied to the indication (3.1.9) to correct for deviation of measurement conditions from reference
conditions
Note 1 to entry: If the correction of the effect of the deviation of an influence quantity requires a factor, the
influence quantity is of type F.
3.1.8
correction summand
G
S
summand applied to the indication (3.1.9) to correct for the zero indication or the deviation of the
measurement conditions from the reference conditions
Note 1 to entry: If the correction of the effect of the deviation of an influence quantity requires a summand, the
influence quantity is of type S.
3.1.9
indication
G
quantity value provided by a measuring instrument or a measuring system
Note 1 to entry: An indication can be presented in visual or acoustic form or can be transferred to another device.
An indication is often given by the position of a pointer on the display for analogue outputs, a displayed or printed
number for digital outputs, a code pattern for code outputs, or an assigned quantity value for material measures.
Note 2 to entry: An indication and a corresponding value of the quantity being measured are not necessarily
values of quantities of the same kind.
3.1.10
influence quantity
quantity that, in a direct measurement, does not affect the quantity that is actually measured, but
affects the relation between the indication (3.1.9) and the measurement result
Note 1 to entry: An indirect measurement involves a combination of direct measurements, each of which can be
affected by influence quantities.
Note 2 to entry: In ISO/IEC Guide 98-3:2008, the concept “influence quantity” is defined as
[11]
in ISO/IEC Guide 99:2007 , covering not only the quantities affecting the measuring system, as in the definition
above, but also those quantities that affect the quantities actually measured. Also, in ISO/IEC Guide 98-3, this
concept is not restricted to direct measurements.
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Note 3 to entry: The correction of the effect of the influence quantity can require a correction factor (for an
influence quantity of type F) and/or a correction summand (for an influence quantity of type S) to be applied to
the indication of the detector assembly, e.g. in the case of microphonic or electromagnetic disturbance.
EXAMPLE The indication given by an unsealed ionization chamber is influenced by the temperature
and pressure of the surrounding atmosphere. Although needed for determining the value of the dose, the
measurement of these two quantities is not the primary objective.
3.1.11
instrument constant
c
i
quantity value by which the indication (3.1.9) of the instrument, G (or, if corrections or normalization
were carried out, G ), is multiplied to give the value of the measurand or of a quantity to be used to
corr
calculate the value of the measurand
Note 1 to entry: If the instrument's indication is already expressed in the same units as the measurand, as is
the case with area dosemeters, for instance, the instrument constant, c , is dimensionless. In such cases, the
i
calibration factor and the calibration coefficient (3.1.3) can be the same. Otherwise, if the indication of the
instrument has to be converted to the same units as the measurand, the instrument constant has a dimension.
3.1.12
measurand
quantity intended to be measured
3.1.13
primary measurement standard
primary standard
measurement standard established using a primary reference measurement procedure or created as
an artefact, chosen by convention
Note 1 to entry: A primary standard has the highest metrological quality in a given field.
3.1.14
quantity value
number and reference together expressing the magnitude of a quantity
Note 1 to entry: A quantity value is either a product of a number and a measurement unit (the unit “one” is
generally not indicated for quantities of dimension “one”) or a number and a reference to a measurement
procedure.
3.1.15
reference conditions
conditions of use prescribed for testing the performance of a detector assembly or for comparing the
results of measurements
Note 1 to entry: The reference conditions represent the values of the set of influence quantities for which the
calibration result is valid without any correction.
Note 2 to entry: The value of the measurand can be chosen freely in agreement with the properties of the
detector assembly to be calibrated. The quantity to be measured is not an influence quantity but can influence
the calibration result and the response (see also Note 1 to entry).
3.1.16
response
response characteristic
R
quotient of the indication, G, or the corrected indication, G , and the conventional quantity value to be
corr
measured
Note 1 to entry: To avoid confusion, it is necessary to specify which of the quotients given in the definition of the
response (that for the indication, G or G ) is applied. Furthermore, it is necessary, in order to avoid confusion,
corr
to state the quantity to be measured, for example the response with respect to fluence, R , the response with
Φ
respect to kerma, R or the response with respect to absorbed dose, R .
K D
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Note 2 to entry: The reciprocal of the response under the specified conditions is equal to the calibration
coefficient, N .
coeff
Note 3 to entry: The value of the response can vary with the magnitude of the quantity to be measured. In such
cases, the detector assembly's response is said to be non-constant.
Note 4 to entry: The response usually varies with the energy and direction distribution of the incident radiation.
It is therefore useful to consider the response as a function, R(E,Ω), of the radiation energy, E, and the direction,

Ω , of the incident monodirectional radiation. R(E) describes the “energy dependence” and R(Ω) the “angle

dependence” of the response; for the latter, Ω may be expressed by the angle, α, between the reference direction
of the detector assembly and the direction of an external monodirectional field.
3.2 Terms related to quantities and units
[12]
Most of the definitions in this subclause have been adapted from ISO 80000-10:2019 and ICRU
[13] [14]
Reports 36 and 51 .
3.2.1
particle fluence
fluence
Φ
number, dN, at a given point in space, of particles incident on a small spherical domain, divided by the
cross-sectional area, da, of that domain:
dN
Φ=
da
Note 1 to entry: The unit of the fluence is m−2; a frequently used unit is cm−2.
Note 2 to entry: The energy distribution of the particle fluence, Φ , is the quotient, dΦ, by dE, where dΦ is the
E
fluence of particles of energy between E and E+dE. There is an analogous de
...

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