Dosimetry for exposures to cosmic radiation in civilian aircraft

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

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 ŕ bord d'un avion. Les méthodes et les modes opératoires doivent ętre considérés comme des exigences minimales.

General Information

Status
Published
Publication Date
12-Jul-2020
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
30-May-2020
Completion Date
29-May-2020
Ref Project

RELATIONS

Buy Standard

Standard
ISO 20785-2:2020 - Dosimetry for exposures to cosmic radiation in civilian aircraft
English language
36 pages
sale 15% off
Preview
sale 15% off
Preview
Standard
ISO 20785-2:2020 - Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil
French language
37 pages
sale 15% off
Preview
sale 15% off
Preview
Draft
ISO/FDIS 20785-2 - Dosimetry for exposures to cosmic radiation in civilian aircraft
English language
36 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

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
CP 401 • Ch. de Blandonnet 8
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
---------------------- Page: 2 ----------------------
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

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
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
---------------------- Page: 4 ----------------------
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

© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
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.

vi © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
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

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

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.
© ISO 2020 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 20785-2:2020(E)
3.1.3
calibration coefficient
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 .
3.1.4
calibration factor
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
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”.

2 © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 20785-2:2020(E)
3.1.6
conventional quantity value
conventional value of a quantity
conventional value
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

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

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
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.
© ISO 2020 – All rights reserved 3
---------------------- Page: 9 ----------------------
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

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

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

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

respect to kerma, R or the response with respect to absorbed dose, R .
K D
4 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
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

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:
−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

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

(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
rate of the particle fluence (3.2.1) expressed as
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
---------------------- Page: 1 ----------------------
ISO 20785-2:2020(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020

Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette

publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,

y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: +41 22 749 01 11
E-mail: copyright@iso.org
Web: www.iso.org
Publié en Suisse
ii © ISO 2020 – Tous droits réservés
---------------------- Page: 2 ----------------------
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

© ISO 2020 – Tous droits réservés iii
---------------------- Page: 3 ----------------------
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
---------------------- Page: 4 ----------------------
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
---------------------- Page: 5 ----------------------
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.
vi © ISO 2020 – Tous droits réservés
---------------------- Page: 6 ----------------------
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

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 ,

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
---------------------- Page: 7 ----------------------
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
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

kerma, N , ou le coefficient d’étalonnage en ce qui concerne la dose absorbée, N .

K D
3.1.4
facteur d’étalonnage
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
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
---------------------- Page: 8 ----------------------
ISO 20785-2:2020(F)
3.1.6
valeur conventionnelle
valeur conventionnelle d’une grandeur
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

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

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
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
---------------------- Page: 9 ----------------------
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

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

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
---------------------- Page: 10 ----------------------
ISO 20785-2:2020(F)
3.1.16
réponse
caractéristique de la réponse

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

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
---------------------- Page: 1 ----------------------
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
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
---------------------- Page: 3 ----------------------
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.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
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

© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/FDIS 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.

vi © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
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

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

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.
© ISO 2020 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/FDIS 20785-2:2020(E)
3.1.3
calibration coefficient
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 .
3.1.4
calibration factor
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
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”.

2 © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/FDIS 20785-2:2020(E)
3.1.6
conventional quantity value
conventional value of a quantity
conventional value
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

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

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
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.
© ISO 2020 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/FDIS 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

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

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

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

respect to kerma, R or the response with respect to absorbed dose, R .
K D
4 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/FDIS 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

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:
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

fluence of particles of energy between E and E+dE. There is an analogous de
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.