prEN ISO 20785-3

Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 3: Measurements at aviation altitudes (ISO/DIS 20785-3:2022)

The following documents, in whole or in part, are normatively referenced in ISO 20785-3:2015 and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
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 measurement (GUM:1995)
ISO 20785‑1, Dosimetry for exposures to cosmic radiation in civilian aircraft ? Part 1: Conceptual basis for measurements
ISO 20785‑2, Dosimetry for exposures to cosmic radiation in civilian aircraft ? Part 2: Characterization of instrument response

Dosimetrie zu Expositionen durch kosmische Strahlung in Zivilluftfahrzeugen - Teil 3: Messungen auf Flughöhen (ISO/DIS 20785-3:2022)

Dieser Teil von ISO 20785 dient als Grundlage für die Messung der Umgebungs-Äquivalentdosis in Flughöhen zur Bestimmung der Expositionen gegenüber kosmischer Strahlung in zivilen Luftfahrzeugen.

Dosimétrie pour les expositions au rayonnement cosmique à bord d'un avion civil - Partie 3: Mesurages à bord d'avions (ISO/DIS 20785-3:2022)

L'ISO 20785-3:2015 donne les principes de base permettant de mesurer l'équivalent de dose ambiant aux altitudes de vol pour l'évaluation de l'exposition au rayonnement cosmique à bord d'un avion.

Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem prometu - 3. del: Meritve na višini letenja (ISO/DIS 20785-3:2022)

General Information

• Status: Not Published
• Publication Date: 17-Mar-2024
• ICS: 13.280 - Radiation protection
• ICS: 17.240 - Radiation measurements
• ICS: 49.020 - Aircraft and space vehicles in general
• Technical Committee: CEN/TC 430 - Nuclear energy, nuclear technologies, and radiological protection
• Drafting Committee: CEN/TC 430 - Nuclear energy, nuclear technologies, and radiological protection
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 13-Jan-2023
• Completion Date: 13-Jan-2023
• Ref Project: oSIST prEN ISO 20785-3:2022 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 3: Measurements at aviation altitudes (ISO/DIS 20785-3:2022)

Relations

• Revises: EN ISO 20785-3:2017 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 3: Measurements at aviation altitudes (ISO 20785-3:2015)
• Effective Date: 19-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 20785-3:2022
01-april-2022
Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem
prometu - 3. del: Meritve na višini letenja (ISO/DIS 20785-3:2022)

Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 3: Measurements at

aviation altitudes (ISO/DIS 20785-3:2022)

Dosimetrie zu Expositionen durch kosmische Strahlung in Zivilluftfahrzeugen - Teil 3:

Messungen auf Flughöhen (ISO/DIS 20785-3:2022)

Dosimétrie pour les expositions au rayonnement cosmique à bord d'un avion civil - Partie

3: Mesurages à bord d'avions (ISO/DIS 20785-3:2022)
Ta slovenski standard je istoveten z: prEN ISO 20785-3
ICS:
17.240 Merjenje sevanja Radiation measurements
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
oSIST prEN ISO 20785-3:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 20785-3:2022
DRAFT INTERNATIONAL STANDARD
ISO/DIS 20785-3
ISO/TC 85/SC 2 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2022-01-28 2022-04-22
Dosimetry for exposures to cosmic radiation in civilian
aircraft —
Part 3:
Measurements at aviation altitudes

Dosimétrie pour les expositions au rayonnement cosmique à bord d'un avion civil —

Partie 3: Mesurages à bord d'avions
ICS: 49.020; 13.280; 17.240
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
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STANDARDS MAY ON OCCASION HAVE TO
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WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 20785-3:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
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RIGHTS OF WHICH THEY ARE AWARE AND TO
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© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

3.1 Quantities and units .......................................................................................................................................................................... 1

3.2 Atmospheric radiation field ........................................................................................................................................................ 4

4 General considerations .................................................................................................................................................................................6

4.1 General description of the cosmic radiation field in the atmosphere ................................................... 6

4.2 General considerations concerning the measurements .................................................................................... 8

4.2.1 General ........................................................................................................................................................................................ 8

4.2.2 Selection of appropriate instruments ............................................................................................................. 8

4.2.3 Characterization of the responses of the instruments .................................................................... 8

4.2.4 Measurements inside an aircraft ......................................................................................................................... 8

4.2.5 Application of appropriate correction factors ......................................................................................... 9

4.3 Safety and regulatory requirements for in-flight measurements ............................................................ 9

5 Measurement at aviation altitude .....................................................................................................................................................9

5.1 Parameters determining the dose rate ............................................................................................................................. 9

5.1.1 Barometric altitude ......................................................................................................................................................... 9

5.1.2 Geographic coordinates ............................................................................................................................................... 9

5.1.3 Solar activity ....................................................................................................................................................................... 10

5.2 Possible influence quantities .................................................................................................................................................. 10

5.2.1 General ..................................................................................................................................................................................... 10

5.2.2 Cabin air pressure .......................................................................................................................................................... 10

5.2.3 Cabin air temperature ................................................................................................................................................ 10

5.2.4 Cabin air humidity ......................................................................................................................................................... 10

5.3 Specific considerations for active instruments ...................................................................................................... 10

5.3.1 Power supply ....................................................................................................................................................................... 10

5.3.2 Vibrations and shocks ................................................................................................................................................. 11

5.3.3 Electromagnetic interferences from the aircraft ............................................................................... 11

5.4 Specific considerations for passive measurements ............................................................................................ 11

5.4.1 Security X-ray scanning ............................................................................................................................................ 11

5.4.2 Background subtraction ........................................................................................................................................... 11

6 Uncertainties ........................................................................................................................................................................................................11

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 ................................................................................................12

Bibliography .............................................................................................................................................................................................................................16

iii
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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 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 technology,

and radiological protection, Subcommittee SC 2, Radiological protection.

This second edition cancels and replaces the first edition (ISO 20785-3:2015), which has been

technically revised.
The main changes compared to the previous edition are as follows:
A list of all parts in the ISO 20785 series can be found on the ISO website.
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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]

Directive which included exposure to natural sources of ionizing radiation, including cosmic

radiation, as occupational exposure. The 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: (i) to assess the exposure of the crew concerned; (ii) to take into account the assessed

exposure when organizing working schedules with a view to reducing the doses of highly exposed

crew; (iii) to inform the workers concerned of the health risks their work involves; and (iv) 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 to be incorporated into laws and regulations

of EU Member States and has to be included in the aviation safety standards and procedures of the

Joint Aviation Authorities and the European Air Safety Agency. Other countries such as Canada and

Japan have issued advisories to their airline industries to manage aircraft crew exposure. ICRP has

recommended a graded approach for radiological protection of flyers by setting three groups: aircraft

crews, frequent flyers, and occasional flyers and encourages frequent flyers to perform self-assessment

of their doses from cosmic radiation so that they could consider adjustment of their flight frequency as

[4]
necessary .

For regulatory and legislative purposes, the radiation protection quantities of interest are equivalent

dose (to the foetus) and 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 dosemeters for routine use are not considered necessary.

The preferred approach for the assessment of doses of aircraft crew, where necessary, is to calculate

directly effective dose rate, as a function of geographic location, altitude and solar cycle phase, and

to fold these values with flight and staff roster information to obtain estimates of effective doses for

individuals. This approach is supported by guidance from the European Commission, the ICRP in

[5] [6]
Publication 75 and the ICRU in Report 84 .

The role of calculations in this procedure is unique in routine radiation protection and it is widely

accepted that the calculated doses should be validated by measurement. As effective dose is not directly

measurable, the operational quantity of interest is ambient dose equivalent, H*(10). Although the new

[7]

recommendations on operational quantities have recently been published by ICRU , there would be

a delay before being introduced into future ISO and IEC standards. As indicated in particular in ICRU

Report 84, the ambient dose equivalent is considered to be a conservative estimator of effective dose

if isotropic or superior isotropic irradiation can be assumed. 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. 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 may 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 radiation workers. Ambient dose equivalent rate as a function of geographic location, altitude

and solar cycle phase is then calculated and folded with flight and staff roster information.

The radiation field in aircraft at altitude is complex, with many types of ionizing radiation present, with

energies ranging up to many GeV. The determination of ambient dose equivalent for such a complex

radiation field is difficult. 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 the calibration of dosimetric

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devices, as well as the techniques for maintaining the traceability of dosimetric measurements to

national standards. Dosimetric measurements made to evaluate ambient dose equivalent have to be

performed using accurate and reliable methods that ensure the quality of readings provided to workers

and regulatory authorities. This part of ISO 20785 gives procedures for the characterization of the

response of instruments for the determination of ambient dose equivalent in aircraft.

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 part of ISO 20785 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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oSIST prEN ISO 20785-3:2022
DRAFT INTERNATIONAL STANDARD ISO/DIS 20785-3:2022(E)
Dosimetry for exposures to cosmic radiation in civilian
aircraft —
Part 3:
Measurements at aviation altitudes
1 Scope

This part of ISO 20785 gives the basis for the measurement of ambient dose equivalent at flight altitudes

for the evaluation of the exposures to cosmic radiation in civilian aircraft.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/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)

ISO/IEC 80000-10:2019, Quantities and units — Part 10: Atomic and nuclear physics

ISO 20785-1, Dosimetry for exposures to cosmic radiation in civilian aircraft — Part 1: Conceptual basis for

measurements

ISO 20785-2, Dosimetry for exposures to cosmic radiation in civilian aircraft — Part 2: Characterization of

instrument response
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 https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Quantities and units
3.1.1
particle fluence
fluence

differential quotient of N with respect to a, where N is the number of particles incident on a sphere of

cross-sectional area a:
Φ =
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-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 where

E,Ω

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 the energy E = E is written as Φ (E ). If no

0 E 0
special values are indicated, the brackets may be omitted.
3.1.2
particle fluence rate
fluence rate
dΦ dN
Φ ==
dt da⋅dt

where dΦ is the mean increment of the particle fluence during an infinitesimal time interval with

duration dt
-2 −1 -2 −1

Note 1 to entry: The unit of the fluence rate is m s , a frequently used unit is cm s .

3.1.3
linear energy transfer (LET)

quotient of the mean energy dE lost by the charged particles due to electronic interactions in traversing

a distance, dl, minus the mean sum of the kinetic energies in excess of Δ, of all the electrons released by

the charged particles and dl :
L =

L (i.e. with ∆ = ∞) is termed the unrestricted linear energy transfer in defining the quality factor.

L is also known as the restricted linear collision stopping power.
−1 −1

Note 1 to entry: The unit of the linear energy transfer is J m , a frequently used unit is keV μm .

3.1.4
dose equivalent

product of the absorbed dose D to tissue at the point of interest and the quality factor Q at that point:

HD= Q

Note 1 to entry: Q is determined by the unrestricted linear energy transfer, L (often denoted as L or LET), of

charged particles passing through a small volume element (domains) at this point (the value of L is given for

charged particles in water, not in tissue; the difference, however, is small). The dose equivalent at a point in tissue

is then given by:
HQ= ()LD dL
L=0
where D = dD/dL is the distribution of D in L at the point of interest.
Note 2 to entry: The relationship of Q and L is given in Reference [2].
Note 3 to entry: The unit of dose equivalent is J kg , called sievert (Sv).
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3.1.5
ambient dose equivalent
H*(10)

dose equivalent at a point in a radiation field, that would be produced by the corresponding expanded

and aligned field, in the ICRU sphere at 10 mm depth on the radius opposing the direction of the aligned

field

Note 1 to entry: The unit of ambient dose equivalent is J kg , called sievert (Sv).

3.1.6
particle fluence-to-ambient dose equivalent conversion coefficient
h(10)*

quotient of the particle ambient dose equivalent, H*(10), and the particle fluence, Φ

H ()10
h()10 =
2 −1

Note 1 to entry: The unit of the particle fluence-to-ambient dose equivalent conversion coefficient is J m kg

2 2
with the special name Sv m , a frequently used unit is pSv cm .
3.1.7
correction factor

factor applied to the indication to correct for deviation of the measurement conditions from reference

conditions
3.1.8
atmosphere depth
mass of a unit-area column of air above a point in the atmosphere
–2 –2

Note 1 to entry: The unit of atmosphere depth is kg m ; a frequently used unit is g cm .

3.1.9
standard barometric altitude
pressure altitude

altitude determined by a barometric altimeter calibrated with reference to the International Standard

Atmosphere (ISA) (ISO, 1975) when the altimeter's datum is set to 1 013,25 hPa

Note 1 to entry: The flight level is sometimes given as FL 350, where the number represents multiples of 100 feet

of pressure altitude, based on the ISA and a datum setting of 1 013,25 hPa. However, in some countries flight

levels are expressed in meters, in which case appropriate conversions should be made before applying the data

given in this part of ISO 20785.
3.1.10
magnetic rigidity
momentum per charge (of a particle in a magnetic field), given by:

where p is the particle momentum, Z the number of charges of the particle and e the charge of the proton

Note 1 to entry: The base unit of magnetic rigidity is the tesla metre (T m) (= V m s). A frequently used unit is V

(or GV) in a system of units where the values of the speed of light, c, and the charge on the proton, e, are both 1,

and the magnetic rigidity is given by pc/Ze.

Note 2 to entry: Magnetic rigidity characterizes charged-particle trajectories in magnetic fields. All particles

having the same magnetic rigidity have identical trajectories in a magnetic field, independent of particle mass or

charge.
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3.1.11
geomagnetic cut-off rigidity
cut-off rigidity

minimum magnetic rigidity an incident particle can have and still penetrate the geomagnetic field to

reach a given location above the Earth

Note 1 to entry: Geomagnetic cut-off rigidity depends on angle of incidence. Often, vertical incidence to the

Earth’s surface is assumed, in which case, the vertical geomagnetic cut-off rigidity is the minimum magnetic

rigidity a vertically incident particle can have and still reach a given location above the Earth.

3.1.12
vertical geomagnetic cut-off rigidity
vertical cut-off
cut-off

minimum magnetic rigidity a vertically incident particle can have and still reach a given location above

the Earth
3.1.13
deceleration potential

cosmic ray modulation parameter deduced from space observations of the abundance variation of the

different species in function of the solar cycle epoch

Note 1 to entry: The deceleration potential could be deduced either from the sunspot index or from Climax

neutron monitor output, using simple linear formula depending upon the phase of the solar cycle.

3.2 Atmospheric radiation field
3.2.1
cosmic radiation
cosmic rays
cosmic particles

ionizing radiation consisting of high-energy particles, primarily completely ionized atoms, of

extra-terrestrial origin and the particles they generate by interaction with the atmosphere and other

matter
3.2.2
primary cosmic radiation
primary cosmic rays
cosmic radiation incident from space at the Earth’s orbit
3.2.3
secondary cosmic radiation
secondary cosmic rays
cosmogenic particles

particles which are created directly or in a cascade of reactions by primary cosmic rays interacting

with the atmosphere or other matter

Note 1 to entry: Important particles with respect to radiation protection and radiation measurements in aircraft

are: neutrons, protons, photons, electrons, positrons, muons, and to a lesser extent, pions and nuclear ions

heavier than protons.
3.2.4
galactic cosmic radiation
galactic cosmic rays
GCR
cosmic radiation originating outside the solar system
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3.2.5
solar cosmic radiation
solar cosmic rays
solar particles
cosmic radiation originating from the sun
3.2.6
solar particle event
SPE

large fluence rate of energetic solar particles ejected into space by a solar eruption

Note 1 to entry: Solar particle events are directional.
3.2.7
ground level enhancement
GLE

sudden increase of cosmic radiation observed on the ground by at least two neutron monitoring

stations recording simultaneously a greater than 3 % increase in the five-minute-averaged count rate

associated with solar energetic particles

Note 1 to entry: A GLE is associated with a solar-particle event having a high fluence rate of particles with high

energy (greater than 500 MeV).

Note 2 to entry: GLEs are relatively rare, occurring on average about once per year.

3.2.8
solar modulation

change of the GCR field (outside the Earth's magnetosphere) caused by change of solar activity and

consequent change of the magnetic field of the heliosphere
3.2.9
solar cycle

period during which the solar activity varies with successive maxima separated by an average interval

of about 11 years

Note 1 to entry: If the reversal of the Sun’s magnetic field polarity in successive 11 year periods is taken into

account, the complete solar cycle may be considered to average some 22 years, the Hale cycle.

Note 2 to entry: The sunspot cycle as measured by the relative sunspot nu
...