prEN ISO 20785-4

Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of codes (ISO/FDIS 20785-4:2026)

This document is intended for the validation of codes used for the calculation of doses received by individuals on board aircraft. It gives guidance to radiation protection authorities and code developers on the basic functional requirements which the code fulfils.
Depending on any formal approval by a radiation protection authority, additional requirements concerning the software testing can apply.

Dosimetrie zu Expositionen durch kosmische Strahlung in Zivilluftfahrzeugen - Teil 4: Validierung von Codes (ISO/FDIS 20785-4:2026)

Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil - Partie 4: Validation des codes (ISO/FDIS 20785-4:2026)

Le présent document est destiné à la validation des codes utilisés pour calculer les doses reçues par les individus à bord des avions. Il fournit aux autorités de radioprotection et aux développeurs de codes, des recommandations concernant les exigences fonctionnelles de base auxquelles le code doit se conformer.
Suivant l'approbation formelle par une autorité de radioprotection, d'autres exigences concernant les essais logiciels peuvent s'appliquer.

Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem prometu - 4. del: Kode za preverjanje veljavnosti (ISO/FDIS 20785-4:2026)

Ta dokument je namenjen validaciji kod, ki se uporabljajo za izračun doz, ki jih prejmejo posamezniki na letalu. Ponuja smernice organom za varstvo pred sevanji in razvijalcem kod glede osnovnih funkcionalnih zahtev, ki jih koda izpolnjuje.
Glede na morebitno formalno odobritev s strani organa za varstvo pred sevanji se lahko uporabljajo dodatne zahteve v zvezi s testiranjem programske opreme.

General Information

• Status: Not Published
• Publication Date: 05-Dec-2027
• 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: 4020 - Submission to enquiry - Enquiry
• Start Date: 14-May-2026
• Completion Date: 14-May-2026
• Ref Project: oSIST prEN ISO 20785-4:2026 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of codes (ISO/FDIS 20785-4:2026)

Relations

• Consolidated By: ISO/FDIS 20785-4 - Dosimetry for exposures to cosmic radiation in civilian aircraft — Part 4: Validation of codes
• Effective Date: 12-Feb-2026
• Revises: EN ISO 20785-4:2021 - Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of codes (ISO 20785-4:2019)
• Effective Date: 21-May-2025

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2026
Dozimetrija za merjenje izpostavljenosti kozmičnemu sevanju v civilnem letalskem
prometu - 4. del: Kode za preverjanje veljavnosti (ISO/FDIS 20785-4:2026)
Dosimetry for exposures to cosmic radiation in civilian aircraft - Part 4: Validation of
codes (ISO/FDIS 20785-4:2026)
Dosimetrie zu Expositionen durch kosmische Strahlung in Zivilluftfahrzeugen - Teil 4:
Validierung von Codes (ISO/FDIS 20785-4:2026)
Dosimétrie pour l'exposition au rayonnement cosmique à bord d'un avion civil - Partie 4:
Validation des codes (ISO/FDIS 20785-4:2026)
Ta slovenski standard je istoveten z: prEN ISO 20785-4
ICS:
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

FINAL DRAFT
International
Standard
ISO/FDIS 20785-4
ISO/TC 85/SC 2
Dosimetry for exposures to cosmic
Secretariat: AFNOR
radiation in civilian aircraft —
Voting begins on:
2026-05-13
Part 4:
Validation of codes
Voting terminates on:
2026-08-05
Dosimétrie pour l'exposition au rayonnement cosmique à bord
d'un avion civil —
Partie 4: Validation des codes
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
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING 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.
Reference number
ISO/FDIS 20785-4:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 20785-4:2026(en)
International
Standard
ISO/FDIS 20785-4
ISO/TC 85/SC 2
Dosimetry for exposures to cosmic
Secretariat: AFNOR
radiation in civilian aircraft —
Voting begins on:
Part 4:
Validation of codes
Voting terminates on:
Dosimétrie pour l'exposition au rayonnement cosmique à bord
d'un avion civil —
Partie 4: Validation des codes
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.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 20785-4:2026(en) © ISO 2026

ii
ISO/FDIS 20785-4:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Quantities and units .2
3.2 Atmospheric radiation field .4
3.3 Software terms.5
4 General considerations . 5
5 Functionality . 5
5.1 General .5
5.2 Measured data .5
5.3 ICRU reference data.6
5.4 Code validation using measurements or reference data.6
5.5 Considerations for the routine dose assessment .6
Bibliography . 7

iii
ISO/FDIS 20785-4:2026(en)
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 document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies, and
radiological protection, Subcommittee SC 2, Radiological protection, in collaboration with the European
Committee for Standardization (CEN) Technical Committee CEN/TC 430, Nuclear energy, nuclear technologies,
and radiological protection, in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 20785-4:2019), of which it constitutes a minor
revision.
The main change is the revision of terms and definitions.
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/FDIS 20785-4:2026(en)
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 recommendations
[1]
of the International Commission on Radiological Protection (ICRP) in Publication 60 , the European Union
[2]
(EU) introduced a Basic Safety Standards Directive (BSS) which included exposure to natural sources of
ionizing radiation, including cosmic radiation, as occupational exposure for aircrew. International guidance
[3]
was also provided by the IAEA Safety Standards Series . This action was confirmed by ICRP Publications
[4] [5] [6]
103 and 132 , and the BSS was revised by EU.
[1] [4]
ICRP has defined the exposure to cosmic radiation as an existing exposure situation, because the source
exists before protection decisions can be made. In addition, exposure of aircraft crew to cosmic radiation is
[5]
occupational, and thus employers have a role to play in protection, even if options are limited in this case .
There is no contradiction in this, as occupational exposures can occur in existing exposure situations, and
this does not imply that protection measure cannot be planned.
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 organising working schedules with a view to reducing
the doses of highly exposed crew;
c) to inform workers concerned with the health effects involved in their work;
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 should be incorporated into laws and regulations of EU Member States and would
be included in the aviation safety standards and procedures of the European Air Safety Agency. Other
[7] [8]
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 dose to the fetus
and effective dose . The cosmic radiation exposure of the body is essentially uniform and the maternal
abdomen provides no effective shielding to the fetus. As a result, the magnitude of equivalent dose to the
fetus 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 thus not needed nor practical, The preferred approach for the
assessment of doses of aircraft crew, where necessary, is to calculate directly the 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
[9] [5] [10]
guidance from the ICRP in Publication 75 and Publication 132 , 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. Effective dose is not directly measurable.
The operational quantity of interest is ambient dose equivalent, H*(10). Indeed, as indicated in particular
in ICRU Report 84, the ambient dose equivalent is considered to be a conservative estimator of effective
dose if isotropic irradiation can be assumed. The operational quantity ambient dose equivalent is a good
estimator of effective dose and equivalent dose to the fetus 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. 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 the results can be compared to 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 code. The alternative is to establish, a priori, that
the operational quantity ambient dose equivalent is a good estimator of effective dose and equivalent dose

v
ISO/FDIS 20785-4:2026(en)
to the fetus 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.
The route dose is the best estimate of ambient dose equivalent for the actual route recorded for the aircrew.
However, the actual route flown for that specific flight may vary due to weather, scheduling, etc.
It should be noted that this document addresses galactic cosmic radiation (GCR) only. First discovered by
Victor Hess more than 100 years ago, GCR is a well understood and permanent source of ionizing radiation
both on Earth and in flight. GCR can be modelled with reasonable precision and accuracy. It should be
recognized that there are other sources of radiation that are intermittent. These sources cannot currently
be modelled prior to their occurrence, and are not a subject of this document. These sources include solar
proton events (often called solar particle events), solar neutron events, solar gamma events, solar magnetic
storms that alter the magnetic shielding and terrestrial gamma flashes which are associated with some
lightning. Exposures can also occur from shipments of radioactive material and also from any medical
procedures required as a condition of employment for aircrew. These intermittent sources can produce
radiation exposures that exceed limits for both aircrew and members of the public.
In order to adequately address the total radiation exposure for occupational workers and for members of the
public who fly, radiation exposure to intermittent sources needs to be addressed after an event occurs with
either radiation monitoring or with modelling.

vi
FINAL DRAFT International
...