ISO 24427
(Main)Radiological protection — Medical proton accelerators — Requirements and recommendations for shielding design and evaluation
Radiological protection — Medical proton accelerators — Requirements and recommendations for shielding design and evaluation
This International Standard is applicable to radiation shielding design and evaluation work for medical proton accelerators with nominal energies of the beam ranging from 70 MeV to 250 MeV, with subsystem such as beamlines, energy selection system (for cyclotron) and nozzle components. The radiation protection requirements and recommendations given in this international standard cover the aspects relating to regulations, shielding design goals and other design criteria, role of the manufacturers, of the radiation protection officer or qualified expert and interactions between stakeholders, source terms and radiations around a proton accelerator, shielding for accelerators and its subsystems (including shielding materials and transmission values, calculations for various room configurations, duct impact on radiation protection), the radiological monitoring (measurements) and area control.
Radioprotection — Accélérateurs médicaux de protons — Exigences et recommendations pour la conception et l'évaluation du blindage
General Information
Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/FDIS 24427
ISO/TC 85/SC 2
Radiological protection —
Secretariat: AFNOR
Medical proton accelerators
Voting begins on:
— Requirements and
2025-06-25
recommendations for shielding
Voting terminates on:
design and evaluation
2025-08-20
Radioprotection — Accélérateurs médicaux de protons —
Exigences et recommendations pour la conception et l'évaluation
du blindage
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
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 24427:2025(en) © ISO 2025
FINAL DRAFT
ISO/FDIS 24427:2025(en)
International
Standard
ISO/FDIS 24427
ISO/TC 85/SC 2
Radiological protection —
Secretariat: AFNOR
Medical proton accelerators
Voting begins on:
— Requirements and
recommendations for shielding
Voting terminates on:
design and evaluation
Radioprotection — Accélérateurs médicaux de protons —
Exigences et recommendations pour la conception et l'évaluation
du blindage
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 2025
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
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 24427:2025(en) © ISO 2025
ii
ISO/FDIS 24427:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Quantities .2
3.2 Definitions other than quantities .4
4 Shielding design goals and other design criteria . 6
4.1 Shielding design goals .6
4.2 Shielding design assumptions and conditions .7
5 Role of stakeholders and the interactions . 7
5.1 General .7
5.2 Manufacturer of the proton therapy system .8
5.3 General contractor/architectural firm .8
5.4 Radiation safety officer or other .9
5.5 The medical physicist or other .9
5.6 The licensee or other .10
6 Radiation sources of a medical proton accelerator . 10
6.1 General .10
6.2 Prompt radiation sources .10
6.2.1 Secondary neutron .10
6.2.2 Photon radiation .10
6.3 Radiation during shut down .10
7 Shielding materials and transmission . .11
7.1 General .11
7.2 Shielding materials .11
7.3 Transmission .11
8 General formalism .12
9 Shielding calculation . 14
9.1 General .14
9.2 Monte-Carlo simulation .14
9.2.1 General .14
9.2.2 Basic requirement on Monte-Carlo simulation . 15
9.3 Analytical methods . 15
9.3.1 Shielding barrier. 15
9.3.2 Mazes .16
9.3.3 Skyshine .16
9.3.4 Duct .16
10 Shielding evaluation. 17
10.1 General .17
10.2 Measuring equipment and methodology .17
10.3 Evaluation .17
Annex A (informative) Monte-Carlo simulation for the radiation shielding of medical proton
accelerators . 19
Annex B (informative) Analytical methods for the radiation shielding of medical proton
accelerators .22
Annex C (informative) Examples of radiation shielding calculation .31
Annex D (informative) Special topics .44
iii
ISO/FDIS 24427:2025(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 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).
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 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, Radiological protection.
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 f
...
Style Definition
ISO/FDIS 24427:2025(en)
...
Formatted: Font: Bold, French (France)
ISO /TC 85/SC 2/WG 23
Formatted: zzCover large
Secretariat: AFNOR Formatted: Left: 1.5 cm, Right: 1.5 cm, Section start:
New page, Header distance from edge: 1.27 cm, Footer
Date: 2025-05-20xx distance from edge: 1.27 cm
Formatted: French (France)
Formatted
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Formatted: Cover Title_A1
Radiological protection — Medical proton accelerators —
Requirements and recommendations for shielding design and
evaluation
Radioprotection — Accélérateurs médicaux de protons — Exigences et recommendations pour la conception et
l'évaluation du blindage
FDIS stage
Formatted: Left
ISO/FDIS 24427:2025(en)
Formatted: HeaderCentered
Formatted: Font: Bold
© ISO 2025, Published in Switzerland
Commented [eXtyles1]: The reference "ISO 2025" is to a
withdrawn standard
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
Formatted: Adjust space between Latin and Asian text,
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
Adjust space between Asian text and numbers
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
Formatted: Default Paragraph Font
at the address below or ISO’s member body in the country of the requester.
Formatted: Default Paragraph Font
ISO copyright office
CP 401 • Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel.Phone: + 41 22 749 01 11
Formatted: French (France)
Fax + 41 22 749 09 47
E-mail: copyright@iso.org
Formatted: zzCopyright address, Adjust space between
Website: www.iso.org
Latin and Asian text, Adjust space between Asian text
and numbers
Published in Switzerlandwww.iso.org
Formatted: French (France)
Formatted: Font: 11 pt
Formatted: FooterPageRomanNumber, Space Before:
0 pt, Line spacing: single, Tab stops: Not at 17.2 cm
ii © ISO 2024 2025 – All rights reserved
ii
ISO/FDIS 24427:2025(en)
Formatted: Font: Bold
Formatted: HeaderCentered
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Quantities . 2
3.2 Definitions other than quantities . 5
4 Shielding design goals and other design criteria . 7
4.1 Shielding design goals . 7
4.2 Shielding design assumptions and conditions . 8
5 Role of stakeholders and the interactions . 8
5.1 General . 8
5.2 Manufacturer of the proton therapy system . 9
5.3 General contractor/architectural firm . 9
5.4 Radiation safety officer or other . 10
5.5 The medical physicist or other . 10
5.6 The licensee or other . 11
6 Radiation sources of a medical proton accelerator . 11
6.1 General . 11
6.2 Prompt radiation sources . 11
6.3 Radiation during shut down . 12
7 Shielding materials and transmission . 12
7.1 General . 12
7.2 Shielding materials . 12
7.3 Transmission . 12
8 General formalism . 13
9 Shielding calculation . 15
9.1 General . 15
9.2 Monte-Carlo simulation . 16
9.3 Analytical methods . 17
10 Shielding evaluation . 18
10.1 General . 18
10.2 Measuring equipment and methodology . 19
10.3 Evaluation . 19
Annex A (informative) Monte-Carlo simulation for the radiation shielding of medical proton
accelerators . 21
Annex B (informative) Analytical methods for the radiation shielding of medical proton
accelerators . 25
Annex C (informative) Examples of radiation shielding calculation . 34
Formatted: Font: 10 pt
Annex D (informative) Special topics . 48
Formatted: FooterCentered, Left, Space Before: 0 pt,
Bibliography . 53
Tab stops: Not at 17.2 cm
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After: 0 pt, Tab stops: Not at 17.2 cm
iii
ISO/FDIS 24427:2025(en)
Formatted: HeaderCentered
Formatted: Font: Bold
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).www.iso.org/directives).
Commented [eXtyles2]: The URL
https://www.iso.org/directives has been redirected to
http://www.iso.org/directives-and-policies.html. Please verify
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
the URL.
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.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
Commented [eXtyles3]: The URL
https://www.iso.org/patents has been redirected to
patent rights.
http://www.iso.org/iso-standards-and-patents.html. Please
verify the URL.
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.www.iso.org/iso/foreword.html.
Commented [eXtyles4]: The URL
https://www.iso.org/iso/foreword.html has been redirected to
http://www.iso.org/foreword-supplementary-
This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies, and
information.html. Please verify the URL.
radiological protection, Subcommittee SC 2, Radiological protection.
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.www.iso.org/members.html.
Commented [eXtyles5]: The URL
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Formatted: Font: 11 pt
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iv © ISO 2024 2025 – All rights reserved
iv
ISO/FDIS 24427:2025(en)
Formatted: Font: Bold
Formatted: HeaderCentered
Introduction
Protons deliver most of their energy at a prescribed, programmable distance inside the body, known as the
Bragg Peak. With this feature, proton therapy is used to treat many cancers and is particularly appropriate in
situations where treatment options are limited and conventional radiotherapy using photon beam presents
unacceptable risks to patients. The use of proton accelerators to administer external beam radiation has been
evolving and the proton therapy centres are rising worldwide.
A typical large proton therapy centre consists of an injector, a cyclotron or synchrotron to accelerate the
particles, high-energy beam selection and transport system, several treatment rooms (fixed beam and/or
gantry) and, occasionally, a research room. Strong secondary radiation, particularly high energy neutrons, is
produced at locations where beam losses occur. Such losses may occur in the cyclotron or synchrotron along
the beam transport system during acceleration, extraction, energy degradation and transport of the protons
to the treatment room, and in the treatment and research nozzles. In addition, the production of proton beam
interactions in the patient, beam stop, or dosimetry phantom also results in stray radiation production. As a
result, meters-thick barriers are generally used around the entire accelerator system. The radiation shielding
of proton therapy centre is quite complex and become one of the key elements to commission a proton therapy
centre, in the perspective of both capital and time consumed.
IEC 60601-2-64 relates to the design and the construction of the light ion, including proton, accelerators to
Commented [eXtyles6]: Not found: "IEC 60601-2-64"
[1] [2][3] [4][5][5] [ ] [ ][ ]
ensure the safety of their operation. Several national or international . 0 Several national 0 0 or
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[ ][ ][ ]
international 0 0 0 reports propose recommendations concerning the installation, the commissioning, and
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the operation of these accelerators, the safety devices, the design and the calculation of protection barriers,
[7][8][9][10][ ][ ][ ][ ]
the radiological control and monitoring. National standards 0 0 0 0 have been established in certain
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countries. Moreover, national regulations generally impose rules of protection against radiation, in particular
relating to the definition of the controlled area and supervised area and the calculation of shielding.
Considering the developments of proton therapy techniques and of new designs of proton therapy facilities
on the one hand, and the variety o
...
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