ISO 23466:2020

INTERNATIONAL ISO
STANDARD 23466
First edition
2020-10
Design criteria for the thermal
insulation of reactor coolant system
main equipments and piping of PWR
nuclear power plants
Critères de conception du calorifuge des composants primaires
principaux et des tuyauteries du circuit primaire principal des
centrales nucléaires REP
Reference number
©
ISO 2020
© 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

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General design procedure. 2
4.1 General requirements . 2
4.2 Reactor safety considerations . 2
4.3 Material selection . 3
4.3.1 General requirements . 3
4.3.2 Primary insulating material . 3
4.3.3 Outer cladding/encapsulating material . 4
4.3.4 Support/fixation material . 4
4.4 Design and test of thermal behaviour . 4
4.4.1 Design of thermal behaviour . 4
4.4.2 Test of thermal behaviour . 6
4.5 Design and test of mechanical properties . 6
4.5.1 Design of mechanical properties . 6
4.5.2 Test of mechanical properties . 7
4.6 Additional requirements . 8
5 Design requirements of RPV thermal insulation . 9
5.1 General requirements . 9
5.2 Safety requirements . 9
5.3 Material selection . 9
5.4 Thermal behaviour requirements .10
5.5 Mechanical properties and structural requirements .10
6 Design requirements of thermal insulation of RCS piping and other equipment .10
6.1 General requirements .10
6.2 Safety requirements .10
6.3 Material selection .11
6.4 Thermal behaviour requirements .11
6.5 Mechanical properties and structural requirements .11
Annex A (informative) Geometry description of metallic thermal insulation .13
Annex B (informative) Geometry description of non-metallic thermal insulation .15
Annex C (informative) Type of RPV thermal insulation with RPV external cooling safety
functionality .18
Annex D (informative) Type of RPV thermal insulation with radiation shield safety
functionality .21
Bibliography .24
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 technologies,
and radiological protection, Subcommittee SC 6, Reactor Technology.
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

INTERNATIONAL STANDARD ISO 23466:2020(E)
Design criteria for the thermal insulation of reactor
coolant system main equipments and piping of PWR
nuclear power plants
1 Scope
This document specifies the basic requirements of thermal insulation design of reactor coolant system
(RCS) equipment and piping.
Among thermal insulation of various RCS equipment and piping, the following two kinds of thermal
insulations are described in detailed based on common design logic and requirements:
— thermal insulation of reactor pressure vessel (RPV);
— thermal insulation of RCS piping and other equipment.
This document is valid for two types of thermal insulation:
— metallic thermal insulation;
— non-metallic thermal insulation.
This document mainly applies to nuclear power plants with pressurized water reactor (PWR). For other
reactor types, this document can be taken as reference.
2 Normative references
The following standards 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 standards (including any amendments) applies.
ISO 7345, Thermal performance of buildings and building components — Physical quantities and definitions
ISO 9229, Thermal insulation — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7345, ISO 9229 and the
following 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 http:// www .electropedia .org/
3.1
metallic thermal insulation
thermal insulation with metallic material as the primary insulating material
Note 1 to entry: The metallic thermal insulation is composed by large number of thermal insulation panels. Each
thermal insulation panel is surrounded by outer cladding and filled by inner metallic reflective foils/sheets. The
geometry of inner packed foils/sheets can be embossed structure or liners in parallel.
Note 2 to entry: The typical geometry of metallic thermal insulation is shown in Annex A. The geometry
mentioned in Annex A can be referred by designers.
3.2
non-metallic thermal insulation
thermal insulation with non-metallic material as the primary insulating material
Note 1 to entry: Geometry of non-metallic thermal insulation can be divided into three categories:
— Thermal insulation composed by large number of thermal insulation panels. Each thermal insulation panel is
surrounded by outer cladding and filled by inner non-metallic insulating material.
— Layers of non-metallic insulating thermal insulation materials strapped together.
— Thermal insulation mattresses (composed by non-metallic insulating material wrapped in fibre clothing).
Note 2 to entry: The typical geometry of non-metallic thermal insulation is shown in Annex B. The geometry
mentioned in Annex B can be referred by designers.
3.3
chimney effect
air circulation between the inner and outer side of thermal insulation originating from heat source
EXAMPLE If clearance and extensive heat exchange paths exist between thermal insulation and the
insulated equipment/piping, external cold air would continuously enter from the lower part due to the density
and pressure difference between inside and outside of the thermal insulation. The incoming airflow will be
heated and thus travels upward to the top of thermal insulation and eventually exits from the upper part.
3.4
thermal bridge
channel with extremely large heat flow due to direct connection between inner/outer surface of thermal
insulation and the material with great heat conductivity of the insulated structure
4 General design procedure
4.1 General requirements
The design procedures of thermal insulation shall be comprehensively considered to fulfil all
functionalities. The safety class, quality assurance classification and seismic category requirements,
which are specified by equipment specification or other relevant documents, shall be satisfied. The
design of thermal insulation should take into account the following processes:
— reactor safety considerations;
— material selection;
— design and test of thermal behaviour;
— design and test of mechanical properties, including seismic and vibration resistance, etc.
In additio
...