ISO 23467:2020

INTERNATIONAL ISO
STANDARD 23467
First edition
2020-11
Ice plug isolation of piping in nuclear
power plant
Mise en œuvre de la technique d’obturation cryogénique sur les
tuyauteries de centrales nucléaires
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General requirements . 2
4.1 Personnel . 2
4.2 Equipment . 2
4.3 Preconditions . 2
4.4 Requirements of process . 3
4.4.1 Material of pipe . 3
4.4.2 Freezing medium . 3
4.4.3 Position of ice plug . 4
4.4.1 Ice plug jacket . 4
5 Preparation before operation. 4
5.1 Working environment . 4
5.2 Construction plan . 4
5.3 Tools of construction . 5
5.4 Protective measures . 5
5.5 Pipe testing before operation . 5
6 Ice plug construction . 5
6.1 Generation of ice plug . 5
6.2 Judgment of ice plug generation . 5
6.3 Removal of ice plug . 6
7 Quality assurance (QA) on ice plugging . 6
7.1 QA before ice plug performance. 6
7.2 QA during ice plug performance . 7
7.3 QA after ice plug performance . 7
8 Records and reports . 7
Annex A (informative) Reference table of ice plug jacket length . 8
Annex B (informative) Ice plug jacket types . 9
Annex C (informative) Flow chart to perfomance of ice plug isolation measure
(construction plan) .14
Bibliography .15
Foreword
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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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
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This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies,
and radiological protection, Subcommittee SC 6, Reactor technology.
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iv © ISO 2020 – All rights reserved

Introduction
This document provides terms and definitions for basic concepts of nuclear energy, nuclear technologies,
and radiological protection. Terminological data are taken from ISO standards developed by ISO/TC 85
sub-committees and other technically validated documents.
In the field of nuclear power, when the equipment or pipeline is to be disassembled or removed to
overhaul, it is often necessary to isolate the equipment or pipeline. Under normal circumstances, the
upstream and downstream of the equipment will be isolated or the internal media will be sprinkled.
Taking into account the safety (some reactor systems like the hot trap needs to be filled at any time and
care need to be taken as some liquid systems are radioactive) and economy (system mass, sparse for a
long time, heavy water degradation, etc.) during the maintenance it is necessary that there will be no
isolation equipment or isolation equipment near the equipment or pipeline.
Based on years of practical experience, the development of this document is feasible. At the theoretical
level, the relevant literature has been studied and reported on the ice plug isolation technology. In the
actual maintenance work, the use of ice plug technology to the pipeline equipment isolation achieve
good results. Based on these theoretical and practical experiences, it is recommended that some
technical indicators in the process of ice plug operation be standardized.
This document is designed to provide a standardized procedure for on-line isolation through the
freezing of the internal medium of the pipeline. This document includes methods for technologies to
isolate equipment without isolation facilities by ice plug technology. Standardized ice plug isolation
technology will facilitate the maintenance work.
INTERNATIONAL STANDARD ISO 23467:2020(E)
Ice plug isolation of piping in nuclear power plant
1 Scope
This document specifies requirements for the ice plug technique with liquid nitrogen or dry ice as
refrigerant (cryogenic medium) on metal pipes of nuclear power plants. The freezing liquid can be
water or water mixture (e.g. boric acid mixture).
This document specifies technical requirements of ice plug generation, formation judgment and
removal, measures before, during and after ice plugging and requirements for personnel and non-
destructive testing.
The application of the ice plug isolation technique is principally not allowed on cladded pipes or pipes
with internal coatings. The application for pressure test is not in the scope of this document and will be
qualified separately.
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 3452 (all parts), Non-destructive testing — Penetrant testing
ISO 9934 (all parts), Non-destructive testing — Magnetic particle testing
ISO 16810, Non-destructive testing — Ultrasonic testing — General principles
ISO 17637, Non-destructive testing of welds — Visual testing of fusion-welded joints
ISO 20769 (all parts), Non-destructive testing — Radiographic inspection of corrosion and deposits in pipes
by X- and gamma rays
3 Terms and definitions
For the purposes of this document 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
ice plug
solid block of ice in the pipe that can withstand a certain system pressure to isolate the pipeline
temporarily
Note 1 to entry: The ice plug can be used for the convenience of maintaining downstream pipelines, valves and
other equipment.
3.2
ice plug jacket
set of device wrapped outside the pipe and containing a refrigerant capable of freezing internal medium
of the pipe to form an ice plug (3.1) for a period necessary for the isolation
Note 1 to entry: The length of jacket depends on the diameter of pipe. See Annex A for the length of jacket.
3.3
ice plug area
defined area on the pipe excluding the ice plug affected zone
3.4
refrigerant
cryogenic medium
medium which is used to generate an ice plug (3.1) inside of the pipes
3.5
freezing medium
freezing liquid
medium inside of pipes and components which have to be frozen
3.6
...