EN 62340:2010

SLOVENSKI STANDARD
01-september-2010
Jedrske elektrarne - Merilna in nadzorna oprema za zagotavljanje varnosti -
Zahteve za obvladovanje odpovedi iz normalnih razlogov (CCF) (IEC 62340:2007)
Nuclear power plants - Instrumentation and control systems important to safety -
Requirements for coping with Common Cause Failure (CCF) (IEC 62340:2007)
Kernkraftwerke - Leittechnische Systeme mit sicherheitstechnischer Bedeutung -
Anforderungen zur Beherrschung von Versagen aufgrund gemeinsamer Ursache (IEC
62340:2007)
Centrales nucléaires de puissance - Systèmes d'instrumentation et de contrôle
commande importants pour la sûreté - Exigences permettant de faire face aux
Défaillances de Cause Commune (DCC) (CEI 62340:2007)
Ta slovenski standard je istoveten z: EN 62340:2010
ICS:
27.120.20 Jedrske elektrarne. Varnost Nuclear power plants. Safety
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62340
NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM
ICS 27.120.20
English version
Nuclear power plants -
Instrumentation and control systems important to safety -
Requirements for coping with Common Cause Failure (CCF)
(IEC 62340:2007)
Centrales nucléaires de puissance -  Kernkraftwerke -
Systèmes d'instrumentation et de contrôle Leittechnische Systeme
commande importants pour la sûreté - mit sicherheitstechnischer Bedeutung -
Exigences permettant de faire face Anforderungen zur Beherrschung
aux Défaillances de Cause Commune von Versagen aufgrund gemeinsamer
(DCC) Ursache
(CEI 62340:2007) (IEC 62340:2007)

This European Standard was approved by CENELEC on 2010-05-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62340:2010 E
Foreword
The text of the International Standard IEC 62340:2007, prepared by SC 45A, Instrumentation and control
of nuclear facilities, of IEC TC 45, Nuclear instrumentation, was submitted to the CENELEC formal vote
for acceptance as a European Standard and was approved by CENELEC as EN 62340 on 2010-05-01.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented

at national level by publication of an identical

national standard or by endorsement
(dop) 2011-05-01
– latest date by which the national standards conflicting

with the EN have to be withdrawn
(dow) 2013-05-01
Annex ZA has been added by CENELEC.
As stated in the nuclear safety Directive 2009/71/EURATOM, Chapter 1, Article 2, item 2, Member States
are not prevented from taking more stringent safety measures in the subject-matter covered by the
Directive, in compliance with Community law. In a similar manner, this European Standard does not
prevent Member States from taking more stringent nuclear safety measures in the subject-matter covered
by this European Standard.”
__________
Endorsement notice
The text of the International Standard IEC 62340:2007 was approved by CENELEC as a European
Standard without any modification.

– 3 – EN 62340:2010
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application 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.
NOTE  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year
IEC 60671 - Nuclear power plants - Instrumentation and -
-
control systems important to safety - Surveillance
testing
IEC 60709 - Nuclear power plants - Instrumentation and EN 60709
-
control systems important to safety - Separation
IEC 60780 - Nuclear power plants - Electrical equipment of the -
-
safety system - Qualification
IEC 60880 - Nuclear power plants - Instrumentation and EN 60880 -
control systems important to safety - Software
aspects for computer-based systems performing
category A functions
IEC 60980 - Recommended practices for seismic qualification - -
of electrical equipment of the safety system for
nuclear generating stations
IEC 61000-4 Series Electromagnetic compatibility (EMC) - EN 61000-4 Series
Part 4: Testing and measurement techniques
IEC 61226 - Nuclear power plants - Instrumentation and - -
control systems important to safety - Classification
of instrumentation and control functions
IEC 61513 - Nuclear power plants - Instrumentation and - -
control for systems important to safety - General
requirements for systems
IAEA Safety Guide - Instrumentation and control systems important to - -
NS-G-1.3 safety in nuclear power plants
IAEA Safety Guide - General design safety principles for nuclear power - -
SG-D11 plants; a safety guide
IAEA Safety 2007 Terminology used in nuclear safety and radiation - -
Glossary protection
IEC 62340
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Nuclear power plants – Instrumentation and control systems important to safety
– Requirements for coping with common cause failure (CCF)

Centrales nucléaires de puissance – Systèmes d’instrumentation et de contrôle-
commande importants pour la sûreté – Exigences permettant de faire face aux
défaillances de cause commune (DCC)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
T
CODE PRIX
ICS 27.120.20 ISBN 2-8318-9452-2

– 2 – 62340 © IEC:2007
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.7
2 Normative references .8
3 Terms and definitions .8
4 Abbreviations .12
5 Conditions and strategy to cope with CCF .13
5.1 General .13
5.2 Characteristics of CCF .13
5.3 Principal mechanisms for CCF of digital I&C systems.13
5.4 Conditions to defend against CCF of individual I&C systems .14
5.5 Design strategy to overcome CCF .15
6 Requirements to overcome faults in the requirements specification .15
6.1 Deriving the requirements specification for the I&C from the plant safety
design base.15
6.2 Application of the defence-in-depth principle and functional diversity .16
6.3 CCF related issues at existing plants.17
7 Design measures to prevent coincidental failure of I&C systems.17
7.1 The principle of independence.17
7.2 Design of independent I&C systems .18
7.3 Application of functional diversity .18
7.4 Avoidance of failure propagation via communications paths .19
7.5 Design measures against system failure due to maintenance activities.19
7.6 Integrity of I&C system hardware.19
7.7 Precaution against dependencies from external dates or messages .20
7.8 Assurance of physical separation and environmental robustness.20
8 Tolerance against postulated latent software faults .20
9 Requirements to avoid system failure due to maintenance during operation .21

Annex A (informative) Relation between IEC 60880 and this standard .

62340 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL
SYSTEMS IMPORTANT TO SAFETY –
REQUIREMENTS FOR COPING WITH
COMMON CAUSE FAILURE (CCF)
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62340 has been prepared by subcommittee 45A: Instrumentation
and control of nuclear facilities, of IEC technical committee 45: Nuclear instrumentation.
The text of this standard is based on the following documents:
FDIS Report on voting
45A/668/FDIS 45A/676/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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