EN IEC 62646:2019

SLOVENSKI STANDARD
01-september-2019
Jedrske elektrarne - Nadzorne sobe - Računalniški postopki (IEC 62646:2016)
Nuclear power plants - Control rooms - Computer-based procedures (IEC 62646:2016)
Kernkraftwerke - Warten - Rechnerunterstützte Prozeduren (IEC 62646:2016)
Centrales nucléaires de puissance - Salles de commande - Procédures informatisées
(IEC 62646:2016)
Ta slovenski standard je istoveten z: EN IEC 62646:2019
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 IEC 62646

NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2019
ICS 27.120.20
English Version
Nuclear power plants - Control rooms - Computer-based
procedures
(IEC 62646:2016)
Centrales nucléaires de puissance - Salles de commande - Kernkraftwerke - Warten - Rechnerunterstützte Prozeduren
Procédures informatisées (IEC 62646:2016)
(IEC 62646:2016)
This European Standard was approved by CENELEC on 2019-06-17. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62646:2019 E
European foreword
This document (EN IEC 62646:2019) consists of the text of IEC 62646:2016 prepared by IEC/SC
45A: "Instrumentation, control and electrical power systems of nuclear facilities", of IEC/TC 45:
"Nuclear instrumentation".
The following dates are fixed:
• latest date by which this document has to be (dop) 2020-06-17
implemented at national level by publication of an
identical national standard or by endorsement
• latest date by which the national standards (dow) 2022-06-17
conflicting with this document have to be
withdrawn
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 and/or security measures in the
subject-matter covered by this standard.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 62646:2016 was approved by CENELEC as a European
Standard without any modification.

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year

IEC 60880 -  Nuclear power plants - Instrumentation EN 60880 -
and control systems important to safety -
Software aspects for computer-based
systems performing category A functions
IEC 60964 2009 Nuclear power plants - Control rooms - EN 60964 2010
Design
IEC 60965 2016 Nuclear power plants - Control rooms - EN 60965 2016
Supplementary control room for reactor
shutdown without access to the main
control room
IEC 61513 -  Nuclear power plants - Instrumentation EN 61513 -
and control important to safety - General
requirements for systems
IEC 61772 2009 Nuclear power plants - Control rooms - EN 61772 2013
Application of visual display units (VDUs)
IEC 61839 -  Nuclear power plants - Design of control EN 61839 -
rooms - Functional analysis and
assignment
IEC 62138 -  Nuclear power plants - Instrumentation EN 62138 -
and control systems important to safety -
Software aspects for computer-based
systems performing category B or C
functions
IEC 62241 2004 Nuclear power plants - Main control room - EN 62241 2015
Alarm functions and presentation
ISO 11064 series Ergonomic design of control centres EN ISO 11064 series
ISO 11064-1 -  Ergonomic design of control centres - Part EN ISO 11064-1 -
1: Principles for the design of control
centres
ISO 11064-3 -  Ergonomic design of control centres - Part EN ISO 11064-3 -
3: Control room layout
ISO 11064-4 -  Ergonomic design of control centres - Part EN ISO 11064-4 -
4: Layout and dimensions of workstations
ISO 11064-5 -  Ergonomic design of control centres - Part EN ISO 11064-5 -
5: Displays and controls
IEC 62646 ®
Edition 2.0 2016-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Control rooms – Computer-based procedures

Centrales nucléaires de puissance – Salles de commande – Procédures

informatisées
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-3650-5

– 2 – IEC 62646:2016 © IEC 2016
CONTENTS
FOREWORD . 5
INTRODUCTION . 8
1 Scope . 11
1.1 Object of this standard . 11
1.2 Context leading to development and use of CPB . 11
1.3 CBP overview . 11
1.4 Use of this standard with related standards . 12
1.5 Organisation of this standard . 12
2 Normative references. 13
3 Terms and definitions . 14
4 Abbreviated terms . 16
5 CBP policy and conceptual requirements. 16
5.1 General . 16
5.2 Computerisation policy . 17
5.2.1 General . 17
5.2.2 Rationale underlying the implementation of CBP . 17
5.2.3 The scope of CBP . 18
5.3 Families of CBP . 19
5.4 Overview of computerisation features . 20
5.4.1 General . 20
5.4.2 Global requirements for computerisation . 20
5.4.3 Provision of guidance to operator . 21
5.4.4 Provision of procedure based automation . 22
5.5 Output documentation . 22
5.6 Design extension conditions . 23
6 Contexts of use of CBP . 23
6.1 General . 23
6.2 Application environments of CBP use . 23
6.2.1 General . 23
6.2.2 Use of CBP in computerised control rooms . 23
6.2.3 Use of CBP in a conventional or hybrid main control room . 24
6.2.4 Use of CBP in conjunction with paper-based procedures . 24
6.2.5 Use of CBP outside the main control room . 25
6.3 Forms of CBP assistance to operator activities . 25
6.3.1 General . 25
6.3.2 Assistance to primary activities of the operator . 25
6.3.3 Assistance to secondary activities of the operator . 25
6.4 Assistance with operator coordination . 26
6.5 Output documentation . 26
7 CBP system and functional requirements . 27
7.1 General . 27
7.2 Safety requirements . 27
7.3 HMI considerations . 28
7.4 Integration of the CBP system into the DPDS . 28
7.5 CBP system implemented externally to the DPDS . 28

IEC 62646:2016 © IEC 2016 – 3 –
7.5.1 General . 28
7.5.2 Sizing and dependability requirements . 29
7.5.3 Connections between the CBP system and the DPDS . 29
7.5.4 Coherent maintenance of both systems . 29
7.6 CBP system failure . 29
7.7 Output documentation . 30
8 Detailed design requirements . 31
8.1 General . 31
8.2 Basic CBP features . 31
8.2.1 General . 31
8.2.2 Basic features necessary for CBP . 31
8.2.3 Presentation rules . 31
8.2.4 CBP display format layout . 32
8.2.5 Requirements for presentation of individual display elements . 32
8.3 Information presented by the CBP . 33
8.3.1 General . 33
8.3.2 Information for Family 1 CBP . 33
8.3.3 Information for Family 2 CBP . 33
8.3.4 Information for Family 3 CBP . 34
8.4 Navigation. 34
8.4.1 General . 34
8.4.2 Navigation for Family 1 CBP . 34
8.4.3 Navigation for Family 2 and Family 3 CBP . 34
8.5 CBP guidance . 35
8.5.1 General . 35
8.5.2 CBP selection, accessibility and execution . 35
8.5.3 Diagnosis assistance . 35
8.5.4 Decision assistance . 35
8.5.5 Computerisation of CBP guidance . 36
8.6 Procedure-based automation . 36
8.6.1 General . 36
8.6.2 Interactions between operators and procedure based automation . 37
8.6.3 Design of CBP to control the plant . 37
8.7 Other CBP facilities . 38
8.8 Output documentation . 38
9 CBP life cycle . 38
9.1 General . 38
9.2 Project organisation . 39
9.3 Project team . 39
9.4 CBP detailed design and implementation quality assurance (QA) . 39
9.5 Verification and validation programme . 40
9.6 Verification and validation of CBP . 40
9.6.1 General . 40
9.6.2 Technical verification of CBP . 41
9.6.3 Functional and ergonomic validation . 41
9.6.4 Output documentation . 42
9.7 Implementation of CBP in NPP . 42
9.8 Output documentation . 43
9.9 Training of the operating staff . 44

– 4 – IEC 62646:2016 © IEC 2016
9.10 CBP and CBP system maintenance . 44
9.11 Feedback of experience . 44
Bibliography . 45

Table 1 – CBP families . 19

IEC 62646:2016 © IEC 2016 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS – CONTROL ROOMS –
COMPUTER-BASED PROCEDURES
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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 62646 has been prepared by subcommittee 45A: Instrumentation,
control and electrical systems of nuclear facilities, of IEC technical committee 45: Nuclear
instrumentation.
This second edition cancels and replaces the first edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) clarification of the way in which the standard is to be used in conjunction with related
standards (in 1.4);
b) replacement, when necessary, of HMI system by DPDS (abbreviation added in Clause 4);
c) new titles for 5.2.2 and 5.2.3 to more closely represent their content;
d) text improvement in 5.2.2, to present the CBP system as a part of the I&C architecture
rather than a stand alone system;
e) text improvement in 5.2.3 and 7.2 to clarify links between safety and CBP;

– 6 – IEC 62646:2016 © IEC 2016
f) new definition of CPB families in 5.3;
g) addition of generic recommendations for computerization in 5.4.2;
h) addition of generic recommendations for CBP guidance in 5.4.3;
i) improvements regarding use of CBP in 5.4.4;
j) addition of 5.6, named “Design extension conditions”;
k) addition of reference standards in 6.2.1;
l) addition of a criterion related to detail compatibility between CBP and operating formats in
6.2.2;
m) addition of references related to HMI in 6.2.3;
n) addition of 7.3 to deal with HMI aspects;
o) text improvement regarding integration of the CBP system into the DPDS in 7.3;
p) text improvement regarding implementation of the CBP into a system independent of the
DPDS in 7.4;
q) text improvement regarding the CBP system failure in 7.6;
r) note added to detail the different types of feedbacks in 8.5.4;
s) text improvement to detail interactions between operators and procedure based
automation in 8.6.2;
t) text improvement regarding design of CBP to control the plant in 8.6.3;
u) clarification of the content of the V&V programme for CBP in 9.5;
v) clarification regarding CBP programming in 9.4;
w) inversion of subclauses 9.4 and 9.5;
x) clarification of the content and requirements of the V&V in 9.6;
y) change of title of 9.7.
The text of this standard is based on the following documents:
FDIS Report on voting
45A/1098/FDIS 45A/1110/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.
IEC 62646 is to be read in conjunction with IEC 60964:2009 and IEC 61839:2000.

IEC 62646:2016 © IEC 2016 – 7 –
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – IEC 62646:2016 © IEC 2016
INTRODUCTION
a) Technical background, main issues and organisation of the standard
This IEC standard focuses on computerisation of procedures used by the operating staff.
Procedures have always contributed to a large extent to nuclear power plant (NPP) safety and
availability and, now, the use of computer technology to provide enhanced guidance to the
plant operators is increasing and becoming current practice. This standard also provides
guidance for the decision of the extent to which the procedures should be computerised.
It is intended that the standard be used by nuclear power plant designers, utilities operating
staff, systems evaluators and by regulatory inspectors.
In June 2013 during the IEC SC 45A meeting held in Moscow, the decision was made to
revise IEC 62646 with the lessons learned from the Tokyo Electric Power Company (TEPCO)
Fukushima Daiichi accident and the late comments from the national committee of Canada.
The resulting improvements are listed in the Foreword of the Standard.
b) Situation of the current standard in the structure of the IEC SC 45A standard series
IEC 62646 is the third level IEC SC 45A document tackling the generic issue of computerised
procedures.
As indicated in the Foreword, IEC 62646 is to be read with IEC 60964 and IEC 61839.
IEC 60964 – supported by IEC 61227, IEC 61771 and IEC 61772 – is the appropriate IEC
SC 45A document providing guidance on operator controls, verification and validation of
design, application of visual display units in the control room, whereas IEC 61839 establishes
functional analysis and assignment guidance for allocating functions between operators and
systems.
For more details on the structure of the IEC SC 45A standard series, see the item d) of this
introduction.
c) Recommendations and limitations regarding the application of the standard
It is important to note that this standard establishes no additional functional requirements for
safety systems.
This standard deals with technical requirements and human factor engineering related to
computer-based procedures (CBP). However it does not provide detailed guidance on
ergonomic design of control centres as it is treated in the ISO 11064 series of standards, nor
on task allocation between humans and systems dealt with in IEC 61839 and on cyber
security, which is developed in IEC 62645. It also excludes the organisation for maintenance
of procedures.
Aspects for which requirements and recommendations have been provided in this standard
are:
• the establishment of a policy for computerisation of procedures, especially which types of
procedure should be computerised and to what extent. The different families of CBP to be
aimed at, with their associated features, are then defined. Finally, the safety aspects of
CBP are considered,
• the use of CBP inside and outside of the MCR (main control room), in possible conjunction
with paper-based procedures, as well as the assistance provided to operator activities,
including user coordination,
• safety and non safety design requirements for the digital system processing CBP, and
considerations about what to do in case of failure of this system,

IEC 62646:2016 © IEC 2016 – 9 –
• detailed requirements and recommendations related to the functional features of CBP,
from the basic ones to the most sophisticated ones, i.e. information, navigation, guidance
and plant control,
• the CBP life cycle, from the set-up of the project to the CBP maintenance and the operator
training via design and implementation.
To ensure that the standard will continue to be relevant in future years, the emphasis has
been placed on issues of principle, rather than on specific technologies.
d) Description of the structure of the IEC SC 45A standard series and relationships
with other IEC documents and other bodies’ documents (IAEA, ISO)
The top-level documents of the IEC SC 45A standard series are IEC 61513 and IEC 63046.
IEC 61513 provides general requirements for I&C systems and equipment that are used to
perform functions important to safety in NPP. IEC 63046 provides general requirements for
electrical power systems of NPP; it covers power supply systems including the supply
systems of the I&C systems. IEC 61513 and IEC 63046 are to be considered in conjunction
and at the same level. IEC 61513 and IEC 63046 structure the IEC SC 45A standard series
and shape a complete framework establishing general requirements for instrumentation,
control and electrical systems for nuclear power plants.
IEC 61513 and IEC 63046 refer directly to other IEC SC 45A standards for general topics
related to categorization of functions and classification of systems, qualification, separation,
defence against common cause failure, control room design, electromagnetic compatibility,
cybersecurity, software and hardware aspects for programmable digital systems, coordination
of safety and security requirements and management of ageing. The standards referenced
directly at this second level should be considered together with IEC 61513 and IEC 63046 as
a consistent document set.
At a third level, IEC SC 45A standards not directly referenced by IEC 61513 or by IEC 63046
are standards related to specific equipment, technical methods, or specific activities. Usually
these documents, which make reference to second-level documents for general topics, can be
used on their own.
A fourth level extending the IEC SC 45 standard series, corresponds to the Technical Reports
which are not normative.
The IEC SC 45A standards series consistently implements and details the safety and security
principles and basic aspects provided in the relevant IAEA safety standards and in the
relevant documents of the IAEA nuclear security series (NSS). In particular this includes the
IAEA requirements SSR-2/1, establishing safety requirements related to the design of nuclear
power plants (NPP), the IAEA safety guide SSG-30 dealing with the safety classification of
structures, systems and components in NPP, the IAEA safety guide SSG-39 dealing with the
design of instrumentation and control systems for NPP, the IAEA safety guide SSG-34 dealing
with the design of electrical power systems for NPP and the implementing guide NSS17 for
computer security at nuclear facilities. The safety and security terminology and definitions
used by SC 45A standards are consistent with those used by the IAEA.
IEC 61513 and IEC 63046 have adopted a presentation format similar to the basic safety
publication IEC 61508 with an overall life-cycle framework and a system life-cycle framework.
Regarding nuclear safety, IEC 61513 and IEC 63046 provide the interpretation of the general
requirements of IEC 61508-1, IEC 61508-2 and IEC 61508-4, for the nuclear application
sector. In this framework IEC 60880, IEC 62138 and IEC 62566 correspond to IEC 61508-3
for the nuclear application sector. IEC 61513 and IEC 63046 refer to ISO as well as to IAEA
GS-R-3 and IAEA GS-G-3.1 and IAEA GS-G-3.5 for topics related to quality assurance (QA).
At level 2, regarding nuclear security, IEC 62645 is the entry document for the IEC SC 45A
security standards. It builds upon the valid high level principles and main concepts of the
generic security standards, in particular ISO/IEC 27001 and 27002; it adapts them and
completes them to fit the nuclear context and coordinates with the IEC 62443 series. At level

– 10 – IEC 62646:2016 © IEC 2016
2, regarding control rooms, IEC 60964 is the entry document for the IEC SC 45A control
rooms standards and IEC 62342 is the entry document for the IEC SC 45A ageing
management standards.
NOTE 1 It is assumed that for the design of I&C systems in NPP that implement conventional safety functions
(e.g. to address worker safety, asset protection, chemical hazards, process energy hazards) international or
national standards would be applied.
NOTE 2 IEC SC 45A's domain was extended in 2013 to cover electrical systems. In 2014 and 2015 discussions
were held in IEC SC 45A to decide how and where general requirement for the design of electrical systems were to
be considered. IEC SC 45A experts recommended that an independent standard be developed at the same level as
IEC 61513 to establish general requirements for electrical systems. Project IEC 63046 is now launched to cover
this objective. When IEC 63046 will be published this NOTE 2 of the introduction of IEC SC 45A standards will be
suppressed.
IEC 62646:2016 © IEC 2016 – 11 –
NUCLEAR POWER PLANTS – CONTROL ROOMS –
COMPUTER-BASED PROCEDURES
1 Scope
1.1 Object of this standard
This standard establishes requirements for the whole life cycle of operating procedures that
the designer wishes to computerise. It also provides guidance for making decisions about
which types of procedures should be computerised and to what extent. Once computerised,
procedures are designated as "computer-based procedures" (CBP).
1.2 Context leading to development and use of CPB
Enhancing safety, easing operation and increasing NPP availability have always been greatly
valued aims which, during NPP operation, rely to a large extent on the operating staff and on
operating procedures. Digital technology contributes not only by providing efficient ways of
automating key functions but also enhances instrumentation, control and the plant’s HMI.
In addition, the use of computer technology to provide formats of operating procedures to the
plant operators , on-line and in real time, is increasing and becoming current practice. This
can be done both for normal operating situations and also as advisory formats for use in
abnormal situations. When properly implemented and kept up-to-date, such operating
procedures can provide enhanced support for greater safety and operator effectiveness
compared to paper-based procedures. Their preparation demands great care and close
interaction with operators and plant designers, and will also need close co-operation with I&C
designers.
CBP have many common points with paper-based procedures. This standard focuses only on
what is specific to CBP.
1.3 CBP overview
Procedures provide the operators with two types of high level elements:
• information, i.e. explanations or data displayed in order to enable the operator to control
the process, assess the plant situation, understand operating strategies and make
appropriate decisions,
• guidance, i.e. a set of ordered steps that prompt and help the operator to monitor and
control the plant processes, systems and equipment.
Information and guidance are combined to minimise operator errors and to optimise the
efficiency of plant operation.
Information and guidance can be of a varying level of detail depending on the procedure
policy, which aims to benefit from operator experience and existing guidelines.
Computerisation of procedures can provide, according to the specified design policy:
– enhanced process and plant equipment information,
– enhanced operator guidance,
___________
Operators may be male or female, so that in this standard, “he” is a shortcut for “he / she” and “his” is a
shortcut for “his / her”.
– 12 – IEC 62646:2016 © IEC 2016
– additional functions to initiate and control automation sequences.
This standard provides guidance on and an overview of policy, philosophy and conceptual
requirements for CBP implementation, including design objectives, assumptions, approaches,
inputs, scope, CBP family types, key CBP features, and output documentation.
1.4 Use of this standard with related standards
This standard intends to deal with aspects that are:
• specific to computer-based procedures, i.e. that are not common with paper-based
procedures. For example, establishing functional scenarios to validate procedures is not
specific to CBP,
• not already dealt with in existing standards, i.e. HFE, life cycle of safety classified
systems, allocation of tasks to human or machines.
In order to design CBP efficiently and properly, some important considerations at the
conceptual design stage of CBPs are addressed in the following related standards:
a) functional analysis and assignment
IEC 61839 specifies functional analysis and assignment procedures and gives rules for
developing criteria for the assignment of functions either to operators or to systems,
b) human factors design guidelines
IEC 61772:2009, especially Clauses 4 and 5, provides guidance on physical
implementation of VDUs (see 4.1), display formats (see 4.4), and implementation into the
MCR (see Clause 5). The ISO 11064 series of standards provides guidance on human-
centered design activities throughout the life cycle of a computer-based interactive
system.
In addition, IEC 60964 and IEC 60965, which provide requirements and recommendations for
the main control room and supplementary control room arrangements, and IEC 61772,
providing requirements and recommendations for implementing VDUs in control rooms, apply
to the implementation of CBP in new nuclear power plants. Complementary advice for
implementing CBP in case of main control room retrofitting is given in 6.2.3.
This standard assumes the simultaneous consideration of the requirements for:
1) computer security, which is necessary to protect the whole life cycle of CBP, but is not
restricted to computerisation of procedures. Nevertheless, this topic should be considered
when computerising operating means (IEC 62645 deals with cyber-security),
2) requirements on the implementation for CBP functions of software and hardware of
computer systems for CBP which should be implemented in line with their safety class in
compliance with IEC 60880, IEC 61226, IEC 62138 and IEC 61513,
3) the design of plant scenarios (including anticipated operating occurrences such as plant
transients, plant upset conditions and/or initiating events) for validating CBPs,
4) the organisation for functional maintenance of procedures.
1.5 Organisation of this standard
Clause 2 lists the reference documents.
Clause 3 gives definitions relevant to this standard.
Clause 4 lists the abbreviations used in this standard.
Clause 5 provides an overview of CBP. It presents recommendations for the development of a
policy for computerisation of procedures, based on the type of procedure to be implemented.
Three generic types (termed “families”) are described, for which general and specific

IEC 62646:2016 © IEC 2016 – 13 –
guidance is provided. Guidance related to the safety requirements of CBP systems is also
provided.
Clause 6 gives requirements for use in different contexts, including main control room (MCR)
upgrading, and different environments, inside and outside of the MCR and possibly in
conjunction with paper-based procedures. It then considers assistance to and coordination of
operator activities.
Clause 7 deals with the digital system which processes CBP. It first considers safety and non
safety requirements, then gives requirements for handling failures of this system.
Clause 8 focuses on the detailed requirements and recommendations related to the functional
features of CBP, from the basic ones to the most sophisticated ones, i.e. information,
navigation, guidance and plant control. Miscellaneous options that could ease CBP use are
also given.
Clause 9 considers the CBP life cycle, from the set-up of the project to the CBP maintenance
and the operator training via design and implementation.
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.
NOTE The output documentation requested by these normative standards that is related to CBP is not addressed
in this standard.
IEC 60880, Nuclear power plants – Instrumentation and control systems important to safety –
Software aspects for computer-based systems performing category A functions
IEC 60964:2009, Nuclear power plants – Control rooms – Design
IEC 60965:2016, Nuclear power plants – Control rooms – Supplementary control room for
reactor shutdown without access to the main control room
IEC 61513, Nuclear power plants – Instrumentation and control important to safety – General
requirements for systems
IEC 61772:2009, Nuclear power plants – Control rooms – Application of visual display units
(VDUs)
IEC 61839, Nuclear power plants – Design of control rooms – Functional analysis and
assignment
IEC 62138, Nuclear power plants – Instrumentation and control important for safety –
Software aspects for computer-based systems performing category B or C functions
IEC 62241:2004, Nuclear power plants – Main control room – Alarm functions and
presentation
ISO 11064 (all parts), Ergonomic design of control centres
ISO 11064-1, Ergonomic design of control centres – Part 1:Principles for the design of control
centres
– 14 – IEC 62646:2016 © IEC 2016
ISO 11064-3, Ergonomic design of control centres – Part 3: Control room layout
ISO 11064-4, Ergonomic design of control centres – Part 4: Layout and dimensions of
workstations
ISO 11064-5, Ergonomic design of control centres – Part 5: Displays and controls
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp.
3.1
back-up system
alternative equipment for plant monitoring and control designed to be used in case of failure
of the normally used HMI system
Note 1 to entry: The back-up system may become unavailable if a beyond design basis accident occu
...