Nuclear power plants - Instrumentation and control systems important to safety - Safety logic assemblies used in systems performing category A functions: Characteristics and test methods

IEC 60744:2018 provides requirements and recommendations for the design, construction and test of safety logic assemblies used in safety systems to perform category A safety functions (in accordance with IEC 61226). Safety logic assemblies include logic such as the hardwired logic assembly interfacing computer-based systems to switchgear, actuators or contactors to provide trip or engineered safety feature actuations. Safety logic assemblies are significant parts of a safety system and may include voting logic between redundant channels. This document provides a general description of safety logic assemblies for safety actuators control. The principles to meet dependability objectives are presented. The main features relating to the design requirements are described and explained.
This new edition includes the following significant technical changes with respect to the previous edition:
a) update of the references to standards published or revised since the issue of the first edition of the current standard, including IEC 61513 and IEC 61226;
b) additional requirements for operational and maintenance bypass use; requirements of voting logic; and others.

Centrales nucléaires de puissance - Systèmes d'instrumentation et de contrôle-commande importants pour la sûreté - Ensembles logiques de sûreté utilisés dans les systèmes réalisant des fonctions de catégorie A: Caractéristiques et méthodes d'essai

L'IEC 60744:2018 spécifie les exigences et les recommandations pour la conception, la fabrication et les essais des ensembles logiques de sûreté utilisés dans les systèmes de sûreté pour réaliser des fonctions de sûreté de catégorie A (conformément à l’IEC 61226). Les ensembles logiques de sûreté réalisent des fonctions logiques comme, par exemple, la logique câblée faisant l’interface entre la partie programmée et les interrupteurs d’arrêt du réacteur, les actionneurs ou les contacteurs pour déclencher l’arrêt du réacteur ou les actions de sauvegarde. Les ensembles logiques de sûreté sont des éléments importants d'un système de sûreté et peuvent comporter une logique de vote entre des voies redondantes. Le présent document décrit de manière générale les ensembles logiques de sûreté pour la commande des actionneurs de sûreté. Il donne les principes permettant d'atteindre les objectifs de sûreté de fonctionnement. Il décrit et explicite également les principales caractéristiques relatives aux exigences de conception.
Cette nouvelle édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) actualisation des références aux normes publiées ou révisées depuis la publication de la première édition de la norme actuelle, y compris l’IEC 61513 et l’IEC 61226;
b) exigences supplémentaires concernant l’utilisation du bipasse de fonctionnement et du bipasse de maintenance; exigences concernant la logique de vote etc.

General Information

Status
Published
Publication Date
13-May-2018
Current Stage
PPUB - Publication issued
Completion Date
14-May-2018
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IEC 60744
Edition 2.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation and control systems important to safety
– Safety logic assemblies used in systems performing category A functions:
Characteristics and test methods
Centrales nucléaires de puissance – Systèmes d’instrumentation et de contrôle-
commande importants pour la sûreté – Ensembles logiques de sûreté utilisés
dans les systèmes réalisant des fonctions de catégorie A: Caractéristiques et
méthodes d'essai
IEC 60744:2018-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60744
Edition 2.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation and control systems important to safety
– Safety logic assemblies used in systems performing category A functions:
Characteristics and test methods
Centrales nucléaires de puissance – Systèmes d’instrumentation et de contrôle-
commande importants pour la sûreté – Ensembles logiques de sûreté utilisés
dans les systèmes réalisant des fonctions de catégorie A: Caractéristiques et
méthodes d'essai
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 21.120.20 ISBN 978-2-8322-5681-7

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60744:2018  IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 9

4 Abbreviated terms and acronyms ................................................................................... 13

5 Safety logic assembly – Principles and description ........................................................ 14

5.1 Safety logic assembly ........................................................................................... 14

5.2 Technology for safety logic assembly .................................................................... 14

5.3 Interfaces of a safety logic assembly..................................................................... 15

5.4 Dependability objectives ....................................................................................... 17

5.5 Modes of operation ............................................................................................... 17

5.6 Principles to reach the safety objectives ............................................................... 18

5.6.1 Safe operation in normal operation mode....................................................... 18

5.6.2 Safe operation in abnormal operation mode ................................................... 18

5.6.3 Protection against human error ...................................................................... 18

5.7 Principles to reach the availability objectives ........................................................ 18

5.7.1 NPP availability objectives ............................................................................. 18

5.7.2 NPP availability in normal operation conditions .............................................. 19

5.7.3 NPP availability in abnormal operation conditions .......................................... 19

5.7.4 Protection against human error ...................................................................... 19

6 Safety logic assembly – Design requirements ................................................................ 19

6.1 General ................................................................................................................. 19

6.2 Functions .............................................................................................................. 19

6.2.1 Specification of the functions ......................................................................... 19

6.2.2 Manual controls ............................................................................................. 20

6.2.3 Response time ............................................................................................... 20

6.2.4 Display – Indicators-alarms............................................................................ 20

6.2.5 Interface ........................................................................................................ 21

6.3 Architecture and redundancy ................................................................................ 21

6.4 Technology ........................................................................................................... 21

6.5 Qualification .......................................................................................................... 21

6.6 Maintenance ......................................................................................................... 22

6.7 Separation ............................................................................................................ 22

6.8 Power supply ........................................................................................................ 23

7 Tests of safety logic assemblies .................................................................................... 23

7.1 General ................................................................................................................. 23

7.2 Type tests ............................................................................................................. 23

7.2.1 General ......................................................................................................... 23

7.2.2 Test sequences ............................................................................................. 23

7.2.3 Functional and performance validation tests .................................................. 23

7.2.4 Qualification tests .......................................................................................... 24

7.3 Production tests .................................................................................................... 24

7.3.1 General ......................................................................................................... 24

7.3.2 Tests of spare parts ....................................................................................... 24

7.3.3 Production tests on manufactured safety logic assemblies ............................. 24

---------------------- Page: 4 ----------------------
IEC 60744:2018  IEC 2018 – 3 –

7.3.4 Tests on substitute components / modules .................................................... 25

7.3.5 Tests on assembled cabinets ......................................................................... 25

7.4 Tests on site ......................................................................................................... 25

7.4.1 Equipment health checks before installation .................................................. 25

7.4.2 Installation validation tests............................................................................. 25

7.4.3 Periodic tests ................................................................................................. 26

8 Quality assurance .......................................................................................................... 26

Annex A (informative) Examples of safety logic assembly applications ................................. 27

Annex B (normative) Safety logic assembly – Hardwired technological solutions ................. 28

B.1 Overview............................................................................................................... 28

B.1.1 General ......................................................................................................... 28

B.1.2 Relays ........................................................................................................... 28

B.1.3 Electromechanical relays ............................................................................... 28

B.1.4 Solid state relays ........................................................................................... 29

B.2 Magnetic amplifiers ............................................................................................... 29

B.3 Fail-safe – dynamic logic ...................................................................................... 30

B.4 Solid state circuits................................................................................................. 30

B.4.1 General ......................................................................................................... 30

B.4.2 Discrete components ..................................................................................... 30

B.4.3 Integrated components – HPD ....................................................................... 31

Annex C (informative) Dependability and its attributes ......................................................... 32

C.1 General ................................................................................................................. 32

C.2 Qualitative and quantitative attributes associated with dependability ..................... 32

Bibliography .......................................................................................................................... 34

Figure 1 – Safety logic assembly: typical interface arrangement in a protection system ....... 16

Figure C.1 – Attributes of dependability – Relationship between reliability and the final

risk regarding safety ............................................................................................................. 32

---------------------- Page: 5 ----------------------
– 4 – IEC 60744:2018  IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS – INSTRUMENTATION AND CONTROL
SYSTEMS IMPORTANT TO SAFETY – SAFETY LOGIC ASSEMBLIES
USED IN SYSTEMS PERFORMING CATEGORY A FUNCTIONS:
CHARACTERISTICS AND TEST METHODS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60744 has been prepared by subcommittee 45A: Instrumentation,

control and electrical power systems of nuclear facilities, of IEC technical committee 45:

Nuclear instrumentation.

This second edition cancels and replaces the first edition published in 1983. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) update of the references to standards published or revised since the issue of the first

edition of the current standard, including IEC 61513 and IEC 61226;

b) additional requirements for operational and maintenance bypass use; requirements of

voting logic; requirements for interfacing with the MCR and SCR.
---------------------- Page: 6 ----------------------
IEC 60744:2018  IEC 2018 – 5 –
The text of this International Standard is based on the following documents:
FDIS Report on voting
45A/1188/FDIS 45A/1200/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 60744:2018  IEC 2018
INTRODUCTION
a) Technical background, main issues and organisation of the Standard

This standard IEC 60744 specifically focuses on safety logic assemblies used in NPPs

(Nuclear Power Plants). Safety logic assemblies were originally hardwired parts of protection

systems mainly used to control actuators. IEC 60744 specifically focuses on the design,

including technology, interfaces with MCR and SCR, tests and qualification. It gives

requirements for display of the safety system inputs and state.

IEC 60744 is the document concerning safety logic assembly functions and performance.

The use of a computer based equipment or software is covered comprehensively by other

standards. The technology used to design SLAs therefore involves mainly hard-wired

technologies and submicronic highly integrated components (HPDs), the implementation of

which is limited due to the very high safety requirements.

The document addresses the design and test characteristics of safety logic assemblies,

especially regarding functional requirements, reliability issues, and associated control means

including alarm, indication and control. Also it suggests the requirements for performance,

testing and qualification for safety logic assemblies, and the interface requirements for

communication between assemblies.

It is intended that the document be used by operators of NPPs (utilities), systems evaluators

and licensors.

b) Situation of the current Standard in the structure of the IEC SC 45A standard series

IEC 60744 is the third level IEC SC 45A document tackling the specific issue of testing and

design characteristics of safety logic assemblies.

IEC 60744 is to be read in association with IEC 61513 which is the appropriate IEC SC 45A

document which provides guidance on I&C safety system, and IEC 60964 which is the

appropriate document for guidance on the Control Rooms, since the safety system has

extensive interfaces with the MCR and SCR.

For more details on the structure of the IEC SC 45A standard series, see item d) of this

introduction.
c) Recommendations and limitations regarding the application of the Standard

It is important to note that this document establishes no additional functional requirements at

safety system level.

Aspects for which special recommendations have been provided in this document are:

• The voting of partial trips to identify each safety actuation
• The output assemblies that provide the trips and actuations
• The design and test characteristics of functional requirements
• The reliability issue of safety logic assemblies
• The performance characteristics of logic assemblies
• Testing, qualification and interface requirements of safety logic assemblies

To ensure that the document will continue to be relevant in future years, the emphasis has

been placed on issues of principle, rather than specific technologies.
---------------------- Page: 8 ----------------------
IEC 60744:2018  IEC 2018 – 7 –

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 NPPs. IEC 63046 provides general requirements for

electrical power systems of NPPs; 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,

defense 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 (NPPs), the IAEA safety guide SSG-30 dealing with the safety classification of

structures, systems and components in NPPs, the IAEA safety guide SSG-39 dealing with the

design of instrumentation and control systems for NPPs, the IAEA safety guide SSG-34

dealing with the design of electrical power systems for NPPs 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 ISO/IEC 27002; it adapts them

and completes them to fit the nuclear context and coordinates with the IEC 62443 series. At

level 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 NPPs 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 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 is published this NOTE 2 of the introduction of IEC SC 45A standards will be

suppressed.
---------------------- Page: 9 ----------------------
– 8 – IEC 60744:2018  IEC 2018
NUCLEAR POWER PLANTS – INSTRUMENTATION AND CONTROL
SYSTEMS IMPORTANT TO SAFETY – SAFETY LOGIC ASSEMBLIES
USED IN SYSTEMS PERFORMING CATEGORY A FUNCTIONS:
CHARACTERISTICS AND TEST METHODS
1 Scope

This document provides requirements and recommendations for the design, construction and

test of safety logic assemblies used in safety systems to perform category A safety functions

(in accordance with IEC 61226). Safety logic assemblies include logic such as the hardwired

logic assembly interfacing computer-based systems to switchgear, actuators or contactors to

provide trip or engineered safety feature act
...

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