IEC TR 63335:2021

IEC TR 63335 ®
Edition 1.0 2021-02
TECHNICAL
REPORT
Nuclear power plants – Instrumentation and control systems, control rooms and
electrical power systems – Specific features of small modular reactors and
needs regarding standards
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IEC TR 63335 ®
Edition 1.0 2021-02
TECHNICAL
REPORT
Nuclear power plants – Instrumentation and control systems, control rooms and

electrical power systems – Specific features of small modular reactors and

needs regarding standards
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.120.20 ISBN 978-2-8322-9331-7

– 2 – IEC TR 63335:2021  IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Abbreviated terms . 9
5 SMR specific features . 10
5.1 General . 10
5.2 Passive design features and systems . 10
5.3 Mutualised operation . 11
5.4 Optimised maintenance . 11
5.5 Mutualised plant systems . 11
5.6 Integrated designs . 11
5.7 Modular construction . 12
5.8 Staged construction . 12
5.9 Consideration of emerging technologies. 12
5.10 Designing for an international market . 12
5.11 Licensing in an international market . 13
5.12 New designs (versus evolutionary designs) . 13
5.13 Remote monitoring and support centres . 13
6 Recommendations to existing working groups . 14
6.1 WGA2: Sensors and measurement techniques . 14
6.1.1 Current portfolio . 14
6.1.2 Topics of interest . 14
6.1.3 WGA2 roadmap . 15
6.2 WGA3: I&C systems: architecture and system specific aspects . 16
6.2.1 Current portfolio . 16
6.2.2 Topics of interest . 16
6.2.3 WGA3 roadmap . 17
6.3 WGA5: Special process measurement and radiation monitoring . 18
6.3.1 Current portfolio . 18
6.3.2 Topics of interest . 18
6.4 WGA7: Functional and safety fundamentals of I&C and electrical power
systems . 19
6.4.1 Current portfolio . 19
6.4.2 Topics of interest . 19
6.4.3 WGA7 roadmap . 20
6.5 WGA8: Control rooms . 20
6.5.1 Current portfolio . 20
6.5.2 Topics of interest . 20
6.5.3 WGA8 roadmap . 21
6.6 WGA9: System performance and robustness toward external stress . 22
6.6.1 Current portfolio . 22
6.6.2 Topics of interest . 22
6.6.3 WGA9 roadmap . 23
6.7 WGA10: Ageing management of I&C and electrical power systems in NPPs . 24

6.7.1 Current portfolio . 24
6.7.2 Topics of interest . 24
6.8 WGA11: Electrical power systems: architecture and system specific aspects . 25
6.8.1 Current portfolio . 25
6.8.2 Topics of interest . 25
6.8.3 WGA11 roadmap . 26
7 Issues of interest not covered by existing working groups . 26
7.1 General . 26
7.2 Systems engineering . 26
7.3 Cross-disciplinary topics . 26
7.4 Safety justification frameworks . 27
Bibliography . 28

– 4 – IEC TR 63335:2021  IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL SYSTEMS,
CONTROL ROOMS AND ELECTRICAL POWER SYSTEMS –
SPECIFIC FEATURES OF SMALL MODULAR REACTORS
AND NEEDS REGARDING STANDARDS
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,
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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
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
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IEC TR 63335 has been prepared by subcommittee 45A: Instrumentation, control and
electrical power systems of nuclear facilities, of IEC technical committee 45: Nuclear
instrumentation. It is a Technical Report.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
45A/1357/DTR 45A/1371/RVDTR
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
The language used for the development of this Technical Report is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/standardsdev/publications.
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.
– 6 – IEC TR 63335:2021  IEC 2021
INTRODUCTION
a) Technical background, main issues and organisation of the Technical Report
Prior the April 2019 Paris meeting, the need to develop a TR to define which orientations
could be followed by IEC SC 45A to cover SMRs (Small Modular Reactors) was identified and
the decision to develop the TR was taken during the meeting.
A team of more than 30 IEC/SC 45A experts to the different SC 45A Working Groups was set
up to cover the multi-disciplinary aspects of the subject.
b) Situation of the current Technical Report in the structure of the IEC SC 45A
standard series
The technical report IEC TR 63335 is a fourth level IEC SC 45A document.
This document draws roadmaps for the different SC 45A Working Groups to define
orientations to cover SMRs. It is worthwhile noting that some of these orientations are also
relevant for all NPPs.
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 Technical Report
It is important to note that a technical report is entirely informative in nature. It gathers data
collected from different origins and it establishes no requirements.
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,
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 (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 part 2 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, IEC 60964 is the entry document for the IEC/SC 45A control
rooms standards and IEC 62342 is the entry document for the ageing management standards.
NOTE 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.
– 8 – IEC TR 63335:2021  IEC 2021
NUCLEAR POWER PLANTS –
INSTRUMENTATION AND CONTROL SYSTEMS,
CONTROL ROOMS AND ELECTRICAL POWER SYSTEMS –
SPECIFIC FEATURES OF SMALL MODULAR REACTORS
AND NEEDS REGARDING STANDARDS
1 Scope
This document identifies a number of issues of particular importance to light water Small
Modular Reactors (SMRs), which are not currently adequately addressed by existing IEC
SC 45A standards, and that could be considered when revising existing publications or that
could be the object of new work item proposals. Whether each of these issues will indeed be
addressed, and if so in which publication, will be the decision of each SC 45A working group.
Though there are a number of advanced Generation IV SMR projects underway, their specific
needs are not covered by this document.
This document is organized as follows:
• Clause 5 presents the main features of SMRs that are not typically found in large reactors
or that are of particular importance for SMRs, and that could require specific or additional
requirements and recommendations over those already provided in IEC SC 45A
standards.
• Clause 6 suggests, for each working group, a number of issues that could be considered
in the revision of existing publications or as subjects for new work items.
• Clause 7 suggests topics of importance to SMRs but that do not fit in the current scope of
existing working groups.
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.
IEC 61513, Nuclear power plants – Instrumentation and control important to safety – General
requirements for systems
ISO/IEC 15026-2:2011, Systems and software engineering – Systems and software assurance
– Part 2: Assurance case
ISO/IEC/IEEE 15288, Systems and software engineering – System life cycle processes
IAEA SSR-2/1, Safety of Nuclear Power Plants: Design
WENRA Report, Safety of New NPP Designs
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
Small Modular Reactor
SMR
small: reactor the electrical output of which is less than 300 MW.
Modular: design and construction approach based in a large part on the assembly of fully
operational modules built and pre-tested in dedicated factories
4 Abbreviated terms
AC Alternating Current
CORDEL Cooperation in Reactor Design Evaluation and Licensing
EMC ElectroMagnetic Compatibility
EMI ElectroMagnetic Interference
EQ Equipment Qualification
HMI Human Machine Interface
IAEA International Atomic Energy Agency
IEC International Electrotechnical Commission
IEEE Institute of Electrical and Electronic Engineers
I&C Instrumentation and Control
LEP Loss of Electrical Power
LOOP Loss Of Offsite Power
MCR Main Control Room
MDEP Multinational Design Evaluation Programme
NEA Nuclear Energy Agency
NPP Nuclear Power Plant
NRC Nuclear Regulatory Commission
OECD Organisation for Economic Co-operation and Development
RF Radio Frequency
RFI Radio Frequency Interference
SBO Station Black Out
SMR Small Modular reactors
TSO Transmission System Operator
VDU Visual Display Unit
V&V Verification and Validation
WENRA Western European Nuclear Regulators Association
WG Working Group
WNA World Nuclear Association
– 10 – IEC TR 63335:2021  IEC 2021
5 SMR specific features
5.1 General
The 2018 edition of IAEA report: Advances in Small Modular Reactor Technology
Developments identifies more than 50 ongoing SMR design projects worldwide. The target of
this document is those design projects that aim at power or industrial production, though
many of the features listed and many of the suggestions proposed are applicable, or could be
applied, to those with different aims (e.g., research). Also, as there is a wide variety of SMR
designs, this document aims to be generic by focussing on commonly found SMR features.
Two key objectives of production SMRs are:
• To be at least as safe and secure as large nuclear reactors.
• To be economically competitive with respect to large nuclear reactors, and also to other,
non-nuclear sources of energy.
Concerning economic competitiveness, SMRs cannot rely on the scale effect like large
nuclear reactors, and need to take advantage of different features such as:
• Modular design (whereby a significant part of a plant construction consists in the
transportation and assembly on site of fully operational modules built and pre-tested in
dedicated factories) in order to lower construction costs and shorten construction
durations.
• Series effect (whereby multiple units are based on a standardised design, possibly with
minor adjustments to take account of site-specific constraints, and of country-specific
requirements in case of worldwide deployment) to lower component costs and build-up
construction experience.
• Simplified design, whereby advantage is taken of smaller size and lower power levels for
simpler, more integrated and more passive designs. Simplified designs also tend to have
positive effects on the safety and security of NPPs.
5.2 Passive design features and systems
Many SMR designs include so-called passive design features and passive systems where the
performance of particular functions (in particular, safety functions) requires little or no
external power and human control. For example, a passive residual heat removal system does
not require the activity of powered pumps, but relies solely on natural convection, possibly
after the opening of a few valves. Such features are not specific to SMRs, but their small size
and low power levels facilitate their introduction.
As such features place less demand on non-passive support systems, they significantly
contribute to design simplification and to cost reduction and hopefully reliability. However, the
extensive use of such design features/systems is relatively new in nuclear power plants: there
is limited experience in operation, and thus few lessons learned regarding design,
construction, maintenance in operating condition, surveillance and periodic testing.
Regulatory experience and international consensus on licensing approaches are also limited.
Also, the categorisation of functions important to safety could benefit from the incorporation of
passive safety features.
5.3 Mutualised operation
As a production SMR generates much less power (with sometimes a factor of up to 10 or 20)
and thus much less revenue than a large nuclear reactor, economic competitiveness needs
not only to be addressed in design and construction, but also in operation. This sometimes
leads to the notion of mutualised operation, whereby multiple SMR units at the same site are
operated by a single team (including control room personnel, field operators and maintenance
staff), approximatively the size of the team for a large reactor, and from a single main control
room. This practice is commonly seen in non-nuclear plants (whether for power generation or
not), but in a nuclear context where safety is of primary importance, this raises a number of
issues such as:
• How to determine an adequate staffing for the different teams involved.
• The operation of multiple units from the same main control room, where the handling of
outage, incidental or accidental conditions in one or more units should not disturb the
operation of units in normal conditions.
• The role and number of supplementary control rooms. For large reactors, the
supplementary control room is essentially a backup to be used when the main control
room is not available. In the case of mutualised operation, to avoid disturbing the
operation of units in normal conditions, one might consider using one or more
supplementary control rooms for units in conditions requiring the intervention of large
numbers of persons, with the need of communication and coordination between the
different rooms.
• How to ensure that each operator action, whether from the control room or in the field, is
performed on the right unit.
5.4 Optimised maintenance
Maintenance represents an important part of the operation and personnel costs, and SMR
projects often look for ways to optimise it, e.g., by using on-line monitoring to promote
condition-based maintenance, or off-site e-monitoring to assist local operators in prognostics
and diagnostics. Longer operation cycles (as is the case for some SMRs) and reduced
inventory of active components (valves, pumps, etc.) may also need to be considered when
addressing on-line and off-site monitoring.
5.5 Mutualised plant systems
Though there could be the occasional case of plants with a single SMR unit, many SMR
design projects have plans for multi-unit plants, where units are in a large part independent,
but where some plant systems are shared by all or some units of the plant. This naturally has
impacts on I&C architectures, control rooms, control room systems, and electrical power
systems.
5.6 Integrated designs
Several SMR projects are based on integrated primary circuit designs, where some or all
steam generators, pressurizer and control rods are integrated within the reactor vessel. This
may have many implications, in particular regarding:
• Hazards analysis and identification of postulated initiating events.
• Instrumentation and access to instrumentation.

– 12 – IEC TR 63335:2021  IEC 2021
5.7 Modular construction
The letter “M” of SMR stands for Modular: the objective is that a significant percentage of a
plant construction is made by assembling modules that are themselves built and verified in
factory, and then transported to the construction site in sealed containers (of standard size
whenever possible). There is then a need to ensure the integrity of these containers and their
contents (absence of damage and absence of malicious tampering) during transportation, and
then to verify that integrity on site. What constitutes adequate on-site verification and
commissioning tests is a key issue.
Conversely, it could be argued that construction of more complete and larger modules in well-
controlled factory conditions could justify less on-site confirmatory testing as these modules
will not have been disassembled before transporting to site.
5.8 Staged construction
As individual SMR units generate relatively low levels of power, a given plant may be
composed of multiple units. If some of them are constructed while others are already in
operation, one needs to ensure that construction or renovation works do not disturb operation
to the point of causing safety or security issues. This is particularly true for mutualised
equipment and rooms, such as the main control room.
5.9 Consideration of emerging technologies
To keep construction and operational costs to acceptable levels, SMR projects often take
consideration of I&C industrial standards and technologies that have emerged in recent years
or of older technologies that have not been extensively used up to now in the nuclear
industry. Examples include OPC-UA (OPC Unified Architecture), TSN (Time Sensitive
Network) remote Input / Outputs and field buses (which have accumulated significant volumes
of experience in operation in other industries), extensive use of multiplexed communications
for NC or Class 3 I&C systems. They may also have benefits for dependability,
interoperability, maintainability on the long term, safety or cyber-security.
5.10 Designing for an international market
Modifying an existing nuclear reactor design is often a lengthy, costly and uncertain process.
When seeking a series effect in an international market as is the case for many SMR projects,
design modifications to meet unexpected country-specific requirements are to be minimised
as far as reasonably possible for the economic case for SMRs to be viable.
Though there have been, and still are, several ongoing international regulatory harmonisation
programmes (such as the work performed by the MDEP programme of OECD NEA, or by the
CORDEL working group of WNA), full harmonisation of country specific requirements has yet
to be achieved, and may be still far away in the future:
• There still are significant differences between many IEC and IEEE standards. This is not
due to lack of will from these organisations, but to well established and different industrial
and regulatory practices and to the fact that each standards corpus is highly integrated
and difficult to modify piecewise.
• Some IEC standards are interpreted in very different ways in different countries: designs
referring to these standards that have been accepted in one country may be (or even,
have been) rejected in another.
• Some key subjects (e.g., levels of defence-in-depth in overall I&C architectures,
identification of postulated initiating events, or necessary trade-offs between conflicting
objectives such as the independence of levels of defence-in-depth and human factors) are
not addressed at a sufficiently practical level in IEC standards and thus fail to provide an
adequate and robust framework for internationally accepted solutions.

Fortunately, even though standards unambiguity and regulatory harmonisation are highly
desirable, they are not an absolute necessity. Also, country’s positions regarding the
interpretation of international standards can evolve over time and the contents of standards
can be revised. Designers mainly need to have an early and clear understanding of the
differences in requirements, in possible interpretations, in acceptable solutions and in
licensing practices. When harmonisation and clarification cannot be achieved in international
standards, such information could be provided by technical reports. If there are not too many
variations, designers can strive to develop a design that would require only minor country-
specific or site-specific adjustments. Such a design would not necessarily be optimal for any
targeted country, but would be so for an international market. In this endeavour, designers
may rely on the smaller size, lower level of power and greater simplicity of SMRs.
5.11 Licensing in an international market
Licensing a new design, in particular an innovative one, in one country may require significant
amounts of effort and time. When aiming at an international market, it is important to be able
to streamline the licensing process and to reuse, as far as possible, licensing effort from one
country to another. To this end, best practices and guidance in the application of justification
frameworks (ISO/IEC15026-2:2011) for both licensees and licensors could be very beneficial.
5.12 New designs (versus evolutionary designs)
As opposed to evolutionary designs, where limited changes are made with respect to designs
that have both licensing and operational experience, many SMR projects incorporate
innovative design features, including but not limited to those listed in the previous subclauses.
While developing an evolutionary design may be done using roughly the same engineering
and licensing approaches as previous designs (sometimes from many decades in the past),
developing a new, innovative design could greatly benefit from more recent and supposedly
more efficient systems engineering approaches such as model-based approaches, with
extensive use of simulation and analysis (including formal verification). These advanced
approaches could enhance reactor efficiency, safety and the economics of construction, and
also provide improved evidence for licensing and enhanced models for operation.
5.13 Remote monitoring and support centres
Though there already are remote support centres for large reactors, they are intended mainly
to provide assistance in case of emergency situations. With the series effect, where the same
SMR design is used for many units at different sites, some projects also consider remote
centres for monitoring and providing assistance in more normal and every day situations, e.g.,
regarding condition-based maintenance.

– 14 – IEC TR 63335:2021  IEC 2021
6 Recommendations to existing working groups
6.1 WGA2: Sensors and measurement techniques
6.1.1 Current portfolio
Reference Title Publication Stability Revision
date date going on?
IEC 60515 Ed. 2.0 Radiation detectors – Characteristics and 2007 2021
test methods
IEC 60568 Ed. 2.0 In-core instrumentation for neutron 2006 2022
fluence rate (flux) measurements in power
reactors
IEC 60737 Ed. 2.0 Temperature sensors (in-core and primary 2010 2023
coolant circuit) – Characteristics and test
methods
IEC 60744 Ed. 2.0 Safety logic assemblies used in systems 2018 2022
performing category A functions:
Characteristics and test methods
IEC 60772 Ed. 2.0 Electrical penetration assemblies in 2018 2021
containment structures for nuclear power
generating stations
Acoustic monitoring systems for detection
IEC 60988 Ed. 2.0 2009 2023
of loose parts: characteristics, design
criteria and operational procedures
IEC 61224 Ed. 1.0 Response time in resistance temperature 1993 2020 Revision
detectors (RTDs) – In situ measurements underway
Merging with
IEC 62397
IEC 61468 Ed. 1.0 + In-core instrumentation – Characteristics 2000 2020 Revision
amendment 1.0 and test methods of self-powered neutron underway
detectors
IEC 61501 Ed. 1.0 Wide range neutron fluence rate meter – 1998 2020
Mean square voltage method
IEC 61502 Ed. 1.0 Vibration monitoring of internal structures 1999 2024
IEC 62397 Ed. 1.0 Resistance temperature detectors 2007 2020 Revision
underway
Merging with
IEC 62651 Ed. 1.0 Thermocouples: characteristics and test 2013 2024
methods
IEC 62887 Ed. 1.0 Pressure transmitters: Characteristics and 2018 2021
test methods
IEC 63186 Ed. 1.0 Criteria for seismic trip system  In development

6.1.2 Topics of interest
WGA2 could consider the opportunity of addressing the following issues in the revision of
existing publications, or in new publications:
• Whether the requirements and recommendations of current publications are also needed
by, and applicable to, smaller cores and lower powers (and thus lower levels of radiation
and flux).
• Impacts of integrated primary circuit designs: no external circuit: how to measure water
levels and flow rate.
• Impacts of factory manufacturing and transport at site (many parts of the reactor are
installed in factory and may be shocked during transportation).
• Impacts of limited space for implementation of sensors : needs for new sensors and
detectors.
• Small volume of the reactor containment and consequences on environmental accident
and post-accident conditions.
• Metallic reactor containment instead of concrete reactor building : Specific penetrations
are needed .
• Reactor electrical penetration assemblies for integrated devices inside reactor vessel like
control rod drive mechanism and reactor coolant pump.
• Intensive use of mineral insulated cables may require specific considerations for splices,
terminations, moisture intrusion corrosion and environmental qualification.
• Use of interconnections between containment and reactor electrical penetration
assemblies housed in flexible metal bellows with sealed back-shell connections for
submergence in water flooded annulus.
• Long life sensors used in confined vessels subject to extreme environments.
• Sensing technologies such as fibre optic sensors, ultrasonic flow meters, and wireless
sensors have been fully developed for industrial applications and may play a role in
nuclear power applications.
6.1.3 WGA2 roadmap
WGA2 standards focus on instrumentation so the impact of SMR architecture needs to have
details on specific instrumentation used. Thus, WGA2 proposes on a first stage to launch a
technical report that gathers the SMR needs in order to decide which standards are missing
or which other one shall be revised.
Topic Action
Technical reports on specific SMR instrumentation
needs:
– Instrumentation in the reactor containment
(requirements for accident conditions ,
maintainability)
– Instrumentation dedicated on SMR transport from
the manufacture to the operational plant
(accelerometers to detect shocks during transport
and installation)
– Instrumentation dedicated to the passive features
of the SMR (flow rate and water level inside the
Technical reports
reactor vessel)
– New instrumentation technologies (smaller size) or
use of existing industrial technologies (for
example: wireless sensors)
– Cabling:
• Reduction (example multiplexing) or mineral
insulated cables
• Lifetime (example mineral insulated cables)
– Integration of existing industrial standards
Penetration assemblies SMR requirements IEC 60772-Amendment

– 16 – IEC TR 63335:2021  IEC 2021
6.2 WGA3: I&C systems: architecture and system specific aspects
6.2.1 Current portfolio
Publication Stability Revision going
Reference Title
date Date on ?
Software aspects for computer-based
IEC 60880 Ed. 2.0 2006 2021
systems performing category A functions
IEC 60987 Ed. 2.0 + Hardware design requirements for Revision
2007 2020
Amendment 1 computer-based systems underway
Data communication in systems
IEC 61500 Ed. 2.0 2018 2021
performing category A functions
IEC 61513 Ed. 2.0 General requirements for systems 2011 2021
Software aspects for computer-based
IEC 62138 Ed. 2.0 systems performing category B or C 2018 2022
functions
Requirements for coping with common Revision should
IEC 62340 Ed. 1.0 2007 2022
cause failure (CCF) start
Development of HDL-programmed
Revision should
IEC 62566 Ed. 1.0 integrated circuits for systems performing 2012 2022
start
category A functions
Development of HDL-programmed
IEC 62566-2 Ed. 1.0 integrated circuits for systems performing 2020 2023
category B and C functions
Platform qualification for systems
IEC TR 63084 Ed. 1.0 2017 2020
important to safety
Hazard analysis: A review of current
IEC TR 63192 Ed. 1.0 2019 2022
approaches
6.2.2 Topics of interest
WGA3 could consider the opportunity of addressing the following issues in the revision of
existing publications, or in new publications:
• Defence-in-depth in I&C architectures, as this topic is very sketchily addressed in
IEC 61513, but is addressed in more detail in IAEA SSR-2/1 and in the WENRA report on
safety of new NPP designs.
• Assessment of emerging industrial standards such as OPC UA (IEC 62541) and TSN
(IEC/IEEE 60802 project).
• I&C architectures in a multi-unit and mutualised operation framework.
• Extensive use of multiplexed digital communication, field buses and remote I/O.
• Extensive exploitation of the information provided by "smart devices".
• Similarities and differences with respect to equivalent IEEE publications.
...