ENERGIFORSK NUCLEAR SAFETY RELATED I&C
2 L I F E T I M E E X T EN S I O N O F N U C L E A R I & C S Y
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Title: Lifetime Extension of nuclear instrumentation and control
systems Author: Fredrik Bengtsson, ÅF LtD ISBN
978-91-7673-006-5
ENSRIC, which is part of Energiforsk, is a research program focused
on safety related I&C systems, processes and methods in the
nuclear industry. The three focus areas of the program are emerging
systems, life time extension and I&C overall. This report
presents conclusions from work that has been done regarding life
time extension of I&C system.
Photo: Forsm ark
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The Nordic nuclear fleet of today consists of a mix of tech-
nologies for instrumentation and control (I&C) equipment. A
large portion of the equipment is still of conventional type but
there are also new digital equipment, systems and platforms
installed. The biggest modernization programs have unfortunately
been done in the power plants that are going to be decommissioned
within near future.
Long Term Operation All of the Nordic plants are approaching Long
Term Ope- ration (LTO), which is operating longer than the original
construction life time, within a short time span. In the coming
years, a considerable amount of I&C systems and equipment must
be replaced or upgraded following various aspects of aging. This
makes it important to have a clear understanding of the different
alternatives on how to handle aging in a LTO perspective. The
equivalent of the big modernization programs that were launched in
the early 00’s will probably not be the solution due to the high
risk and costs. At that time, the trend for life time extension was
to replace considerable part of the plant with digital
Instrumentation and control systems in Nordic nuclear power
plants
I&C platforms. Extending the lifetime with different app-
roaches of maintenance was not taken into account or not considered
as a credible alternative.
Maintaining systems – a credible alternative The ENSRIC research
program has studied the area of lifetime extension of present
systems and concluded that maintaining systems is really a credible
alternative. This approach is also used in many other industries,
including safety related. A number of different options can be
explo- red, to find the right measure for a specific system. Which
method to choose depends on several factors, for example purpose of
the system, remaining lifetime of the plant, if documentation for
the current system is available etc. This summary briefly describes
some of the available options. The information is based on market
surveys and interviews with plants and suppliers. More detailed
information can be found in the ENSRIC reports listed in the
reference section.
Photo: Energiforsk
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It is important to have a strategy for the installed I&C
systems that shows what to do and when. The lead time for replacing
a system with new technology is quite long, hence planning is
important.
To be able to produce I&C strategy the status of the installed
systems needs to be known. Also, the supply and condition of spare
part needs to be mapped along with the available staff that are
familiar with the different systems. The work should start with
prioritizing the I&C systems so that the most important and
critical systems are mapped first. The outcome of the strategy
could be to maintain or replace a system, together with actions
that need to be taken care off. The maintenance alternative needs
to be penetrated very well, both from a technical perspective but
also from an economic perspective. If the analysis points to that
the maintenance alternative is not a feasible option, efforts can
be used as a reference when preparing the busi- ness case for a
replacement investment.
Replacement strategy
It is important to have a good knowledge of the require- ments for
the specific system or component, to be able to include that early
in the development of the strategy. There is of course a difference
in the requirements if the component/system is used in a safety
function or not, but there are no formal obstacles for extending
the lifetime of a safety related component. It is just more
complex.
Overall Strategy An overall strategy should be agreed upon before
the plant system strategy is decided because this will guide and
ease the decision. An overall strategy could look like the one
that’s presented in Figure 1, which is based upon the recom-
mendation in report [1].
Photo: Vattenfall
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including Human
System Interface?
Does the exiting system or component fulfil today’s requirement
including Human System Interface?
Is it possible to maintain the current system or component?
Replace, Repair, Refurbish, Remanufacture, Reverse Engineering,
Reegineering
Don’t introduce unique solutions. Observe others and don’t be
first.
Try to maintain the original function in the existing systems and
implement new functions in separate systems.
Try to maintain the boundaries as they are.
Stay with technical standard used at the utility.
YESNO
NO
YES
Figure 1. An overall strategy should be agreed upon before the
plant system strategy is decided because this will guide and ease
the decision. Here is one example, which is based upon the
recommendation in report (1).
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Maintaining systems
A Smorgasbord of options The efforts performed within ENSRIC has
shown that there are several different ways of maintaining the old
system, and these could be valid both for analogue systems and
digital systems. The reports are talking about the 7R’s which are
Replace, Repair, Refurbish, Re-manufacture, Reengineering, Reverse
Engineering and Redesign. (See page 7 in this report). Replace and
Repair have been used at the plants for many years. The method of
extending lifetime of I&C system through Reverse Engineering or
Reengineering are in many ways new to the Nordic nuclear power
plants, but has frequently been used outside the Nordic countries.
Complexity and cost increase from Repair
to Reverse Engineering which Figure 2 illustrates. For
Remanufacture/Reengineering/Reverse Engineering
the unit price is of course dependent of how many units that is
produced, and large series will decrease the price significantly,
see also presentation in reference [7]. The optimum solution for a
specific system – what “R” to choose - will however vary, depending
on the prerequites.
The obsolescence awareness at the utilities must increase and get
management attention, because there is a poten- tial for saving a
lot of money in this area. Available spare parts mean that an
upgrade project can be avoided. If the required spare part is not
available at the plant, available tools like databases RAPID and
POMS offering spare parts could be used.
Legal aspects For Re-engineering and Reverse Engineering the legal
aspects must be considered and analysed case by case. In many case
this isn’t a problem since the equipment was procured in the 70’s
or the 80’s, the main concern will be if there are any contractual
restraints still effective between the parties. Experience from
interviews is that legal issues is usually not the show stopper,
but that no supplier will engage in a project if the legal issues
are not clear.
Competence and networking The utilities must understand the
potential of having experts in the obsolescence area and make this
area more attractive. Mapping competence needs is a vital part of
the analysis that is required when deciding on the replacement
strategy for a component and strategy. Competence regar- ding these
old systems is important so skills transferring must be
prioritized.
It is also important to prioritize networking, for example user’s
groups like Nuclear Utility Obsolescence Group, NUOG and the newly
founded European Nuclear Utility Obsolescence Group, E-NUOG.
The nuclear market, especially in the Nordic countries, is limited
and the utilities are in many cases dependent on the original
equipment manufacturer (OEM). This needs to be considered both from
the utility side and the OEM side. The importance of support
agreements should not be underestimated even if they cost money.
They can however prove to be cost efficient in the long term.
Does the exiting system or component
fulfil today’s requirement
Replace
Figure 2 Complexity and cost differs between the different options.
The optimum solution from a lifetime cost perspective differs from
project to project.
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1. REPLACE
Parts that are obsole- te (not manufactured or supported by the
original equipment manufacturer (OEM) any more) might still be
available in other places: warehouses at other vendors, spare part
storage at other nuclear plants, plants that have shut down, fossil
power plants, or chemical process industries or bought on the open
market.
2. REPAIR
Circuit boards can be repaired, exchanging the broken compo- nent
with an identical one (same properties, same manufacturer). This
can be done either by the OEM or, if the product is out of support,
by another vendor or by the utility itself.
3. REFURBISH
When a circuit board is refurbished, an as-found inspection and
testing is perfor- med. Components are evaluated with historical
failure rates and broken as well as age sensitive compo- nents are
identified and exchanged. The circuit board is cleaned up and the
container/box/front cover is exchanged if needed. Then the board is
tested, calibrated, burned-in and qualified.
4. RE- MANUFACTURE
Parts that are not ma- nufactured any more by the OEM can be
remanufactured. A small special run can be done either by the OEM
or by another vendor.
5. RE- ENGINEERING
Re-engineering is when a third party manufacturer or OEM uses
origi- nal requirements, specifications and documentations to
produce new items. Some modifications might be done, typi- cally
within physical construction and/ or mounting. The logical
functions and layout of intercon- nections between discrete
components are usually kept.
6. REVERSED ENGINEERING
Reverse engineering is when a third party manufactu- rer or OEM
takes an item apart to understand its functions. None or only some
original requirements, specifications and documentations are
available. Mo- difications might be done. If the logical functions
and layout of interconnections between discrete compo- nents are
modified, or larger modifications are made within the physical
construction and/or mounting, the activity is called a black-box
reverse engineering. The functionality, size and outer connections
are the same as for the old item.
7. REDESIGN
In some cases keeping the old tech- nology is not a viable option.
A redesign can be carried out either by the OEM or by another
vendor who then would need all documenta- tion from the plant and
the OEM and perform testing on the old equipment. Crucial to
redesign is identifying all new failure modes and any differences
in functionality.
Definition o the Seven R’s
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When maintaining a system is not a viable option, or if there are
other reasons for replacing the system, a number of good practices
have been identified in work performed by ENSRIC [6]. Some of these
good practices are highlighted here:
• The lifecycle cost shall be considered when new systems are
installed. The cost for installation is 20-30% of the system’s
total lifecycle cost and therefore good planning from the beginning
will save money in the long run.
• When a system shall be replaced, requirement specifica- tion and
good knowledge about the system is necessary. The supplier should
be invited to work on site to make sure that the supplier
understands the existing system, functions and the different
interfaces.
• There are many advantages if the nuclear power plant staff can be
involved in the project as much as possible. This is a good
opportunity for them to really learn and understand the system.
It’s very hard to get this kind of in depth knowledge when the
system is installed and up and running.
• During the design of the system, be restrictive with implementing
new functions and don’t develop non-standard functions that are not
part of the product.
• When choosing the supplier, try to use those that are familiar
with the nuclear industry. Use standard I&C systems, because
this will ease future obstacles like com- petence, spare parts and
tools; thereby lowering the life cycle cost.
• The complexity of a system or equipment is utterly determined by
the design - minimize interactions between systems and number of
functions in the system
Replacing or upgrading a system
It is essential that the nuclear power plant staff are involved in
replacing the system. This is a good opportunity for them to really
learn and understand the system and to get in depth
knowledge.
Photo: C urtiss-W
right Photo: Spherea
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• non-safety classified • has comprehensive documentation • well
understood function and purpose • problem to find spare parts •
degrading performance • declining system experience and
knowledge.
Following the experience from the modernization projects replacing
large parts of the analogue I&C systems with digital platforms
in Ringhals 1 & 2 and Oskarshamn 1 & 2, the pendulum has
turned in the opposite direction with a strong trend towards
extending the lifetime of the system, which usually means that
analogue systems will remain analogue. There are however cases
where the benefits of digital technology overweigh the costs and
man hours needed. Several medium sized exchange projects were
investigated to identify the obstacles and opportunities of
computerized technology.
In non-safety systems or equipment, the benefits, such as
self-monitoring and versatility, are considered to outweigh the
drawbacks with the technology, such as the shorter life cycle.
Avoiding customized solutions in favour of industry off the shelf
products is also a key in this. The complexity of a system or
equipment is utterly deter- mined by the design, rather than
whether it is computeri- zed or not. Therefore, it’s important
during design phase to minimize interactions between systems and
number of functions in the system.
Gradual replacement of systems/equipment and working step by step
is preferred, and the supplier should be invited to work on site to
get familiar with functionalities and system architecture.
From analogue to computerized
KEY FACTORS FOR SUCCESSFULLY UPGRADED SYSTEMS The following key
factors were identified for successfully upgraded systems:
• Use a dedicated system or equipment suitable for the task. • Only
incorporate enough functionality to serve its purpose (but no
more). • Only have a few interfaces to other systems and equipment.
• Only have one, or possibly a few, clearly defined
functions.
An option to using computerized technology is the use of Field
Programmable Gate Arrays, FPGA:s. They are high-density logic chips
with the ability to simulate any digital logic design. FPGAs
contain blocks of logic gates and registers that can be
interconnected to produce an applica- tion-specific processing
function by loading a specific set of gate interconnections into
the chip. That is, the logic functions are implemented directly in
hardware.
FPGA based solutions are becoming more common in
Computerized in hardware format the nuclear industry as their
advantages are increasingly recognised by the industry. The
verification and valida- tion process of this technology however
resembles that of microprocessors, so it’s more complex than that
of analogue technology. There is a wide range of installations
using FPGA technology, from small components to platform
installations. This technology might play a role in future plant
modernization projects.
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Nordic applications
The process of extending the lifetime of the I&C structures in
the Nordic nuclear power plants has only just started. A few
projects have though been performed, for example:
System/Scope Method Description
CombiX Remanufacture The CombiX platforms are widely used in the
Nordic nuclear power plants. Pilot projects have been performed in
Forsmark and TVO, letting the OEM ABB remanufacture components from
Combimatic/Combitrol/Combiflex. Different approaches were chosen in
the two pilot projects. Forsmark did both design and installation.
TVO let ABB do the design but made the installations themselves.
Both approaches turned out to be successful. For more information
see [7].
Plant Computer Re-Engineering/ Reverse Engineering
Replacing old obsolete computers from the 80’s with a modern PC
computers. Emulator is developed so that the existing applica- tion
software can be reused together with existing interface.
Leak detection Reverse Engineering Old digital “scanner” from the
80’s which malfunctioned and there were no available spare parts.
The “scanner” was replaced with a modern digital system.
Functionality was restored with reversed engineering and the
existing interface was maintained.
Photo: O KG
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Conclusions
References 1. Life time extension of present analogue I&C
systems,
Energiforsk REPORT 2015:159, Annika Leonard, Vatten- fall AB
2. Replacing obsolete nuclear instrumentation and control
equipment, Energiforsk REPORT 2016:307, Annika Leo- nard,
Anna-Karin Sundqvist, Vattenfall AB
3. Reengineering and reverse engineering – Two methods of replacing
obsolete equipment, Energiforsk REPORT 2016:338, Anna-Karin
Sundqvist, Annika Leonard,
Vattenfall AB 4. Field Programmable Gate Arrays in safety related
instru-
mentation and control applications REPORT 2015:112, Catherine
Menon, Sofia Guerra, Adelard LLP
5. Verification and validation techniques for I&C applica-
tions in Nordic NPPs, Energiforsk REPORT 2016:268, Samuel George,
Sofia Guerra, Cathereine Menon, Ade- lard LLP
6. Upgrading to modern Computerized I&C Systems, Energiforsk
REPORT 2016:324, Christoffer Calås, Karin Ferm, Tommy Krogell,
Semcon Sweden AB
7. Documentation from seminar “Life time extension of nuclear
I&C 2016”, http://www.energiforsk.se/program/
karnkraftens-styr-och-kontrollsystem-ensric/seminars/
life-time-extension-of-nuclear-ic-2016/
ENSRIC has investigated several ways of extending the I&C
systems life time in the Nordic nuclear power plants. This report
summaries this extensive work and would like to highlight the
following findings for maintaining and replacing systems.
Maintain
• Develop a strategy for all installed I&C systems, showing
which systems are prioritized, what measures to take and when they
need to be taken.
• Increase the attention regarding obsolescence awa- reness,
especially from management – this leads to savings.
• Promote networking • Build and transfer competence – before it’s
too late • The nuclear market is decreasing, but utilities
and
original equipment manufacturers are dependent on each other –
consider support agreements.
Replace/upgrade
• Don’t introduce unique solutions. Observe others, internationally
and in other lines of business, and learn from them.
• Try to maintain the original function in the existing sys- tems
and implement new functions in separate systems. Maintain the
boundaries as they are.
• Stay with technical standard used at the utility, don’t introduce
new platforms.
• Keep it simple. Complexity of the system or equipment is utterly
determined by the design – minimize interac- tions between systems
and number of functions in the system.
LIFETIME EXTENSION OF NUCLEAR INSTRUMENTATION AND CONTROL SYSTEMS
The Nordic nuclear fleet has/is about to approach 40-years
lifetime, and several instrumentation and control systems in the
plants need to be modernized. This makes it important to have a
clear understanding of the different alternatives on how to handle
aging in a LTO perspective. The alternatives range from a simple
repair to a complex reversed engineering or even redesign, and the
optimum choice must be decided from project to project. Key factors
in the decision-making process are for example available
documentation, status of the existing system, remaining lifetime of
the plant etc. This report summarizes findings regarding cost
efficient lifetime extension from several activities within R&D
program Energiforsk Safety Related Nuclear Instrumentation and
Control system (ENSRIC).
Energiforsk AB | Phone: 08- 677 25 30 | E-mail:
[email protected] | www.energiforsk.se Office: Olof Palmes
gata 31, Stockholm. Nordenskiöldsgatan 6, Malmö |Address: 101 53
Stockholm