LIFETIME EXTENSION OF NUCLEAR INSTRUMENTATION AND …

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 S T EM S
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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
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 S T EM S 3
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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 approaches 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 business case for a replacement investment.
Replacement strategy
It is important to have a good knowledge of the requirements 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 recommendation 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 potential 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 regarding 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 obsolete (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 component 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 performed. Components are evaluated with historical failure rates and broken as well as age sensitive components 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 manufactured 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 original 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 interconnections between discrete components are usually kept.
6. REVERSED ENGINEERING
Reverse engineering is when a third party manufacturer 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 components 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 technology is not a viable option. A redesign can be carried out either by the OEM or by another vendor who then would need all documentation 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 competence, 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.
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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 determined by the design, rather than whether it is computerized 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 validation 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.
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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 applications 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 awareness, 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 systems 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 interactions 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

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