Power Systems and Simulation

Providing more than just training devices, our simulator solutions—powered by L3 MAPPS' unparalleled Orchid® suite of simulation products—will take your engineering team to new heights in approaching plant design issues, procedural deficiencies and reliability improvements.

Full Scope Simulators

Superior Training Systems from the World’s Leading Simulation Company

L3 MAPPS simulators provide superior real world power plant training. L3 MAPPS offers a variety of products and services including full scope power plant simulators, part-task trainers, simulator retrofits and upgrades. We provide conception to completion turnkey systems, specific components, and simulator design tools as required by the customer. With worldwide presence, a solid leadership position and the ability to provide any level of customer support, L3 MAPPS ensures the success of your simulator projects. Our simulators offer the highest quality in simulation fidelity and training to provide trainees and instructors with userfriendly tools for learning, controlling and exploring complex power plant systems.

The superior training environments of our simulators provide clear advantages for operator licensing, optimizing plant operating procedures and reducing costs. Operators trained on L3 MAPPS simulator environments gain the skills necessary to increase plant performance, minimize downtime, and provide confident emergency response. Simulator uses include interactive team training, severe incident management, plant design testing, and startup/shutdown optimization. L3 MAPPS’ replica-quality hardware controls and touch-screen virtual panels create realistic and credible control environments. Real-time response to operator actions and interactive instructor control ensure maximum training effectiveness and adaptability. Any scenario, no matter how complex or dangerous in a real plant, can be reproduced, monitored and varied in real-time, providing a valuable tool for training and plant engineering. Our commitment to customer support extends far beyond industry norms. L3 MAPPS’ unique knowledge transfer program allows customers to gain expertise and total confidence in the simulator. Users can directly implement simulator modifications to exactly reflect plant changes, evolve their training programs and expand simulator use into other areas.

Uses and Advantages

Cost effective training for:

  • Both experienced operators and new recruits
  • Overall plant and individual system operation and control
  • Team training to study interaction and improve performance
  • Emergency plan implementation and incident management
  • Command of malfunction and transient situations
  • I&C familiarization
  • Plant process computer training and testing
  • Classroom simulator trainings

Other Benefits:

  • Operations optimization, including startup and shutdown
  • Reduced unplanned outages
  • Improved plant safety
  • Easy to upgrade simulator and keep current with plant
  • Multiple configurations on one simulator
  • Analysis of plant response to equipment and/or instrument failure
  • Efficient plant design planning and upgrading
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Simulator Upgrades


There are many power plant simulators worldwide developed by different companies. Rapid advances in computing technology now permit simulator owners to get maximum value from their simulators by implementing cost-effective updates. Evolving training needs, greater fidelity expectations, changing standards, plant modifications and plant life extensions fuel simulator updates.

Now, it’s possible to evolve your simulator to the state-of-the-art in an economical manner.

The first phase of simulator updates usually involves updating the major simulator platforms including the simulation computer, the instructor station and/or the panel interface system. L3 MAPPS responds to its customer update needs with a variety of solutions. Every customer has specific requirements – and our solution is customized to address those needs individually.

  • Simulation Computer Replacements

    A large majority of simulators are equipped with dated computers running proprietary operating systems with limited computing resources and almost no scalability.

    L3 MAPPS re-platforms simulation computers with open PC-based systems. A PC server or workstation acting as a simulation computer provides a low-cost, scalable and easy to maintain solution. But, there are other ways to achieve the results needed which consider our customers’ corporate strategies, IT needs and available resources. L3 MAPPS offers its simulation computer updates and associated simulator executive systems on a choice of operating systems – either on various Microsoft Windows operating systems or on the Linux operating system.

    Instructor Station Replacements

    Accompanying simulation computer replacements, it is natural to expect more from the instructor station – the simulator’s control centre. L3 MAPPS provides Orchid® Instructor Station (Orchid® IS), a powerful instructor station that truly puts the instructor in full command of simulator session management. Orchid® IS is provided on a PC with the Windows operating system. To enrich the instructor’s experience and the total learning experience, L3 MAPPS' high-end graphics of plant controls (virtual panels) and active system schematics provide additional flexibility and ease-of-use. Instructors can also use the photo-realistic virtual panels and system schematics on the simulator to monitor control panel response and insert malfunctions and overrides.

    The virtual panels and system schematics can also be manipulated by trainees to exercise simulated plant operations on the full-scale simulator. Unlocking even further value, the exact same graphics coupled with the simulation can be utilized on other stand-alone computers as Classroom Simulators.

    Panel Interface System

    Simulators are equipped with various interface (I/O) systems, depending on who the original vendor was and which interface system technologies were available at the time the simulator was developed. The interface system is a crucial element in any full scope nuclear power plant simulator as it acts as the gateway between the simulation computer and the majority of the switches, indicators and annunciators on the simulator control room panels. Today, with the computing power and advanced software technologies that are available, there is no reason to settle for device response times short of real-time. At L3 MAPPS, we have a proven record of equipping simulators with reliable interface systems, with various third-party interface systems, depending on customer preference and economics.

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The second stage of simulator updates typically involves exploiting some of the additional computing resources to improve modeling fidelity, once the simulation computer replacement has been validated. The first system models to be updated are the reactor core and nuclear steam supply systems as these updates yield maximum simulation fidelity improvements at a low cost. It is also common to include other model updates in the second stage if required, such as improving the containment and HVAC models.

  • Reactor Core Model Replacement

    L3 MAPPS’ Comet™ and Comet Plus™ are advanced models for the simulation of reactor neutron kinetics based on a rigorous application of first principle physics and advanced numerical techniques. The models have been installed worldwide on numerous simulators currently certified for training.

    Orchid® Core Builder (Orchid® CB) is a dynamic utility for easy creation and validation of cycle-specific reactor data and allows users to monitor, in realtime, all the quantities of interest in the reactor core using two-dimensional and three-dimensional maps and plots. Orchid® CB runs on L3 MAPPS and third-party simulators.

    Advanced Nuclear Steam Supply System Models

    L3 MAPPS’ advanced thermal-hydraulic model (ANTHEM™) is based on a rigorous application of the equations of mass, momentum, and energy conservation and implicit numerical techniques combined with the latest developments in computer technology. ANTHEM has been successfully installed and validated on numerous simulators and simulator upgrades currently certified for training.

    ANTHEM2000™ couples the proven ANTHEM model into the Orchid® Modeling Environment (Orchid® ME) graphical simulation environment, providing superior visibility and model maintenance facilities to the user.

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Once the simulator’s primary system models are of high fidelity, its prudent to take advantage of other software technologies that will allow the simulator owner to have full access to the latest in technology and securing a reliable simulation future – across all simulated systems.

  • High Performance From All Simulation Models

    Whether your electrical switchyard, feedwater system or any model needs to be updated, the improvements can be made at the simulator owner’s own pace. Furthermore, all models are developed entirely graphically using graphical symbols of your plant components from extensive component libraries built up by L3 MAPPS for over 15 years. This model implementation method is made possible with L3 MAPPS' Orchid® ME simulation environment and allows users to easily keep their models up-to-date with routine plant changes. Orchid® ME runs on L3 MAPPS and third-party simulators.

    Orchid® ME creates a realistic "working picture" of the entire plant, with every component interactively linked. Each component’s variables (temperature, flow, pressure, etc.) are controlled, monitored and recorded in real-time.

    Programming knowledge is not required. Simply place or move components around on the screen, and Orchid® ME automatically generates the underlying simulation models. The Orchid® ME models are dynamic, graphical representations of proposed plant designs or modifications complete with interactive controls.

    System developers, operators and instructors are free to explore and test new configurations, operational procedures and "what-if" scenarios without any complex calculation or coding. Orchid® ME is a powerful tool to improve plant efficiency without actually affecting the plant before the changes are tested and validated.

    Advantages for training include true flexibility and total control of present and future training programs and objectives.

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The fourth upgrade phase is to replace the simulator’s information or control system. Whether an update is required to the original simulator plant process computer (PPC) or a new distributed control system (DCS) is being implemented as a result of a plant modernization, there are two solutions that are possible on the simulator to ensure that the PPC or DCS appears and behaves exactly the same as at the plant, and responds to all simulator commands – simulation and stimulation.

  • Simulation Or Stimulation

    With stimulation, the original supplier’s equipment is used as part of the simulator and software is developed to allow that equipment to communicate with the simulation computer and to accommodate simulation commands.

    With simulation, L3 MAPPS utilizes its Orchid® Control System (Orchid® CS) package. The foundation for Orchid® CS is a real-time data acquisition and control system comprised of geographically distributed nodes used for the monitoring and automation of electrical substations, nuclear power plants, hydroelectric power plants, and fossil power plants. Its well-integrated architecture provides a complete solution to customers, including I/O, redundancy, and operator user interfaces. Orchid® CS is offered on Windows.

    L3 MAPPS' simulation solution relies on the control system functions of Orchid® CS to provide the necessary functionality of the target PPC or DCS, the operator interface’s look-and-feel is replicated and simulation commands (e.g. freeze, run, etc.) are already built into Orchid® CS.

    The choice of utilizing stimulation or simulation depends on customer preference and economics.

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Learning Technologies


The objectives of a nuclear training program are well documented and the methods which to accomplish the learning objectives are clearly identified. With L3 MAPPS Learning Technologies, the use of visualization is designed to further those objectives by adding another tool in the arsenal to improve or augment the learning experience with a higher degree of efficiency, retention and accessibility. Visualization components can be used in standalone training media or can easily be integrated with the existing full scope simulator and/or existing classroom training programs.

Studies have shown that learning efficiency and retention are augmented by using a visually rich, interactive and immersive teaching environment, which can be summarized by these two principles:

  • Seeing is understanding
  • Interacting helps remember

To enhance existing training programs or to support the establishment of newcomer training programs, L3 MAPPS has devised learning technologies based on these principles. L3 MAPPS has coupled computer visualizations with high-fidelity simulation to bring real-time, simulation-driven animated components and systems allowing immersive and participatory, individual or classroom learning.

Learning Modules:
Getting the Fundamentals Right

Experiential learning yields the highest student retention rates. But typical classroom training is still characterized by textbooks, lectures and presentations. Until now, that is. L3 MAPPS introduces Learning Modules to augment the generic fundamentals training currently used in today’s curriculums. With Learning Modules, colleges and operators can empower students to gain maximum learning value with hands-on experience. Learning Modules help students visualize various equipment such as valves, pumps and heat exchangers. Remove the uncertainty of mentally picturing equipment construction and operation—touch it, assemble it, watch it work—in the classroom and on portable student tablets.

Learning Modules are powered with Bridgeworks, a trademark of Bridgeborn, Inc.

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System Knowledge Modules:
Making Plant Drawings Come Alive

Introducing System Knowledge Modules, a powerful new hands-on training tool for power plant systems training that achieves high student retention rates through experiential learning. Unlike the uncertainty of traditional classroom learning where students must imagine how plant systems behave, college instructors and plant operators can now empower students to run them, control them and get instant feedback on actions taken.

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Learning Simulators:
Enhancing Nuclear Plant Learning

As the world’s preeminent supplier of full scope operator training simulators, L3 MAPPS introduces Learning Simulators to bridge the gap between early nuclear worker training and operator training. This innovative software environment leverages our detailed and accurate plant models. But instead of focusing on the procedural aspects of operating your plant, Learning Simulators provide a fully interactive and visual environment designed to facilitate true understanding of your plant’s behavior. Learning Simulators can be delivered with pre-recorded scenarios or can even be connected to your full scope simulator for real-time feedback. Learning Simulators are available for different power plant types.

Learning Simulators are powered with Bridgeworks, a trademark of Bridgeborn, Inc.

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Training Delivery:
Flexible Learning Technologies for Flexible Training Delivery

L3 MAPPS’ learning technologies are designed to provide you with maximum learning potential in a host of training environments. Learning Modules, System Knowledge Modules and Learning Simulators are well suited for classroom training, individual learning and/or team building using desktop or tablet PCs with or without touch technology.

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Learning Modules are powered with Bridgeworks, a trademark of Bridgeborn, Inc.

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Classroom Simulators

Extending The Benefits Of Classroom training

Simulator users have already invested in their high fidelity simulators with L3 MAPPS virtual panels which run on the instructor station and which are also available in student mode. Take it a step further with Orchid® Touch Interface (Orchid® TI). Offload the demands on your full scope simulator by reusing the exact simulation software and virtual panels without a significant investment. With new and improved large touch screen technology, L3 MAPPS now brings classroom training to another level with Orchid® TI.

Hardware Configuration

Orchid® TI takes L3 MAPPS' control and auxiliary room panel displays to a new level of realism. High fidelity panel graphics are displayed on large touch screen monitors with 1080p (full HD) resolution. The monitors are mounted on frames and can be arranged in many different configurations to mimic different control rooms. Orchid® TI can be used on one bay of large touch screens capable of displaying all panels of the control room or several monitor bays configured differently to replicate different control room layouts.

Use one bay of large touch screen monitors or reproduce the entire control room with multiple monitor bays.

The top monitor of three-monitor bay articulates allowing passage through a standard 32" x 84" doorframe. Each bay is mounted on swivel casters for easy manoeuvring from one room to another. Levelling pads are also provided in each bay to fix them in place once they are rolled into their final destination.

A two-monitor version is also available for desk operations.

Orchid TI Image

User Interface

Orchid® TI's touch screen interface allows students to operate the panel graphics manually and obtain life-like visual and audible real-time responses.

To keep training as realistic as possible, the popular panning and zooming of the soft panels in the instructor station are disabled for Orchid® TI, providing individual students and teams the opportunity to know the actual location and orientation of panel devices that are vital to operating your plant. Navigation can be performed from one panel to another without the risk of having an unrealistic layout of panel devices.

In an environment where all panels are not visible at the same time, off-view annunciators can be missed, creating a gap in training. With Orchid® TI, any time an off-screen alarm actuates (annunciators located on panels in an area that the learner is not presently looking at), an indicator appears to warn the student. With a simple touch of that same indicator, an overview of the control room is displayed, indicating which panel is in alarm. From that same interface, the student can then navigate to it quickly.


  • Full scale control room training environment at a fraction of the cost of your full scope simulator, capitalizing on the investment you have already made.
  • Life-like training environment to augment your current full scope simulator environment, for both individual and team training.
  • Offload your full scope simulator by using a device that fits the needs of young learners.
  • L3 MAPPS' client-server architecture guarantees realistic response times for all virtual panels, whether the simulated plant is in normal conditions or a severe transient is being experienced.
  • Take full advantage of the powerful instructor station capabilities you already have through Orchid® Instructor Station with Orchid® Touch Interface
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Simulation Environment

Total Development & Simulation Environment

L3 MAPPS has always been known for delivering high-quality simulators. With its current suite of simulation products, the Orchid® product suite, L3 MAPPS continues this tradition with a complete, cutting-edge simulation software environment.

The Orchid® tools have been designed to be highly integrated with one another to create an effective and efficient working environment. Each tool follows a standardized approach, providing the same guidelines for menu structure, icons, documentation and even training material. By focusing on the use of common icons, layouts, themes and menus, we have been able to minimize our users’ learning curve in adopting the Orchid® products.

Features and benefits

Orchid® features the latest in graphical user interfaces using an enhanced, modern look and feel, and providing an unparalleled level of customizability. Each Orchid® application comes loaded with new features that help our users utilize our tools as efficiently as possible. User manuals, help menus and tool tips are all accessible directly from within the tools. All Orchid® tools also come with Install-Shields, making each Orchid® application easy to install and to upgrade to newer versions.

Our tools are now faster and easier to maintain than ever. Orchid® supports recent releases of third-party software operating systems, database management tools and software compilers.

Using important feedback from our user community, we’ve incorporated hundreds of new features, making the Orchid® product suite a powerful and complete set of tools for all your simulation needs.

With its complete Orchid® product suite, L3 MAPPS continues to provide the highest standards of quality to all of our customers, aiming for even higher levels of customer satisfaction.

Advanced Models

Advanced Reactor and Thermal-hydraulic Models

L3 MAPPS’ advanced reactor (Comet™ and Comet Plus™) and thermal-hydraulic (ANTHEM™) models unlock maximum fidelity and performance from your simulator. The models are based on first principles and advanced numerical techniques, and are extensively proven with installations worldwide.

Comet™/Comet Plus™

Comet™/Comet Plus™

Advanced Reactor Kinetics Models



Advanced Steam Supply System Model

Severe Accident Simulation

L3 MAPPS can address your nuclear power plant severe accident simulation needs. The L3 MAPPS solution is backed by proven results on full scope real-time simulators.

Due to events in Japan in the wake of the 11 March 2011 earthquake and tsunami, nuclear regulators throughout the world will now more closely scrutinize the capability of nuclear power plant operators to manage situations caused by beyond design basis and severe accidents. This close scrutiny will require that operators are trained in handling situations involving severe accidents, and that their training includes knowledge on and experience in performing recovery operations safely.

A severe accident can occur if a loss of fuel cooling is not mitigated in time. L3 MAPPS' thermal-hydraulic model simulates various effects related to loss of cooling such as steam formation, core heat-up, fuel failure and hydrogen generation. However, the primary assumption in ANTHEM™ is that there is no change in the geometry of the fuel or the surrounding structures. This is also true for all other thermal-hydraulic models used for power plant simulation. If such conditions must be simulated, then additional codes are required. Therefore, for the purposes of simulation, a severe accident is defined as any initiating event whose evolution results in a change of geometry of the fuel or the surrounding structure.

Highly sophisticated computer codes have long existed to analyze plant designs. They are designed to be used in an off-line, stand-alone, non-continuous and non-real-time application. An example of such a design code is MAAP (Modular Accident Analysis Program). MAAP is an internationally recognized model used to analyze severe accidents and provided under license from EPRI. L3 MAPPS supports both MAAP4 and MAAP5. The code considers a number of processes that occur during severe accident conditions such as:

  • Steam formation
  • Core heat-up
  • Cladding oxidation and H2 evolution
  • Vessel failure
  • Core debris-concrete interactions
  • Ignitions of combustible gases
  • Fluid entrainment by high-velocity gases
  • Fission product releases transport and deposition

The plant systems included in the scope of MAAP models are:

  • Reactor Coolant System
  • Steam Generators and Main Steam Header
  • Reactor Core
  • Containment
  • Spent Fuel Pool

While the models for these systems are sophisticated, they are designed specifically to simulate severe accident conditions. Other plant systems, such as core cooling systems, balance of plant systems and control systems, are treated as boundary conditions or functionally simulated. For this reason, MAAP is used for severe accident simulation and cannot be considered a model that can be used for all plant operations that are typically considered in a real-time simulator.

Implementing MAAP-based Severe Accident Simulation on Real-time Simulators

L3 MAPPS has chosen to integrate the MAAP code directly within its Orchid® simulation environment rather than treating it as a separate external application. Integration within the Orchid® Simulator Executive removes the need for any communication software and ensures that MAAP is properly synchronized with other models in the simulator. Integration within the Orchid database ensures that MAAP is transparently included within Orchid® Instructor Station initial conditions. Orchid® Instructor Station is used to run the simulator with MAAP models for severe accident training or with the conventional models for non-severe accident training.

L3 MAPPS adapts the MAAP application to be able to control the time-step and thus ensures that MAAP runs synchronously with the rest of the simulator model applications.

L3 MAPPS also adapts MAAP to the simulated reference plant. This includes customization to the plant-specific data (particularly geometry) of the reference plant and replacement of boundary systems within MAAP with interfaces to the dynamic full scope simulator models. Adaptations by L3 MAPPS to the MAAP code are kept to a minimum so that (a) the fidelity between the simulator and offline version of MAAP is ensured, (b) benchmarking the simulator version of MAAP against the offline version can be done easily, and (c) future upgrades of MAAP routines can be easily implemented on our simulators.

Simulators can also be equipped with 2-D and 3-D animated, interactive visualizations of the reactor vessel, containment building and spent fuel pool to provide operators and engineers with additional insight into the behaviour of the plant during severe accidents.

SAS Dual Monitor Image

L3 MAPPS has successfully integrated MAAP4 for the Krško (PWR) full scope simulator (FSS) for Nuklearna Elektrarna Krško and MAAP5 for China’s Ling Ao Phase II FSS (PWR). L3 MAPPS is also delivering a real-time implementation of MAAP4 for the Olkiluoto 3 (OL3) FSS - the world's first full scope simulator for a Generation III plant and a MAAP5-based severe accident simulation for the Susquehanna FSS (BWR).


  • FMAAP is widely accepted in the industry as an accurate analysis code in the area of severe accident analysis
  • The integration of MAAP models in the simulator ensures that effective training can be provided to operators during severe accident conditions
  • Emergency procedures can be developed and validated on the full scope simulator
  • The simulator can be used for emergency planning drills
  • Enhanced visualization makes it possible to truly comprehend the effects of severe accidents

MAAP is an Electric Power Research Institute (EPRI) software program that performs severe accident analysis for nuclear power plants, including assessments of core damage and radiological transport. A valid license to MAAP from EPRI for customer’s use of MAAP is required prior to a customer being able to use MAAP with Licensee’s simulator products.

EPRI (www.epri.com) conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent nonprofit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, health, safety and the environment. EPRI does not endorse any third-party products or services. Interested vendors may contact EPRI for a license to MAAP.

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Simulator DCS Solutions

Distributed control systems (DCS)

Sometimes known as Digital Control Systems, DCSs are being applied extensively to nuclear power plant refurbishments and new plant builds. L3 MAPPS has been engaged in numerous simulator projects—both modernizations and new full scope simulators―that require the implementation of DCSs from various vendors. There are different techniques for adding DCSs to the process simulation and for ensuring that the process simulation and the DCS interact correctly. Through our experience with power generation professionals, we have found that these techniques are not always that apparent. Some of these techniques are reviewed below.

What is a DCS?

The following (adapted from Wikipedia) adequately describes a DCS:

A DCS typically uses custom-designed processors as controllers with vendor-specific control software and uses both proprietary interconnections and communications protocols for communication. Controllers have extensive computational capabilities and in addition to proportional, integral and derivative control, can perform logic and sequential control. Input and output (I/O) modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (a.k.a. field sensors) and the output modules transmit control signals calculated by the controller to actuators in the field. Computer buses connect the processor and I/O modules. Buses also connect the distributed controllers to the human-machine interface (HMI) or control consoles.

Incorporating DCSs on simulators

The three techniques that are commonly used for adopting DCSs on simulators are stimulation, emulation and simulation. The following definitions are adapted from the IAEA publication IAEA-TECDOC-1500, Guidelines for upgrade and modernization of nuclear power plant simulators :

DCS stimulation

Implementation of a replica of the reference plant DCS on the simulator using actual DCS hardware and application software as installed on the reference plant.

DCS emulation

Implementation of the reference plant DCS on the simulator using the same application software installed on the reference plant but running on the lower cost simulator hardware and operating system. In the case of DCS controls, emulation is sometimes referred to as “virtual machine,” “virtual stimulation” or “virtual controllers.”

DCS simulation

Implementation of the reference plant DCS by simulating the DCS functionality using simulator vendor tools.

On the surface, these definitions appear straightforward enough. However, each of these techniques has advantages and disadvantages, and the right choice for a particular project will depend on a number of factors including the architecture of the DCS, the availability of a simulator-ready solution from the DCS vendor, the availability of upstream proprietary DCS data, the data delivery schedule, the cost, end-user preferences and whether the simulator is intended for engineering, training or both. It should also be noted that a particular project may use different techniques for different DCSs and even different techniques (a hybrid solution) for the control and HMI parts of the DCS. Advantages and disadvantages of each technique as they apply to DCS controls and HMI are explored below.

DCS Control

Stimulation and emulation have the advantage of running the same control software (as generated by the DCS configuration tools) that runs in the DCS controllers of the actual plant. This provides maximum fidelity, facilitates updating the simulator when the plant DCS software changes and is, of course, particularly useful if the simulator is being used as a validation tool for the DCS. Nevertheless, stimulation and emulation typically appear as external applications to the simulator environment and, as such, modifications are required to be compatible with the simulator environment. The proprietary nature of the software and hardware dictates that the modifications are available, if at all, only from the DCS vendor or its partners. For a simulator, the DCS application software must be adapted to support simulator functions such as freeze, run, backtrack and store/restore either by adding this functionality to the DCS software itself or by adapting the DCS software to run as an application within the simulator environment. These modifications must be extensively evaluated. In addition, a stimulated solution may also require specialized hardware and software to interface the process simulation to the control application software running on the DCS controllers. The design of this interface is dependent on the design of the DCS itself. In the case of emulation, a communications interface is also required between the process simulation environment and the emulation, unless the emulation has been adapted to run in the simulation environment.

Of the three techniques, the stimulation solution provides the highest possible fidelity, but at the highest cost due to the modifications and the cost of hardware acquisition and software licenses. In fact, the high cost of the proprietary DCS hardware means that this solution is in practice rarely chosen for the control application software on the simulator. Emulation of the control application software addresses this problem by eliminating the need to use the actual DCS controllers, though the cost of software licenses from the DCS vendor may still be substantial. This is an important consideration when the simulator consists of a suite of simulation instances such as the full scope simulator, development platforms and classroom simulators.

With simulation, the logic represented by the DCS function plans is reproduced using the modeling tool. Simulation can take place either by manually redrawing the function plans or by automatically importing (translating) the function plans. The latter is more efficient, but requires that the function plans contain all interface information and be available in a known electronic format. Simulation also requires object libraries that reproduce the functionality of the DCS functions blocks. Most DCS vendors use a combination of off-the-shelf function blocks (AND, OR, etc.) and custom function blocks. For the latter, access to a functional specification (or ideally the code itself) is required to accurately reproduce the functionality of the controls.

The fact that stimulation and emulation use the same application code as the real station has the potential of facilitating engineering simulator applications and simulator maintenance in terms of commissioning the plant DCS, validating future DCS changes and implementing plant changes on the simulator. There are nevertheless potential disadvantages related to whether the DCS vendor’s implementation of initial conditions (ICs) allows efficient updates of existing ICs and whether there is support for multiple configurations and configuration rollbacks. Another possible disadvantage if the simulator is implemented in parallel to the plant controls is the cycle time required to receive the application software and modifications that address logic errors detected on the simulator, since this is typically determined by the plant design cycle.

Technique Potential Advantages Possible Disadvantages

- Highest functional and physical replication of control and HMI
- Fast implementation of plant changes
- Pre-testing of plant changes

- Highest hardware and software license cost
- Implementation and validation of simulator-specific functionality
- Efficiency of IC maintenance
- Delivery and modification of simulator DCS application software highly dependent on actual progress of plant DCS design process
- Availability of multiple configuration support


- High functional and physical replication of control and HMI
- Lower hardware cost than stimulation
- Fast implementation of plant changes
- Pre-testing of plant changes

- High software license cost if provided by third parties
- Implementation and validation of simulator-specific functionality
- Efficiency of IC maintenance
- Delivery and modification of simulator DCS application software highly dependent on actual progress of plant DCS design process
- Availability of multiple configuration support


- High fidelity replication subject to data availability
- Lower hardware and software license costs
- Automatic/inherent support for simulator-specific functionality

- Logic can be implemented and modified quickly before implementation on DCS

- Access to proprietary data from DCS vendor
- More time consuming for validation of functional and physical fidelity

On the other hand, a major advantage of simulation is the built-in compatibility with the simulation environment including IC management tools and configuration management. The imported functions plans can be used to generate simulation code directly, either through a purpose-built code generator or by generating editable graphic schematics for the model building tool, provided all the topological data is available in the upstream data. The latter facilitates graphical modifications and debugging. An additional advantage for engineering simulators is that modifications to the logic can be implemented, interfaced to the process and tested directly within the simulation environment faster, before they are implemented on the DCS itself. In addition, licensing multiple copies of a simulation is usually more economical since it is fully controlled by the simulation vendor. This makes simulation the tool of choice during the basic design phase of the DCS. In fact, for new builds, early simulation followed by eventual emulation delivers the best of both worlds.


In the case of the DCS HMI, a stimulated or emulated solution also requires a communication interface and adaptation for the simulator functions. Emulation is particularly of interest when the HMI runs on expensive, safety qualified hardware. For HMIs that run on commercially available computer hardware, the choice between stimulation/emulation and simulation depends on the sophistication of the HMI itself. Simulation requires the faithful reproduction of all aspects of the look and feel of the HMI. While some parts of this process can be automated―such as the reproduction of operational pages—a fair amount must be manually reproduced. While simulation is technically feasible, the increasingly sophisticated nature of the HMI graphics usually makes stimulation the solution of choice. Nevertheless, as is the case for controls, simulation is a good choice for engineering applications for the initial design and verification and validation of the HMI, due to its rapid prototyping features and modest licensing costs.

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CANDU Plant Control Systems

The Evolution Continues

The first CANDU* reactor (Pickering A, Unit 1), began commercial operation in 1971 at Ontario Hydro's Pickering A reactor site, just east of Toronto. In 1973, the Pickering A Nuclear Generating Station equipped with four CANDU reactors, produced more electricity than any nuclear power station in the world at that time.

Through cooperation with CANDU designer Atomic Energy of Canada Ltd. (AECL) and/or Candu Energy, or directly with power generation utilities, L3 MAPPS has been supplying CANDU plant computer systems - known as Digital Control Computer (DCC) systems - for nuclear power plants since 1970. DCC systems are used to monitor and control all the major reactor and power plant functions. In response to demand, L3 MAPPS has continued to upgrade the technology over the last four decades.

L3 MAPPS has sold DCC systems for CANDU nuclear power plants in Argentina, Canada, China, Italy, Korea and Romania. Since 2006, L3 MAPPS has been working with the CANDU Owners Group (COG) to enhance the DCC technology and documentation to serve as a reference for future DCC projects. A current generation DCC system resides at L3 MAPPS' main Montréal, Canada facility and is used to provide support to all participating COG members until 2035.

System Overview

A typical system consists of two DCCs. DCC X and DCC Y are redundant on-line controllers, which control the nuclear reactor. Each controller uses a computer with purpose-built process I/O interface and peripherals housed in cabinets, and utilize additional freestanding peripherals such as keyboards, printers and monitors. A contact scanner is used to scan relay contacts, limit switches, or other similar types of contacts. The scanner is connected to both DCC X and DCC Y, but communicates with only the annunciating DCC.

Technology Basis

The DCC system architecture is centered on two technologies – the central processing unit (CPU) and the input/output (I/O) system. On a majority of the CANDU stations, the CPU technology has evolved from the initial Varian 70 family of microcomputers to the current Second Source Computers Inc. (SSCI) CPU, first the SSCI-125 generation and now the SSCI-890. Ontario Power Generation's (OPG) Darlington Nuclear Generating Station employs a DEC CPU architecture. The I/O system, based on the Datapath 50 data acquisition and control system technology is designed and manufactured to monitor and control CANDU reactor units. Every consideration has been taken into account throughout all stages of design and construction to ensure that the system operates with maximum efficiency and reliability.

CPU Progression


The SSCI-890 computer features a single board CPU, a cache board and 2MB memory modules. The CPU and memory communicate over a special system connector plane that eliminates inter-connect cables. The SSCI- 890 CPU includes mapped main memory. A map on the CPU board can perform efficient memory management for up to sixteen million bytes of main memory with full memory protection. The memory modules combine 2MB of metal-oxide semiconductor (MOS) memory with error-correcting code (ECC) on a single plug-in module.

Along with the SSCI-based CPU architecture, L3 MAPPS has supplied and supported the PDP-11/70 DCC CPU architecture. This implementation, in service for two decades at OPG's Darlington site, has recently been the subject of an innovative L3 MAPPS replacement through a fit, form, and function hardware emulation which included the processor, various system controller boards, system backplanes and an enhanced operator control panel.

Peripheral Systems and Interface Controllers Updates

In addition to the continuous enhancement of CPU performance of the DCCs, L3 MAPPS has updated and re-designed several peripheral equipment and interface controllers related to the data storage, printing, and the data acquisition interface with PCs. The new Bulk Storage Memory Unit increases the total memory size to 128MB and provides for an extended area of housing software applications and historical data storage buffers. The new technology of network printing – using fast laser printers – required an adaptation of printer controllers for alarm messaging and hardcopy functions.

Committed to continuous improvement of the DCC design, L3 MAPPS has successfully emulated the functionality of the Main Control Room Display System with the use of its VME-based technology. This emulation solution has resulted in a complete replacement of Ramtek equipment while maintaining the same DCC software developed by utilities and used on the original display system hardware. Along with the VME-based technology, L3 MAPPS is providing OPG's Darlington site with a new display system controller which adds enhanced performance through TCP/IP-based network capability.

The same VME-based technology was the baseline for replacing the Contact Scanner equipment. Presently, this implementation is in operation in units at the Qinshan Phase III Nuclear Power Project (Zhejiang, China), on Unit 2 at the Cernavoda Nuclear Power Plant (Cernavoda, Romania) and on Units 1 and 2 at the Bruce Nuclear Generating Station (Ontario, Canada).

Long-Term Support

L3 MAPPS' goal is to ensure that COG has a solid, reliable supplier on whom it can rely for its maintenance and support services. L3 MAPPS has been supporting the DCC for more than 40 years and L3 MAPPS is firmly committed to not only continue, but to enhance its support for the product line for the next 20 years.


*CANDU, Enhanced CANDU 6 and EC6 are registered trademarks of Atomic Energy of Canada Limited, exclusively licensed to Candu Energy Inc. CANDU is an acronym for CANada Deuterium Uranium. The CANDU system is a design that uses deuterium oxide (heavy water) as the moderator and coolant, and natural uranium as fuel.

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