Distributed Control System (DCS) Emulation vs. Simulation: Which is Better for Your Nuclear Power Plant Simulator?

The decision to use the distributed control system (DCS) vendor supported emulated (or virtual) solution versus the vendor’s traditional “simulated” approach is creating a lot of discussion in nuclear training.

You might be surprised to hear a simulation provider tell you that simulating the DCS is not always your best option. Well, that’s exactly what we’re saying. What you ultimately decide on depends on what’s best in the long run, from your training program to your pocketbook.

There are times when an emulated/virtual solution is unavailable. For example, a distributed control system provider may not have an emulated version of their software. However, this is becoming increasingly unlikely.

Many DCS vendors are developing emulated or virtual solutions for their products. Both GE and Westinghouse now have emulated/virtual solutions. Keep in mind the industry’s challenge of Delivering the Nuclear Promise for increasing efficiency and finding ways to lower costs. You should consider three key factors when evaluating emulated versus simulated DCS solutions for a simulator: fidelity, cost, and virtual commissioning benefits.

Why Does it Matter if I Have a High-Fidelity DCS?

With an emulated solution, the simulation vendor uses the actual proprietary plant software code and data file from the DCS vendor to create the solution in the simulator. This produces the highest fidelity simulator solution possible. With a simulated solution, a software engineer will produce a lower fidelity, simplified functional model based on a functional description of the plant system. This method relies on the system knowledge of the simulation vendor. However, even the most seasoned simulation engineer will never know all of the inner workings of the proprietary DCS code. The higher the fidelity of a nuclear power plant simulator, the less risk of negative training.

Negative training can happen when the simulator doesn’t operate like the real plant. There have been several industry events where the simulator operated differently than the plant, even to the extent that the NRC (Nuclear Regulatory Commission) issued findings.

As recent as 2015, they issued a level white inspection finding for a simulator failing to demonstrate the expected plant response. A single plant event, such as a trip or an extension of an outage, can be a very costly consequence of negative training on the simulator. Avoiding negative training increases the safety and reliability of the plant. This directly influences economic performance and helps the industry deliver the Nuclear Promise.

Reduce your Operation & Maintenance (O&M) Budget

As the plant is upgraded and maintained, plant control and logic and human machines interfaces (HMI) or human system interfaces (HSI) will change. When the plant software gets an update, your simulator needs to be updated to reflect those changes or you risk falling out of compliance.

The process for implementing plant software changes in the simulator can be significantly more difficult and time-consuming with a simulated DCS than with an emulated DCS. The additional time and potential vendor costs of maintaining a simulated DCS will negatively impact your simulator O&M budget, hindering your ability to deliver the Nuclear Promise.

For an emulated DCS, your simulator team simply has to run the new plant data file through the emulator. Then, they implement the new simulator software that is output from the emulator. Because the simulator software was created using the plant data files and transformed through the emulated software tool, the simulator will be exactly in sync with the plant. Therefore, it will provide the lowest risk and lowest upgrade cost option.

Implementing the new plant software into a simulated DCS solution requires much more forethought, analysis, and testing. Your simulator team will need to study each change and determine how to apply it to the simplified, estimated functionality simulator software. This method requires extensive care and testing. You must make sure that the updated simulator will operate the same as the real plant and this carries a high risk of error.

The process is not only more time-consuming, but it often requires a contracted simulation vendor, which increases the cost of the upgrade. Time and costs start to add up in scenarios where the new plant functionality was not anticipated when the simplified solution was designed.

Virtual Commissioning for DCS Upgrades

Gen II and Gen III plants are undergoing and are expected to undergo more instances of digital control and HMI/HSI upgrades. Utilities are recognizing that their high-fidelity plant simulator is a powerful virtual commissioning tool. Simulators allow operators to test drive plant changes before anything goes live, from HMI/HSI and control room design to alarms and indications.

Virtually testing these plant changes lowers the risk of costly plant outage extensions and field changes during and after DCS upgrades. These outage extensions and field changes can cost utilities tens of thousands of dollars, or more, per incident.

Virtual commissioning is one way to avoid these incidents. It is also key to increasing efficiency and supporting a plant in Delivering the Nuclear Promise. But here’s the catch. To take advantage of virtual commissioning, the utility must have a high-fidelity emulated DCS solution. Virtually commissioning a digital control system upgrade on a simulator is only possible if the control system models on the simulator are exactly the same as the plant. You can’t trust the simplified models of a simulated DCS solution to verify the appropriate functionality of the plant system.

Conclusion

Nuclear power plants are required to have a high-fidelity simulator for operator training and evaluation. The plant is also tasked with maintaining the simulator fidelity throughout the life of the plant. When faced with the decision between an emulated or simulated DCS solution, there are many factors to consider. While you might be tempted to go with the initial lower price tag of a simulated DCS solution, you can’t ignore the risks of:

• Negative training
• Long-term maintenance costs
• The inability to effectively test plant changes

As you search for ways to deliver the Nuclear Promise, consider how your DCS simulator solution’s fidelity will affect your plant’s ability to run efficiently and safely.

The bottom line? Go emulated!

• Higher fidelity lowers the risk of negative training.
• Reduce your O&M budget with lower maintenance costs.
• Make virtual commissioning of plant upgrades possible.