Wireless versus wired solutions

Wireless systems are popular in today’s high tech environment, but they will always pose a problem for a nuclear safety system. The concern for wireless safety systems is mostly security. As anyone who works with wireless systems can verify, any system that is wireless is vulnerable. It is vulnerable to jamming, it is vulnerable to hacking, and it is a potential interferer for other signals. Even with encryption techniques and spread spectrum techniques it is unlikely that wireless communication will be implemented for primary signal communications in safety systems.2627

Another constraint arguing against wireless communications in safety systems is channel separation, and safety to non-safety separation. Wireless communication separation is more difficult to prove/ensure than wired communications for keeping signals and channels separated.

Wireless networking and programming of non-safety I&C devices is a different matter. The wireless HART system is a wireless communication system employed currently in large PWR plants, which allows transmitters that are equipped with the system to communicate information to an end user or device. This programming and control system protocol is encrypted and authenticated and has little risk of being hacked or sabotaged. Since it is not responsible for the primary safety communication (for safe plant shutdown), it is free to be used throughout NSSS and BOP control systems. This technology allows plant maintenance personnel to set up, tweak, and network transmitters remotely, and will most likely be used regularly in iPWR systems, for ease of access reasons.28

BOP instrumentation has the most flexibility for wireless communications. Although the wireless solution still has to be tested for signal integrity, immunity, and non­interference with other signals, the potential to use wireless solutions for sensor to processing electronics is greater in BOP systems than in the NSSS or safety system applications.

Wireless voice communications have been widely used in nuclear power plants for many decades. From the handheld radio to cell phones, wireless communications are a continuing trend. As many applications in the new iPWRs will be digital, and digital on a smaller scale than ever before, there will be more intense testing and qualifying of wireless voice communication devices than before. The potential of a wireless voice communication device to interfere with a safety or control signal is a condition that must be fully tested and verified in any nuclear plant environment. The wireless communication of voice or ancillary data is very different from the wireless communication of safety parameter signals. While wireless voice communications are used and will continue to be used in the future, complete testing of these wireless systems will also continue to a necessity for electro-magnetic compatibility (EMC) reasons.

Wireless plant computer data is already a popular technique in power plants. As long as the plant computer data is not relied upon for safety system processing, wireless plant computer data is a solution that benefits everyone. Currently, much diagnostic information, such as vibration data and temperature data, is sensed in the field and transmitted through wireless hubs to a computer system. It is expected that this trend will continue in the iPWR environment.2627

The flip side of the coin in wireless systems is the potential for the wireless transmission to jam or interfere with other systems, both wired and wireless. EMI/ RFI issues, concerns and guidelines for nuclear plants are covered in Electric Power Research Institute (EPRI) report TR-102323-R3 published in November 2004, and EPRI report ID# 1011960 published in 2005.

1.3 Conclusion

iPWRs are a new and elegant incorporation of 50 years of operation in nuclear power plants. Lessons learned and evolutionary improvements are being and have been incorporated into the designs. The instrumentation design, typically the last design detail to fit into the overall design, is in its initial design phase at the current time. Many traditional I&C options are still being considered for iPWRs, but some of these traditional options will not work in the new iPWR designs, either because of the geometries involved or because of the environment. It is up to the iPWR I&C designer to find the appropriate I&C solutions to the problems of pressure, flux, level, temperature, and flow measurement. The opportunity to use state-of-the-art technologies that offer improved accuracy, ease of installation, ease of maintenance, and less drift should not be passed up, even if it means new qualification programs. Economics will bear out the use of new technologies, but only if a long-term view is used. The next ten years should tell the story.

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