- Upgrading systems helps extend current reactor operating lifetimes
- Culmination of more than three years of industry-NRC interaction
- Digital instrumentation boosts plant safety, reliability and efficiency
Digital technologies are so commonplace in today’s world—from bank ATMs and airplane cockpits to our office desks and home appliances—that it is hard to believe there are corners of our industrial society still using nondigital, “analog,” instruments and control (I&C) technologies.
One of these analog places is where you’d least expect it—America’s commercial nuclear reactors. Other countries with civilian nuclear power programs, such as Japan, France, China, South Korea, Russia and the United Kingdom, are further ahead in the use of digital I&C systems for their reactors.
But with nearly all U.S. nuclear utilities having extended their reactors’ operating lifetimes to 60 years and some beginning to seek 80-year operating licenses, the need to upgrade their I&C systems to digital is growing in importance. And many promising next-generation advanced reactor designs are just over the horizon, which will come with all-digital I&C systems.
“If we can’t innovate, we can’t continue to operate,” says NEI Chief Nuclear Officer Bill Pitesa.
There are a few reasons for the resistance to change in the United States. One is that there simply haven’t been many new reactors built in the U.S. since the boom years of the 1970s. Another major reason has been the U.S. Nuclear Regulatory Commission’s outdated and unwieldy regulations, which have discouraged industry innovations such as upgrading plant I&C systems to digital technologies.
In a major milestone last week, the NRC showed its willingness to climb aboard the digital train when—after more than three years of collaborative effort with the industry and more than 50 public meetings—it issued an endorsement of industry guidance on upgrading nuclear plant I&C systems to digital.
The document issued by the NRC—the first of several to come—is a supplement to an existing regulatory issue summary (RIS), outlining how reactor owners can use “qualitative assessments” to show that proposed digital I&C modifications to safety-related systems will not increase the likelihood of system malfunctions due to software or other issues.
To achieve this breakthrough, NEI formed a working group of industry experts and NRC staff to resolve technical issues, improve the regulatory infrastructure and facilitate the implementation of I&C upgrades.
The goal was to allow plant operators to implement digital modifications without undue regulatory burden.
The industry already has been busy for the past 20 years installing digital upgrades to the nonsafety-related systems for most of the nuclear fleet. These systems include turbine control, feedwater control and other secondary support systems. As an example, Duke Energy’s McGuire and Catawba power stations near Charlotte, North Carolina, performed a major nonsafety-related digital upgrade in a project beginning in 2006 and lasting four years.
One of the primary benefits seen from the Catawba and McGuire upgrades is the new ability to automatically control steam generator water levels in low power ranges of operation. This previously entailed tricky manual manipulations by control room operators, sometimes resulting in reactor trips. The NRC’s RIS will allow the clear benefits of digital upgrades to be applied to the many safety-related systems that are currently using antiquated analog control systems.
The new digital systems can also automatically detect bad data signals and switch to good channels, enhancing plant security and reliability. In addition, as the RIS indicates, digital technology can be designed to provide continuous diagnostic information to plant operators and provide preventive maintenance alerts, decreasing plant operations and maintenance costs.
“Digital I&C shows it can enhance safety, reliability and efficiency while addressing the issue of obsolescence of analog components,” Pitesa said.
Next steps include setting up informational and training workshops among industry and NRC inspectors, he added.