Much of the U.S. nuclear power industry is facing the same support challenge: Plants built in the 1960s and 1970s are still equipped with “vintage” controls. These pneumatic and electronic systems are aging, becoming obsolete and causing instrumentation maintenance backlogs to increase.
“We started doing digital upgrades as point solutions, really because we had no choice,” said Dave Hooten, supervisor of electrical, instrumentation and controls engineering at Progress Energy’s Harris 1 nuclear power plant near Raleigh, N.C. But pretty soon, the various digital control upgrades—pursued on an ad hoc basis and with no long-term plan—led to a range of different digital systems from a variety of vendors, all of which operated differently and did not communicate with each other. “We realized we had to spend smarter—in a more long-term, intelligent fashion,” Hooten said in his presentation to the Honeywell User Group gathering this week in Phoenix.
“We realized we had to spend smarter—in a more long-term, intelligent fashion.” Progress Energy’s Dave Hooten discussed his company’s implementation of the Experion PKS control platform at its nuclear power stations, the first Experion installations in the U.S. commercial nuclear fleet.
So it was that Progress Energy set about a long-term plan to unify its nuclear power plant control systems on the Honeywell Experion Process Knowledge System platform—the first U.S. nuclear power plants to do so. Progress Power’s nuclear fleet consists of five different plants in the southeastern U.S., each with its own operating budget, Hooten explained. The first obstacle overcome was getting corporate funding for the basic Experion infrastructure, including plant-wide fault-tolerant Ethernet server cabinets and the like, so that initial Experion applications would not have to bear the cost of an infrastructure build-out.
Once the infrastructure was in place, however, several identified Experion projects were put off for a variety of reasons until a “perfect” first application was identified: the reactor auxiliary building ventilation system at Harris 1. The aging ventilation controls constantly demanded attention because of frequent failures, Hooten said, and while the application was not high-risk, systems failures were irksome to employees’ working routine. The company replaced the older pneumatic controllers with Experion PKS and HART-equipped field instruments. Honeywell’s PID-PL (Profit Loop) was used to auto-tune the various loop involved, “saving us countless hours of trial and error,” Hooten said.
The recommendations and lessons learned by Hooten and his team during this first successful Experion application include:
- Stay current with software releases during systems development. This should help to reduce the number of problems identified—and patches required—on a one-at-a-time basis.
- Test over all known operating conditions and address process noise in the transmitters themselves. Upon start-up, Hooten found that the “expedient” step of damping process noise in the control system function block caused several unanticipated interactions that had to be identified and resolved.
- Moving to a digital control system may expose longstanding problems. “When we finally had a decent control system, all these old problems came to the forefront,” Hooten warned.
All in all, plant management sees this first Experion migration as a significant milestone, Hooten said. Other Experion projects currently identified include upgrade of the radiation monitoring systems, plant vent stack monitoring and main turbine controls. “We fixed what we set out to fix, and it’s given our industry tangible proof that distributed control is a good thing.”