As Bill Meldrum was walking to get a signature from a welder supervisor at Duke Energy’s Oconee Nuclear Station in South Carolina, he spotted two welders deeply engaged in their work.
One was measuring where to cut I-beams and remove and replace piping around a reactor coolant pump. The other was planning how to cut out a heat exchanger, part of the reactor coolant system.
The amazing part? They were doing it all from an office, wearing virtual reality headsets.
That’s possible thanks to digital twin technology. Duke Energy’s Metrology Services team used laser scans to create 2D and 3D models – precise to 1/16th of an inch – of all three reactor units at Oconee. The technology makes it easier to plan maintenance projects and accomplish them in a safer, faster and more efficient way.
“Usually, you'd bring in a bunch of pipes and a bunch of valves and then you'd spend days and days welding this to that and that to the other thing,” said Meldrum, a planner in the Radiation Protection department at Oconee. “But what these measurements let them do is put together pipe and valve assemblies in their clean shop.”
Welders can do much of the preparation in their street clothes rather than while wearing protective suits and respirators inside the reactor building. It’s safer, too, since it greatly reduces the amount of time in the reactor building. It also means less time is required to complete a project during a planned outage.
Planned outages take place on each unit every two years at Oconee, which centers around how often the reactor needs to be refueled; these outages also accommodate a variety of maintenance work. An outage typically lasts several weeks but is scheduled down to the hour.
Reducing each project’s timeline means getting the unit back online faster to continue generating carbon-free, reliable energy for customers.
Take, for example, a recent project at Oconee to replace a motor, about the size of an ambulance. Removal required a precise sequence of steps to lift, drift and turn the motor without hitting equipment or I-beams on either side, Meldrum said.
Usually, it takes at least a full 12-hour shift to lift the motor and place it on a trailer. But, with the help of metrology, he said, “we did it in 2 1/2 hours.”
That also affects the bottom line since each hour cut from a planned refueling outage means regained generation capacity.
“You save thousands of dollars by getting the plant online for that extra hour,” said Brad Medlin, senior products and services manager at Oconee, who oversees much of the day-to-day operations of digital twin technology.
Duke Energy has been using the technology for individual components at nuclear facilities on projects for years, he said, but now it has moved to scanning entire plants. That allows work to happen faster and eliminates delays from unexpected findings.
The technology is being used across other generation fleets, too, like hydro and fossil fuel plants. It can even be used underwater now for hard-to-reach areas.
“The use cases are really endless, once digitized,” said Ron Dottorelli, metrology and reality capture project manager. He believes every engineering group can utilize it in some form.
Under the non-regulated Duke Energy One affiliate, outside companies can contract for 3D metrology services.
It’s useful outside the energy sector, too, said D. Manning, whose company, Luxpoint, provides laser scanning to clients like building developers, architects and construction companies.
He said Duke Energy’s metrology team helped one of his clients solve a construction layout issue: A 100-foot-tall turntable was built in the wrong location and the changes had never been updated in architectural drawings. That discrepancy led to a construction error of multiple feet and required a costly redesign.
“Using high-accuracy laser tracking, we were able to document all the necessary as-built conditions to ensure, moving forward, mistakes similar to this wouldn't be repeated,” Manning said.
Digital twin technology saves time by capturing everything you need plus things you don’t realize you need until later, Manning said. “It’s just the best tool for the job.”