See how a nuclear power plant refuels

An outage is a brief interruption in power production to swap out old fuel for new, and it happens on a schedule set years in advance.

While nuclear power plants produce large amounts of energy around the clock, every 18 to 24 months the plants shut down for roughly a month for maintenance, inspections and refueling.

Duke Energy schedules refueling outages to occur during spring and fall, when energy demand is lowest. This results in greater efficiency and reliability when electricity is needed the most: hot summers and cold winters.

During these focused outages, workers conduct inspections and maintenance at the same time as refueling, eliminating the need to power down the plant at other times to perform the same work. This allows plants to produce electricity continuously for months and even years at a time – a feature no other electricity source provides.

American nuclear plants provide the most efficient form of generation, producing electricity 93% of the time, on average. In the Carolinas, Duke Energy’s six nuclear plants are a reliable, clean energy source providing more than half of the electricity delivered to customers.

Check out these videos for a behind-the-scenes look at what happens at the plants during a planned outage:

Video: Catawba Nuclear Station fuel loading

During a refueling outage, about one-third of a reactor’s used nuclear fuel is replaced, as seen in this video. The blue light coming from the reactor is known as the Cherenkov effect, which occurs when electrically charged particles travel through a clear medium like water.

Video: Brunswick Nuclear Plant refueling

Here’s a time-lapse of the refueling process. Nuclear plants use uranium as fuel, which comes in the form of pellets enclosed in metal rods. At Brunswick, there are about 350 pellets per rod, 92 fuel rods in a fuel assembly and 560 fuel assemblies in each reactor core.

Video: New turbine rotor at Robinson Nuclear Plant

With units temporarily shut down for refueling, planned outages provide nuclear workers the opportunity to replace major equipment. This video shows a new rotor – the part of a turbine that spins – being lifted into place.

Video: New transformer at McGuire Nuclear Station

Here’s another example of a major piece of equipment replaced during a refueling outage. Transformers, like this one, allow the large amount of electricity nuclear plants generate to be transmitted to customers. This one is more than 37 feet tall and weighs more than 1 million pounds.