Out with the Old, In with the New (Fuel)

The days are starting to get longer, March Madness is in full swing and pastel Easter candy has hit the shelves. Spring has sprung.

As many of us start to leave our windows open while we swap our winter coats for rain jackets, thousands across the country are preparing for or are in the midst of an essential time for the nuclear industry: outage season.

Why is outage season so important time for the nuclear industry? Read the questions and answers below to find out.

What is a refueling outage?

In the nuclear power industry, an “outage” does not refer to a power outage or blackout as people may think. A “refueling outage” is when utilities safely power down a nuclear reactor to replace one-third of the used fuel assemblies with new ones. During these scheduled outages, a number of equipment maintenance tasks and upgrades that are difficult to do when the plant is generating power are completed.

How often are nuclear plants refueled?

Most nuclear plants shut down for refueling every 18 to 24 months.

Why are these done in the spring?

Utilities conduct refueling in the spring or fall when electricity demand is generally lower, so that it minimizes the impact to the electricity grid.

Although a nuclear unit is unable to produce electricity during a refueling outage, Duke Energy’s diverse fuel mix of generating stations ensures the company can adequately meet its customers’ demands for energy.

How long are nuclear plants shut down?

NEI reports the average refueling outage duration is 36 days (according to 2015 data).  U.S. average refueling outage days from NEI

However, the length of refueling outages varies based on the type of work, maintenance and modifications scheduled to be completed while the unit is off line.

What happens during a refueling outage?

During a typical nuclear plant outage, workers replace about one-third of the fuel in the reactor. Outages also include routine inspections and maintenance, but they can also be a time to replace equipment ranging from valves to steam generators.

A member of the fuel team helps guide a new fuel assembly into the used fuel pool.
A member of the fuel team helps guide a new fuel assembly into the used fuel pool.

Why aren’t both reactors refueled at the same time?

Although a nuclear plant could potentially perform refueling on two reactors at the same time, it is generally not done. A refueling outage requires a significant amount of human and financial resources, and since nuclear plants provide baseload electricity, when they are not operating, it is sometimes difficult and/or costly for the utility to purchase electricity from other sources.

What are the economic impacts of refueling outages on the local community?

During a typical 30-60-day nuclear plant outage, an additional 700-2,000 outage workers are brought to the nuclear plant to help with the many jobs involved in refueling and maintenance activities.

These extra workers, some company employees from other locations and some contract employees, offer an economic boost for the local communities, as they shop, eat and stay at area stores, restaurants, hotels and short-term rental properties.

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