Fall: Prime Time for Outages

For most people, the transition from summer to fall means back to school, the kickoff of football season and the leaves changing colors.

Fall has a different meaning for those in the nuclear industry: outage season.

Across the country and across the Duke Energy Nuclear fleet, the cooler temperatures make fall a prime time for nuclear plants to temporarily shut down to refuel and perform routine maintenance. Cooler temperatures in the fall lead to less demand for electricity than in the summer heat or the winter chill. Most nuclear plants shut down for refueling every 18 to 24 months.


A crew works to move used fuel during a recent outage at Harris Nuclear Plant.

During a typical nuclear plant outage, workers replace about one-third of the fuel in the reactor. The process for refueling is different for pressurized water reactors (PWRs) and boiling water reactors (BWRs). In a PWR, typically all of the fuel is removed from the core and placed in a used fuel pool, making it easier to conduct maintenance on the reactor core itself. This process occurs when the fuel assembly is turned on its side and then moved through an underwater canal to the fuel pool, which is usually
located in a different building from the reactor. Once all of the fuel is in the fuel pool, the plant workers will remove one-third of the fuel and replace it with the new fuel. They will also conduct what’s called a “core shuffle,” which means the new fuel is intermixed with older fuel—that will continue to power the reactor—in order to ensure efficient use of the fuel. In a BWR, the reactor operators typically do not remove all of the fuel—only the used fuel. This saves time, especially since BWRs have more fuel assemblies than PWRs. During the refueling process, the used fuel is pulled out of the reactor from the top and is placed in the spent fuel pool, which in most BWRs is located next to the reactor. The operators then conduct the core shuffle and insert the new fuel.

Outages also include routine inspections and maintenance, but they can also be a time to replace equipment ranging from valves to steam generators. During outages, usually 1,000 to 2,000 extra workers are on site, depending on the scope of the maintenance, with shifts working around the clock seven days a week. During a refueling outage, plant workers have greater access to many areas of the plant that are sometimes difficult to access during normal operations, such as areas close to the reactor core. This lends itself to being a great opportunity to conduct routine inspections and maintenance and perform any necessary repairs.


A worker inspects equipment associated with the high-pressure turbine during a recent outage at Harris Nuclear Plant.

The type of maintenance that is conducted varies by plant, but an example includes inspecting or testing pumps and valves to ensure that they are working properly. The plant will place many of these routine maintenance activities on a schedule so that certain equipment and instrumentation is evaluated each refueling outage, whereas others may only need to be inspected every other outage or less frequently.

Although a nuclear plant could potentially perform refueling on two reactors at a time, it is generally not done for two reasons. First, a refueling outage requires a large amount of human and financial resources. Second, nuclear energy facilities provide baseload electricity—meaning they pump out electricity around-the-clock—and when they are not operating, it is sometimes difficult and costly for the utility to purchase electricity from other sources, sometimes in other states. Again, this is why utilities conduct refueling in the spring or fall when electricity demand is generally low, so that it minimizes the impact to the electricity grid.

Career Spotlight: Work Control Center

Bill Mason WCC2

Bill Mason in the McGuire Nuclear Station Work Control Center

It takes a dedicated team to handle the day-to-day functions of running a nuclear station, and Work Control Center (WCC) teammates ensure plant operations run smoothly with the authorization of all work prior to it being performed. Bill Mason (Senior Reactor Operator) gives us an inside look at how the WCC contributes to the overall success of nuclear operations.

Q: What is the WCC responsible for?

A: WCC teammates authorize all work activities that occur within the plant. From maintenance tasks such as tool calibration, valve lubrication and repairs to the testing of electrical breakers and pump pressures, the WCC approves everything prior to work beginning.

Q: Why is the WCC important to nuclear operations?

A: There are technical specifications (laws) mandated by the Nuclear Regulatory Commission (NRC) that have to be followed, and WCC teammates make sure the plant is in compliance with the specifications related to its safe operation.

Q: Who staffs the WCC?

A: All teammates who work in the WCC are Senior Reactor Operators (SROs). Licensed by the NRC, SROs are responsible for monitoring and operating equipment in the control room in a safe and efficient manner and directing the licensed activities of Reactor Operators.

To support the WCC supervisor, the shift technical advisors assist with additional workload and help with the plant evaluation. The field supervisors provide oversight in the plant of anything that may arise. The WCC team rotates day-to-day, shift-to-shift with SROs in the Control Room and at times may serve as the plant supervisor.

Q: How does the workload change during a refueling outage?

A: During a refueling outage – when plants replace approximately one-third of the fuel, conduct inspections and make repairs and upgrades – the WCC team is split with half supporting the Outage Command Center (OCC) in various functions based on their level of expertise. All work performed during an outage is dispatched from the OCC.

Q: What is the most enjoyable part of working in the WCC?

A: The variety of work and working as a team to ensure safe and efficient plant operations.

STEM: A Critical Focus for Duke Energy

20150807_105221What do sheep eyeballs, robots, tornadoes, and balloon cars all have in common?

Nearly 100 campers recently visited the EnergyExplorium at McGuire Nuclear Station, to take part in “Exploring Science,” a program designed to boost student’s interest in science, technology, engineering and math (STEM). The one day camp immersed students ages 8-12 in hands-on, team-based learning activities focusing on robotics, energy, chemistry, physics, biology and more.

While the science day camp was the first of its kind held at the EnergyExplorium, STEM has been a critical focus for Duke Energy. By fostering a growing interest in the STEM fields for students, programs like “Exploring Science,” engage students in core fundamentals and helps build a strong foundation for future leaders.

WorkforceWhile the demand for energy is increasing, the amount of students entering the STEM fields is declining. And with 60 percent of Duke Energy employees eligible to retire during the next decade, the company is partnering with communities and organizations to help peak interest in and  transition younger generations into the workforce.

Just over half of Duke Energy’s current workforce is made up of “baby boomers” and “traditionalists,” who are nearing retirement in the next decade or so – down from more than 60 percent in 2011. In 2013, “Generation X” exceeded one-third and “millennials” exceeded 10 percent of the workforce for the first time.

The company’s workforce planning efforts are paying off, as they recruit new hires and work to ensure a full pipeline of employees with the right qualifications and skills.

Duke Energy partnered with the STEM Career Path Project, to bring “Exploring Science” day camp to the EnergyExplorium at McGuire Nuclear Station. The STEM Career Path Project is a non-profit organization that promotes science, technology, engineering and math education by inspiring young minds through hands-on, interactive activities and workshops.