Nuclear Power Frequently Asked Questions

  • Nuclear energy is:

    Clean. Nuclear energy is one of the cleanest power sources today. Nuclear power plants produce no greenhouse gases and are America’s largest source of carbon-free electricity.

    Reliable. Nuclear power plants consistently generate large amounts of electricity to meet customers’ energy needs, even during periods of extreme heat or cold when electricity demand increases. In fact, nuclear energy provides electricity to one in five businesses and homes in the U.S.

    Always-on. Nuclear energy facilities generate electricity around-the-clock, only taking a break every 18 to 24 months to refuel.

    An economic driver. Duke Energy’s nuclear plants support local economies through jobs and tax revenues. Plus, nuclear employees give time, talent and financial support to local schools, service agencies, arts programs, civic and environmental organizations and more.

  • Safety and security are the highest priority of the nuclear industry. Each nuclear station has strictly controlled safety and security programs and features, including:
    • Redundant, engineered safety systems that are frequently tested 
    • Plant personnel that are trained extensively to manage situations that might arise, including “what if” scenarios.
    • Detailed and comprehensive emergency plans that are practiced throughout the year in coordination with local, state and federal emergency management officials to ensure plans, equipment and personnel can appropriately respond to an emergency.
    • Reactor operators that are rigorously trained and carefully screened. Operators have stringent standards on continuing training, which is one week out of every five weeks.
    • Well-trained, armed security forces to protect all U.S. plants 24 hours a day.
    • Multiple physical intrusion barriers including concrete structures and razor wire fences that surround the plants.
    • Advanced surveillance equipment which continuously monitors areas around the plants.
    • Low concentration of fuel (uranium-235) which makes it physically impossible for a commercial nuclear power plant in the U.S. to explode like a nuclear bomb.

    Additionally, all nuclear plants are built to withstand a wide variety of external forces, including hurricanes, tornadoes, fires, floods and earthquakes. Learn more.

  • Duke Energy operates 11 nuclear units in the Carolinas at six plant sites.  Our nuclear fleet generates about half the electricity provided to our customers in the Carolinas.

    Affordable, reliable and clean nuclear energy has been part of Duke Energy's generation mix for 40 years. More than 40 percent of the electricity the company generated in 2015 was from carbon-free sources, including nuclear, hydro, wind and solar.

  • Since the terrorist attacks of Sept. 11, 2001, U.S. nuclear stations have been subject to several Nuclear Regulatory Commission (NRC) orders related to cybersecurity. Each licensee is required to provide high assurance that digital communication systems and networks are adequately protected against cyber attacks.
    • Duke Energy has a detailed cybersecurity plan for its nuclear stations and continues to perform plan assessments, update the plan and implement new standards/controls.
    • Duke Energy complies with all cybersecurity orders and programs related to nuclear operations and, through national and industry networks, remains abreast of new information. 
    • Safety and control systems at U.S. nuclear power plants are not connected to the Internet. Unlike industries for which two-way data flow is critical (e.g., banking), nuclear power plants do not require incoming data flow. 
    • Nuclear power plants have security attributes (technologically advanced detection, insider mitigation programs and behavior testing) not found at other critical infrastructure, and safety system functions are securely protected from cyber attack.
    • Nuclear plants are protected from grid instability with backup power supplies that provide for safe reactor shut down in the event of a blackout.
  • The NRC initially licenses U.S. nuclear power plants to operate for 40 years. After the initial operating license, current federal regulations permit nuclear plant owners to renew their plants’ license for an additional 20 years. To renew a license, the NRC must be satisfied the plant can operate safely for an additional 20 years. All Duke Energy nuclear plants have renewed licenses. 

    Nuclear power plant licensees are considering the option to renew the operating licenses of nuclear power plants a second time for an additional 20 years. Continuous upgrading and replacement of parts and systems, rigorous NRC oversight and learnings from research and operating experience will ensure nuclear energy facilities continue to operate safely. Learn more about the NRC license renewal process.


  • The federal government has responsibility for permanently disposing of used nuclear fuel.  Duke Energy continues to support the government's efforts to fulfill its obligation to accept and manage used nuclear fuel. 

    Until a permanent disposal facility is licensed, used nuclear fuel is safely and securely stored at plant sites in storage pools or specially designed dry storage containers. 

    Duke Energy has more than 40 years of experience handling used nuclear fuel. Our employees are well-trained, environmentally conscious professionals who take pride in their work.

    If all the used fuel produced in nearly 50 years of U.S. nuclear power plant operations was stacked end to end, it would cover a football field to a depth of less than 10 yards. Ninety-six percent of this material could be recycled.

  • Radiation is a natural part of our environment. We receive radiation from the sun, minerals in the earth, the food we eat and building materials in our houses. Even our bodies give off small amounts of radiation. Some radiation also comes from manmade sources such as medical and dental X-rays, televisions and smoke detectors.

    The amount of radiation a person receives is measured in millirems. The average person receives about 620 millirems of radiation each year — about 80 percent comes from natural sources and the rest from manmade sources.

    Nuclear power plants contribute a very small amount of radiation to the environment which is carefully monitored, meets established regulations and is reported to the appropriate local, state and federal agencies. A person living next to a nuclear plant will receive less than one additional millirem per year due to plant operations.

    Visit the U.S. Environmental Protection Agency’s website to enter RadTown USA, an interactive tool to help you learn about radiation sources and radiation-treated items.

  • The white cloud — or plume — is simply water vapor being released from the plant's cooling towers. Some of Duke Energy's plants use lakes to cool the water, so cooling towers are unnecessary. Lake or river water flows through thousands of tubes to cool steam and turn it back into water. It is then discharged down a long canal (for further cooling) and eventually enters the main part of the lake or river. The lake or river water does not mix with other water used at the plant.

    At other plants, the cooling water is circulated through cooling towers to remove the extra heat it has gained. The water is pumped to the top of the cooling towers and pours down through the structure. At the same time, a set of fans at the top of each tower pulls air up through the condenser water to cool it even more. The condenser water then flows back into the turbine building to begin condensing steam again.


Nuclear Glossary

Here are a few commonly used words in the nuclear industry. Visit the NRC website for additional words and phrases. 


The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core called a nucleus, which contains protons and neutrons. Electrons revolve in orbits in the region surrounding the nucleus.

Atomic Energy

Energy produced in the form of heat during the fission process in a nuclear reactor. When released in sufficient and controlled quantity, this heat energy may be used to produce steam to run a conventional turbine generator to produce electrical power. Atomic energy is more correctly called nuclear energy.

Background Radiation

Radiation in the environment from cosmic rays and radioactive material that naturally exists in soil, water and air. The amount of radiation a person gets is measured in millirems, and the average person receives about 360 millirems of radiation each year — about 80 % from natural sources and the rest from manmade sources.

Boiling Water Reactor (BWR)

A kind of commercial power reactor Duke Energy operates. The water flows upward through the core, where it is heated by fission and allowed to boil in the reactor vessel. The resulting steam then drives turbines, which activate generators to produce electrical power.

Capacity Factor

A measure of reliability, reflecting the amount of electricity a generating unit provides versus how much it could provide if operating at all times.

Combined Construction and Operating License (COL)

A license issued by the NRC authorizing a licensee to construct and operate a nuclear power plant at a specific site in accordance with established laws and regulations. A COL is valid for 40 years, with the possibility of a 20-year renewal.

Containment Building

The structure housing the nuclear reactor, pressurizer, reactor coolant pumps, steam generators and other associated piping and equipment. It is an airtight structure, steel-lined, with heavily reinforced concrete walls several feet thick. It is designed to withstand tremendous physical forces.

Control Rods

Rods made of material that absorbs neutrons. When inserted into the nuclear fuel, the rods stop the fission process, thereby shutting down the reactor.

Cooling Tower

A heat exchanger designed to aid in the cooling of water that was used to cool exhaust steam leaving the turbines of a power plant. Cooling towers transfer exhaust heat into the air, instead of into a body of water.


The central portion of a nuclear reactor, which contains the fuel assemblies, moderator, neutron poisons, control rods and support structures. The reactor core is where fission takes place.


The splitting of the atom, which releases tremendous amounts of heat energy.

Fuel Rod

A long, slender, zirconium metal tube containing pellets of fissionable material, which provides fuel for nuclear reactors. Fuel rods are assembled into bundles called fuel assemblies, which are loaded individually into the reactor core.

Pressurized Water Reactor (PWR)

The kind of commercial power reactor Duke Energy operates. The reactor heats water in a closed system that then transfers its heat to another closed system in the steam generators to produce steam for a turbine generator.


Particles and/or energy given off by unstable atoms as they undergo radioactive decay to stability.


A cylindrical, steel vessel that contains the core, control rods, coolant and structures that support the core.

Steam Generator

A large heat exchanger. In a pressurized water reactor, it’s the large steel tank where steam is produced. It is located inside the containment building.

Turbine Generator

A structure housing the steam turbine, electric generator and much of the feedwater system.


A critical element used in nuclear power reactors because of the ability of its atoms to undergo fission when it absorbs neutrons.

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