Duke Energy’s Nuclear Fleet Braves 2015 Cold Snap


Photo provided courtesy of the Nuclear Energy Institute (NEI).

In the Carolinas, the fruit trees are blooming and the official start of spring is here.  It’s easy to forget that just a month ago winter came in with a vengeance and tested the company’s power delivery system.  Record cold temperatures were like an unwanted dinner guest – they came and wouldn’t go away.  In such cold weather, electricity demand increases dramatically as customers struggle to stay warm.  Duke Energy Carolinas set an all-time record for peak electricity demand at 21,101 megawatt-hours on Feb. 20, 2015, exceeding the previous all-time record of 20,799 megawatt-hours set on Jan. 30, 2014.

The company’s nuclear power plants played a pivotal role in providing power to residential, commercial and industrial customers during the cold snap.  The Duke Energy nuclear fleet operated at 100 percent power during the most challenging portion of the February deep freeze, providing 10,679 megawatts of electricity.

The stellar performance of the nuclear fleet is no “accident.”  While low fuel cost, minimal greenhouse gas emissions and low environmental impacts are well-known characteristics of nuclear power, its reliability and availability is sometimes overlooked.  Nuclear plants are refueled about every 18 months, in contrast to coal or natural gas plants which need a continual supply of natural gas or coal to run.  For the most part, nuclear plants operate uninterrupted day and night, rain or shine until the next refueling outage.

The availability of the Duke Energy nuclear plants during the February cold weather was a result of good performance by well-maintained equipment and well-trained personnel.  The company places a strong emphasis on equipment reliability through preventive maintenance and early diagnosis of potential equipment problems.  As frigid temperatures approached, special measures were taken at each nuclear plant to ensure availability.  As soon as company meteorologists identified the looming weather challenge, nuclear teammates began carrying out special actions to cope with the anticipated high demand.  Each nuclear site ran through cold weather checklists to ensure key components would not freeze or become inoperable as temperatures plummeted. One site postponed a planned refueling outage, while another delayed system testing and preventive maintenance to help meet demand. Delaying the outage alone provided more than 930 megawatts of electricity to customers when it was needed the most (to learn more about refueling outages, click here to read a previous article).

The 2014 Polar Vortex highlighted the value of nuclear plants in the Midwest and northeast in dealing with extreme cold weather.  Similarly, during the extended cold weather in February 2015, the Duke Energy nuclear fleet performed in an exemplary manner to help cope with an unprecedented demand for power.  These incidents emphasize the value of generating assets that can supply large quantities of power reliably around the clock and during adverse weather conditions.

What are Small Modular Nuclear Reactors?

Small Modular Nuclear Reactors (SMRs) are nuclear power plants that are smaller in size than most commercial nuclear power plants today. The plants in the Duke Energy nuclear fleet are large baseload power plants, which mean they are designed to provide a steady amount, or base, of power around the clock.  All of Duke’s reactors are more than 800 megawatts in size; SMRs are 300 megawatts or less. But it is that smaller size that makes them attractive options for the future.

One of the biggest potential advantages of SMRs is their cost. Because of the smaller, more compact design, SMRs require less of a footprint than today’s baseload nuclear power plants. That means reduced siting costs.

The SMRs are designed to be factory built and transported by truck or rail to a nuclear power site. This production would result in economies of scale that can benefit all buyers – an advantage not possible with larger, customized nuclear plants.

SMRs could be used to provide power to locales, including remote sites, where smaller power capacity is all that’s required to meet load requirements.

Many SMRs are designed with improved safety and security features. Their reactor buildings, fuel pools and control rooms are housed underground to withstand earthquakes, tsunamis, tornadoes, hurricanes and terrorist threats.

While they are not envisioned to replace existing nuclear plants in the future, they may help replace some of the power produced by today’s fossil fuel plants, and their emergency planning zone is designed to be no more than about a 300 meter radius.

To help ensure the continued development of SMRs and other clean energy options for the future, the U.S. Department of Energy is helping accelerate the timelines for the commercialization and deployment of SMR technologies. Several manufacturers currently have SMR designs in the works, and the Nuclear Regulatory Commission anticipates it may receive the first applications for review by late 2015.

Going Critical is a Good Thing: Debunking Nuclear Myths

Nuclear power plants are among the safest, most affordable and environmentally friendly options for powering billions of homes around the world. So why do so many negative myths surround the industry?

Let’s take a look at some of the most common misconceptions about nuclear power.

Myth: If a nuclear reactor is critical, it’s out of control.
Fact: In popular culture, nuclear power is often fictionalized to create suspense, like when reactors go “critical” in movies and books. In the nuclear context, critical simply means that the reactor is in a configuration that will let it operate at a steady power level.

When a uranium atom is hit by a neutron it splits apart; a process known as fission. The atom splits into two smaller atoms and also emits a few neutrons. To keep reactor power steady, one of those neutrons needs to cause another fission. When the reactor is in a configuration where one neutron from each atom fissioned causes another fission, the reactor is said to be critical. For a reactor operator, criticality is desired and is certainly nothing to fear.

Myth: Nuclear energy is dirty.
Fact: Nuclear energy is one of the cleanest sources of energy in the United States. The fissioning of uranium atoms, how nuclear energy is created, does not produce greenhouse gases. In 2012, the Energy Information Administration reported that greenhouse gas emissions in the power sector were 15 percent below 2005 levels, due in part to carbon-free electricity produced by nuclear energy. There are no smoke stacks at nuclear plants. The white plume often seen rising from nuclear plants with cooling towers is clean water vapor.

Myth: Nuclear plants emit dangerous amounts of radiation.
Fact: Radiation occurs naturally in our environment. You can be exposed to non-harmful radiation levels by drinking a glass of orange juice, taking a plane ride or having a medical procedure like a chest X-ray. Even the bricks and construction materials in buildings have low levels of radiation. A person who stands just outside of a nuclear plant for one full year will be exposed to less than one millirem, the standard unit for radiation measurement, of additional radiation. That’s less than one single procedure chest x-ray, which is about 4 millirem.  The average annual radiation dose per person in the U.S. is 620 millirem

Myth: Nuclear energy isn’t safe.
Fact: Nuclear power plants are among the safest, most secure facilities in the United States.

According to the U.S. Department of Labor, it is safer to work at a nuclear plant than at a fast food restaurant, grocery store or in real estate. The nuclear industry is heavily regulated and safety is the cornerstone of all operations at nuclear plants. Multiple layers of safety systems and structures protect workers and surrounding communities. No radiation-related health effects have been linked to nuclear plants during the nearly 60 years of operation in the United States.

Myth: Nuclear power plants can explode.
Fact: It is physically impossible for a U.S. commercial reactor to explode like a nuclear weapon. The fuel used does not have enough uranium to be explosive and reactors are designed with layers of safety systems and automatic shutdown capabilities. It is not possible for a person to intentionally or unintentionally modify a commercial nuclear reactor to cause an explosion.

So next time you are watching a movie and hear that the reactor is critical, you’ll know that means the nuclear plant is running and the lights are on.