Duke Energy Nuclear Employees Participate in Earth Day

Earth Day is April 22, 2015. Each April 22, for the past 45 years, citizens around the world have honored a commitment for a clean environment by hosting festivals, rallies and environmental activities, all with support  from a  world-wide community.

Duke Energy and its nuclear employees  also support a clean environment. Did you know that nuclear energy is America’s largest source of clean-air, carbon-free electricity, producing no greenhouse gases or air pollutants — 64 percent of carbon-free electricity is produced by nuclear energy.

In recognition of Earth Day this year, Harris Nuclear Plant near Raleigh, N.C., will be the host of local sixth graders for a program on nuclear, renewables and energy efficiency. This will be the first visit to the nuclear facility by many of these students.

Catawba Nuclear Station and Oconee Nuclear Station employees will be participating in roadside  cleanups.

Employees at Catawba Nuclear Station, located in York, S.C., including members of the Catawba chapters of Women in Nuclear (WIN) and North American Young Generation of Nuclear (NAYGN), will spend the afternoon picking up litter along the road to the plant, as part of adopt-a-highway program.

Employees at Oconee Nuclear Station, located in Seneca, S.C.,  in partnership with the Keep Oconee Beautiful Association (KOBA), will participate in the Adopt-A-Spot program by l doing a litter sweep along the roads near the plant’s entrances. In addition, Oconee Maintenance  Department employees  have “adopted” their own section of local highways as part of their commitment to the community and the environment.

trash

Duke Energy nuclear employees keep local roads clean.

 

Nuclear Fuels Engineers Are Masters of Interior Design

Nuclear power plants in the United States produce electricity 24/7 and are baseload generating plants. Baseload power refers to generating resources that operate continuously and provide reliable power to customers, only shutting down for scheduled refueling and maintenance.

Nuclear power plants use uranium fuel, in fuel assemblies, to produce heat through fission (splitting of atoms). When uranium atoms split, they release energy in the form of heat.

Uranium Fuel

Source: Nuclear Energy Institute

Source: Nuclear Energy Institute

Fuel
This heat is used to heat water for creating steam, which turns the turbine-generator to make electricity.

How a Nuclear Plant Works

Source: U.S. Nuclear Regulatory Commission

Source: U.S. Nuclear Regulatory Commission

During power operation, the nuclear fuel assemblies are located in the reactor vessel in a cylindrical arrangement called the reactor core. Just like an automobile, nuclear power plants are refueled on a regular schedule – normally an 18 or 24-month fuel cycle – meaning that every 18 or 24 months, the nuclear generating unit is shut down for refueling. Once shut down, about one-third of the nuclear fuel assemblies (the oldest assemblies) are removed from the reactor core and placed in the used fuel pool for storage. This fuel has typically been used in the reactor for four-and-a-half to six years.

Used Fuel Pool

Source: Nuclear Energy Institute

Source: Nuclear Energy Institute

The remaining fuel in the reactor is rearranged and combined with new fuel assemblies that replace the ones that were permanently removed – this makes up the reactor core for the next operating cycle. The arrangement of the fuel assemblies, known as the core design, is analyzed to provide for maximize energy use from each fuel assembly.

At Duke Energy, our in-house Nuclear Fuels Engineering group is responsible for designing and managing each nuclear reactor core to ensure the fuel is safely used and satisfies the energy requirements of the next operating cycle. This takes a comprehensive understanding of plant operations, careful monitoring and detailed fuel analysis. The effort to model, analyze, establish limits and provide data for operating the cycle is roughly an 18-month effort. However, if changes must be made, the team at Duke Energy has demonstrated its ability to adjust the core design in as little as a few weeks. This can only be accomplished because of the high degree of automation, streamlined processes and expertise of Nuclear Fuels Engineering.

In past years, most nuclear plants operated on 12-month fuel cycles. Over the years, these cycle times were extended due to improvements in fuel design, maintenance and operations. These improvements have allowed for fewer refueling outages and improved on-line reliability, which also results in less labor to refuel the plant and lower costs for our customers.

Below are cross sections of a nuclear fuel assembly and a nuclear reactor core design. In Duke Energy’s boiling water and pressurized water reactors, the fuel assemblies contain from 80 to 264 individual fuel rods. These assemblies are selectively arranged to create core designs of 157, 177, 193 assemblies for the pressurized water reactors and 560 assemblies for the boiling water reactors.

Cross section of typical fuel assembly (Each circle represents a fuel rod; color coding represents rod type)

Cross section of typical fuel assembly (Each circle represents a fuel rod; color coding represents rod type)

Cross section of typical reactor core (Each square represents a fuel assembly; color coding represents regions)

Cross section of typical reactor core (Each square represents a fuel assembly; color coding represents regions)

Although not unique, Duke Energy is one of only a few U.S. utilities licensed by the U.S. Nuclear Regulatory Commission to perform its own nuclear core design analyses. This in-house design has enhanced competitive fuel supply, resulted in more economical fuel designs and provided the ability to respond swiftly to changing needs. It also provides for a number of interesting and challenging career paths for the Nuclear Fuels engineers.

Nuclear Energy: More Prepared Through FLEX

It has been just over four years since an earthquake and subsequent devastating tsunami led to a serious accident at Japan’s Fukushima Daiichi nuclear energy facility. The flooding from the tsunami led to a loss of power and cooling capability at the facility.

Soon after the March 11, 2011 accident, the US Nuclear Regulatory Commission (NRC) set up a task force to identify the lessons that the U.S. nuclear energy industry should learn to avoid similar situations from occurring here. Based on the NRC’s findings, Duke Energy’s nuclear fleet and other nuclear power plants across the nation rolled out their emergency response plan, dubbed Diverse and Flexible Coping Strategies (FLEX).

FLEX calls for:

  • Portable equipment to assure that multiple means of obtaining power and cooling water are available to support key safety functions for all reactors at a site. Equipment includes portable pumps, generators, batteries, battery chargers, compressors, hoses, couplings, tools, debris clearing equipment and other materials.
  • Reasonable protection of portable equipment to guard it from the severe natural phenomena predicted for that site by locating the equipment in safe locations.
  • Procedures and guidance for emergency response personnel for the use of FLEX equipment and capabilities.
  • Program controls to ensure regular maintenance and testing of FLEX equipment.
  • Trained personnel in FLEX capability and response.

The rationale for FLEX is that if a set of equipment is kept ready in a safe location, there would be working equipment available in the event of an emergency, no matter the disaster that befalls the facility.

Duke Energy’s FLEX Buildings

MNS FLEX Building

McGuire Nuclear Station FLEX Building.

FLEX has led to changing landscapes across Duke’s nuclear fleet as one or more safe locations have been established for the FLEX equipment. McGuire Nuclear Station has three separate FLEX buildings, while Brunswick, Oconee, Robinson and Catawba nuclear stations have erected dome-shaped buildings to house equipment. Harris Nuclear Plant is using its existing Emergency Diesel Generator Building.

Regional Centers

Memphis, Tennessee FLEX regional center

The FLEX regional center in Memphis, Tenn. opened in June 2014.

In addition to the new equipment housed at the individual nuclear facilities, two regional emergency centers exist in the United States to provide portable equipment in the event of a Fukushima-like event. Duke’s nuclear fleet is served by the center in Memphis, Tenn. that can respond to an emergency within 24 hours. The second facility is located in Phoenix, Ariz.

“This facility is important,” said Mike Pacilio, the executive sponsor for national response centers on the Nuclear Energy Institute’s Fukushima Response Steering Committee, when the Memphis facility opened in June 2014. “It expands our defense-in-depth safety commitment and adds tremendously to our ability to manage any extreme event.”

Equipment stored at the Memphis center includes: portable backup generators portable high pressure pumps, portable low pressure pumps, diesel fuel transfer pumps, diesel fuel tanks, diesel powered light towers, water treatment, booster pumps, electrical distribution cabinets, cables, and hoses. Each center houses five full sets of equipment, with four ready to be moved to any U.S. nuclear power plant at all times. The equipment undergoes regular testing for operability.

Commitment to Safety

“The lessons learned from this significant event have forever changed our strategies for responding to natural disasters,” said Bill Pitesa, Duke Energy’s chief nuclear officer. “Like others in the industry, we have made plant modifications to give us added confidence that we can successfully deal with severe events. We also have staged additional response equipment both locally and regionally and improved our procedures and training. Pitesa recognizes the importance of the people who work in nuclear facilities to operate the facility safely and deal with emergency situations.

“Fukushima symbolizes the nuclear industry’s unique responsibilities. While safe, reliable electric generation remains paramount, nuclear plant workers are the first line of defense should an extreme natural or other event occur. Our employees are well trained and have the experience, skills and now FLEX to deal with unexpected events.”