Inside the Byron Nuclear Power Plant

Illinois has more nuclear power plants than any other state, but what exactly happens at these plants? Discover how Byron Nuclear Power Plant positively impacts our local economy and why some people are concerned about unresolved problems.

The twin cooling towers of the Byron Generating Station, visible for miles around the area, loom large on the local landscape. Located just two miles south of the town, the nuclear power plant sits on a hill overlooking the nearby Rock River and produces electrical energy for nearly two million customers.
The federal Department of Energy (DOE) is responsible for research and development of commercial energy sources and manages the nuclear weapons program. According to it, there are 99 nuclear reactors located in 61 power plants producing electricity in our country. Fourteen reactors are shut down and in the process of being decommissioned (deconstructing retired reactors and making the sites radiologically safe). There are four new nuclear power plants (NPPs) under construction.
Illinois has more NPPs than any other state – 14 total, 11 operating at six locations, three closed permanently (Dresden #1 and Zion #1 and #2). According to the Chicago-based Nuclear Energy Information Service (NEIS), an anti-nuclear watchdog group, if Illinois were a nation, it would be the 11th largest nuclear power in the world, just behind Ukraine.
We also have the longest history with nuclear energy, since the first controlled nuclear reaction occurred at the University of Chicago in 1942, as part of the Manhattan Project. Almost half (48.2 pecent) of the electricity produced in Illinois comes from nuclear energy; the national average is 19 percent.
Exelon Corporation, which owns and operates all of the NPPs in Illinois, has a national “fleet” of 23 reactors in 14 power plants, making it the largest commercial operator in the U.S. It formed in 2001 and took over ComEd’s Byron plant the same year; ComEd is one of Exelon’s many subsidiaries.


Groundbreaking for construction of the Byron plant occurred in 1975, but almost a decade passed before the plant began producing electricity. In 1979, a major accident at the Three Mile Island NPP in Pennsylvania galvanized anti-nuclear protest groups throughout the country, including some in northern Illinois.
Several organizations in the Rockford area, including the League of Women Voters, the Sinnissippi Alliance for the Environment (SAFE) and DeKalb Area Alliance for Responsible Energy, decided in 1983 to file a legal “intervention” during the Byron licensing hearings of the Nuclear Regulatory Commission.
Evidence presented in the four months of hearings regarding safety procedures and construction complaints convinced the Atomic Safety and Licensing Board that paperwork submitted by ComEd didn’t fully address the problems. Consequently, ComEd was initially denied a license to operate the plant.
“As far as I know, that was the first time in our history that a NPP was denied its license,” recalls Stanley Campbell, a founding member of SAFE. He’s now the executive director of Rockford Urban Ministries. “A year later, during the re-hearing, ComEd claimed it had re-inspected every one of the specific concerns the intervention had raised. ComEd finally got its 40-year license to operate.”
According to Campbell, at least four other utility companies in the U.S. later abandoned plans to construct NPPs, partly as a result of their intervention and growing national anti-nuclear sentiment.
“A good majority of NPPs in the U.S. experienced some kind of intervention before being given a license to operate,” says Paul Dempsey, communications manager at Exelon’s Byron Station. “Lots of people didn’t want the plants to be built, more out of fear than science. We’ve had a lot of people change their position over the years, from anti- to pro-nuclear energy.”
Construction at the Byron Generating Station was completed in 1985 at a cost of $4.5 billion. Unit #1 went on line that September, Unit #2 in August 1987.

How It Works

In simplest terms, a nuclear power plant is a very expensive and complicated – although reliable – way to produce electricity by heating water into steam. The Byron Generating Station contains two pressurized water reactors that utilize a controlled nuclear reaction called fission. This occurs when subatomic particles called neutrons split the nucleus of uranium atoms, freeing other neutrons to split other atoms in a chain reaction. Energy in the form of tremendous heat is released.
The reaction is controlled and can be stopped by inserting control rods into the reactor, which absorb the free neutrons like a sponge. The uranium used in a nuclear reactor is not “enriched” or refined enough to produce a nuclear explosion, so there is no chance the reactors might someday disappear in a mushroom cloud.
The chain reaction takes place inside a reactor vessel, a 60-foot-tall capsule-shaped container made of eight-inch thick steel. Water in a self-contained, pressurized loop circulates around the reactor core, becoming heated to more than 600 degrees. This is the only water exposed to radiation. The heat is carried by water to a heat exchanger, where it produces steam in another closed loop of pipes containing water. This steam, now at 890 psi pressure, enters huge turbines and drives the blades which rotate a shaft connected to an electric generator.
The turbines are housed in an 830-foot-long building, large enough to contain a World War II aircraft carrier. Each generator produces about 1,120 megawatts of continuous electricity, which is then fed into the local power grid.
Meanwhile, a third closed loop of pipes circulates water from a storage pond between the cooling towers, which is used to cool the steam from the turbines back into water. This last loop gives up much of its heat in “fill packs” at the base of the 495-foot cooling towers, which are essentially very large chimneys. The source of the pond water is the Rock River, which is pumped uphill from the river at the rate of 30-40,000 gallons per minute. As the water evaporates, it rises through the hollow towers, where it condenses into small droplets, creating the clouds we see continuously floating from the tower tops.
About one third of the water pumped from the river is reused in the storage pond, another third escapes into the atmosphere in those clouds, and the rest is returned to the river. A 26-acre “mixing zone” around the discharge pipe allows the water to match the ambient temperature of the river before floating downstream.
“Periodically, we remove dump trucks full of debris from the base of the towers, which used to be in the Rock River,” says Dempsey. “We consider ourselves stewards of the environment, so we put water back into the river in better shape than what we took out.”
Each reactor, located below grade level, and four steam generators, are housed within a 199-foot-tall containment building made of 3.5-foot thick steel-reinforced concrete walls with a steel liner, and wrapped with steel cables on the outside. The nuclear fuel in the shape of small ceramic pellets is held in fuel rods, which are placed in assemblies about one foot square and 12 feet long. Each reactor core holds 193 assemblies at one time.
About every 18 months, one of the reactors is shut down and one third of the oldest fuel is removed and replaced with new assemblies. The spent fuel is still extremely radioactive, and produces “decay heat” which must be actively cooled. These assemblies are stored in a spent fuel pool adjacent to the containment building for about five years.
Eventually, these spent fuel assemblies are placed in a steel “dry” cask, 32 bundles per cask, while under water in the storage pool. The cask is sealed and removed from the pool, then placed in a concrete and steel shell or “overpack,” 11 feet in diameter, 16.5 feet tall, weighing 180 tons when fully loaded. The overpack’s outer walls are 27 inches of steel-reinforced concrete. Since the spent fuel continues to create much heat due to the ongoing radioactive decay, the overpacks are vented to allow the heat, but not the radiation, to escape into the atmosphere.
The casks, or overpacks, are transported from the fuel-handling building to an outside storage pad by a 90-ton custom-built “crawler.” There they will remain until a national repository for spent nuclear fuel is chosen. All the spent fuel, now called high-level radioactive waste (HLRW), generated at Byron since 1985, is still there in storage. The same holds true at every other NPP in the country. Presently, there are 2,651 used fuel assemblies in the spent fuel pool at Byron, with another 640 bundles in 20 casks on the concrete storage pad at the back of the plant.
“While that sounds like a lot, all the used fuel itself could fit into a three-car garage,” says Mark Rasmussen, senior reactor operator at Byron Station. “It’s very compact.”

Where to Put Radioactive Spent Fuel

While spent fuel from nuclear power plants is no longer viable to produce electricity, it remains dangerously radioactive for thousands of years, if not longer. Since the 1960s, most nuclear scientists have agreed such waste should be placed in a geological repository – a big, deep hole in the ground – to protect the biosphere from its effects. What hasn’t been agreed to is where that hole should be.
The 1982 Nuclear Waste Policy Act stipulated that the federal government would create such a repository, and that HLRW would start being transported there by 1998. The DOE studied Yucca Mountain in Nevada, 80 miles from Las Vegas, as a potential site from 1978 to 2011, but politics intervened. Most of the citizens of Nevada, who have no nuclear plants in their state, don’t want it there, and the states which must be traversed in order to get the HLRW there objected, too. The Obama administration cut off federal funding for Yucca Mountain in 2011.
A Blue Ribbon Commission, established by the Secretary of Energy in 2009, recently recommended that the DOE use a “bottom up” procedure called consent-based site selection to find another location, and public meetings to start that process began in Chicago in April. According to the DOE, there are about 75,000 metric tons (MT = 2,000 kilograms) of HLRW currently stored around the country where it was used, and another 2,000 metric tons is added each year. According to Dempsey, that total volume would fill a football field 15 feet deep.
The federal government has been shipping nuclear waste from Department of Defense facilities to a deep geological repository 26 miles east of Carlsbad, N.M., since 1979. Called the Waste Isolation Pilot Plant (WIPP), it is currently the only facility in the U.S. licensed to permanently dispose of HLRW, but it only accepts defense program waste. Because it’s a pilot project, WIPP’s storage capacity is limited. Researchers have incurred some problems of contamination in recent years, most recently a fire and canister rupture in 2014.
Lacking an operating repository for HLRW, the federal government owes utility companies between $300 and $500 million per year in compensation for failing to comply with the contract it signed to remove the spent fuel by 1998. This is the amount collected by the federal government from utilities to build the repository, which was never done. Partly in order to reduce this liability, the DOE has suggested creating interim sites where HLRW can be centralized while waiting for a permanent site to be chosen.
Anti-nuclear groups like NEIS object to this plan, insisting that such waste should stay where it is and only be moved once – to its final destination. They suggest that the Nuclear Regulatory Commission (NRC) adopt a program called Hardened On-Site Storage (HOSS), whereby each nuclear waste storage cask would be surrounded by earth berms to hide them from ground-level view. They would need to be able to withstand a terrorist attack with an anti-tank missile or a crashing commercial aircraft.
Although this plan was successfully implemented at some reactors in Europe, the NRC and industry spokespersons have rejected the HOSS idea as expensive and unnecessary.

Economic Impact

The nuclear power industry has a huge economic impact on the nation and Illinois. According to Dempsey, Exelon employs almost 6,000 workers in Illinois and another 21,000 people have jobs because the plants are here. Almost $300 million in real estate taxes is paid annually to taxing bodies in the state from the six Exelon plants.
“Byron Generating Station has been a massive economic boon for the Byron area,” says Dempsey. “We pay nearly $30 million a year in property taxes and employ nearly 860 permanent workers in good, high-paying jobs. Most of them live and shop in the area, buy houses, pay taxes themselves. We estimate that the Byron plant alone has had a $1 billion impact on the state in the 30 years of operation.”
About every 18 months, the Byron plant shuts down one of the reactors for scheduled maintenance and refueling. The latest “outage” started on April 18. During outages, an additional 1,200 workers from 26 Illinois counties and 30 other states make the Rock River Valley their temporary home as they take part in more than 13,000 inspections and maintenance activities, many of which can’t be done while the unit is operating.
“Exelon averages five outages a year in Illinois,” says Dempsey. “Many of these same workers move from plant to plant to help with our maintenance and inspections.”
The city of Byron doesn’t receive any tax dollars directly from the Exelon plant, but several other local taxing entities do, including Byron’s school, fire, forestry, museum and library districts.
“It’s been very exciting for this community to go through all the transitions the nuclear power plant has experienced,” says Chris Millard, Byron’s mayor for the past seven years. Millard retired from the Byron Fire Department four years ago, after 35 years of service. He’s also the current fire chief at Chicago-Rockford International Airport.
“The school district is the biggest recipient of tax dollars,” says Millard. “We have widows in town who’ve added onto their homes, just so they can rent space to those temporary workers who come here during a refueling outage. Some make enough money during those few weeks to pay their property taxes. Byron today wouldn’t be the same town without our Exelon friends on the hill.”
But not everyone is enthused about the presence of nuclear plants.
“There are fundamental differences between the Exelon plant in Byron and, say, Caterpillar in Peoria,” says David Kraft, director of Nuclear Energy Information Service (NEIS). “Every nuclear reactor in the country has a finite operating license, beyond which they must close down – if not sooner, because of an accident or economics. And every plant that closes must go through the ‘decommissioning’ process – tearing it down to the ground, making it radiologically safe and ‘available for unrestricted public use.’ It’s a costly process, but Illinois had the foresight to set up escrow accounts for such events.”
The loss of income from jobs and taxes when a plant closes is another matter. The NPP in Zion, constructed and operated by ComEd, began operations in 1974, with a 40-year license to operate until 2014. A series of breakdowns and technical difficulties resulted in ComEd’s unilateral decision to close the plant in 1998, almost 16 years early.
“Zion understood the cost of locating a nuclear power plant in our community,” says Al Hill, mayor of Zion. “That cost included giving up 400 acres of lakefront property, having limited access, etc. In exchange, we benefitted from 800 new jobs, and more than $19 million a year in taxes. But we assumed that when the license expired, the 400 acres would be returned to us in pristine condition, available for development.”
Instead, because of the government’s failure to build a national repository, Zion has become a de facto storage site in which 2.2 million pounds of spent fuel still sit in 61 dry cask storage containers on a concrete pad, guarded by armed security forces around the clock. The decommissioning process began in 2011 and is still ongoing. The “gravy train” of jobs and taxes has long departed.
Byron’s Mayor Millard says he’s not worried about his community’s future.
“While the loss of tax base will be a problem, I think Byron will be OK,” he says. “There are a lot of things built into this community that will help keep it driving forward. The people who moved here because of the power plant have become ‘Byron people.’ They participate in community events and support community organizations.
They’re not quitters. When there’s a need, we come together and make it happen. We will come back.”
The nuclear accidents at Three Mile Island in New York (1979), Chernobyl in Ukraine (still part of the U.S.S.R. in 1986), and Fukushima in Japan (2011) have reminded us all that, while the odds of an accident happening at a nuclear power plant may be small, the consequences of such an accident are enormous. All three accidents, although caused by different circumstances, threatened or created a reactor core meltdown.
A meltdown happens even when the chain reaction has been stopped, if the facility is unable to control and remove the tremendous heat still being produced by the radiated materials. In both the Soviet and Japanese accidents, the reactor vessels and/or the containment buildings were breached, sending radiation into the atmosphere and contaminating the surrounding area.
While fewer than 100 people died immediately or soon after, as a direct result of these accidents, thousands were exposed to enough radiation to worry about developing deadly cancers later on. Both Fukushima and Chernobyl are still active contamination zones, and many scientists believe they will remain uninhabitable for decades, if not centuries.
“The designers, builders and operators have gone to a great deal of trouble to make sure that this plant is safe,” says Rasmussen. “We’re not going to negatively affect the public, even if an accident should occur. We have measures in place to address those issues, and we learn from such events to make our measures stronger, better and more capable. There are undeniable hazards associated with this technology, but incredible benefits.”
Disaster and evacuation drills, including first responders from all surrounding communities on a rotating basis, are held annually at Byron Station. Lectures, seminars and tours are conducted to inform the general public about the functions of the power plant. In reaction to the Fukushima disaster, a flexible response package of extra equipment and training was instituted at NPPs across the country. The FLEX building at Byron, built to withstand an E-5 tornado (as all the main structures are), contains extra generators, communication gear and heavy equipment that would be available in just such an emergency.
Exelon representatives insist that nuclear power used to generate electricity is “clean, green and reliable,” since it doesn’t discharge carbon emissions into the atmosphere like coal, natural gas or oil-fired plants. Nuclear plants can produce power 24/7, whether or not the wind is blowing or the sun is shining. The Byron plant was in operation 94.7 percent of the time in 2015; all Exelon plants had an availability rating of 93.4 percent.
“Without nuclear power plants like Byron, Illinois will not be able to meet the EPA emission standards by 2030,” says Dempsey. “Almost 90 percent of the carbon-free power in Illinois comes from nuclear energy.”
“NEIS disagrees with this characterization,” says Kraft. “While not emitting carbon during operations, the mining and production of nuclear fuel creates large amounts of unnaturally concentrated radioactive materials, as well as huge quantities of spent fuel which require isolation from the environment for thousands of years. This can hardly be called clean and green.” Learn more about NEIS views at
While the debate continues, the Byron Generating Station on the hill keeps humming along. After a lengthy hearing process, its 40-year license was recently extended for another 20 years. The plant continues to provide electricity for our homes and industries in northwest Illinois and beyond.