Byron Nuclear Generating Station

Byron Clean Energy Center

Company type	Nuclear power plant
Industry	Energy
Founded	1975
Founder	Commonwealth Edison
Headquarters	Byron, Illinois , United States
Area served	Northern Illinois, Chicago metropolitan area
Products	Electricity generation (nuclear power)
Owner	Constellation Energy
Number of employees	600+ (2009)

Byron Clean Energy Center

The Byron Clean Energy Center is a nuclear facility situated in Ogle County, Illinois, approximately two miles east of the Rock River. Built by Commonwealth Edison, it contains two Westinghouse Four-Loop pressurized water reactors, designated as Unit 1 and Unit 2, which commenced operations in September 1985 and August 1987, respectively. Ownership and operation of the plant are managed by Constellation Energy.

Providing electricity to northern Illinois and the Chicago metropolitan area, Byron produced close to 2,450 MWe in 2005—sufficient to supply power to roughly two million households. The facility employs over 600 staff members, primarily from Ogle and Winnebago counties, and is equipped with two natural draft cooling towers each standing 495 feet tall.

In 1981, the plant was involved in controversy due to litigation concerning tritium contamination in groundwater. This problem, which also affected other nuclear sites across Illinois, led to state legislation mandating nuclear plants to report tritium leaks within a 24-hour timeframe.

History

Construction of the Byron Clean Energy Center began in 1975 on a 1,782-acre (7.2 km²) property located 17 miles southwest of Rockford, Illinois, near the town of Byron in Ogle County. Sargent & Lundy acted as consulting engineers during development, while Babcock & Wilcox was responsible for completing the reactor vessels. Prior to its completion, the plant faced legal challenges in 1981 from organizations such as the League of Women Voters and the DeKalb Area Alliance for Responsible Energy, who questioned both its safety and necessity. In 1984, the Atomic Safety and Licensing Board of the U.S. Nuclear Regulatory Commission (NRC) initially refused operational authorization citing quality control issues with contractors. Following a thorough re-inspection of more than 200,000 components, the board reversed its decision in October 1984 and granted approval for operation.

Byron Station consists of two pressurized water reactors: Unit One and Unit Two. Unit One obtained its NRC operating license on February 14, 1985, followed by Unit Two on January 30, 1987. Commercial service for Unit One began on September 16, 1985. The original licenses were set to expire in October 2024 for Unit One and November 2026 for Unit Two. In May 2013, Exelon Generation submitted applications for license renewal; after thorough safety reviews and environmental impact assessments, the NRC extended both licenses by an additional twenty years in November 2015. This extension allows operations through October 2044 for Unit One and November 2046 for Unit Two.

In August 2020, Exelon announced intentions to shut down Byron by September 2021 due to economic factors despite having valid licenses. The company sought policy interventions to avoid closure but indicated in August 2021 that a proposed federal production tax credit (PTC) of $15/MWh would not be implemented soon enough to prevent shutdowns at Byron and Dresden plants. However, on September 13, 2021, the Illinois Senate approved nearly $700 million in subsidies for state nuclear facilities including Byron. This development led Exelon to reverse its decision to close the plant.

Facilities and output

Byron’s infrastructure includes two Westinghouse four-loop pressurized-water reactors with individual electrical outputs exceeding 1,000 MWe. Combined net generation capacity totals approximately 2,347 megawatts (MW). In 2009, these reactors operated at a capacity factor of 96.4%, producing nearly 19.7 million megawatt-hours (MWh), sufficient to serve around two million average American households. The site also features two cooling towers each standing at a height of 495 feet (151 m).

The plant draws cooling water from the nearby Rock River, located about two miles (3.2 km) west of the facility. Water utilized during electricity production is cooled within these towers and then recirculated back into the river through a blowdown line. Water from Byron’s Radioactive Waste Treatment system undergoes processing in the Refueling Water Storage Tank (RWST), is tested for contaminants, and is released only after meeting strict quality standards.

Prior ownership by Exelon reported employing approximately 850 full-time workers along with around fifty permanent contractors at Byron, with most employees residing within Ogle and Winnebago counties. In fiscal year 2009 alone, the plant contributed $31.1 million in local tax revenues.

The Nuclear Regulatory Commission authorized two power uprates: a five percent increase approved on May 4, 2001—adding roughly 175.6 MWt per reactor—and a subsequent increase of about 1.6% authorized on February 7, 2014—adding an additional 58.4 MWt per unit.

Electricity generation

Monthly and Annual Output (MWh) of Byron Nuclear Generation Station

Year	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total Annual Output
2001	1,729,864	1,564,673	1,717,255	1,158,782	1,751,100	1,641,486	1,783,835	1,786,297	1,695,657	1,712,548	1,747,359	1,799,626	20,088,482
2002	1,783,147	1,598,042	1,197,804	1,735,914	1,747,443	1,532,673	1,760,733	1,764,931	1,296,911	1,453,548	1,700,911	1,793,412	19,365,469
2003	1,792,766	1,615,781	1,789,987	1,721,516	1,777,377	1,717,579	1,766,450	1,760,659	1,424,700	1,317,227	1,695,495	1,762,715	20,142,252
2004	1,712,598	1,636,413	1,485,923	1,420,552	1,740,796	1,677,204	1,728,362	1,730,918	1,676,216	1,747,429	1,693,338</ small >	< small > 1754 , 815 < / small >	20 , 004 , 564
2005	< small > 1752 , 875 < / small >	< small > 1547 , 345 < / small >	< small > 998 , 271 < / small >	< small > 1682 , 708 < / small >	< small > 1744 , 558 < / small >	< small > 1664 , 504 < / small >	< small > 1727 , 387 < / small >	< small > 1725 , 907 < / small >	< small > 1501 , 951 < / small >	< small > 1318 , 779 < / small >	< small > 1697 , 970 < / small >	< small > 1757 , 302 < / small >	19 ,119 ,557
2006	< small > 1774 ,974 < / small >	< small > 1586 ,440 < / small >	< small > 1757 ,645 < / small >	< small > 1689 ,540 < / small >	< small > 1744 ,722 < / small >	< small > 1681 ,211 < / small >	< small > 1717 ,429 < / small >	< small > 1725 ,840 < / small >	< small > 1091 ,778 < / small >	< small > 1266 ,352 < / small >	< small > 1698 ,807 < / small >	< small > 1757 ,033 < / small >	19 ,491 ,771
2007	< small > 1757 ,322 < / small >	< small > 1585 ,181 < / small >	< small > 1717 ,230 < / small >	< small > 870 ,553 < / small >	< small > 1603 ,866 < / small >	< small > 1677 ,391 < / small >	< small > 1730 ,460 < / small >	< small > 1725 ,752 < / small >	< small > 1680 ,381 < / small >	< small > 1068 ,411 < / small >	< small > 1680 ,786 < / small >	< small > 1755 ,434 < / small >	18 ,852 ,767
2008 ... (Excerpt shortened to maintain data accuracy and brevity) Groundwater in the vicinity and increased tritium concentrations Located within the initial 230 feet (70.1 m) beneath the power plant are two subterranean aquifers: the upper Galena-Platteville Aquifer and the lower St. Peter Sandstone Aquifer, which are divided by a shale stratum. In February 2006, Exelon disclosed increased tritium concentrations in the groundwater underneath the facility. Out of six monitoring wells, two revealed tritium levels reaching 86,000 pCi/L (2.3 MBq/L) in stagnant water located within underground concrete vaults along the plant’s blowdown pipeline. Exelon affirmed that these measurements did not present any safety hazards to employees or the public. This disclosure coincided with comparable tritium findings at Exelon's Braidwood Nuclear Generating Station in Illinois. By September, elevated tritium was identified at Byron in three surveillance wells near vacuum breaker vaults along the blowdown line, predominantly within the Galena-Platteville Aquifer. Tritium emits low-level beta radiation and has a half-life of 12.3 years; its primary health concern arises from ingestion or inhalation. None of the September samples surpassed the U.S. Environmental Protection Agency’s drinking water limit of 20,000 pCi/L. On April 12, 2006, the Illinois Environmental Protection Agency (IEPA) issued a violation notice to Exelon for contaminating groundwater resources and releasing pollutants beyond authorized discharge points at Byron. Following tritium contamination incidents at Byron, Braidwood, and Dresden, Illinois enacted legislation mandating nuclear facilities to notify the state within 24 hours of any radioactive releases into soil or water—previously only reported at the federal level. Sponsored by State Representative Careen M. Gordon and Senator Gary G. Dahl, and signed into law by Governor Rod Blagojevich on June 11, 2006, this measure also required quarterly inspections by IEPA and the Illinois Emergency Management Agency. The state criticized Exelon for delayed leak reporting, which local officials near Braidwood initially uncovered. Safety By the second quarter of 2007, Byron Clean Energy Center received predominantly "green" ratings across nearly all Nuclear Regulatory Commission (NRC) inspection categories, reflecting minimal safety concerns. Unit One earned "green" status in every category, whereas Unit Two was rated "white"—one tier below green—due to issues found during heat removal system evaluation. Other critical aspects assessed included unplanned scrams, alert and notification protocols, and emergency AC power systems. Between 2001 and 2005, Byron consistently maintained only "green" inspection outcomes, accumulating a total of 71 such designations during that timeframe. From 1997 through 2007, Byron was subject to five NRC Escalated Enforcement Actions resulting in fines totaling $150,000. In 1997 alone, two penalties of $50,000 each were levied for excessive silt accumulation on-site. Later that year, a $55,000 fine was imposed for failure to comply with surveillance requirements regarding Emergency Core Cooling System (ECCS) pump casing venting; this infraction was deemed low risk to safety. The latest enforcement action occurred in 2005 when an engineer submitted falsified surveillance documentation; although fines up to $60,000 were possible, no monetary penalty was ultimately applied. On February 24, 2006, a fire ignited within the Unit 1 Refueling Water Storage Tank heater. The situation was controlled by cutting power to the heater without necessitating shutdown of either reactor, both operating at full power during the incident. The plant declared an "unusual event," which represents the NRC’s lowest emergency classification level. On January 30, 2012, Byron Unit 2 experienced an unplanned shutdown after a switchyard insulator failure caused loss of a startup transformer phase and reduced voltage on emergency power buses. This led to automatic tripping of reactor coolant pumps and reactor shutdown. Operators manually opened breakers supplying startup transformers to initiate emergency diesel generators and restore power levels. To assist cooling efforts, steam was vented from the secondary side; a minor tritium release occurred but was deemed non-threatening to public safety according to NRC evaluations. A similar insulator malfunction on February 29 at Unit 1 triggered automatic breaker trips and emergency generator activation without requiring plant shutdown. Subsequently, Exelon took both units offline to replace all switchyard insulators as a precautionary measure. Surrounding population The Nuclear Regulatory Commission identifies two distinct emergency planning zones around nuclear facilities: a 10-mile plume exposure pathway zone that addresses airborne radioactive hazards, and a 50-mile ingestion pathway zone that focuses on the risk of contaminated food and beverages. As of 2010, the number of residents living within 10 miles of Byron was 25,679, representing a 5.9% growth since 2000. The population within a 50-mile radius reached 1,273,771, marking a 14.5% increase over the same period. The city of Rockford lies approximately 17 miles from the site. Security Initially, security services at Byron were contracted to The Wackenhut Corporation (currently known as G4S Secure Solutions), but following a 2007 incident involving security personnel found asleep at another facility, responsibility for security transitioned to Exelon, the plant’s owner and operator. In response to the events of September 11, 2001, the United States Coast Guard established a "security zone" around Byron as part of heightened nuclear security measures; this zone was later removed in 2004 to facilitate the creation of a security area surrounding the Hammond Intake Crib on Lake Michigan. Seismic risk According to a 2010 assessment by the Nuclear Regulatory Commission, the likelihood of an earthquake resulting in core damage at Byron is estimated at one in 172,414 annually. See also Nuclear safety in the U.S. Nuclear accidents in the United States List of largest power stations in the United States Largest nuclear power plants in the United States External links