Byron Nuclear Generating Station

Construction on Byron Clean Energy Center began in 1975, at a 1,782-acre (7.2 km) site, 17 miles (27 km) southwest of Rockford, Illinois, south of the city of Byron in Ogle County. The firm of Sargent & Lundy acted as consulting engineer during construction and Babcock & Wilcox oversaw the completion of the reactor vessels. Byron Station consists of two pressurized water reactors, termed Byron Unit One and Byron Unit Two, and the surrounding grounds and facilities. On September 16, 1985, Unit One entered commercial service and power began to be generated at Byron. and a supplemental environmental impact statement (July 15, 2015), the Nuclear Regulatory Commission renewed both operating licenses for an additional 20 years. The renewed licenses authorize Unit One to operate through October 31, 2044, and Unit Two through Nov. 6, 2046. In August 2020, Exelon decided to close the plant in September 2021 for economic reasons, despite the plant having licenses to operate for another 20 years. Exelon stated it would continue discussions with policymakers to try to obtain support to prevent the closure. In August 2021, Exelon stated a proposed $15/MWh federal production tax credit (PTC) would not be legislated in time to avoid closing Byron and Dresden. However, by September 13, 2021, the Illinois Senate approved a bill containing nearly $700 million in subsidies for the state's nuclear plants, including Byron, causing Exelon to reverse the shutdown order. ==Facilities and output==

, 17 miles (27 km) from Rockford, Illinois. The two Westinghouse four-loop pressurized-water reactors each have an electrical output of over 1,000 MWe. Byron has 2 units capable of generating 2347 net megawatts (MW) of electricity. In 2009 the reactors operated at 96.4% capacity and produced 19.7 million MWh of electricity; enough power for 2 million average American households. The two cooling towers at Byron rise 495 feet (151 m) over the site. According to former plant owner Exelon, the Byron station is operated by about 850 Exelon employees and another 50 permanent contractors. == Electricity production ==

==Surrounding groundwater and elevated levels of tritium ==

There are two underground aquifers within the first 230 feet (70.1 m) below the power station: the upper aquifer is known as the Galena-Platteville Aquifer and the lower aquifer is known as the St. Peter Sandstone Aquifer. The two bodies of water are separated by a layer of shale and thus not connected. The company stated that the levels posed no risk to public or employee safety. In September, elevated tritium levels were found at Byron in three monitoring wells adjacent to vacuum breaker vaults along the blowdown line. Two of the areas with elevated tritium were found in the shallow portions of the Galena-Platteville Aquifer, while the third location contained elevated tritium levels at the bottom of the same aquifer. None of the September levels exceeded the 20,000 pCi/L U.S. Environmental Protection Agency drinking water standard. . Due to the tritium contamination at Byron, Braidwood and Dresden nuclear power plants in Illinois, the state government passed a law requiring power plants to report the release of radioactive contaminants into the soil, surface water or ground water to the state within 24 hours. ==Safety==

s, in August 2005 As of the second quarter of 2007, Byron Clean Energy Center scored in the "green" in every Nuclear Regulatory Commission (NRC) inspection category but one. The NRC has four levels of inspection findings; the levels are color-coded and the colors equate with risk levels. Green inspection findings represent very low risk significance. Higher levels, from white, to yellow, to red, show increasing levels of risk. For any inspection findings greater than green, the NRC conducts follow-up inspections. Unit One scored "green" in every category, while Unit Two scored "white", a step down from "green", on the inspection of the heat removal system. The inspection covered several other significant areas, including unplanned scrams, the alert and notification system and the emergency AC power system. From 2001–2005, no inspections of Byron Clean Energy Center found any condition that merited a greater than "green" designation, during the same time period inspection found 71 green conditions at the Byron plant. Byron, like most U.S. nuclear plants, has been the subject of various actions by the NRC. Escalated Enforcement Actions represent one type. From 1997–2007 the Byron plant has received five such actions, two of which resulted in a total of $150,000 in fines. The NRC levied an additional $55,000 in fines in October 1997 when the plant failed technical specifications surveillance guidelines. Specifically, they violated rules that require the Emergency Core Cooling System (ECCS) pump casing and discharge piping high points be vented once every 31 days. The potential safety consequence of the violation affiliated with the second fine was considered "low." A small fire occurred at the plant on the morning of February 24, 2006. As a result of the fire the plant declared an "unusual event", the least serious of the four categories of emergency declarations by the Nuclear Regulatory Commission. On January 30, 2012, the Byron Unit 2 was shut down and depressurized after a failed insulator in the plant's switchyard caused the loss of one phase to the plant's startup transformers. This caused low voltage conditions on the plant's emergency power buses and also for two of the reactor coolant pumps to trip which caused the plant to shut down. The trip of the plant then caused the other two reactor coolant pumps to trip (as they had been receiving power directly from the main generator) and natural circulation had to be used during the shutdown. When operators discovered the loss of the single phase, they manually tripped the breaker feeding the startup transformers, allowing the emergency diesel generators to start and restore normal voltages to the safety buses. Steam was vented from the non-radioactive, secondary side of the plant to aid in the cooling process while the turbines remained offline. A small amount of radioactive tritium was released into the local environment during the initial venting procedure, but was deemed no threat to the public by the Nuclear Regulatory Commission. A similar insulator failure occurred at Unit 1 on February 29 again affecting the unit's startup transformers. In this case the breaker feeding the transformers tripped automatically and the emergency diesel generators immediately started up to restore power to the safety buses. Additionally, all of the non-safety power generation buses transferred to the unit auxiliary transformers, which receive power from the plant's turbine generator, preventing a trip of the plant. After this second failed insulator event, Exelon took both units offline and replaced all of the insulators in the plant's switchyard. On March 10, 2026, a Hydrazine exposure accident occurred causing a mass casualty incident during an outage on reactor one. ==Surrounding population==

The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of , concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about , concerned primarily with ingestion of food and liquid contaminated by radioactivity. The 2010 U.S. population within of Byron was 25,679, an increase of 5.9 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within was 1,273,771, an increase of 14.5 percent since 2000. Cities within 50 miles include Rockford (17 miles to city center). ==Security==

Security at Byron was provided by The Wackenhut Corporation (now G4S Secure Solutions) until a story broke in late 2007 involving videotape that captured Wackenhut security guards asleep at the Peach Bottom Nuclear Generating Station in Pennsylvania. Security is now handled in-house by Exelon which owns and operates the power plant. After the attacks of September 11, 2001, a "security zone" was established by the United States Coast Guard around the Byron Clean Energy Center as part of a broader effort to secure nuclear facilities in the U.S. On December 10, 2004, the security zone at Byron was removed to allow for a security zone around the Hammond Intake Crib on Lake Michigan. ==Seismic risk==

The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Byron was 1 in 172,414, according to an NRC study published in August 2010. ==See also==