Limerick Generating Station

Limerick Generating Station is a two unit nuclear power plant located at 3146 Sanatoga Road in the Sanatoga area outside Pottstown, Pennsylvania, with the site itself sitting in Limerick Township, Montgomery County, along the east bank of the Schuylkill River. The station is owned and operated by Constellation Energy and is one of the largest single sources of electricity in the Commonwealth of Pennsylvania. Its two reactors together have a generating capacity of roughly 2,317 megawatts, an output commonly described as enough to serve the equivalent of more than 1.7 million homes.

The facility occupies several hundred acres of riverside land and is best known visually for its pair of natural draft hyperbolic cooling towers, which rise slightly more than 500 feet and are visible from highways, neighborhoods and hilltops across Montgomery, Chester, Berks and Bucks counties.

History and Development

Limerick was developed by Philadelphia Electric Company, later known as PECO Energy, during the era of large scale nuclear construction in the United States. Site work and construction began in the mid 1970s. Unit 1 entered commercial operation in February 1986, and Unit 2 followed in January 1990 after a period in which the second unit's completion was in question because of shifting demand forecasts and financing conditions.

Operational responsibility passed to Exelon Generation after the 2000 merger of PECO Energy and Unicom, the parent company of Commonwealth Edison. In February 2022, Exelon separated its competitive generation business, and Limerick became part of Constellation Energy, which today operates one of the largest carbon free generating fleets in the country. In October 2014, the U.S. Nuclear Regulatory Commission approved 20 year license renewals for both units, extending authorized operation of Unit 1 into 2044 and Unit 2 into 2049.

Reactor Technology and Operations

Both units at Limerick use General Electric boiling water reactors of the BWR-4 design housed in Mark II containment structures. In a boiling water reactor, water circulating through the reactor core is heated directly into steam, which is piped to the turbine generator to produce electricity. The steam is then condensed and returned to the reactor vessel in a closed loop. This differs from the pressurized water design used at many other American plants, where a separate secondary loop generates the steam.

Each unit operates on a refueling cycle of roughly 24 months. During a refueling outage, a portion of the uranium fuel assemblies in the reactor core is replaced, and the station carries out maintenance, inspections and equipment upgrades that cannot be performed while the unit is online. These outages bring hundreds of additional specialized contract workers to the Pottstown area for several weeks at a time, creating a recurring seasonal boost for local hotels, restaurants and services. Over the years, the units have also undergone power uprates and component modernization that increased output beyond the original design ratings.

Cooling Towers and Water Use

The two cooling towers are the plant's most recognizable feature. They are not chimneys or smokestacks and do not carry reactor steam or combustion exhaust. Instead, they use a closed circulating water system in which warm water from the condensers is cooled by ambient air drawn upward through the tower's chimney like shape. The visible plume is condensed water vapor, and it is most pronounced in cool, humid conditions, which is why it appears largest on winter mornings and often disappears entirely on hot, dry afternoons.

Because evaporative cooling consumes a significant volume of water, Limerick draws from the Schuylkill River and is supported by a supplemental supply system that transfers water from the Delaware River at Point Pleasant through Bradshaw Reservoir and the Perkiomen Creek during periods of low flow. Additional supplemental water has historically been made available from Schuylkill County sources. Water withdrawals and discharges are regulated by the Delaware River Basin Commission and the Pennsylvania Department of Environmental Protection.

Safety, Regulation and Emergency Planning

Limerick operates under licenses issued by the Nuclear Regulatory Commission and is subject to continuous federal oversight, including resident inspectors assigned to the site full time and periodic performance reviews published by the NRC. The station maintains its own security force, on site emergency response organization and training facilities, including a control room simulator used for licensed operator training and requalification.

As with every U.S. commercial nuclear plant, Limerick is the center of a 10 mile emergency planning zone coordinated with county emergency management agencies in Montgomery, Chester, Berks and Bucks counties. That framework includes an outdoor warning siren network, annual public information mailings to households within the zone, potassium iodide availability through the state health department and regularly graded exercises involving state and federal agencies. Used fuel is stored on site in spent fuel pools and in dry cask storage on a reinforced concrete pad.

Economic and Community Role

The station is a major employer in the Pottstown and Limerick region, with a permanent workforce numbering in the several hundreds, including reactor operators, engineers, radiation protection technicians, maintenance crews, security officers and administrative staff. It is also one of the largest taxpayers supporting local municipalities and the school districts in its immediate area, and Constellation and its employees participate in regional charitable giving, STEM education outreach and environmental stewardship programs.

Because nuclear generation produces electricity without carbon dioxide emissions during operation, Limerick accounts for a substantial share of Pennsylvania's carbon free power and feeds into the PJM Interconnection grid that serves much of the mid Atlantic region.

Location and Practical Information

The site address is 3146 Sanatoga Road, Pottstown, PA 19464, a short distance from U.S. Route 422 and within easy reach of Royersford, Limerick, Sanatoga, Linfield and Spring City. The towers are a familiar orientation point for drivers on Route 422 and for pilots using nearby general aviation fields.

Visitors should note the following:

• The plant is a secured industrial and federally regulated facility. Access beyond public roads requires authorization, and there is no walk in public tour program.
• Administrative and visitor areas offer wheelchair accessible entrances and wheelchair accessible parking.
• General inquiries, including questions about emergency planning materials, community outreach and educational requests, can be directed to 1-800-483-3220.
• Additional information about the station, its operations and Constellation's broader generating fleet is available on the company website.