The 2.32GW Limerick generating station (LGS) powers two million homes with carbon-free electricity generated by two operating units of approximately 1.15GW capacity each.
The power plant is located in the Limerick Township area on a 645-acre site along the Schuylkill River from where it sources water for its needs. Exelon Nuclear owns the plant and operates it through its subsidiary Exelon Generation.
The first unit of the plant began operating on 01 February 1986, while the second unit came online on 08 January 1990.
Refuelling outage activity at the nuclear power plant commenced in April 2020 amid the COVID-19 pandemic. The activity resulted in five site employees including contractors testing positive for the coronavirus. In addition, 38 employees were quarantined in the first week of April 2020.
Limerick generating station location
The LGS plant site is located approximately 34km northwest of Philadelphia and is connected by several highways including US Highway 422 within 8km of the site area.
The site is spread partly in Montgomery County in Limerick Township and Lower Pottsgrove Township, and partly in Chester County in East Coventry Township.
Montgomery County houses major plant structures in 491 acres. A portion of the cooling tower blowdown discharge line and associated channel stabilisation structures, which are submerged in the Schuylkill River are located within Chester County occupying an area of 154 acres.
Limerick generating station development
The LGS plant was developed by Pennsylvania Electric Company, now PECO, a subsidiary of Exelon.
Unit one was initially licensed to operate till 26 October 2024 and unit two till 22 June 2029 under the NRC Operating Licences NPF-39 and NPF-85, respectively, of the US Atomic Energy Act of 1954.
The licenses were renewed for another 20 years after Exelon applied for a license extension to NRC in 2011.
Limerick generating station make-up
The LGS uses General Electric’s Boiling Water Reactor (BWR), housed within a GE Mark II wet containment, to generate electricity. The reactor requires refuelling every two years and goes for a power outage during this period. Inspection and maintenance work, which requires up to 1,000-1,500 workers, at the site are also performed during this period.
The Montgomery County site encompasses the reactor enclosures, turbine enclosures, two 155m high natural-draft hyperbolic cooling towers, and in site electrical substations of 230kV and 500kV. In addition, independent spent fuel storage installations, Schuylkill River pumphouse, and spray pond are part of the site.
Unit one has three main power transformers connected to a 230kV substation, while Unit two has three main power transformers connected to a 500kV substation.
Two 230kV transmission lines connect the 230kV Limerick substation to the Cromby substation, which transmits the electricity to the regional grid. A 500kV transmission line connects the 500kV Limerick substation to the 500kV Whitpain substation, which connects to the regional electricity grid.
The power plant’s reactor was installed by the Irex Contracting Group.
The plant original engineering, procurement and construction contract was awarded to Bechtel Power Corporation, which began the construction work at the site in 1974.
Joseph Jingoli & Son was awarded the contract for construction of the nuclear spent fuel storage facility along with maintenance facility.
Safety measures at the plant site
NRC-approved safety measures implemented at the plant site include the construction of a large reservoir of water beneath the reactor, which works as a boiling water reactor’s suppression pool, designed to cool steam rapidly in the event of a loss-of-coolant accident.