Sign In




837 MW​​Generation capacity
800,000​​Customers served
96.3%<strong>​​​Capacity Factor</strong><div><strong></strong>​​​​Amount of time our Three Mile Island nuclear facility is on and operating</div>



Three Mile Island<div class="intro-content copy-section">​​​​​​​​​​​​​​​​​Three Mile Island is a nuclear power plant located in central Pennsylvania about 10 miles south of Harrisburg in Londonderry Township. </div><div class="copy-section"><p>Exelon owns and operates Unit 1 of the power plant which is built on an island in the Susquehanna River and began commercial operation on September 2, 1974. Three Mile Island Unit 1 is a pressurized water reactor designed by Babcock and Wilcox. The unit is capable of generating 837 net megawatts (MW), enough electricity to power over 800,000 average American homes. Three Mile Island Unit 2 is owned by First Energy Company of Akron which was damaged during an accident in 1979 and never reopened.</p></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>Committed to safety</h4></div><div class="grouper-content"><div class="cta-generic"><p>We use "defense-in-depth" design, which means there are redundant, diverse, and reliable safety systems to supply water to the reactor core. Every safety system has at least one independent back-up system and many have more than one. Plant safety systems are also run by multiple, redundant power sources. Certain equipment is designed to automatically shut down the plant if the need arises due to a condition outside of normal operations.</p><p>We also count on our people. Before they become Exelon employees, job applicants must pass thorough background checks. Exelon Nuclear then invests in training programs - both initial training and continuous programs for existing, experienced operations staff. </p><p>Much of our operations training is done in a full-scale electronic simulator of a control room. Initial training includes 12 weeks in the classroom, 25 weeks in the control room simulator and 16 weeks of on-the-job training. Once an employee is licensed by the NRC, that operator will continually train by spending one week in a control room simulator for every five weeks spent on shift in the control room. Even our most senior reactor operators receive training every six weeks, for a total of 8.5 weeks of training every year. </p><p> <a href="/_layouts/15/FIXUPREDIRECT.ASPX?WebId=7628dbb4-4e0e-44ff-8ad0-757ff755058a&TermSetId=4edbe393-511d-4d44-ae11-d078f6633c49&TermId=4e57e9f3-21ec-4324-acf4-c7167186d0c8">Learn more about the safety of Exelon's nuclear energy plants.</a></p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>License renewals mean clean, zero-carbon energy well into the future</h4></div><div class="grouper-content"><div class="cta-generic"><p>In 2009, Three Mile Island Unit 1 received a 20 year extension to the plant's operating license from the U.S. Nuclear Regulatory Commission. With license extension, Three Mile Island is well positioned to help meet the growing demand for energy well into the future as power needs across central Pennsylvania and the United States are projected to increase. The operation of Three Mile Island produces no greenhouse gas emissions and improves the air quality of the region.</p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>Generating more low-carbon electricity</h4></div><div class="grouper-content"><div class="cta-generic"><p>Today's nuclear energy facilities produce 64 percent of America's clean, carbon-free electricity. As America confronts climate change and seeks to reduce carbon emissions, nuclear energy is a vital part of the mix. It's a 24/7 provider of base load power, far more productive than other clean energy sources and far more reliable, too. </p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>Sophisticated emergency planning</h4></div><div class="grouper-content"><div class="cta-generic"><p>Safety is Exelon Generation's first and highest obligation. Nuclear power plants are among the best-protected private sector facilities in America, with monitoring and inspections by plant owners, local officials and the federal government. </p><p>All nuclear energy facilities in America are required to develop and test detailed emergency response plans to protect the public. The U.S. Nuclear Regulatory Commission (NRC) reviews and approves these plans. The NRC also coordinates approval of these plans with the Federal Emergency Management Agency (FEMA).</p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>Plant Security</h4></div><div class="grouper-content"><div class="cta-generic"><p>By design and construction, nuclear facilities are very difficult to penetrate. That, plus a well-armed paramilitary security force, and multiple backup safety systems, delivers layer upon layer of safety.</p><p>The nuclear energy industry maintains very strict security to prevent unauthorized persons from gaining access to critical equipment or approaching close enough to harm the facility either by land or air. America's 62 nuclear sites are protected by sophisticated surveillance systems and approximately 9,000 highly trained, armed officers.</p><p>The U.S. Nuclear Regulatory Commission now considers new threat scenarios and protections in emergency preparedness in light of the threat of terrorist attacks. After September 11, 2001, all those involved in emergency planning reevaluated those plans and put additional practices in place. Exelon Generation has open lines of communications with the Dept. of Homeland S​ecurity.</p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>Supporting the local economy</h4></div><div class="grouper-content"><div class="cta-generic"><p>The majority of Three Mile Island's approximately 725​ Exelon employees live in Dauphin and Lancaster Counties. The power plant's annual payroll is about $60 million. During refueling outages, Three Mile Island employs several hundred temporary contractors who boost the local economy during their stay.</p></div></div></div></div><div class="grouper"><div class="row"><div class="grouper-section"> </div><div class="section-header"><h4>We live here too, and we're good neighbors</h4></div><div class="grouper-content"><div class="cta-generic"><p>Three Mile Island aims to be a good neighbor and is very active in the local community.</p><ul class="styled-bullets"><li> <strong>Sponsorship.</strong> The power plant sponsors several community events including the Middletown Music Fest and other community activities.</li><li>​<strong>Charitable Giving & Volunteering.</strong> Three Mile Island contributes annually to numerous community and charitable organizations. Each year employees give generously to the community including local United Way chapters. The station also sponsors blood drives throughout the year, helping the Central Pennsylvania Blood Bank supply the needs of area hospitals. They also run Toys for Tots fund drives to support The Salvation Army.</li></ul></div></div></div></div>​Three Mile Island




Three Mile Island, /locations/Documents/Three%20Mile%20Island%20Emergency%20Planning%20Brochure%202016.pdf, /locations/Documents/Three%20Mile%20Island%20Generating%20Station%20Fact%20Sheet%20-%202017.pdfGP0|#036d7cad-49e3-4a98-8821-efa704301d6d L0|#0036d7cad-49e3-4a98-8821-efa704301d6d|Exelon Generation GTSet|#bb697efb-4d63-4298-b4d0-ab279caf3fe8 Mile Island, Planificacion de Emergencias

About this facility