Sign In

Three Mile Island Decommissioning

Three Mile Island

Three Mile Island Generating Station Unit 1 (TMI Unit 1) permanently shut down on September 20, 2019, leaving a 45-year legacy of safe, reliable, carbon-free electricity generation and service to the community.  It now enters a new era—the safe decommissioning and dismantlement of its components, systems and buildings.
Exelon Generation owns TMI Unit 1. The unit started operating on September 2, 1974.
FirstEnergy, which owns TMI Unit 2, announced the pending sale of that unit to Energy Solutions in July 2019.  Unit 2 has been shut down since 1979.

TMI Unit 1 Legacy
  • Exelon purchased TMI Unit 1 in 2000, producing 16,000 megawatts of carbon-free electricity, enough to power about 800,000 homes, annually for almost two decades with virtually no greenhouse gas emissions. 
  • Along the way, it’s estimated the station and its employees have pumped more than $3.5 billion into the local economy, including wages, taxes, and local purchasing. 
  • Since 2000, TMI Unit 1 has contributed $6 million to local charitable organizations and non-profits with employees spending almost 40,000 hours volunteering in the community.  
  • Safety and performance excellence are a top priority with more than 5.9 million hours and counting worked safely in that time span. 
  • Since 2000, TMI Unit 1 has offset more than 95 million metric tons of carbon, the equivalent of nearly 20 million cars off the road. 
  • The station is such a landmark in the Londonderry Township community that artwork of the island is painted on the side of several fire engines and the Lower Dauphin Communities That Care “Bookmobile.” 

Decommissioning Nuclear Power Plants
Decommissioning is the process by which nuclear power plants are safely retired from service. The progression involves decontaminating the facility to reduce residual radioactivity, dismantling the structures, removing contaminated materials to appropriate disposal facilities and releasing the property for other uses. The owner remains accountable to the NRC until decommissioning has been completed and the agency has terminated its license. 

Here’s a brief look at what will occur at TMI Unit 1:

1. The reactor is powered down. This will remove 836 megawatts of electricity from the regional grid.

2. TMI Unit 1 fuel will be removed from the reactor vessel and placed in the spent fuel pool to cool.

3. Cooled fuel will be placed in stainless steel canisters and transported to the Independent Spent Fuel Storage Facility (ISFSI) on station property by 2022.

4. Radioactive equipment and components are dismantled per an approved long-term plan.

5. Contaminated components are dismantled, securely packaged and transported to a licensed off-site facility.

6. The site is inspected by state and federal agencies to ensure the property has been returned to conditions outlined in the decommissioning plans. Both the State and Federal agencies will continue to monitor the site.

Our Decommissioning Team

Long after TMI Unit 1 ceases operations, a team of employees will remain on site. Here's a look at what we will be doing. 

  • Health Benefits  


    A security force will safeguard the facility until all nuclear fuel has been removed from the site.

  • Retirement Benefits  


    A highly qualified, skilled staff of experts will oversee and conduct the entire dismantlement process.

  • Life Insurance and Diability Benefits  


    Using company employees and contracted experts, Exelon will continue a strong environmental monitoring program through decommissioning.

  • Employee Stock Purchase Plan  


    Teams of qualified employees, both on and off-site, will be on-call all day, every day to work to protect the plant and the public in an unlikely emergency situation.

Overview of Decommissioning Process
  • To decommission a nuclear power plant, the licensee must submit a post‐shutdown decommissioning activities report to the NRC. This report provides a description of the planned decommissioning activities, a schedule for accomplishing them, and an estimate of the expected costs.
  • The licensee must reduce the residual radioactivity to levels that permit release of the property and termination of the facility’s operating license. The site must be decommissioned within 60 years of the plant ceasing operations.
  • The decommissioning process involves removing the used nuclear fuel from the reactor; dismantling systems or components containing radioactive products (e.g. the reactor vessel); and cleaning up or dismantling contaminated materials from the facility.
  • Contaminated materials can be disposed of in two ways: decontaminated on site or removed and shipped to a waste processing, storage or disposal facility.