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Is Three Mile Island Still Operating? Current Status & Safety Facts

Three Mile Island remains a focal point for discussions about nuclear safety, energy policy, and regional economics. Understanding whether Three Mile Island is still operating r...

Mara Ellison Aug 05, 2026
Is Three Mile Island Still Operating? Current Status & Safety Facts

Three Mile Island remains a focal point for discussions about nuclear safety, energy policy, and regional economics. Understanding whether Three Mile Island is still operating requires examining its current status, history, and regulatory context.

This article clarifies the operational status of the facility, provides relevant timelines, and addresses frequently asked questions about its present and future.

Current Operational Status Overview

The following table summarizes the key operational and ownership details related to Three Mile Island as of the most recent available data.

Facility Unit Status Owner / Operator Last Commercial Operation
Unit 1 Active (as of 2023) Constellation Energy Continues commercial power production
Unit 2 Permanently Shutdown Exelon Generation / Constellation Energy Final shutdown in 2019
Annual Energy Output (Unit 1) Approx. 8 TWh Constellation Energy Recent operational years
Refueling Cycle Approx. every 24 months Constellation Energy Scheduled outages for safety checks

Unit 1 Operational Details

Unit 1 of the Three Mile Island facility continues to operate under Constellation Energy. It is a pressurized water reactor that underwent upgrades to maintain compliance with modern safety and environmental standards.

Regulatory reviews remain stringent, and the plant commits to transparency regarding performance metrics. Local stakeholders monitor operations closely due to the facility's visibility in regional energy markets.

Unit 2 Shutdown History

Unit 2 was permanently taken offline in 2019 after operating for several decades. Economic pressures, market dynamics, and the evolving energy policy landscape influenced the decision not to pursue a license renewal.

The decommissioning process is ongoing, with careful management of spent fuel and site restoration handled in accordance with federal regulations. This phase is expected to extend over multiple years.

Safety, Regulation, and Community Impact

Three Mile Island Unit 1 operates under continuous oversight by federal and state agencies. Routine inspections, incident reporting, and public communication are integral parts of its licensing agreement.

The plant contributes reliable baseload power to the Mid-Atlantic grid and supports employment in the region. Community engagement initiatives remain active to address concerns about environmental impact and long-term site management.

Key Takeaways

  • Unit 1 remains operational and is owned by Constellation Energy.
  • Unit 2 was permanently shut down in 2019 and is in decommissioning.
  • The plant undergoes regular refueling and regulatory inspections.
  • It continues to supply significant clean energy to the regional grid.
  • Local stakeholders stay engaged on safety and environmental considerations.

FAQ

Reader questions

Is Three Mile Island still operating in 2024?

Yes, Three Mile Island Unit 1 is still operating in 2024 under Constellation Energy. Unit 2 remains shut down permanently.

Who owns Three Mile Island now?

Constellation Energy is the current owner and operator of the facility.

When did Unit 2 shut down?

Unit 2 was permanently shut down in 2019. By providing steady baseload nuclear power, Three Mile Island helps stabilize regional energy supply, which can contribute to predictable electricity pricing for consumers.

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