Three Mile Island restart clears an early environmental step

In Dauphin County, Pennsylvania, Constellation’s effort to bring the Christopher M. Crane Clean Energy Center back to power operations has reached a federal checkpoint. The U.S. Nuclear Regulatory Commission, or NRC, has issued a draft environmental assessment and draft finding of no significant impact, known as a FONSI, for proposed actions tied to reauthorizing power operations. For nearby communities and the regional grid, the immediate question is whether the restart can keep moving without triggering a deeper environmental review.

Comment deadline: July 8, 2026 Submit comments: https://www.regulations.gov Effective date: June 3, 2026

The plant was formerly Three Mile Island Nuclear Station, Unit 1. Constellation Energy Generation, LLC is seeking one exemption and three license amendments to support a return to power operations through April 19, 2034.

What the draft review covers

The draft assessment looks at land use, air and water, noise, ecological resources, historic and cultural resources, health, waste, transportation, accident risks, greenhouse gases and climate change. NRC staff says the impacts in each area are not significant. That kind of finding can keep a project on the environmental-review track without forcing a full environmental impact statement unless public comments change the agency’s view.

The review is tied to concrete federal action: the NRC is weighing the exemption and license amendments Constellation requested to support the potential reauthorization of power operations at the center. The agency also says the no-action alternative could have significant impacts, while no other option met the project’s need.

The financing track

The Department of Energy’s Office of Energy Dominance Financing is a cooperating agency on the review. DOE’s proposed action is a decision on federal financial assistance, specifically a loan guarantee, for refueling and resumption of power operations. In other words, the restart is not just a licensing problem. It is also a financing problem.

The agency says the project would provide 835 megawatts-electric of baseload power to the Pennsylvania, New Jersey and Maryland grid. Constellation also points to a 20-year power purchase agreement signed in 2024 with Microsoft to supply carbon-free energy to Microsoft’s data centers in PJM.

July 8 is the public window

Public comments are due July 8, 2026. After that, NRC staff will issue a final environmental determination and decide whether a full environmental impact statement is needed or whether the draft FONSI stands.

DOE would then issue its own separate notice or decision document if it moves forward. For now, the restart remains under review, with both the environmental and financing tracks still open.