US clears environmental review for 835 MW Three Mile Island reactor restart

A US nuclear reactor that stopped generating power in 2019 has passed an environmental review tied to its proposed restart.

The Christopher Crane Clean Energy Center in Pennsylvania, formerly known as Three Mile Island unit 1, could return 835 MW of power to the grid in 2027.

The Nuclear Regulatory Commission (NRC) and the Department of Energy’s Office of Energy Dominance Financing issued an environmental assessment and a finding of no significant impact for proposed federal actions related to reauthorizing power operations.

The finding clears an environmental review step, but Constellation Energy still needs NRC approval to resume generation.

What the environmental finding covers

The NRC evaluated the reasonably foreseeable environmental effects of the proposed federal actions. It released a draft environmental assessment and draft finding of no significant impact for public comment in June before issuing the final documents.

The NRC served as the lead agency for the review, while the Office of Energy Dominance Financing participated as a cooperating agency. The latter closed a $1 billion loan to Constellation Energy Generation last year to help finance the reactor’s restart.

The environmental finding does not itself reauthorize power operations. Constellation has submitted a request for an exemption and three license amendment requests for NRC approval, all aimed at allowing the reactor to operate again.

A reactor with an existing license

Three Mile Island unit 1 shut down for decommissioning in 2019, although its renewed operating license was valid until April 19, 2034. Constellation is seeking approval to resume operations through that existing expiration date and has previously said it will look to extend operations to 2054.

The closure was driven by economics. Then-owner Exelon said the plant had lost money for more than five years as low wholesale electricity prices reduced its revenue.

It also failed to secure payments in three consecutive regional capacity auctions. Exelon argued that existing market rules did not adequately value nuclear power’s emissions-free generation, while proposed Pennsylvania policy changes failed to advance in time.

The reactor is separate from Three Mile Island unit 2, the site of the 1979 accident. Constellation’s restart plan concerns unit 1, which operated for decades after the accident before its 2019 closure.

Returning a closed reactor to service requires more than preparing its equipment. Constellation must also obtain the regulatory approvals needed to resume power operations, making the environmental finding one part of a wider restart process.

Constellation targets a 2027 return

Constellation says work at the plant is progressing ahead of schedule. Employees, contractors, skilled craft workers and local partners are preparing the facility to generate electricity again.

“Thanks to their dedication, the restart remains ahead of schedule, and we’re on track to return 835 megawatts of dependable, emissions-free power to the grid in 2027,” the company told World Nuclear News.

The proposed restart would restore a source of nuclear generation in central Pennsylvania that has been offline for seven years.

For now, the key remaining question is whether the NRC grants Constellation’s exemption and license amendment requests, allowing the plant to move from restart preparations back to power operations.