Exelon Generation, which plans to shut down Three Mile Island Unit 1 nuclear reactor in September unless Pennsylvania lawmakers come to the rescue, would take nearly 60 years and $1.2 billion to completely decommission the Dauphin County, Pa., site.

The company, in a report filed Friday with federal regulators, said it plans to remove Unit 1’s nuclear fuel from the reactor immediately after shutdown. The uranium fuel-rod assemblies would cool in spent fuel pools for three years until they are moved to sealed canisters in 2022.

But the reactor’s iconic cooling towers and other large components would remain standing until 2074, according Exelon’s Post-Shutdown Decommissioning Activities Report filed Friday with the Nuclear Regulatory Commission. All radioactive material would be safely stored or removed from the site by 2078.

A nuclear critic said that Exelon’s choice to decommission the reactor site over the long-term is an attempt to increase pressure on policymakers to enact a proposed nuclear rescue and keep TMI open.

“This is a veiled extortion attempt,” said Eric Epstein, chairman of Three Mile Island Alert, a Harrisburg nuclear watchdog group.

Epstein feared that Exelon’s prolonged decommissioning schedule would delay the completion of cleanup of the damaged TMI Unit 2, which permanently shut down in 1979 after America’s worst commercial nuclear accident. FirstEnergy Corp., which owns Unit 2, has said it plans to coordinate the final cleanup of its dormant reactor with Exelon’s work.

“Exelon is retreating from a timely cleanup of TMI-1, and this announcement means the damaged reactor — TMI-2 — will not be cleaned up until almost 100 years after the meltdown,” Epstein said.

Neil Sheehan, an NRC spokesman, said the timeline for the final cleanup of the damaged reactor still needs to be sorted out in light of Exelon’s report.