The Blue Ridge Environmental Defense League, the Bellefonte Efficiency and Sustainability Team and the Southern Alliance for Clean Energy asked federal regulators to suspend a request by the Tennessee Valley Authority to renew construction permits at Bellefonte.
The groups said TVA has not addressed the possible environmental impact of work at Bellefonte, along the Tennessee River at the town of Hollywood.
The utility had no immediate response.
TVA has not decided whether to finish the two existing reactors at Bellefonte, which was never completed, but it is considering such a project.
Ken Clark, a spokesman with the Nuclear Regulatory Commission, said the government was in the early stages of reviewing requests to reinstate construction permits for the unfinished Bellefonte reactors and to possibly build two more reactors at the plant.
"There have been no decisions yet," he said. "It's all under consideration."
TVA supplies electricity to about 8.8 million consumers in Alabama, Georgia, Tennessee, Kentucky, Mississippi, North Carolina, Tennessee and Virginia.