The T.V.A. does not answer to state regulators. It has no shareholders to worry. As a federally chartered corporation established in 1933 as part of the New Deal, it is overseen by nine directors who are appointed by the president and confirmed by the Senate. Today it supplies electricity across parts of seven states, serving roughly nine million people.

It also enjoys financial advantages that most public utilities lack, borrowing money at rates similar to those paid by the United States Treasury, which is critical for building hugely expensive reactors.

That makes it one of the very few American builders that could pull off a nuclear power comeback in this climate. With the exception of Watts Bar 1, another T.V.A. plant that was mothballed for a time but was finished in 1996, no new reactor construction has been started since the early 1990s. Two new plants in Georgia and South Carolina are awaiting construction permits, and the authority is working on finishing a second Watts Bar reactor similar in vintage to Bellefonte 1 that is expected to be completed next year.

Authority managers have said they would ask their board this summer for money to complete Bellefonte 1; last year the board voted to allocate $248 million just to explore that possibility.

Image Residents say the reactor will benefit the local economy.

Currently, the T.V.A. gets 60 percent of its energy from fossil fuels, mostly coal, and in addition to the 18 generators it recently agreed to shut at the urging of the E.P.A., it must decide whether to scrub or close several more. The authority’s goal is to have 50 percent of its generation come from “low or zero carbon-emitting sources” by 2020, which is why Bellefonte 1 is a dinosaur back in play.

Bellefonte 1 is the most on-again, off-again nuclear project in the country. In 1970, the T.V.A. said that within eight years it would build two nuclear reactors here for $650 million. Construction did not start until 1974, and by 1988, the authority had spent more than six times what it had budgeted.