Exelon Generation officials told The (Harrisburg) Patriot-News that the plant's Unit 1 was returned to service Saturday when operators connected the turbine generator to the regional power grid.
Nuclear Regulatory Commission spokesman Neil Sheehan says once the reactor has cooled, workers will be able to access the containment building and try to solve the problem.
Officials said Thursday's shutdown, the second such event in as many months, posed no threat to the public. The partial reactor meltdown in Unit 2 at the plant in 1979 is considered the worst commercial nuclear power plant accident in U.S history.
Information from: The Patriot-News