The Tennessee Valley Authority, the nation’s largest public power producer, decided yesterday to restart a troubled nuclear reactor at its Browns Ferry plant in northern Alabama. The reactor has been out of use since 1985, when all three of the plant’s reactors were shut down after engineers discovered that the reactors did not match their blueprints. Two of the three reactors were restarted in the 1990s; restarting the third one will cost $1.7 billion and is in keeping with the energy vision of President Bush, who strongly supports nuclear power. The TVA decision drew criticism from area residents, who are concerned about possible terrorists attacks, and from environmental groups, which say that the reactor is too old to be salvaged and that the money should go toward cleaning up fossil fuel plants instead. “It’s like trying to dust off an eight-track tape player rather than buying a DVD system — they’re not getting good value for their money,” said David Lochbaum, a nuclear-safety engineer with the Union of Concerned Scientists.