ATLANTA (AP) — A nuclear power plant in Georgia has begun splitting atoms in one of its two new reactors, Georgia Power said Monday, a key step toward reaching commercial operation at the first new nuclear reactors built from scratch in decades in the United States. A third and a fourth reactor were approved for construction at Vogtle by the Georgia Public Service Commission in 2009, and the third reactor was supposed to start generating power in 2016. Its costs and delays could deter other utilities from building such plants, even though they generate electricity without releasing climate-changing carbon emissions