WASHINGTON (AP) - About 40 percent of the nation's nuclear power plants have begun moving spent fuel out of cooling pools and into massive dry casks, embracing a storage approach that a National Academy of Sciences panel said offers safety advantages. The nation's 64 active nuclear power plants, which together house 103 reactors, all now store nuclear waste in pools of water after it is removed from reactors. Eventually, the spent fuel is supposed to be shipped to a national nuclear waste dump planned for Yucca Mountain in Nevada. As Yucca Mountain has been delayed, utilities are increasingly moving some...