Eventually the U.S. will come around, too, since it must replace as much as 50 gigawatts of existing nuclear power by midcentury. (One very large power plant produces a gigawatt.) "Describe to me how it works by 2040 if you don't have new nuclear plants built, " says JohnRice, the 48-year-old vice chairman, who started out with Immelt in GE's plastics division.