The small West Texas city of Abilene is better known for country music and rodeos than advanced nuclear physics. But that's where scientists are entering the final stretch of a race to boot up the next generation of American atomic energy. Amid a flurry of nuclear startups around the country, Abilene-based Natura Resources is one of just two companies with permits from the U.S. Nuclear Regulatory Commission to construct a so-called "advanced" reactor. It will build its small, one megawatt molten salt reactor beneath a newly-completed laboratory…