I would not go into an undergraduate program assuming that you will be required to do graduate school to get the job you want without ever having set for on campus. There’s no telling how well you will do as an undergraduate or how willing you will be to go through additional schooling by the time your 4 (or more) years are up. If your goal is to be a nuclear engineer, try to get an undergraduate degree that puts you on a path to be a nuclear engineer even if you don’t decide to go to graduate school. Physics may set you up for that (though I am not sure, as nuclear engineer and nuclear physicist are definitely distinct). Mechanical engineering (or maybe even chemical engineering) would likely qualify you for many nuclear engineering positions.