Congrats on your service selection. I went through the nuke power pipeline back in '92....through the enlisted side of the house when it was still in Orlando. The officer side is a bit more technical, though most officers have the math and science to back that up whereas many of the enlisted didn't know a damn thing (except high school courses) before they went through it.
Overall, the program is tough. At power school, there are those who do and those who don't. You'll figure out what I mean when you get there. Are you married? If not, find a willing partner and get hitched. For whatever reason, married guys (women couldn't be nukes when I went through) always did better than the single guys...usually with less after school studying. Regardless of what your degree is in or how high your GPA was, don't show up thinking you own the place. The navy has its own way of teaching engineering, thermo, math, electrical theory, etc. Smart people fail out of the program all the time. Believe me, if you couldn't make it through the program, Naval Reactors would not let you go there.
Use the instructors like there's no tomorrow. It's not college anymore. They are there to ensure you are successful and that you learn as much as you can. They may not know a lot in all aspects of the program, but the areas that they are responsible for teaching, they are very knowledgable. Unless they do it differently now, you will have a mixture of officer and enlisted instructors. The enlisted guys know more than you do. They always will. Accept that right away and you'll be ok.
Aim for perfection on your exams, but realize that its never going to happen. Grading is done a little differently in the nuke program than any other academic program I've been through....navy or otherwise. Don't expect multiple choice exams. In fact, don't expect to see even one mulitple choice question unless it's for a course critique. If you're getting anything over a 3.5, you're doing just fine and have no reason to complain. Learn from your mistakes and move on...don't get hung up on to stupid errors you made on the exam. If you're getting between a 3.2 and 3.5, you should be pretty happy with yourself. If you're getting below a 3.2, you need to talk to the instructors more. Never forget, it's two-five-stay-alive. That's not something to be made fun of...you'll see guys sweatin bullets for one or two points on the exam review just to squeak by. Oh yea, one more thing. Help your fellow classmates out.
Find a few other O's you like to hang around with and make time to get away from the studying each week. When I went through, my friends and I had a golden rule. We never studied on Friday night....period. That rule was sacred. Saturday during the day was ok, but not Saturday night. And then normally, we would all meet back again Sunday evening at the school house for a couple hours to finish up anything and just get warmed up for the next week. You're gonna get more stuff thrown at you than you'll know what to do with. Try not to forget any of it. At the end of power school, you'll get to take a lovely test....comprehensive in nature that covers everything....yes, everything. It's all fair game.
Please keep your hands and feet inside the vehicle at all times, and enjoy the ride!