Read the wiki, it's pretty good: http://en.wikipedia.org/wiki/Nuclear_Power_School
My recruiter was pretty honest with me. Bootcamp would suck: part physical, part mind game. During bootcamp, as a male recruit, I was given the opportunity to volunteer for submarine services. One thing they tell you when you are there is that you're only volunteering, it doesn't mean you will definitely get in. Unless you are physically disqualified from sub service, this is not true. You will be a submariner if you volunteer at that point. Sub sailors get a bit higher pay at the expense of quality of life. The hardest part of boot camp is the mind game. The division commanders are not your friend, nor your enemy. They're sailors who have been in only a few years more than you, and they're trying to filter out the punks, assholes, and people who aren't fit for military service while getting you into shape. You will be at your peak physical condition after boot camp. You will likely never again be in better shape.
A-School: It depends on how you are at 'high speed' schooling. I went to a college prep middle and high school. I stopped and went to a public school for my last semester of high school. Public high school does not prepare you at all for the level of information they throw at you in NNPTC. A-school is relatively simple: No reactor physics. Just mechanical, electric, or electronics, with a heavy dose of math (from addition/subtraction to early calculus 2). 1 hour of physical fitness, 4 hours of classroom, cafeteria lunch, 4 hours of classroom, 2-6 hours of study/homework. A-School is an extension of high school, and the next step in filtering out people.
Between A-school and power school is likely the first time you'll be able to take leave (or vacation) and go home, or about 26 week after you left home. The next few weeks you will wait until the next power school class up begins.
Power School is where the physics and reactor information gets thrown at you. 6 months of schooling, similar to A-School schedule. You will be presented with new materials of study on actual reactor design theory. But that's all you get presented in this school, theory. NPTU, or prototype, is your next stop. The Boy Scouts of America really do provide a top notch preparation for the military's qualification program. NPTU is there to ensure you are able to learn the Navy qualification process. Your job there is to qualify to operate as either a mechanical, electrical, or reactor operator, depending on your rate. Qualifications cards give you checklists of things you need to learn. For each item, you need to learn the basics of each part of the system in question, it's block diagram or higher level drawing, it's function, and it's interactions with other systems. The important part isn't the information... it's learning how to find the info quickly in a book, regurgitate it, get assigned followup questions, and repeat.
Joining as a nuke does not guarantee service as a nuke. When we went through, about 10% of the recruits who signed up as nukes didn't make it through boot camp. A similar amount dropped out at A-school, another 10% or so at Power School, and around 5% didn't make it through prototype. By the end of the pipeline, we're down to ~68.5% of the number of people who signed up for the program. About 8-10% of navy recruits qualify for the nuclear program, but only 3% of the navy is actively in the program.
Your first year on ship is a repeat of prototype: Qualifications. You are the bottom of the barrel. You will spend time washing dishes, cleaning/busing tables, ejecting trash, doing crap mess work, on the scale of months. Simultaneously you will need to make progress towards qualifications. Your tracking will be percentage complete over time, with a difficult to achieve goal rate. This is a hard time on any sailor. You're away from home, away from your friends/classmates from the last year and a half, away from shore potentially. Your future friends, your division mates? You are holding one of their billets, but not supporting their duties... You are now a NUB, or Non useful body.
You should complete ship qualifications in under 12 months, fully qualified nuclear by 18 months on board. At this point, you're at the top of your game. 4 ish years in, with only 2 years to go. This is when they'll hit you up for star-reenlistment. If you haven't made E-5 yet, they will offer it to you, for a 4 year re-enlistment. They will, however, drop 2 of your initial 6 year obligation off, for a total of 8 years required. Over 50% of nukes that make it this far do it. Oh, about 10% of the nukes that made it through school never finish their first required 6 years. And if you drop out during a-school, power school, or prototype, you still owe the full 6 years you signed up for, but without any of the extra benefits.
Every enlisted sailor should, during this period, be tracking his work for the related civilian field. I, for example, was an electrician. I should have been recording journeyman hours for my training and work. Always have an exit strategy. After completion of your senior in rate qualifications, that is the time to take advantage of schooling, if possible. Use any tuition assistance given, but don't over-reach.
During your time in the Navy, you will meet some of the most incredible people you can imagine. Some, not for the better. Looking back at it, it's not the job or the training I miss, it's the people. You can grow closer to your shipmates than you do with some siblings. The sad thing is, it's a constant cycle of new people coming, and older people going. Being 30 years old in the Navy is OLD. The service is full of adult children. It's not something that you think of when you're 18 and joining... you don't see yourself as only a kid. Now, I see people that were my age thinking of joining a service and I want to scream at them, You're just a KID!
One of the worse things I remember of the nuclear power program was the lack of integrity. Cheating on academics, at every level, from boot camp to qualifications to nuclear certification examinations underway. People usually get caught, but not right away. It was so rampant that it was almost justified by those who had been in for a while. I hope things have changed since I've gotten out, but I doubt it.
Another problem is the retention: The military isn't good about keeping good people. They tend to keep people who are too afraid to venture out into the real world. The incompetent can get promoted simply because there isn't a large volume of good people that stay in. There are, of course, exceptions... but not as many as I'd want to be.
Much of the work you do is simply because the paperwork needs to be generated. Work, for the sake of work. Working hours for Just In Case. Cleaning for 6 hours because that's the way it's been done for decades, and that's the way it will continue to be done.
After serving for 8 years, my family was started. When I left the service I was not able to jump in and go use my MGIB. I had a family to take care of. I was able to get a good job coming out as a field service technician. I drove around my state and surrounding states, travelling, paid windshield time. Now I work at the 'best company in America' taking care of building maintenance. I get paid well, in the top % of the World, but at a cost.
Enlisted Nuke is NOT the easiest way to become an officer. I think that was one of the biggest lies I heard from others in the program. Going to college and joining as an officer is the easiest way to become an officer.
I'll add to this and edit it as time goes on.