If you do not know what you want, go to college where you will have plenty of time to figure it out. Joining the Navy right out of high school commits you to 6 years before you can actually do what you want. The world at 24 will be a whole lot different then at 18.
The nuclear power curriculum is not all the difficult to master if one had the luxury of time college education provides. It is a lot of material to absorb and understand in the compressed period of time the Navy demands. If you have the aptitude to visualize systems and theories, it will be a snap. If not, there will be many hours of study. I dozed through most of my time at NucPwrSch, and spent more hours hung over at prototype then not, and still managed to graduate in the top percentiles of each training phase.
All that aside. If your interest is only about money, you will spend a miserable 6 years, after which, you'll ask why you did it. If your desire is to actually serve in the Navy, and do not mind the challenge of NucPwr, then go for it.
If I were you, as I stated at the start of this missive, go to college and give yourself some time to understand life and your place in it.