I had two friends who were nuke.
They were enlisted though, so they may have had different experiences than the officers (I didn't ask).
One was on subs, one was on carriers. Both hated every minute of it. There is a reason the Navy offers 100k+ re-up bonuses to the enlisted and rarely do people take it. If I remember correctly, on the carrier it was a 12 hour shift in a locked room(s) with no breaks/head calls. Guys would have to crap etc. into the trashcans if they had to go. All that time was spent watching gauges and pushing a button to prevent SCRAMing the reactor.
As for time at sea.... same as anyone else assigned to a ship.
My knowledge is limited and dated (2005 and before) so don't take my post as gospel, continue to get other information so you can make an informed decision on if this is a good career choice for you.