Turns out the Russians have already done this:
https://en.wikipedia.org/w/index.php?title=Russian_floating_nuclear_power_station&oldid=1038656914
They use the same reactor types as their icebreakers.
I noticed that the "ships" will not be self-powered, so that helps mitigate the hijacking issue.
@Pat hijacking really isnt even my top concern. You can always have military protections to help with that.
@Pat Except none have been produced yet, thankfully.