Military ships are "safe", because they can generally defend themselves. Commercial container ships would be the target of hijacking, to steal the reactor / fuel, or use them as 9/11 ship equivalents.
Regulation is not always bad.
We could find a way to make the reactor so integral to the ship and the fuel so integral to the reactor it’d be almost impossible to remove either. We can compound that with fuel cycles with materials less useful for making bombs.
Correct. And military nuclear vessels are also operationally safe because superpower navies are willing to spend a fortune on training and paying qualified nuclear engineers and technicians. Despite those large budgets they still struggle to maintain minimum crewing levels. Merchant lines can't afford the personnel expense.