

The conclusion of the NS Savannah was that it would have been economical after the oil crisis of the 1970s caused a price spike in fuel costs. Ports also need facilities and training to handle nuclear fuel. Once you have that, it’s perfectly viable.
Unlike energy generation on land, there isn’t a lot of alternatives for decarbonizing marine transport.
China has built a couple of reactors recently. They also went overbudget and overschedule.