If we can operate submarines and aircraft carriers with nuclear, there is no reason why container ships and other cargo ships can't be nuclear powered. We could decarbonize the seas very effectively. It's not done simply because it is more profitable to use oil. 
Capitalism and nuclear ships is a real bad combination, seems like most commercial transport ships are already half falling apart.
Titanic but it irradiates the entire coastline from Madagascar to Singapore
With the proper reactors, it shouldn't be that bad. The Soviets had a bunch of nuclear sub accidents but they never caused a major ecological disaster.
I don't trust companies to not cut corners.
Yeah I'd want these to be nationalized too
AFAIK running barely functional ships until they absolutely die is pretty normal for a lot of shipping firms.