US nuclear submarines consume highly-enriched uranium, that's nearly as (and sometimes more) pure as the weapons-grade version. That doesn't mean oceanic reactors aren't possible, it just means that military subs are a bad example.

French nuclear submarines run on 7% enriched fuel, so it's certainly possible to build military submarines that don't need HEU.

There are nuclear icebreakers.

Nuclear powered non military ships do exist, it just not economically feasible .

Much more economically feasible than battery powered ones.

Prove it.

There are operating nuclear powered ocean vessels for decades.

The parent poster means to say prove it is more economical, not that it is doable.

It is hard to compute the economics of small nuclear reactors that use highly enriched fuel. A lot of it is funded by defense needs.

Mixed use is largely to keep defense manufacturing active not because they are economically effective.

If nuclear civilian ships were cheaper, there would be efforts to make a lot of them (In Russia and China if not other countries etc)

Russia is operating nuclear civil vessels (icebreakers) since 1957

Yep, was just lookin up their recent news on this: https://www.allseas.com/en/who-we-are/news-and-media/allseas...

While perhaps not practical for oceanic shipping as is, it's a fun exercise to demonstrate the energy density of nuclear power.