How much heavy fuel does a suezmax vessel carry? Less than 1% of the full deadweight, I assume.

Costs of carrying fuel are negligible.

Ships don’t use all that much fuel. A Panamax ship has a capacity of 2 million gallons of fuel and that would be ~2,600 tons. The total tonnage of a Panamax ship is ~52,000 tons.

Most cargo shipping saves fuel by just running slower.

This makes me wonder if the Navy nuclear reactors used on their ships could be used on shipping vessels to lower the cost of shipping in some manner.

Perhaps a sky high dream but wouldn’t this effectively given ships unlimited fuel?

We tried it but ports wouldn't let the ships dock and they were too small. Now it might be easier.

Capital costs would probably be way too much.

Crew requirements to operate a navy reactor are also probably pretty high. A cargo ship usually has a shockingly small crew.

There's proliferation concerns and you likely wouldn't be able to operate on some routes.

Also, skilled nuclear engineers cost a lot more money than traditional ship labor.

There have been nuclear powered merchant ships. Probably the most famous being the NS Savannah from the 50s. https://en.wikipedia.org/wiki/NS_Savannah

Nope. The safety and security issues make nuclear powered merchant vessels a non starter (except for a few niche cases like icebreakers that operate in Russian territorial waters). Few nations are willing to allow an accident or terrorist attack to sink a reactor in one of their harbors. Plus you can't hire qualified nuclear engineers for low wages.

A more realistic option would be to build more large reactors on land, then use the heat and power to manufacture synthetic liquid fuel to burn in ship engines. Or to charge batteries for short range vessels.

I wonder if there is a nuclear reactor design nowadays that offsets at least some of these fears. I sometimes wonder, though admittedly as a non expert, if some of these fears that linger around nuclear power sources are behind the times.

For example, I saw a demonstration of a nuclear powered device (don’t want to say reactor per say) that was taped for a documentary I saw on PBS, it was the size of a water heater or so and had a self protection system in case of something like a rupture, that at least during the demonstration stopped it cold in its tracks preventing meltdown and made any recovered materials from tampering worthless. It was in the testing phase though, and this was at least 5 years ago. My understanding is they wanted it to power critical infrastructure onsite like hospitals but feasibly it could power a home if I recall correctly or possibly a couple homes.

Another thing I read about was using some form of partially enriched uranium as energy source for heating homes and water heating. It won’t power one but it’s not (and can’t possibly be if I recall correctly) weapons grade by any stretch of the imagination

Maybe we should as a society look a little closer at smaller reactors. Hard to say, I’m no expert

You might be thinking of radioisotope thermoelectric generators. Those can be useful for generating relatively small amounts of electric power in isolated areas. But they're very inefficient and can't scale up to the level required to propel large ships. The risk of contamination from a sinking would still remain. So not a realistic solution.

There are a small number of nuclear commercial vessels, but nobody is building new ones.

You should also count that in order to refuel the ship needs to take a longer route