Exactly.
Proliferation will always be a risk with nuclear reactors. We will never have nuclear powered civilian ships, as long as there exist pirates out there. Sure, Russia operates nuclear powered ice-breakers, but there are no pirates in the Arctic Ocean, plus, for Russia the distinction between civilian and military is not all that clear.
As for hydrogen, I think ships are the killer app. High pressure tanks or cryogenic tanks benefit from the square-cube law. If you want them to be economical, they need to be really large. They will never make sense for cars, or even trucks, but they can make sense for trains, and certainly for ships.
> Proliferation will always be a risk with nuclear reactors.
Wasn't one of the promises of thorium reactors a much lower risk of non-proliferation? (Here's a fun question, can one make a pebble bed reactor design with pebbles designed such that if a ship sank, could a special magnetic sphere of a 'correct' size pull in the pebbles but keep a safe distance? IDK but trying to think outside the box here...)
I think it's worth remembering that for the sake of many ships, we do not need the power-density of an SXX or even an AXX per-se.
> As for hydrogen, I think ships are the killer app. High pressure tanks or cryogenic tanks benefit from the square-cube law. If you want them to be economical, they need to be really large. They will never make sense for cars, or even trucks, but they can make sense for trains, and certainly for ships.
The bigger the tank, the more rigorous the inspection has to be to avoid risks due to hydrogen embrittlement.
I'll admit, I'm -less- worried about that property on a train than a ship, but on a ship I think we'd first need to see good evidence we can maintain things of such size on ground safely.
As a lay person, it seems like trains are pretty much always suited to electricity. Adding a power line alongside the existing right of way seems like it’s a pretty straightforward option. What are the conditions in which on-board power storage is preferable?
Hydrogen fuel for merchant ships isn't going to happen. Despite some issues with toxicity and pollution, the industry seems to have settled on ammonia as the main replacement for fossil fuels.
We might actually get more "nuclear powered" civilian ships, in a way. The reactors will be on land, where they can be properly guarded. And the heat and power will be used to manufacture carbon-neutral liquid fuel.