[fuoqi]

Submarine, aircraft, and icebreaker reactors usually operate on military-grade fission materials. You don't want those to be exported all over the world. And a bigger reason is that they simply can not compete with bigger plants. 1 GW class nuclear reactors generate much cheaper electricity even after factoring in their huge CAPEX. There is one example of using a small nuclear ship-scale reactor for civilian power generation in Russia [0], but I would say it's a very edge scenario, not applicable to the most of the world.

[0]: https://en.wikipedia.org/wiki/Russian_floating_nuclear_power...