The US Navy doesn't use nuclear reactors because of economics (they're quite expensive) or environmental concern. They use nukes because of the operational advantages of having a ship that only needs refueling once per decade. Any comparison to the naval use case is mostly useless when it comes to commercial power production.
The reasons are not simply refueling concerns, although that is a factor. The boats still need to refuel the humans onboard, ie. food supplies and occasionally munitions.
The reactor powers the boat using less mass than a typical diesel-electric, is more quiet, and can remain underwater for an entire deployment if necessary - something that's simply not possible with other power generation methods.
Quantity. One of the big issues with nuclear power is that we aren’t building frequently enough, and therefore lose expertise and capability, which drives up costs, both from screw-ups and from not being able to amortize over a large production run. To give an analogy, imagine if Boeing only made one 737 every five years. That aircraft would be insanely expensive.
Personally, I’m bullish on the companies in the micro reactor space that have minimal site construction. I’m less bullish on Oklo, given that their application had some glaring omissions and got denied an NRC license.
What are the numbers? What’s the TCO difference to similar systems without atmospheric carbon emissions?