If we disregard legal issues, is it possible to build a reasonably safe nuclear reactor (I’m assuming fission) to power & heat a house or alternatively a small neighborhood (up to 50 houses or so)? I’m assuming the answer is yes, since submarines can do it, but I’m not sure about what kind of risk is seen as reasonable in the nuclear submarine business What could happen - worst case scenario - with a small reactor assuming we use a well tested design?
Also, how much would the fuel cost - would it be economical compared to buying electricity/heating from the power companies? What about the reactor itself, would that be very expensive?
Thirdly, assuming everybody moved to nuclear, how long until we run out of reasonably affordable fuel?
I don’t think anyone wants to sell a reactor that small. If you mean build it yourself I’m not sure companies would want to sell you the components even if it is legal for them to do so. They don’t have any reason to design smaller reactors except for the military and they would not want to sell those to you.
The nuclear fission power plants used in submarines are not failsafe designs, which is particularly notable in poor safety record of the vessels former Soviet Navy. The US and RN vessels have enjoyed a nearly flawless safety record through intensive and continuous safety training. It just isn’t possible (by any conventional design) to make a failsafe reactor that compact.
The Department of Energy’s Nuclear Regulatory Commission regulates the transportation and sale of fissile material and the disposition of radioactive waste products as well as licensing power generating nuclear reactors. In order to operate your own nuclear reactor (for commercial power generation, industrial use, or experimental/training operation) you would have to apply for a license and submit to regular inspections. Although technically voluntary, the operating authority for such a reactor would probably have to belong to or comply with the Institute of Nuclear Power Operations with regard to standards for operation.
The short answer to your question is “No, you could not operate your own personal nuclear fission reactor,” or at least, not legally within the United States.
Particularly if you don’t care if the reactor is rather big and inefficient. Doubly so if you are only using it to heat the house.
Commercial and naval reactors run dayum hot, they try to be as efficient as possible, and they try to make em as compact as possible too.
All this makes them prone to blowing up, having barely controlled reactions, and bad things happening when they do.
If you’ve got the cash for enough enriched uranium or plutonium, there is no reason you can’t make a reactor the size of a small house (rough guess size here) that likely requires no control system and can’t get more than warm enough to heat a house or just barely make enough LOW temp steam to run a tiny household generator.
Such a reactor really wouldn’t require a containment vessel either. And a big pile running at such a low power level could probably run centuries undisturbed.