A small nuke in the basement would be a very useful thing-you could have an endless supply of hot water! And, you could heat your house for virtually nothing!
Technically, how small could a sub-critical reactor be to supply the heating needs of a house?
Would I need permission from the AEC to build one? And,how do I purchase the necessary fuelrods?
If Homer Simpson can run a reato, why can’t I?
Not to throw COLD water on your parade, but …
No not nothing. The cost of a small reactor would be out of the question.
Not small enough unless you have a HUGE basement.
It’s call a license! The answer is YES!
Find a vendor and ask them for quotes.
You have to have a license for that too!
IOW Forget it.
One guy I know in near Oak Ridge, TN was a retired Nuclear Engineer. For his senior project he managed to get a little 50 Watt nuclear reactor installed at Cal Poly SLO (my alma mater). It was there for about 10 or 12 years before it was removed. I can’t say I remember the size of it though; but someone told me it was about a cubic yard in size. It required licencing from the AEC at the time (now the Department of Energy). Removal required the DOE’s involvment to guide the disassembly and removal of the poor man’s reactor. The reason given was that computer models were cheaper to run. But I always suspected that with the Diablo Canyon Nuclear power plant next door and the hornet’s nest of anti-nuclear protesters was more the reason…
So yeah, if your willing to shell out the bucks you can build your own, but assuming 50 Watts per cubic yard–you’re better off investing in a solar hot water heater. Which is cleaner and less prone to terrorist attack.
Can I Build a Small Nuclear reator In My Basement?
Absolutely not, mister! Now put those leggos away, and get ready for your bath.
Yes, you can. This boy scout did.
However, get ready for governement officials, men in white suits, and a very low powered reactor…also death.
For compact instalations you may try a radioisotope thermoelectric generator; you won´t get much juice from it, but compared to a nuclear reactor it´s simpler. Even better, you may just pack your things and take your holidays trecking along Russia´s northern shores, you may get your hands on a still hot leftover.
[sub]N.B.: You may want to store some sperm on a sperm bank, in case you want to have non-mutated offspring in the future. [/sub]
Cecil mentions the radioactive Boy Scout as well in this column on Radioactive Camp Lanterns.
You could check out the SlowPoke reactor. It can heat your house (and several of your neighbours’ houses) with a core that is less than a foot square.
It does need a tank of coolant water 2.5 m in diameter by 6 m deep, but hey, it’s light water, not that calorie loaded heavy stuff!
Plus, you can let it run overnight without supervision, so you’re not tied to the house.
That’s the way I’d go.
The University of Alberta has one - IIRC they use it to create isotopes for medical use at the UofA hospital. Perhaps your local institution of higher education has one you can take notes on. 
There’s also the Argonne Low Power Reactor/“SL-1” “Operating power was 200kW electrical, 400kW thermal, for space heating.” The control rods were manually raised and lowered…by ropes.
I can’t find much info on size/weight, however. Well, aside from that when there was an accident during testing, the “nine tonne” reactor vessel was flung less than ten feet into the air.
Yeah, the SlowPoke might be your best bet.
If you want an actual fissioning reactor, Slowpoke is about as small and as safe as they go. Put it in your basement and let it fill your house with lovely warm damp steam…
Non-fissioning sources of nuclear energy release heat from decay of radioisotopes. I’m not sure what licensing is needed - it’s worth pointing out that some pacemaker power supplies are radio-isotope thermoelectric generators containing plutonium 238 (not fissile). Maybe a crematorium would have a bunch of old ones you could wire up in series!
http://www.orau.org/ptp/collection/Miscellaneous/pacemaker.htm
So you may be able to have a small thermoelectric source in your house. It’s also worth noting that those Russian thermolectric generators Ale linked to will provide several times their electric output as waste heat.
A “green” alternative that gives much the same effect is to use a BIG pile of woodchips…
http://journeytoforever.org/biofuel_library/methane_pain.html
(I put “green” in quotes because it seems to me that if everyone had one of these built to Pain’s design, the uncovered outer heap would serve to convert atmospheric CO2 into methane, which in terms of greenhouse gases is a bit of an own goal. A different design might fix this problem.)
OP nitpick - a fissioning reactor, by definition, is critical. A sub-critical reactor doesn’t do very much.
It is extremely sad that Tom Weller’s wonderful satire Science Made Stupid is out of print. If you can locate a copy, there’s a priceless one-page description of “How to Build Your Own Nuclear Reactor” You need a big plastic garbage can, several pieces of PVC tubing (cut to the right lengths), a garden hose, a keyhole saw, several rods of enriched uranium, several cadmium rods, and a lot of Moderator material (“The “pros” use graphite, but potting soil will work fine”).
You can use the water to heat your hot tob, then drain it off into your garden, “which will produce interesting and unusual blooms.”
Check out the sequel, Cvltvre Made Stupid, too.
<philo>Today, we’re going to learn how to make plutonium… from common household items.</philo>
The Russians built quite small SNAPs.