To be fair, nuclear power does make a little sense there even with a plentiful supply of oil/gas: every bit of fuel they burn to generate electricity is a bit they aren't exporting to generate money instead. Similarly, oil wells in the West are starting to experiment with other fuel sources to drive the oil extraction process: solar water heating to generate some of the steam needed for some older wells in California, for example, and I think nuclear power for some of the tar sand processing in Canada. None of it involves weapons-grade uranium of course...
As for the source of Iran's uranium ore, uranium is actually one of the most common elements in the earth's crust; there are large deposits in Kazakhstan, and might even be some in Iran itself: it's the enrichment process which is the real barrier to weapons programs, rather than obtaining the ore itself.