Is there enough Uranium or other fissionable material to provide our energy needs into the future?
Yes. Since the dawn of the nuclear age, there has been concern about limited supplies of uranium. In the 1950’s the estimates were so low that extracting the considerable amount of uranium in coal ash was considered a reasonable option. Since that time, more and more large resources have been uncovered. Also, the low-impact method of in-situ extraction (no mining and environmentally benign) has opened up many more terrestrial sources. Finally, although it would be much more expensive than terrestrial uranium, uranium in the oceans is so plentiful that it could provide an economically viable source in the future.
There are other factors, as well. Today, most nuclear power production relies on the scarce isotope of uranium U-235 which is less than 1% of natural uranium. With breeder reactors, the remaining 99%, U-238, can be converted to fissionable Plutonium-239 in a breeder reactor.
Then there is Thorium. Thorium can be converted in a suitable breeder reactor to fissionable U-233. Thorium is plentiful throughout the world. It is almost four times as abundant as natural uranium, therefore hundreds of times more abundant than our usual nuclear fuel, U-235.