> can't we use many different things for nuclear though?(and uranium is just the most efficient?)
Strictly speaking, U-235 is the only fissile isotope of any element that is found in any significant amounts in nature. However, breeder reactors can also be useful. The only two starter points I'm aware of in nature for significant energy extraction are U-238 and Th-232. U-238 breeder reactors are politically complicated because they can relatively easily be used to generate significant amounts of Plutonium which is usable in bombs.
Th-232 reactors have technical hurdles that are probably surmountable; specifically the neutron economy is significantly tighter than U-238 breeder reactors (this is why you often see liquid-salt reactors proposed for Th; chemically separating the decay products gives plenty of breathing room in the neutron economy). The U-233 it generates is also usable in bombs, but since it will tend to also generate U-232, which is both difficult to work with and easy to detect, it's considered less of a proliferation risk.
This all misses my original point though. At any point in the first half of the 20th century we had enough oil to last us for centuries at then-present day usage. Yet here we are.
Strictly speaking, U-235 is the only fissile isotope of any element that is found in any significant amounts in nature. However, breeder reactors can also be useful. The only two starter points I'm aware of in nature for significant energy extraction are U-238 and Th-232. U-238 breeder reactors are politically complicated because they can relatively easily be used to generate significant amounts of Plutonium which is usable in bombs.
Th-232 reactors have technical hurdles that are probably surmountable; specifically the neutron economy is significantly tighter than U-238 breeder reactors (this is why you often see liquid-salt reactors proposed for Th; chemically separating the decay products gives plenty of breathing room in the neutron economy). The U-233 it generates is also usable in bombs, but since it will tend to also generate U-232, which is both difficult to work with and easy to detect, it's considered less of a proliferation risk.
This all misses my original point though. At any point in the first half of the 20th century we had enough oil to last us for centuries at then-present day usage. Yet here we are.