firstly, the supply of known uranium deposits will only last 80-100 years if we don’t recycle it and start burning MOX. I’d like to note that today’s light water reactors are horribly inefficient — they only extract 3% of the available energy from their fuel before it is considered “spent” and reclassified as waste. If we use high burn-up reactors such as the EPR, we can get a whole load more energy out of the same amount of fuel. And if we use fast breeders and run a plutonium cycle we can convert U238 into Pu239 and burn that instead of U235: there’s 500 times as much U238 lying around.
Secondly, we haven’t even tried to build a thorium reactor yet, although we’ve got good reason to believe it would work — and thorium is considerably more abundant than uranium.
As I have mentioned before, nuclear really should be part of the future energy mix of any industrialised country. Renewables can provide a large chunk (depending on local availability) of our energy needs but that still leaves a gap that needs to be plugged with something reliable and non-carbon-dioxide emitting.