Issues of potential output and safety considerations aside: > Surely Fission provides us with unlimited carbon free energy (given enough fissionable material).

Issues of potential output and safety considerations aside: > Surely Fission provides us with unlimited carbon free energy (given enough fissionable material). The crux of the problem is, there is a limited supply of fissionable material. If we manage to survive as a species, our energy demand will continue to grow, and one day we would meet a hard cap, limiting what humanity as a species, is able to do. As a very very rough estimate, if we burnt through all the fissionable material that we have available on earth, it would be about enough energy to launch the mass of Mt. Everest into orbit. Long term (as in, many generations from now) we will need more energy than that.