Whilst nuclear fission is an excellent power source for the current population of Earth, and even with new fast-breeder reactors, the fuel to power nuclear reactors will not last forever. Given that nuclear fuels are heavy elements and generally heavy elements tend to be rarer why not use light elements like hydrogen which are in abundance.
I am of course talking about Nuclear fusion, where rather than splitting heavy elements into lighter ones, we fuse light elements into heavier ones.
Considering that 75% of the universe is made up of Hydrogen I don't think fuel supplies will be a concern.
Therefore while I am an advocate of nuclear fission, I think nuclear fusion is a much more viable alternative in the long term. (I'm talking very long term, nuclear fission fuels will last longer with the newer reactors).
I expect many people on these forums support nuclear power of all types. Therefore people may be interested in this place:http://www.fusion.org.uk/
I recently took a tour of this facility and we are on the brink of being able to harness fusion to its full potential. The next large fusion reactor (ITER) will be 10 times larger and should produce more energy than it took to start the reaction. (At the moment we use up the same amount of energy starting the reaction as we produce).
I hope that many more people become more aware of the potential of fusion and that it gets more funding from governments in the future.