There is a nearly unlimited energy source, but quite complex, and have some danger and can be target of terrorism.
Breeder reactors. It can convert not ideal fuel into nuclear fuel. I don't remamber details but it could generate rich uraniun or plutoniun (not sure if one of this or both) from poor uranioun. It would recicle radioative waste into new nuclear fuel. But one critic was that could easily convert fuel for nuclear weapons.
The good side is that it would solve the problem or nuclear waste storage.
https://en.wikipedia.org/wiki/Breeder_reactor
But after the dumbsh...t event in Fukushima, where a disaster happened for lack of water-cooling after a tsunami... for lack of a really good emergency system to generate electricity to pump water to cool the reactor... Who can ensure a system proof of fail for a much more complex reactor ???