Fission is crazy expensive to even start up, and with expensive safety mechanisms still a risk.
Then you get to the expensive and very risky / guaranteed to leak long term storage of the very dangerous waste.
Fission is expensive to start up primarily due to regulation. Modern designs are extremely safe (fail-safe instead of fail-unsafe) and produce little in the way of dangerous waste. Politics is what killed fission.
What is the state of the art in fission that is already available?