The nation that should have been the primary driver of nuclear technologies (the US) saw an explosion in the cost of development. This was not seen in other countries, which is evidence that it's because of cultural/institutional problems rather than fundamental technical ones.
http://www.vox.com/2016/2/29/11132930/nuclear-power-costs-us...
> Fusion? Was said to be ready in 20 years - 40 years ago, and today? Still 20 years to go...
This is a common misconception. In fact, the authoratative government body on energy research made it very clear 40 years ago what it would cost to develop fusion power. Fusion power never got the required funding so it never materialized -- as predicted.