I was a demolition site coordinator for a NPP demolition specialist. So no I'm not a nuclear physicist. I am however alert to the fact that most American plant operators go around telling everybody that their sites are far more advanced than they are. No nuclear power station can survive without people there. This hundreds of years idea is not true and considering that no US plant has been designed to last "hundreds of years" I'd love to know where your friend gets that quote from. For even the most advanced self aware power plants it requires a significant human presence to maintain, update, fix and generally take care of a plant. Decommissioning a site can take decades and costs billions. Does anybody really believe that if they could simply put a plant to sleep like some have suggested and it be safe that a power company would spend billions of dollars and decades with great risk decommissioning a site? No, obviously they would not. They would use this magical system that renders a nuclear power station able to last without human intervention for hundreds of years.