The problem with large-scale fission is that any one failure has the potential to disrupt the entire workings of the machine, which is whatever country happens to be downwind. There is no resiliency in the network - you have people telling you the accident will probably never happen, but when it does, you could get anything from Three Mile to Chernobyl.
Maybe we could have a wider network of smaller plants that pose smaller risks individually, and any one failure wouldn't be a big deal. But that's probably not economically or socially (who wants a mini-reactor in their neighborhood?) feasible.