I see. So people can vote if something is possible or not regardless of is it possible in reality?
This is annoying because impossible things are happening here when it is completely unnecessary and they don't add anything to the game.
Let me start out by saying that I am no expert on the subject. With that in mind, I cannot really claim to know what would happen if there was a major accident in these plants.
That being said, there seems to be quite a few opinions out there - from self proclaimed experts and professionals alike - about what the risks of these plants are. You may claim that these plants blowing up is something that may not happen in real life, yet it has happened in Chernobyl. Now I care not to go into the technicalities of what exactly happened, but we can both agree that it was quite devastating. Something that mimics this may very well be in civ. It needs not be an explosion or something similar, but something nasty.
Also there are examples of accidents that were within the foreseen risks, and therefore nothing happened even though the plants were destroyed. Those incidents can have a place in the game as well.
So here I have two expremes, these were accidents that actually happened with plants. One was devastating, one was not. How can you claim that this is not realistic? It is very much realistic in my opinion and therefore it can very well be in the game. It is not needed per se, just like slave revolts and fires that cause youto lose a forge are not needed to be in the game per se, but it does add some uncertainty which is exiting all in itself for some.
In the end this thread demonstrates that even people who supposedly know a bit about these plants cannot get to an agreement about the risks involved with using these plants. So there you have it: if experts cannot agree what the risks of these powerplants are, how are you and I supposed to decide if in-game incidents are realistic or not? Devastating accidents may happen and it did happen and it may as well be in the game. Less horrible accidents happen as well, these may be in the game as well. Everything in between is therefore fair game as well, it may be in the game if you leave events on.