probably because it is? just because we have ways to safely deal with it now doesn't make it not dangerous. also they are probably a high value target in a war, you drop some bombs on a countries nuclear plant and you fuck them over badly.

this website explains it better than i can:https://www.cfr.org/backgrounder/targets-terrorism-nuclear-facilities

specifically: >What kind of damage could such attacks cause to a nuclear power plant? Experts say that an attack on a nuclear power plant, all of which are guarded by private security forces hired by the plants and supervised by the NRC, couldn’t lead to a nuclear explosion. The danger, they say, is that attackers could cause a meltdown or a fire or set off a major conventional explosion, all of which could spew radiation into nearby cities and tow