Containment buildings do. Small reactors - even a cluster - wouldn't be worth slamming an airplane into; not going to damage them.

More baseless fear of the invisible nuclear boogyman.

The tons and tons of concrete that shield the reactor core would, though. You would be better off slamming a plane into a dam - much easier to crack, much less chance of containing the disaster it if you do manage to crack it.

As seen previously: there are more attractive targets, like skyscrapers.