There would be an intermediate size asteroid that would be able to penetrate the containment and damage the core. That same size asteroid wouldn't be much of a

There would be an intermediate size asteroid that would be able to penetrate the containment and damage the core. That same size asteroid wouldn't be much of a worry if it just hit a field next to a town. On the other hand, that same asteroid could topple over some skyscraper and kill a few thousand people, which is more than the aforementioned nuclear-asteroid accident would.