You can thank the environmental lawyers for holding up construction at Yucca Mountain.
So when do the AA batteries go in?
It's exactly what it is, the old radiated rods that have been "cycled out" and are left there because their is no place for their disposal.
They're not a threat if they are kept in water. These pools usually have no protection what so ever.
In fact the H.B. Robinson Reactor in SC is just basically a tin roof structure that's removable.
In most reactors in wouldn't take a big plane to create massive damage.