Chernoble. In other words, no explosion (nuclear), but there would likely be a meltdown. The hole left in the containment vessel (from the airplane) would then vent gasses and radiation to the atmosphere. Depending on wind conditions (speed and direction) is what the contamination zone would be.

Workers not killed in the jet fuel explosion would likely die of radiation exposure within days (if not hours). I can't recall the rings of damage and death for Chernoble, but such an event would be devastating for years to come.

I imagine that someone would know if a Nuclear Reactor containment vessel (typically a concrete doom, er "dome") can withstand the force of a sub-sonic commercial aircraft.

One thing in our favor is that hitting the target could prove very difficult, and if not hit dead-on, then the risks of nuclear contamination go way, way, way down.

Jim