Having worked in Sizewell A I can assure you that a C150 would barely scratch the paint. A 747 would damage the buildings but the reactor core and the waste handling facilities would be intact after the impact.
At least 10 years ago there was a safety review of the Sizewell plant. Any pipework that might cause a leak of radioactive gases to atmosphere if ruptured was buried (at great expense). This was specifically to prevent an aircraft accident causing a radioactive incident.
Flaps is right regarding the turbulence. All the heat is inside and long may it stay so.
COnventional station swith their cooling towers and hot exhausts can cause turbulence though. Also beware of flying over refineries as they occasionally vent excess process gases through the flares which can produce quite spectacular flames.
As an aside, it is reckoned that when the Israelis bombed the Iraqi reactors it was a diversion to cover the fact that they were blown up from inside. It is virtually impossible for a bomb to hit the spherical reactor core at a sufficiently steep angle to penetrate it. The wall of the core is rather thick plus the whole shebang is surrounded by an extremely thick "biological shield" ie reinforced high density concrete.