M20P INSTRUCTOR AND STUDENT FLEW OVER A NUCLEAR POWER PLANT WHILE FLT TRAINING.

Narrative

DEPARTED YYY; US; ARPT VFR FOR A TRAINING FLT (CFII AND STUDENT PLT). CLIMBED VFR TO CLEAR AIR OVER AN OVERCAST LAYER WITH A FEW BREAKS. FLEW N AWAY FROM 'ENHANCED' CLASS B AIRSPACE AT 6500 FT AGL AND CONDUCTED FLT TRAINING (TURNS; CLIMBS; STALLS; SLOW FLT; ETC). WE HAD ONLY VERY LIMITED VISUAL CONTACT WITH THE GND THROUGH SMALL BREAKS IN THE UNDERCAST. VIA VOR/DME WE REMAINED APPROX 55 DME NNE OF ZZZ IN UNRESTRICTED AIRSPACE PER WAC AND LOW ALT IFR CHARTS; AND GPS DATA. UPON COMPLETION OF OUR AIRWORK WE NAVIGATED BACK (SW) TOWARD ZZZ; DESCENDED THROUGH A BREAK IN THE UNDERCAST AND EXECUTED A PRACTICE VOR/DME APCH TO ZZZ TO A LNDG. WE WENT TO THE ARPT RESTAURANT AND ORDERED LUNCH. TWO LOCAL POLICEMEN CAME IN; ASKED IF WE WERE THE PLTS OF THE PLANE OUTSIDE. WE SAID YES. THEY SAID THEY WERE TO HOLD US FOR THE FAA WHICH WAS ENROUTE. THEY TOOK OUR ID AND CERTIFICATES. ONE WATCHED US EAT; THE OTHER OFFICER WAS ON TELEPHONE WITH (?) FAA. AFTER LONG TELEPHONE CONVERSATION (OUT OF OUR EARSHOT) OFFICERS RETURNED OUR DOCUMENTS SAID THAT WE WOULD HEAR FROM FAA; BECAUSE WE HAD FLOWN OVER A NUCLEAR POWER PLANT; AND THEY HAD SCRAMBLED TWO F16'S TO INTERCEPT US. GUESS OUR 4 PLACE 210 HP MOONEY WAS TOO FAST FOR THEM. ANYHOW; WE DIDN'T/COULDN'T SEE THE GND OR A POWER PLANT; NONE WAS MARKED ON ANY OF THE CURRENT CHARTS WE HAD ON BOARD.