A rather lengthy thread below iscussed the difficuly of X-Ray detection of the repair in drilled chip. David Spragg hypothesised that the heat would seal the surface but not the internal part of the plug.

If that is the case most X-rays are probably not sensitive enought to detect the gap but an ultra sound based system such as a pulse-echo commonly used in the aerospace industry to locate unbonded areas in structural adhesives or delaminations in Graphite-Epoxy or Fiberglass-Epoxy laminates would work magnificently. The sound waves reflect off of any internal material seperations and can be calibrated to detect areas as small as a couple of hundredths of a square inch.