No thoughts on how to get plastic frames and foundation clean, but as to the
second question, I would be very careful about irradiating plastic frames.
 While you won't end up with radioactive frames, some plastics change with
irradiation.  You could end up with frames too brittle to use.
 
Suggest you try a few frames as a test and see what happens (and also contact
your frame supplied to find out exactly what plastic they are made from).
 
W. G. Miller
Gaithersburg, MD