I am late to this thread but will add a few thoughts. I had great germination on some Big Zac and then I sent the rest to Fusion-he then had poor germination.
I recieved some BTieDye from Bruce and got zip
I had a particular variety from Neil that I used up the whole packet and got zip nothing. I know that was fresh seed. I had a hard time with the Witty dwarf as well
As far as radiation goes, I am an Xray tech and my DH is a Radiologist. It would take a whole lot of radiation to kill seeds. I have not seen any data on the subject but that would interesting to see. I do believe the goverment if they were doing such would not tell everyone what zipcode they were using it on.
Interesting thread.