Yes, Line 15: /#{eval eval if eval==instance_eval}}/.i rescue##/

They are checking the two instances and rescuing the corrupted one. But how exactly it works is beyond me.

Yes, and I was thoroughly disappointed by this result. So - new challenge: a radiation hardened quine in less than two times the characters of the equivalent non-radiation hardened version.

I didnt look at the code and am not knowledgeable in this kind of coding but unless I am wrong, if the program simply would contain the same code twice each of these 2 codes would have to contain the same code twice ad infinitum.