I checked the cfg file and the B61 bomb had a blast radius of 0. I'm guessing that means forever. It doesn't make sense because if I am 20 km away from the B61 and it explodes I explode immediately.
Edit: The B61, B83, TSAR Bom-a, and Castle Bravo all have a blast radius of 0 meters. 0 meters? Either it goes on forever or the blast is nothing. I can't escape it?