http://www.globalsecurity.org/milita...ground/m65.htm
According to this web site's review of "Atomic Annie", the canon had a 20 mile range. The warhead that was tested was a 15 kiloton blast.
http://nuclearsecrecy.com/nukemap/
Based on this website posted earlier here in another part of the forum, a 15 KT has a known death radius of about 1.3 - 2.0 miles. So IF you are 7 miles from BANG, you have a chance to live.
I WOULD NOT WANT TO BE 7 MILES FROM BANG!!!!!!!
So I guess, the math works as far as the survivablilty.
My $0.02
Mike