"The ones most worrisome are those left over from clandestine Soviet infiltration of key locations in the continental US during the 1950s and early 60's."
And your evidence of the existence of these mythical weapons is what, exactly? Please provide source information.
He read a REALLY SCARY BOOK by a former Russian spy named Stanislav Lunev.
My face is sure red.
Well, I just went back to find the source as you requested, and note that it is solely in WND and not anywhere else - so that's not a good source in my opinion.
I'll keep looking, but like you indicate, on reflection this seems quite low-to-zero probability.