There's a reason there's no plan. There's a purpose in not admitting that there is no way to survive a large-scale nuclear exchange. Our ignorance of it is vital for maintaining the fantasy of defense.
Any realistic plan would be so horrifying it would make people question the arsenal. Fallout shelters would have to be equipped with food, water, crates of drugs for compassionate euthanasia and boxes of lye to sanitize mass graves.
For a first-person account of what the Hiroshima blast-survivors navigated after they emerged from shelters, the comic-book series Barefoot Gen is a great place to start. en.wikipedia.org/wiki/Barefoot_…
Keeping in mind that the nuclear fission bombs dropped on Hiroshima and Nagasaki now serve as the "match" that lights the far more destructive thermonuclear weapons of today.
The Great Saint Turtleneck (aka Carl Sagan) devoted much of his later career to this: smithsonianmag.com/science-nature… Scientists have a role here, and a legacy to uphold.
