More like 2.3 miles for a 1MT airburst, that's just for a 15 PSI blast shelter. If you're building these for real, with concrete and so on in a real Civil Defense program, that's easy. It's pretty easy, if you have the time, to build an expedient blast shelter with wood and earth that'll handle 15 PSI.
And most warheads are less powerful (see my other comments); using my handy "RAND" nuclear effects calculator from the back of my copy of The Effects of Nuclear Weapons, 15 PSI for the following weapon air bursts (targeting cities, not ground bursts against ICBMs etc.):
500 Kt: 1.8 miles
300 Kt: 1.5 miles
100 Kt: a bit over 1 mile
50 Kt: 0.85 miles
So we're really talking a mile or two, depending on the standards to which the shelters are built. 1 MT 1 mile requires 45 PSI, call it 50 per the above. Don't know how intense a real shelter would have to be, then again that's an uncommon threat level.
The lower 48 states are only 3,119,884.69 square miles if you inclde waterways. With just land it's only 2,959,064.44 square miles.
So, 10k nukes let's you carpet bomb the lower 48 and have one within 10 miles of just about every point. Focus on population centers and I suspect you could easily get 95+% of the population within 5 miles of a detonation.
Where do you get 10K nukes (Russia now? Soviet Union circa 1984?) Do you mean warheads or delivery vehicles? Do you assume that every one of those 10K will be delivered to the lower 48? Or that every one of those 10K will be successfully launched and reach its target? That there won't be any out of commission for maintenance or second strikes? Or that a western pre-emptive strike won't hit any? Or that there might be BMD systems that will make an incoming strike suffer attrition? Are you factoring in that some targets will get much more than a single warhead?
That was just a nice round number. According to Wikipedia from ~1970 - 2000 Russia had 10,000+ nukes with a peak of ~40,000 in ~1985. No idea what the actual numbers where though. http://en.wikipedia.org/wiki/Nuclear_arms_race
Mostly, I was just pointing out that fairly soon they could branch out and target just about any population center. I don't think they ever actually targeted death valley for example.
Anyway, the important thing to remember is by the mid 1970's many of these bomb shelters had been unused for 20+ years. It's very natural to look at something like that and say spending more on this is probably pointless.
The Soviets never had 10k strategic weapons. And even big strategic nukes (5MT) would not have a lethal radius of 30 miles. Even if you were outside, naked and facing it.
A well built bomb shelter would be very effective at reducing the lethal range of nuclear weapons.
Most of the stockpiles during the peak of the cold war were tactical nuclear weapons with low yields designed for the battle field.
And most warheads are less powerful (see my other comments); using my handy "RAND" nuclear effects calculator from the back of my copy of The Effects of Nuclear Weapons, 15 PSI for the following weapon air bursts (targeting cities, not ground bursts against ICBMs etc.):
So we're really talking a mile or two, depending on the standards to which the shelters are built. 1 MT 1 mile requires 45 PSI, call it 50 per the above. Don't know how intense a real shelter would have to be, then again that's an uncommon threat level.