IMO, if it makes you feel safer and you have the disposable finances to construct one, knock yourself out. Do I think it will help? It could, depending on your location from ground zero, prevailing wind patterns, how long you'd have to stay in there, etc..., but I think you'd still get some effects from the radiation/fall-out unless you built a completely secure shelter with it's own air filtration system and dedicated water supply.

My $.02

Given that if this happens there will be not much of anything left but a long slow death in the long term i would invest in having a good life and if the siren goes just crack open a bottle of good wine and relax. Better to go out with a drink in your hand then in a hole for a year starving.

well i beleive there are massive underground vaults in all the top countries around the world ,because think of security around the world and all the secrets and hoax's that go on around the world ,goverments doin this and that and having these massive budgets to spend , ask urself this could u tell exactly how much and f-22 raptor costs per unit and every signle peice of equip fitted and its exact value ,i beleive secret projects get made to look like what histeria tells them too and while ur lookin 1 way the goverment is doin what it needs to do for today , its a fact with rouge states aroun the world have nuclear faccitlities that make inriched materials for bomb making ,ppl think cos that vast populace is dum that that means there isnt a few brainy 1's that are US and UK educated from around the 50s and onwards that wont be able to have the knowhow to makes such weapons as i beleive its a matter of time until they suitcase bomb at same time all over the free world

WEll, I don't think it's hype, but I don't think it's cost-effective, either.

I don't know if you've ever done a formal threat analysis and quantification, but you'd have to have to make some interesting assumptions (in my never-humble opinion) to place a nuclear bomb going off in your neighborhood (or a general exchange, which is in everybody's neighborhood) as one of the top ten most likely threat scenarios.

However, as Fiber Optik says, if you have the money and you're pretty sure you've ameliorated most of the other, more likely, threats, then why not?

Finally, if you haven't read "Pulling Through" by Dean c. Ing, you might want to get a copy.