yep they are fine for that I would bank on civil unrest long before a nuclear war, for a lot of people an internal safe room that's fireproof and has a buried air intake to the outside, is cheaper than excavating a hole and sticking a box down it or an external block house with a metal door (he uses marine doors like you see on ships, they are nothing special) The important bit is 'can you get into it safely with zero warning', like in the middle of the night or rushing back from work in a car because something is happening. And then, 'does it cost more to dig you out than it would be to go some place else' home security is all about layers, attrition and not being an obvious target