Unfortunately, that's the US's definition of "Safe". And yeah, in reality, radiation isn't that dangerous. Take a dirty bomb, for instance. If you were at the exact center after it went off, you would suffer just under a lethal dose. After 1 year. Of standing still. So yeah, not very dangerous. Just make sure you stay the **** away though for the first little bit.This is actually a fallacy. Post-nuclear explosion life will not be nearly as hard as common myth dictates. Explosions from nuclear weapons, even crude ones, are quite clean compared to the controlled reactions you find in nuclear power plants. Ground explosions do indeed create a lot of fallout as one logically expects, however the half-life of fallout is pretty short and most fallout comes down pretty fast.