yea i see no reason it doesn't travel at the speed of light.
so the radiation would expand out in a sphere and you'd get hit with a single blast wave of radiation. seems like you could fly through the blast zone as soon as the fire went away.
if, somehow, doubtfully, there was still radiocative "dust" it would be flung away at a bazillion miles an hour. the surface area of the expanding sphere increases geometrically compared to rate at which it moves so something like 10 kilometers away from the big fireball should be more than enough to avoid a blast of radiation from an earth-nuke.
also there wouldn't be a "crush" at all after the explosion either, since there was no expanding air for the vacuum to crunch back, just a big flash and then it would get bigger and then fade away.