Actually, the majority of the nuclear fallout is in the soil and all the other bits and pieces that get thrown up. Things that easily absorb radiation. The more dense the material the harder it is for radiation to penetrate. Lead, etc.
Ground Zero of Hiroshima and Nagasaki for example have no lingering radiation.
I'm pretty sure a tank wouldn't survive a Hydrogen bomb though.
https://www.google.co.uk/amp/io9.gizmodo.com/the-atomic-tank-survived-a-nuclear-test-then-went-to-w-1542451635/amp