[Wolfman77]

Radiation only damages stuff it hits. Gamma radiation being made of photons, doesnt occupy much space (compared to a neutron for neutron radiation). Atoms are mostly empty space, so there is less chance of it hitting anything. Photons also have less mass than neutrons, but their damage is due to the high energies. At least thats how I understand it right now, I'm sure sure someone else could explain it better.

Depleated uranim (DU) does release some radiation, but the amount is considered safe. That, of course, depends on who you ask. U235 is the radioactive part, Uranium ore in nature is about .7% U235 and is considered safe to mine (with certain precautions I think). DU contains .2-.4% about half of what is found in nature, but still requires it to be stored, long term, as low level radioactive waste.

Uranium ore is about as abundant as tin, and durring refinement about 89% is left as depleated uranium. The US has ove 775,000 tons of it.