[Protect the Bill of Rights]

When detonated the radioactive debris is spread over a wide area.

I understand the variables make this a difficult question to answer, so I am only asking for ballpark examples. Can you give an example (or examples) regarding the size of the dirty nuke and the size of the affected area?

[Procyon]

You don't need a detonation, which would be noisy and attract attention by the blast damage. Instead, you could have a thermite bomb that melted the radioactive material and spewed it into the atmosphere (similiar to a Chernobyl or uncontained Three Mile Island incident). The affected area would be many square miles. And a real mess to clean up.

[Ciexyz]

Most scary. Maybe the isolated farms and ranches in places like Montana and Wyoming are the safest places to be?

[databoss]

Just imagine a small truck or car bomb laced with nuclear waste and you have the essence of the weapon. It could affect the immediate area surrounding the blast and then be carried by air currents (West to East normally) and effect many things/peolpe in it's path. Depending on where it is placed, and how much waste is in the weapon, and how effectively it is packed around the charge, are all contributing factors to the effectiveness of such a device.