They have predicted that a radioactive bomb would be easier for terrorists to obtain than a nuclear device.

Packed around them were the "dirtiest" early, radioactive atomic bombs, outlawed because of their extreme pollution potential.

In April 2007 it was revealed that he planned to use limousines packed with explosives and radioactive "dirty" bombs for the attacks.

Perhaps the radioactive bomb had speed up the evolution.

But unless you have specific knowledge about the way things act, it's going to fail, and the best you can get is a dirty, radioactive bomb.

Q. What is your take on how the government has communicated the potential risks of radioactive "dirty bombs"?

Those tools, government officials have come to fear, can range from a small amount of chemical explosive to the makings of a radioactive bomb.

Nonnuclear radioactive ("dirty") bombs and chemical or biological devices would kill in the thousands.

He was described by the Bush administration as a Qaeda operative on a mission to detonate a radioactive "dirty bomb" and blow up apartment buildings.

A radioactive nuclear bomb can give off a faint green glow.