[jlogajan]

"On the other hand, the threat of a dirty bomb or radiological bomb, is much more plausible," he added.

It's more plausible in that it would be far easier to obtain and build. But it is still a stupid idea for a weapon. If you have dirty radioactive materials, you just go spread them around by hand. Using a bomb is stupid because it isn't particularly targetted, wasting you material and calling attention to the event.

[PUGACHEV]

Calling attention to the event is just what they would want to do; remember, this is terrorism. Spreading the radioactive material by hand, as it were, might be more effective, but what else can focus your attention like a large explosion?

[Timesink]

It's more plausible in that it would be far easier to obtain and build. But it is still a stupid idea for a weapon. If you have dirty radioactive materials, you just go spread them around by hand. Using a bomb is stupid because it isn't particularly targetted, wasting you material and calling attention to the event.

And nobody discovers you've done it until everyone in town starts coming down with rare forms of cancer 30 years later. Not really the best way to terrorize a particular population.