[DBrow]

Backpack nukes I know nothing about. I suspect that if Islam had a deliverable device they would have used it within a year of getting it.

But a dirty bomb yields to analysis. If you have enough radioactive junk to seriously contaminate, say, an acre of land to the point where people would be harmed from a three hour exposure, spread out thinly- then you scrape it all up in one pile a foot square, the dose rate from the material will go up by a factor of 40,000 or so.

How are you going to carry it around? Unshielded, it would kill you quickly. And if you shield it with a foot of lead on each side, the problem gets worse in that it would weigh tons and require a truck.

So a dirty bomb only works as long as the hysterical American media can frighten people- "The radiation rate in this block is well over 120 dpm/square meter!"

From a military viewpoint (area denial, casualties) the dirty part of a dirty bomb is not that significant.

[js1138]

At least 10 years ago I read a very good science fiction story about a terrorist group trying to make a dirty bomb. They were eventually done in by the handling and fabrication of the material. I believe they were trying to grind it into a powder for maximum dispersal.