2. It seems that radioactive iodine would be an excellent candidate for a "dirty
bomb."
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That's an interesting opinion.
For some reason though, it isn't shared by our (Canadian) authorities (see DRDC Suffield First Responder Course - 2001, posted at http://www.dres.dnd.ca/Meetings/FirstResponders/8%20-%20Radiological%20Dispersion_final.pdf -- starting on page 9).
Certainly iodine has the potential for high doses immediately following the RDD attack, but it causes no long-term contamination, and I doubt there are very large single batches available which could potentially be stolen.
But its interesting that way back in the cold war days, one wacky defence idea suggested was that in the event of a massive conventional attack by forces of the Warsaw Pact on western Europe, contained explosions of neutron bombs could be used to instantly produce enormous quantities of short-lived, and therefore highly radioactive isotopes. Sodium was the material of choice. It could be quickly dissolved in water and sprayed all along the border line, making it impassable. Obviously, no long-lived isotopes, like the Am-241 suggested in the RDD First Responder Course referenced above, would come anywhere close to achieving such a formidable barrier.
On the other hand, intermediate-lifetime isotopes like the cesium that figured in the Goiania incident can cause a great deal of harm, if some fairly concentrated bits & pieces make contact with people.... Undoubtedly, that's why isotopes in this category are (or ought to be) of the greatest concern.
In the big picture though, concern about the whole RDD business seems way out of proportion to the more likely "soft target" attacks seen recently. Media reports this past couple weeks drew particular attention to "cruise ships" filled with thousands of vacationers (sort of a horizontal version of the World Trade Centre in NYC), plying waters where no significant security measures can be easily enforced.
Jaro