Dirty Bomb Predictions

["Levi, Michael" <mlevi@fas.org>]

As the researcher behind Henry Kelly's dirty bomb testimony, I'd like to

clear up some confusion that's been passing on this list:



1)  We didn't give weather parameters, nor did we give the technical

construction of the bomb, for security reasons, as directed by the

committee.  Our approach was reviewed in private by physicists from

Princeton, CalTech, Columbia, Council on Foreign Relations, and the

Senate Foreign relations committee.  It was also reviewed by a member of

the National Academy of Sciences Radiological Weapon study.  They all

found our assumptions and conclusions to be highly plausible.



2)  For cesium and cobalt, and other gamma emitters, the % of inhalable

particles is largely irrelevant.  In fact, we assume 0% respirable.



3)  Our scenarios don't involve a very large dose per year.  We were

asked by the committee to see when the 1E-4 EPA threshold would be

violated -- this doesn't take much of a dose.



4)  The 4E-5/rem cancer risk includes inhalation.



5)  The lost cesium in North Carolina was an event that was communicated

to us by the Foreign Relations Committee (it was in fact discovered by

the staff of Jesse Helm (R-NC)).  The information was released publicly

by Sen. Biden (D-DW) at the start of the hearing.



6)  "Small Medical Gauge" was a misstatement, but doesn't affect the

conclusions.  The source size was considerably bigger than 1 mCi, but,

as I mentioned earlier, came from the Foreign Relations committee,

certainly a credible source.



7)  You must all know that it's pretty easy to shield a Co-60 rod enough

to transport it for several hours.  When it comes to working directly

with it, one would expect several workers to rotate in shifts.  We never

said this was easy, just that it's a plausible, though challenging,

scenario.



8)  Cs-137 binds to asphalt and concrete.  Scandinavian cities

contaminated by Cs-137 from Chernobyl have roughly the same

contamination level as ten years ago due to this phenomenon.  Any old

book on nuclear war fallout will explain the chemistry of this.  Of

course there are chemicals that remove the Cs, but they have the

downside of converting it into a form that is easily absorbed by the

gastrointestinal system, making contaminated water a much greater

problem.



9)  The plume models are poor at short distances (~explosion radius),

but quite good (factor of 5 SD) at longer distances. 



10)  Bare cobalt rods would of course survive an explosion.  The

knowledge of how to aerosolize the material is out there, as confirmed

by many we spoke with.



11)  Agreed, the NPR story the the best of the lot, but in general the

reporting was ok.  (The Reuters piece was also quite good.)



12)  Re the NIH poster -- 1 Ci/m^2 is a totally unrealistic -- even the

chernobly closed zone was 40 microcuries/m^2 Cs-137.





I look forward to further comments and discussion on the report.



Cheers,

Michael Levi

Director, Strategic Security Project

Federation of American Scientists

1717 K St. NW

Washington DC 20036

mlevi@fas.org

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