Dirty bomb predictions

["Strickert, Rick" <rstrickert@signaturescience.com>]

Excerpted from a Reuters news story at

http://story.news.yahoo.com/news?tmpl=story&u=/ap/20020306/ap_on_go_co/d

irty_bombs_1

----------------

Federation of American Scientists President Henry Kelly referred to a

small amount of the radioactive material called cesium that was recently

found abandoned in North Carolina and outlined its impact if used by

terrorists. 

If this small medical gauge of cesium was exploded in Washington, DC,

residents over a five city-block area would have a 1 in a 1,000 chance

of getting cancer while those over 40 city blocks would have a 1 in

10,000 chance. 

If decontamination were not possible, these areas would have to be

abandoned for decades because of health risks, he said. 

Giving another example of a cobalt bomb in New York City, he said the

contamination would be far more serious and people living for 40 years

within a 300-block radius would have a 1 in 10 risk of death from

cancer.

-------------- 

Missing in the new report were scenario assumptions on time, distance,

shielding, and pathways.  However a transcript of  Dr. Kelly's testimony

is available at http://www.fas.org/ssp/docs/kelly_testimony_030602.pdf.

Although the amount of "cesium" (presumable Cs-137) was not specified,

according to that transcript, the calculated Washington, DC, cancer

risks are for people who continue to reside in the cesium-contaminated

area (for an unspecified number of years).   Also, 20 percent of the

cesium was assumed to be inhalable particles, created from an explosion

using ten pounds of TNT.  It's not clear if inhalable includes both

respirable and non-respirable particles. Wind speed was assumed to be a

constant 1 mph.  



The cobalt scenario is for a single sealed rod from a Co-60 food

irradiator.  Again, 20 percent of the cobalt was assumed to be inhalable

particles (the amount of explosive was not specified), and the cancer

*death* risk was for residents living in the contaminated area for 40

years after the explosion.



Do these scenarios seem a little less than realistic to anyone else?

Also, using the 0.0004/rem cancer risk factor (does this include

inhalation?) doesn't give a very large equivalent dose/year for the

cesium scenario.  



Rick



Richard G. Strickert, Ph.D.

Principal Scientist

Signature Science LLC 

8329 North Mopac Blvd.

Austin, TX 78759

(512) 533-2009 (Phone)

(512) 533-9563 (Fax)

rstrickert@signaturescience.com

http://www.signaturescience.com



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