Re: Dirty bomb predictions

[BERNARD L COHEN <blc+@PITT.EDU>]

	The cesium would be mostly washed away by the first rain, going

down sewers. A little work with hoses along with radiation detection

meters would be even more efficient. On soil, as in parks, it could be

covered with dirt, but that would be a very small part of the exposure.



Bernard L. Cohen

Physics Dept.

University of Pittsburgh

Pittsburgh, PA 15260

Tel: (412)624-9245

Fax: (412)624-9163

e-mail: blc@pitt.edu





On Thu, 7 Mar 2002, Strickert, Rick wrote:



> 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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