RE: Dirty bombs - radionuclide mobility

["George J. Vargo" <vargo@physicist.net>]

I started this before Jim Dukelow's reply posted earlier today, but I

still think it adds something to the body of knowledge on the subject.

As I recall, the sorption of cesium depends somewhat on the soil type;

however, it is almost always tightly bound.  As an example, Cs deposited

on surface soil test plots at Hanford (100F Area) showed virtually no

movement over 40 years, while Sr was observed to move (downward) at ~1

cm/year.  Most of the Pu compounds in the Hanford processes also bound

very tightly to soil, making their recovery and cleanup a very difficult

problem - even microwave-assisted acid digestion was essentially

ineffective. Significant portions of the careers of several very

distinguished chemists were spent trying to find methods to recover Pu

that was chemically bound in soil.



As for Cs mobility in concrete, after ~25 years exposure in the K-East

fuel basin, an unpainted concrete structure having typical Cs-137

concentrations of 3-5 uCi/L, the contaminants migrated between 3-5 cm

below the surface.  That was conformed by a combination of MCNP analyses

and confirmatory core samples.  The mobility of the Cs in concrete

certainly depends on the porosity, surface roughness (all concrete is

not created equally), pH and a whole bunch of other variables.  It's

been nearly 10 years since I worked on that project, but that's the data

as best I recall.   The analogy to NaCl deposition for ice removal is

probably not an appropriate comparison



Any Cs that ends up in a sewage treatment system would almost certainly

be bound in sludge. 



George J. Vargo, Ph.D., CHP

vargo@physicist.net

610-925-1954

610-925-5545 (fax)





-----Original Message-----

From: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of Van Dorp

Frederik (vdf)

Sent: Friday, February 28, 2003 10:39 AM

To: 'BERNARD L COHEN'; Tom Hazlett

Cc: Tom Mohaupt; internet RADSAFE

Subject: AW: Dirty bombs





Diffusion of cesium might be less of a problem than sorption of cesium.

Cesium does sorb on many materials much stronger and by different

mechanisms than sodium. Quite some research has been done in Europe on

decontamination of urban environments and results have been published,

in particular after Chernobyl.



Frits van Dorp

Nagra

Wettingen

Switzerland

e-mail: vandorp@nagra.ch



> -----Ursprüngliche Nachricht-----

> Von:	BERNARD L COHEN [SMTP:blc+@PITT.EDU]

> Gesendet am:	Freitag, 28. Februar 2003 15:30

> An:	Tom Hazlett

> Cc:	Tom Mohaupt; internet RADSAFE

> Betreff:	Re: Dirty bombs

> 

> 

> On Thu, 27 Feb 2003, Tom Hazlett wrote:

> 

> > My understanding is that Cs diffuses into concrete.  That makes it 

> > impossible to wash away.

> 

> 	--Does cesium diffuse into concrete more rapidly than sodium? We



> spread enormous quantities of NaCl for de-icing purposes, and it seems



> to wash away rapidly, even without human effort such as hosing.

> 	Do you know a reference on Cs diffusing into concrete?

> 

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