Re: Uranium Analysis

["Andrew Karam" <akaram@safety.rochester.edu>]

>     In bioassay and environmental samples analyzed isotopically for 
>     natural uranium, U-234 activity is often higher than U-238 activity, 
>     even though you would expect them to be in equilibrium and to have 
>     equal activities.  I have heard this attributed to higher 
>     'environmental mobility' of U-234 relative to U-238, although I've 
>     never seen an exact explanation of how this occurs.

My understanding is that successive radioactive decays (especially the
alphas) damage the crystal structure, making it easier for the U-234 to
escape the crystal when in contact with water.  In addition, you can have
some recoil out of the crystal and, statistically, some portion of the
recoils will be in just the right direction to push the U-234 out of the
crystal.  Other than this effect, the two U isotopes should behave the same
geochemically.

Andy

Andrew Karam, MS, CHP				
RSO, University of Rochester			  
(716) 275-3781 (voice)						
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akaram@safety.rochester.edu

"The mind is not a vessel to be filled  but a fire to be lighted" 
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