[ RadSafe ] Uranium Geochemistry References

[Dan W McCarn]

Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA 
HotGreenChile at gmail.com           UConcentrate at gmail.com

For the group:

1) PHREEQC is one of the USGS computer codes for geochemical modeling developed by Dave Parkhurst:
http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/


2) And that's Donald, not Doug... And I've known him since the 70s! Yikes!  Normally I call him "Professor".

Donald Langmuir's Aqueous Environmental Geochemistry (ISBN: 9780023674129)
http://www.pricegrabber.com/search_getprod.php/isbn=9780023674129

Donald has developed experimental geochemical data for uranium since the 1970s including well characterized mineral stability fields for common uranium minerals.

3) Secular equilibrium would take about 1 million years with 226Ra and daughters.

4) Another way to immobilize uranium in a barrier is zero-valent iron.

Dan ii

-----Original Message-----
From: Geo>K0FF [mailto:GEOelectronics at netscape.com] 
Sent: Sunday, May 11, 2008 5:54 PM
To: 'radsafelist'; Dan W McCarn
Subject: DU on the surface.

Doug is that Donald Langmuir's Aqueous Environmental Geochemistry (ISBN: 
9780023674129) ??



What is the second book or report you recommend in the post below?


Thanks for bringing the geologist's point of view to the issue. I barely 
kept up with our telephone conversation the other week, but it enlightened 
me and gave me a lot of leads for further research on the subject.



At the time I was trying to understand how bacterial action could help with 
remediation uranium in the water table. Now I see how simple it actually is. 
Certain bacteria are injected into the ground, and then methane is injected 
into the ground. The bacteria metabolize the methane, and in the process, 
free electrons are generated which attach to the uranium atom, changing its 
oxidation state. One the oxidation state is changed, the atom is no longer 
soluble, and drops out of the water. Clever.



Anyway, concertinaing DU on the surface of the ground, my calculations 
indicated that U-238 metal would take one million years to obtain secular 
equilibrium with the Ra-226 daughter. Out to ten thousand years the Ra-226 
would remain nil. Does that sound near right?



Thanks



George Dowell

NLNL

New London Nucleonics Lab



GEOelectronics at netscape.com

----- Original Message ----- 
From: "Dan W McCarn" <hotgreenchile at gmail.com>
To: "'radsafelist'" <radsafe at radlab.nl>
Sent: Sunday, May 11, 2008 3:44 PM
Subject: RE: [ RadSafe ] Re: uranium smoke is a teratogen


Dan W. McCarn, Geologist; 3118 Pebble Lake Drive; Sugar Land, TX 77479; USA;
HotGreenChile at gmail.com           UConcentrate at gmail.com

I make no such assumption, but you seem to have your language about what 
constitutes "weathering" completely upside down. "Primary" (reduced) uranium 
minerals "weather" to "secondary" (oxidized) species. This reaction involves 
the exchange of electrons and constitutes a redox reaction.  Reduced uranium 
species are virtually insoluble e.g. uraninite with a 10^-12 molar 
solubility.  Oxidized species have far greater solubility.

UO2(s) as uraninite oxidizes to become UO2+2, attaches two hydroxl ions, and 
becomes UO2(OH)2:H2O(s) - Shoepite. Shoepite reacts with the bicarbonate in 
water (CO2 reacts with water and speciates to form a weak diprotic acid - 
H2CO3 which speciates to HCO3- and CO3-2) and becomes an anionic aqueous 
species UO2(CO3)2-2(aq) in groundwater at neutral pH values.  This reaction 
is quite fast, if you've ever taken the time to observe it.  The kinetics 
are so good, in fact, that it allows ISR/ISL mining on a commercial scale. 
Head grades for production wells are several hundred milligrams per liter 
uranium (mg/L U).

You should buy Doug Langmuir's book on geochemistry; and get a copy of 
PHREEQC.


Dan ii


-----Original Message-----
From: James Salsman [mailto:jsalsman at gmail.com]
Sent: Sunday, May 11, 2008 2:44 PM
To: hotgreenchile at gmail.com; radsafelist
Subject: Re: [ RadSafe ] Re: uranium smoke is a teratogen

Dear Dan,

Thank you for your critique:

> Ben or James or whomever is wrong!

On the contrary, you assumed that UO2 would weather (water or
humidity) into UO3, when in fact UO3 weathers into UO2.

The question that I hope one of us will be able to find out is:  what
is the rate of that transition?  This should probably be expressed
both in traditional terms and as the half-life of a single dissolved
UO3 molecule for purposes of elucidation.

James Salsman, as Ben Fore