[ RadSafe ] Fw: Uranium contamination

Wed Mar 31 19:48:20 CDT 2010

<snip> I imagine that U was chosen because the DOE has responsibility for
sites where U is the main contaminant and not other toxic metals... Or it
might be that there isn't a bacteria that can "fix" the other metal species.
<snip>

Dear Group:

Technically-enhanced uranium from nuclear fuel cycle activities is not the
only source of environmental uranium. Large tracts of the USA are underlain
with uranium-bearing black shales such as the Pierre Shale, Chattanooga
Shale, Mancos Shale, etc. not to mention the Kolm Shale in Sweden and other
types of rock (granites & phosphorites). Remobilization via irrigation
waters from uranium-bearing sediments is another way that geogene uranium
may enter the environment.  From this, several modes of ingestion might
occur: 1) direct as water; 2) uptake in crops; 3) dust (inhalation); 4)
transfer from animals (milk, meat, etc.), 5) external radiation, etc.

That being said, I don't think that there is very much data to support upper
soil-zone reconcentration and introduction of uranium into crops.  The
reason is simply that U+6 is highly soluble and will only precipitate when a
redox barrier is encountered. At least in the desert areas that I have
investigated or reviewed (Colorado & Kazakhstan), uranium concentration in
soils does not seem to be an issue.

The bacteria that "fix" uranium do so via a drop in redox potential acting
on the U+6/U+4 redox couple. Uranium is highly soluble at the U+6 state and
virtually insoluble in the U+4 state (about 10 orders of magnitude
difference in solubility). Quite a few other metals are redox sensitive and
would precipitate in the same manner (e.g. Se, V, As, Mo, etc.).  Other
metals (e.g. iron, Fe+3/Fe+2 couple) are far more soluble reduced than
oxidized. 

Remobilization of redox-controlled uranium can be easily accomplished by
oxidizing waters passing through the mineralized sediments. This can be done
via high volume irrigation wells causing waters to move through the redox
zone.  This is done commercially for in situ recovery (ISR) uranium mining
by placing wells on both sides of the uranium-bearing zone (redox zone) and
injecting oxygen-bearing waters on one side and recovering uranium-bearing
waters on the other side.

I suspect that a significant amount of uranium is mobilized via high-volume
irrigation pumping in the large western basins. These uranium features do
not have to be commercial deposits. I identified one of these basins in
Colorado (Alamosa Basin) and have briefly looked at other major basins (e.g.
Central Valley in California).  Both of these basins are favorable for
regional redox-controlled roll-front uranium. The redox or alteration front
provides a locus for precipitation of U+6 to U+4 valent uranium.  The
uranium-bearing feature in the Alamosa Basin is a sinuous ribbon feature
continuous over 60 km in length through the basin. Interception of
irrigation wells with this feature allowed me to confirm the presence of
uranium associated with the regional redox / alteration fronts.  GENII was
used to develop a multi-pathway model.

D. McCarn (2004): Natural and anthropogenic multi-pathway risks associated
with naturally occurring uranium mineralization in aquifers: Scoping
calculations, IAEA-TECDOC-1396, pp.289-315. 
http://tinyurl.com/IAEA-TD-1396 

High-volume irrigation has been done in the San Luis Valley (the surface of
the Alamosa Basin) for over 100 years. Estimated water withdrawal per year
(based on consumptive water use for the plants + irrigation efficiency
losses + off-season irrigation - precipitation) is about 1 million acre-feet
per year (1,268 × 10^6 m^3 or 1.3 × 10^12 L / year). This has likely
produced several thousand tonnes of uranium during the history of
irrigation. Likewise, the amount of radon emanated from spray irrigation
(assuming 1500 pCi/L) is about 2000 Ci / year as radon-222 alone (not
counting progeny).  I did not analyze for radium and the other progeny. The
radon estimate is based on USGS values for the basin.

Note that I also did not estimate selenium concentrations or other heavy
metals (no budget for the analyses), but I would imagine that selenium
associated with irrigation from the redox front over 100 years might likely
provide relatively high soil concentrations. Selenium buildup from using
excess waters in mining has caused at least one uranium producer to clean up
a section (square mile) of cropland on which alfalfa was produced.  Note
that the source of selenium used for this 20 year project were "drinking
water quality" waters.  Farming use does not require cleanup of heavy metals
however mining use does!

Dan ii
--
Dan W McCarn, Geologist
2867 A Fuego Sagrado
Santa Fe, NM 87505
+1-505-310-3922 (Mobile – New Mexico)
HotGreenChile at gmail.com (Private email)
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Cary Renquist
Sent: Wednesday, March 31, 2010 16:50
To: Jerry Cohen; radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] Fw: Uranium contamination

Why?  
Public perception and politics.  
(especially since we are dealing with evil weapons radiation and not benign
natural or medical radiation)

The driving issue is that there is likely a regulatory requirement to clean
up this material -- the health and safety decision was made when the
decommissioning criteria were set (which means that it is probably more of a
political decision that a true health-n-safety one).
I imagine that U was chosen because the DOE has responsibility for sites
where U is the main contaminant and not other toxic metals... Or it might be
that there isn't a bacteria that can "fix" the other metal species. 

Does "technologically enhanced" U concentration in the soil constitute a
credible threat -- not bloody likely.  There could very well be a geological
formation a few miles down the road that leads to U levels that are far
higher than the "enhanced" DOE sites, but unfortunately regulatory
requirements demand that we be good boy scouts and leave our licensed site
in the same condition that we found it (if not better condition).

It is a bit similar to the fact that as a rad licensee, I need to be very
careful to monitor what goes out of my facilities and how I transport rad
material, but I can pick up a family member from the hospital on my way home
and transport 150 mCi+ of I-131 unshielded/labeled/etc, have dose rates
greater than 2 mR in any one hour outside my house, and release unmonitored
material through the sewer.  If I dump 150 mCi of I-131 on the bushes
outside of my licensed facility I'll be in big regulatory trouble -- if my
family member gets car sick and throws-up 150 mCi on the bushes outside of
my house, there is no problem.

Cary

---
cary.renquist at ezag.com

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jerry Cohen
Sent: Wednesday, 31 March 2010 14:43
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] Fw: Uranium contamination

Uranium is just one of the 92+ elements in soil.  Why choose it for such a
study. Why not lead, cadmium, mercury, etc.  I would assume, that for some
reason, U is considered to be an exceptionally hazerdous material to justify
expenive remediation. I was trying to learn what that reason might be.
Jerry Cohen

----- Forwarded Message ----
From: Jerry Cohen <jjc105 at yahoo.com>
To: Cary Renquist <cary.renquist at ezag.com>; radsafe <radsafe at radlab.nl>
Sent: Fri, March 19, 2010 8:14:02 PM
Subject: Re: [ RadSafe ] Uranium contamination

Does the existence of Uranium contamination in soil constitute a credible
threat to heath and safety, or is this just another costly federal
"feel-good" program? If such uranium contamination is really a problem, what
should be done with the millions of tons of uranium in the oceanic coastal
waters. We even allow children to swim in it. 
Jerry Cohen

________________________________
From: Cary Renquist <cary.renquist at ezag.com>
To: radsafe at health.phys.iit.edu
Sent: Fri, March 19, 2010 6:10:01 PM
Subject: [ RadSafe ] Argonne scientists seek natural remediation for
uranium-rich sites

They are looking to understand and optimize the conditions under which
bacteria can 
transform U(IV) <soluble> to U(VI) <insoluble>

Argonne scientists seek natural remediation for uranium-rich sites 
Link  http://j.mp/b3AHAh

Cary
-- 
Cary.renquist at ezag.com

_______________________________________________
You are currently subscribed to the RadSafe mailing list

Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html

For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu
_______________________________________________
You are currently subscribed to the RadSafe mailing list

Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html

For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu
_______________________________________________
You are currently subscribed to the RadSafe mailing list

Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html

For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu