[ RadSafe ] Fw: [NoMoreDU] Fw: DU bill PASSED!! New challenge:Gov.Lingle

[Dan W McCarn]

Dear Mike:

Nope, not at all.  Your observations are completely correct!  And it's
because weak leach systems tend to have a higher U234/U238 ratio than the
isotopic "equilibrium" abundances would suggest (assuming equilibrium
conditions in the uranium minerals).  Strong leach conditions tend to be in
"equilibrium" with isotopic abundances.  There would be an asymptotic
approach to equilibrium the stronger the "leach" was.

Agricultural produce would tend to have a higher U234/U238 ratio because
well waters in natural conditions tend to cause "weak" leaching to occur on
the mineral grains.

This is an issue with ISL mining for uranium (In Situ Leach) where the
leaching solutions preferentially mobilize U234 in favor of U238 because of
dislocations in the mineral lattice due to alpha recoil.

Cogema gave a paper on this problem back in 1998 or 1999 at an IAEA meeting
in Vienna because it increases the total activity of the enriched uranium
(following enrichment) when there is "too much" U234 present.

Addition of a tiny amount of DU would shift the ratio, but I think that the
natural abundance of uranium would swamp the signal.

But I would be interested in looking at your agricultural waters data.  I
have a little project north of you in the Alamosa Basin (San Luis Valley)
where I discovered regional redox-controlled, roll-front deposit years ago.
I published a paper in 2004 about it through the IAEA.

McCarn (2004), "Natural and anthropogenic multi-pathway risks associated
with naturally occurring uranium mineralization in aquifers: Scoping
calculations"

http://www-pub.iaea.org/MTCD/publications/PDF/te_1396_web.pdf

Dan ii

-----Original Message-----
From: Michael McNaughton [mailto:mcnaught at lanl.gov] 
Sent: Thursday, April 12, 2007 17:47
To: HotGreenChile at gmail.com; 'radsafelist'
Subject: RE: [ RadSafe ] Fw: [NoMoreDU] Fw: DU bill PASSED!! New
challenge:Gov.Lingle

Dan, are you suggesting that leached minerals could mimic DU? Such has not 
been my experience. In northern New Mexico, we almost always find U234 
greater than U238 in water, and also sometimes in irrigated produce. 
However, we have never found any evidence of U238 being greater than U234 
in leached minerals or in natural biota.

mike

At 01:39 PM 04/12/2007, Dan W McCarn wrote:
>Remembering that U234 is preferentially leached from uranium-bearing
>minerals in groundwater, U238/U234 disequilibrium may occur in nature under
>weakly-leached conditions*.
>
>Is there a database somewhere of the distribution of U238/U234 values in
>ground waters?

Mike McNaughton
Los Alamos National Lab.
email: mcnaught at LANL.gov or mcnaughton at LANL.gov
phone: 505-667-6130; page: 505-664-7733