RE: Uranium mill tailings

["Brennan, Martin Jr" <mbrenn@sandia.gov>]

What is a "typical" uranium mill tailings pile???

Giving and receiving information of this sort is a bit of a double edged
sword, especially w/o context.  The data provided by one responder
pertaining to UMTRA sites is fine.  I concur that the "MAX" for Slick Rock
is incorrect-can't tell You precisely what it should be but from auditing
the site several times during remediation as well as reviewing documentation
during and after remediation, the maximum should be in the 1E+03 pCi/g range
for Ra-226.  Typical Ra-228 [C] at the sites I'm familiar with were <10
pCi/g.

My concern is the purpose for this information (I don't need to know what it
is specifically).  The comment made regarding assay of the ore effecting the
[C] is so true.  But there's more!  Was there a single method for U
extraction or several?  If several, did the extraction process utilize these
on the same feed material or was the process altered during the life of the
mill?  Was solvent extraction used or acid-base methods?  Are the tailings
themselves acidic?  There were UMTRA sites where 40 CFR 192 criteria were
met for radium but excavation continued in sub-pile areas and off-pile areas
due to migration of Th-230 (sometimes 100s of pCi/g, even > 1000) which
becomes soluble in acidic environments (pH </= 4 in this case).  Radon
freely moves through the pile, and what has not escaped can lead to
disequilibrium concentrations of Pb-210 (T 1/2 = 22.4 yrs)and its daughters.
It is not uncommon for gross beta activity on air sample filters collected
from work areas on uranium mill tailings piles to be an order of magnitude
higher than expected if equilibrium were assumed.

Then there are considerations such as the length of time the tailings have
been in place.  What is the annual rainfall?  Is the pile covered with clean
soil or watered routinely to keep dust down?  One of the UMTRA sites,
initially ore was being processed not for uranium but for vanadium.  These
two elements along with copper in some cases are often found together on the
Colorado Plateau.  (As an aside to those following the fossil RAD thread,
some of the richest uranium finds on "The Plateau" occur in petrified tree
trunks).  At one of the UMTRA sites that had ore bodies close by, because of
geochemical considerations, the decay chain daughters were not even in
equilibrium in the initial ore that went through the mill.

Thus, a uranium tailings pile is a complex, heterogeneous system.  Depending
on what your mission is, perhaps little or most of the above is relevant.
Hopefully it is at least informative.  Feel free to contact me if You have
further questions either through RADSAFE or as indicated below.

M. J. Brennan
SNL, NM
(505) 844-1783

-----Original Message-----
From: BLHamrick@aol.com [mailto:BLHamrick@aol.com]
Sent: Wednesday, May 05, 1999 2:48 PM
To: Multiple recipients of list
Subject: Uranium mill tailings


Does anyone have some ballpark numbers on the average concentration of 
radium-226 and radium-228 in typical uranium mill tailings?  (In pCi/g)?

Thanks.

Barbara Hamrick
BLHamrick@aol.com
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