Occupational Dose Evaluation in Support of the Development of the
October, 2012
Rare Element Resources, Inc. Bear Lodge Project
13
An oxide high grade ore containing a mass percentage of Total Rare Earth Oxide (TREO)
greater than 1.5 percent
An oxide-carbonate ore containing a mass percent of TREO greater than 1.5.
An oxide stockwork containing a mass percent of TREO greater than 1.
An oxide low grade ore containing a mass percent of TREO greater than 0.5.
Table 2.1 summarizes the natural thorium and uranium content of these materials. These data
demonstrate that thorium is much more abundant than uranium in the BHM ores.
Table 2.1 Thorium and Uranium Content of Important Materials at
Proposed Bear Lodge Project
a
Process
Material
Thorium Content
(wt %)
Uranium Content
(wt %)
Bull Hill Mine
High grade oxide ore
0.036
0.01
OXCA ore
0.11
0.008
Oxide Stockwork
-
-
Oxide low grade
-
-
PUG
Waste Rock
0.005
0.001
Pre-concentrate
0.21
0.016
Hydromet
REO
<0.001
<0.006
Iron Hydroxide
0.259
0.016
Sulfate Sludge
< 0.001
< 0.001
Tailings to TSF
0.049
0.003
a
Adapted from
Technical Report on the Mineral Reserves and Development of the Bull Hill Mine
(RER,2012)
2.4.2
PUG process
The PUG process will generate two types of material: 1) a pre-concentrate material with a REE
mass percent near 14 and 2) a waste rock with a REE mass percent less than 0.5. Table 2.1
summarizes the natural thorium and uranium content of these materials. The waste rock stream
contains 14 and 12.5 percent of the thorium and uranium concentrations in the ore, respectively.
Other radionuclides in the thorium and uranium decay series are expected to be present at low
levels, because REE is physically concentrated in the PUG (i.e., there is no chemical treatment).
The pre-concentrate thorium and uranium content is about twice as high as the OXCA ore, but
their ratios are similar.
2.4.3
Hydromet Process
The Hydromet plant will generate a carbonate-based REE concentrate with a REE mass
percentage near 45 percent, and tailings. The tailings will be comprised of two intermediate
materials, generated independently within the process but conveyed collectively to the TSF as a
mixture. Table 2.1 summarizes the natural thorium and uranium content of the material produced
at the Hydromet. Clearly, the iron hydroxide contains the highest amount of natural thorium. As
mentioned earlier, the Hydromet is the first point where feed material is chemically treated. As a
