Preliminary Public Dose Evaluation in Support of the Development of the
November 2012
Rare Element Resources Bear Lodge Project
21
4.1.4
Surface
The meteorological data obtained from Trinity Consultants also included land surface profile (i.e.
surface roughness) data for the area of interest.
4.2
Source Terms
Three sources of dust and radon at the BLP were chosen to represent the predominant
emission sources: 1) the BHM, 2) the low-grade ore stockpile (LGOS), and 3) the
Tailings Storage Facility (TSF). The BHM and the LGOS are located near Sundance. The
TSF is located near Upton. Figure 1.1 shows the locations of these sources.
As model inputs, each source was assigned dust and radon emission rates. An important
parameter for radon emission and dose from dust inhalation is the activity concentration
of natural thorium and uranium in the source term material. Table 4.1 provides the
activity concentrations used for this dose assessment.
Other sources at the BLP, such as stacks and mine overburden piles, were not considered
in this evaluation, because the magnitude of emissions from these sources are expected to
be minimal when compared to the sources in Table 4.1.
Table 4.1 Thorium-232 and Uranium-238 Activity Concentrations
for Material Used in Dose Evaluation
Material
Thorium-232
Concentration
(pCi/g)
a
Uranium-238
Concentration
(pCi/g)
a
Source
Comments
BHM
55
41
RER, 2012
Natural thorium % wt. adopted
as 0.05 percent to represent
the cutoff for source material,
which is more conservative
than values in Table 8.1 and
8.2 in RER, 2012. Uranium
content is based on Table 8.1
and 8.2 in RER, 2012.
LGOS
5.5
7.1
Discussion
with RER
From mass balance process
flow sheet.
TSF
242
51
Analytical
Data
Analytical data from analysis of
tailings material obtained from
pilot testing of process.
Notes:
a
Activity units were converted from mass units using a specific activity of 1.1 x 10
-7
and 3.3 x 10-7 Ci/g for thorium-232 and uranium-238,
respectively.
BHM = Bull Hill Mine
LGOS = low-grade ore stockpile
pCi/g = picocuries per gram
RER = Rare Earth Resources, Inc.
TSF = tailings storage facility
