Preliminary Public Dose Evaluation in Support of the Development of the
November 2012
Rare Element Resources Bear Lodge Project
31
4.5
Public Dose Estimates
The equation below was used to estimate total internal doses from inhalation of NORM in dust,
radon-222, and radon-220.
= ∑ ( × ) + (
222
222
) + (
220
220
)
Where:
D
= annual estimated dose (mrem)
M
i
= Predicted concentration of particulate matter for source (i) (μg m
-3
)
DF
i
= Particulate dose factor for source i (mrem μg
-1
m
3
)
Rn
222
= Predicted concentration of radon-222 (pCi
-1
L)
DFC
222
= Dose conversion factor for radon-222 (mrem pCi
-1
L)
Rn
220
= Predicted concentration of radon-220 (pCi
-1
L)
DFC
222
= Dose conversion factor for radon-220 (mrem pCi
-1
L)
Table 4.7 is a statistical summary of the estimated doses at 484 gird points in and around the
Bear Lodge and Upton areas. Figures 4.1 and 4.2 show the iso-dose contours around the Bear
Lodge and Upton areas, respectively. For purposes of developing iso-dose contours, one
receptor in the Bear Lodge area (receptor number 253) was omitted as recommended by
AERMOD because it was located directly over the BHM pit.
Table 4.7 Radiation Dose Estimates to the Public at the Bear Lodge Project
Radiation Dose Estimate
(mrem y
-1
)
Area
Mean
Median
Max
Average % Contribution
Dust
Rn-220 Rn-220
Bear Lodge Area (Total)
1.06
0.52
82.1
73.3
12.9
13.8
LGOS
0.14
0.02
66.4
0.50
92.1
7.42
BHM
0.92
0.52
15.8
84.6
0.65
14.8
Upton Area
3.98
0.16
840
10.8
87.6
1.6
Town of Upton
3.14
—
—
6.8
92.1
1.1
Town or Sundance
0.16
—
—
84.7
15.3
0
Notes:
a
Internal doses are based on expected uranium and thorium concentrations from the PUG and are intended to provide a conservative
estimate of occupational doses resulting from BLP activities.
BHM = Bull Hill Mine
LGOS = low-grade ore stockpile
mrem y
-1
= millirem per year
