Preliminary Public Dose Evaluation in Support of the Development of the
November 2012
Rare Element Resources Bear Lodge Project
30
based on uranium-238 and thorium-232 concentrations in Table 4.1 using the following
equations:
= � �
ℎ
1 10
6
×
ℎ
� + � 1 10
6
× �� 1 10
−3
Where:
DF
i
= Particulate dose factor for source i (mrem μg
-1
m
3
)
C
Thi
= Concentration of thorium-232 for source (i) (pCi g
-1
)
C
Ui
= Concentration of uranium-238 for source (i) (pCi g
-1
)
CDF
Th
= Concentration dose factors for thorium-232 (mrem pCi
-1
L)
CDF
U
= Concentration dose factors for uranium-238 (mrem pCi
-1
L)
1x10
6
= factor to convert g to μg
1x10
3
= factor to convert L to m
3
Table 4.6 summarizes the DFs for the three sources used in this assessment.
Table 4.6 Dose Factors for Source Terms
Source Name
Particulate
Dose Factor
(mrem μg
-1
m
3
)
Dose Conversion
Factor Radon-222
(mrem pCi
-1
L)
Dose Conversion
Factor Radon-220
(mrem pCi
-1
L)
LGOS
1.1 x 10
-2
79.2
25.9
TSF
3.9 x 10
-1
79.2
25.9
BHM
1.1 x 10
-1
79.2
25.9
Notes:
LGOS = low-grade ore stockpile
TSF = tailings storage facility
BHM = Bull Hill Mie
4.4
Receptors
The AERMOD model was run for the Upton and Bear Lodge areas. A 20 by 20 km receptor grid
(with grid nodes at every km) was established at each area, with the respective facilities centered
in the grid system. Radon-222, radon-220 and dust concentrations were estimated for each grid.
This spacing allows for the development of iso-dose contours around each facility using
interpolation methods within ARC-GIS, computer software. Additionally, the towns of Sundance
and Upton were specific receptors because they are the closest population centers to each
facility. Figures 4.1 and 4.2 show the grid layout for each area.
