Occupational Dose Evaluation in Support of the Development of the
October, 2012
Rare Element Resources, Inc. Bear Lodge Project
24
Table 4.3 Input Parameters Used to Estimate Worker Radiation Dose
Parameter Name
Variable ID
Value
Units
Source
Worker Inhalation Rate
W
inh
1.2
m
3
h
-1
ICRP, 1994b
Worker dust ingestion rate
W
ing
0.05
g d
-1
EPA, 1991
Worker exposure time to
ore and dust in a year
t
2000
hr y
-1
Based on 8 hours a day for
250 days
Working days per year
t
d
250
d
Based on 5 day per week for
50 weeks
Mass-based dust
concentration
C
d
0.001 and
0.01
g m
-3
Section 4.1.2
High grade ore U-238
concentration
U
hgo
33
pCi g
-1
Table 4.1
High grade ore Th-232
concentration
Th
hgo
40
pCi g
-1
Table 4.1
Pre-concentrate U-238
concentration
U
Pre
50
pCi g
-1
Table 4.1
Pre-concentrate Th-232
concentration
Th
Pre
230
pCi g
-1
Table 4.1
External Radiation Dose
Coefficient U-238
DCU
ext
1.2 x 10
-3
mrem hr
-1
/ pCi g
-1
Section 4.1.1
Inhalation Radiation Dose
Coefficient for uranium
series
DCU
inh
9.3 x 10
-2
mrem pCi
-1
Table 4.2
Ingestion Radiation Dose
Coefficient for uranium
series
DCU
ing
5.6 x 10
-3
mrem pCi
-1
Table 4.2
External Radiation Dose
Coefficient Th-238
DCT
ext
1.5 x 10
-3
mrem hr
-1
/ pCi g
-1
Section 4.1.1
Inhalation Radiation Dose
Coefficient for thorium
series
DCT
inh
1.8 x 10
-1
mrem pCi
-1
Table 4.2
Ingestion Radiation Dose
Coefficient for thorium
series
DCT
ing
3.7 x 10
-3
mrem pCi
-1
Table 4.2
Table 4.4 Radiation Dose Estimates for Workers at the Bear Lodge Project (mrem y
-1
)
Pathway
Thorium
Series
Uranium
Series
Total
% Contribution
Typical
Dust
MSHA
TLV
External
118
78
196
61
15
Inhalation (MSHA TLV)
a
994
112
1105
-
84
Inhalation (typical dust level)
a
99
11
111
35
-
Ingestion
a
4
11
14
4
1
Total
(MSHATLV)
1122
193
1316
(typical dust level)
228
93
321
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.
