Preliminary Public Dose Evaluation in Support of the Development of the
November 2012
Rare Element Resources Bear Lodge Project
23
4.2.2
Dust Emission Estimates
Dust containing NORM will be emitted from the BLP and has the potential for delivering an
internal radiation dose to the public, predominantly by way of inhalation. Methods used to
estimate dust emissions from the three sources are described in the following sub-sections.
4.2.2.1
Tailing Storage Facility and Low Grade Ore Stockpile
Estimates of dust emissions from the TSF and the LGOS were obtained from methods described
in NRC Regulatory Guide (RG) 3.59
Method for Estimating Radioactive and Toxic Airborne
Source Terms for Uranium Milling Operations
(NRC, 1987). While the BLP is not a uranium
milling operation, the practices
of ore and tailings storage at the BLP are similar and the methods
used in RG 3.59 are applicable.
Table 4.2 shows how the dust emission factor for the TSF was derived based on wind speed
frequency at Spearfish. For the TSF, the method described in Section 1.2.1 of RG 3.59 was used
to estimate dust emissions.
Table 4.2 Dust Emission Factor for Tailings Storage Facility
Wind Speed
Range
a
(m s
-1
)
Wind Speed
Frequency
(%)
Dust Emission
Rate
b
(g m
-2
s
-1
)
Dust Emission Factor
c
(g m
-2
s
-1
)
< 1.54
19.2
0
0
1.54 – 3.09
17
0
0
3.09 – 5.14
32
3.92 x 10
-7
1.25 x 10
-7
5.15 – 8.23
19.7
9.68 x 10
-6
1.91 x 10
-6
8.23 – 10.8
5.6
5.71 x 10
-5
3.20 x 10
-6
> 10.8
2.2
2.08 x 10
-4
4.49 x 10
-6
Total
95.7
—
9.72 x 10
-6
Total with reduction factor of 90%
9.72 x 10
-7
Notes:
a
4.3 percent of the wind speed data was missing
b
Values from NRC Regulatory Guide 3.59
Method for Estimating Radioactive and Toxic Airborne Source Terms for Uranium Milling
Operations(NRC, 1987)
.
c
Value is product of Dust Emission Rate and Wind Speed Frequency.
g = gram
m = meter
s = second
A particulate emission reduction factor of 90 percent was used, because the tailings are
comprised of about 30 percent moisture and primarily are sulfate based, forming a hard crust that
is similar to a chemical stabilizer when dry. Based on these assumptions, an emission factor of
9.72 x 10
-7
g m
2
s
-1
(30.7 g m
2
y
-1
) was used to estimate dust emissions from the TSF.
