Interim Baseline Radiological Investigation Report
November 14, 2012
Bear Lodge Project, for Rare Element Resources, Ltd.
Rev.1
23
4.3
Other Radionuclides
Table 4.3 presents summary statistics for Ra-226, Ra-228, Th-228, Th-230, Th-232, and U-nat.
U-nat results are reported in pCi/g. although the laboratory reported the results in mg/kg. The
conversion to activity concentrations (pCi/g=0.667 x milligrams per kilogram) was performed to
provide a basis of directly comparing U-nat to the other concentrations of long-lived
radionuclides in the uranium and thorium series.
Table 4.3. Summary Statistics for Radionuclide Concentrations in Soil Samples
Radionuclide Concentration
Estimator/Endpoint
Ra-226
(pCi/g)
Ra-228
(pCi/g)
Th-228
(pCi/g)
Th-230
(pCi/g)
Th-232
(pCi/g)
U-nat
(pCi/g)
Mean (arithmetic)
1.7
4.5
2.9
0.6
2.4
1.4
Standard deviation
1.8
13.0
10.3
1.5
8.4
2.9
Median
1.3
1.7
0.4
0.3
0.3
0.6
Minimum
0.3
0.3
0.1
0.08
0.0
0.2
Maximum
9.8
71.9
57.0
8.4
46.0
16.5
1st quartile
1.0
0.3
0.2
0.2
0.2
0.4
3rd quartile
1.7
2.9
1
0.4
0.9
0.8
IQR
0.7
2.6
0.8
0.2
0.7
0.4
Count
32
32
32
32
32
32
Average of 29
Random Samples
1.2
2.1
1.0
0.3
1.0
0.7
Notes:
Non-detected values in the data set were changed to the associated reporting limit. The eight and 17 non-detects for Ra-226 and Ra-228,
respectively, were changed to 0.3 pCi/g.
IQR = interquartile range
pCi/g = picocuries per gram
In general, the concentrations of all long-lived radionuclides are similar across the Project. The
last row in Table 4.3 shows that, on average, concentrations in the random samples are similar,
with the exceptions of Ra-228 and Th-230. The higher averages of radionuclides other than Ra-
226 and Th-230 were driven largely by one or two higher results for biased soil sample SS-35-
SS-081311 and random sample SS-19-SS-081211. The highest maximum concentrations are
observed in thorium series radionuclides (Ra-228, Th-228, and Th-232).
