Interim Baseline Radiological Investigation Report in
Support of the Upton Rare Earth Processing Plant
November 15, 2012
21
According to the laboratory results, the radium-226 concentrations are higher to those of natural
uranium. However, assuming there is secular equilibrium in the uranium decay series, radium-
226 concentrations should be about 48 percent of those of uranium-238, which comprises the
majority of mass in natural uranium. Thus, the laboratory results for radium-226 and/or natural
uranium may be biased.
The laboratory results indicate that natural thorium concentrations are higher than those of the
other primary radionuclides in soils at the Upton Project.
Table 4.4. Summary Statistics for Other Radionuclide Concentrations in Soil Samples
Estimator/Endpoint
Ra-228
(pCi g
-1
)
a
Th-nat
(pCi g
-1
)
a
U-nat
(pCi g
-1
)
a
Mean (arithmetic)
0.9
2.4
1.3
Standard deviation
1.1
0.6
0.4
Median
0.0
2.5
1.4
Minimum
0.0
1.4
0.7
Maximum
2.4
3.2
2.0
1st quartile
0.0
1.9
1.2
3rd quartile
2.2
2.9
1.4
IQR
2.2
0.9
0.1
Count
16
16
16
Notes:
a
Sample and duplicate results average.
IQR = interquartile range
pCi g
-1
= picocuries per gram
4.4
Surface Soil Radium-226 and Natural Thorium Estimates Based on Gamma-Soil
Radium Correlation
Gamma-soil radium-226 and natural thorium correlations were established using the surface soil
analytical results documented in Section 4.2 for all random soil sample locations where
integrated gamma measurements were taken (n=16). The data were collected to estimate radium-
226 and natural thorium concentrations corresponding to each of the gamma survey points
shown in Figure 3.3.
One-minute integrated direct radiation measurements were collected at each of these 16
locations, using the same radiation detection equipment used in the GPS gamma survey. These
measurements then were correlated to radium-226 and natural thorium concentrations in soil, as
discussed below. Table 4.5 lists the observations.
Linear regression methods were employed to derive the correlations. It will be shown that
radium-226 concentrations in soil do not reliably predict gamma count rates. However, natural
thorium concentrations provide a reasonable prediction of gamma count rates.
