Interim Baseline Radiological Investigation Report in
Support of the Upton Rare Earth Processing Plant
November 15, 2012
30
8.1.1 Radioactive Particulates
The resulting concentrations for each radionuclide and high volume sampler were compared to
effluent concentration limits listed in Table 2 of 10 CFR 20 Appendix B and reported in Table 8-
2 as percentages of the respective effluent limits. The most conservative effluent limit was
applied to thorium-230 (3x10
-12
µCi ml
-1
). The Class D and W limits were applied to natural
uranium (3x10
-12
µCi ml
-1
) and radium-226 (9x10
-13
µCi ml
-1
), respectively. There is no 10 CFR
20 limit for natural thorium. A limit for natural thorium (8x10
-15
µCi ml
-1
) was calculated for this
baseline investigation, by assuming equal activities of the constituents of natural thorium
(thorium-228 and thorium-232) and Class W limits for thorium-228 (4x10
-12
µCi ml
-1
) and
thorium-232 (4x10
-15
µCi ml
-1
). The unity rule is 1/(0.5*(4x10
-12
+ 4x10
-15
)) = 8x10
-15
µCi ml
-1
.
To date, there have been three monitoring events at UAMS-01 and two each at UAMS-02 and
UAMS-04. With the exception of natural thorium, the average Site-wide concentrations of
radionuclides were on the order of 10
-17
µCi ml
-1
. The average natural thorium concentration is
1.2x10
-16
µCi ml
-1
. The data are summarized in Table 8-3, according to location, averages,
standard deviations and ranges.
Site-wide, the data can be summarized as follows:
•
Natural uranium concentrations ranged from 3.0x10
-17
to 1.2x10
-16
µCi ml
-1
and averaged
7.3x10
-17
µCi ml
-1
.
•
Thorium-230 concentrations ranged from 2.8x10
-17
to 1.7x10
-16
µCi ml
-1
and averaged
8.2x10
-17
µCi ml
-1
.
•
Radium-226 concentrations ranged from 5.5x10
-17
to 1.8x10
-16
µCi ml
-1
and averaged
9.7x10
-17
µCi ml
-1
.
•
Natural thorium concentrations ranged from 2.9x10
-17
to 2.7x10
-16
µCi ml
-1
and averaged
1.2x10
-16
µCi ml
-1
.
With limited data, it is premature to evaluate temporal or spatial patterns in the radionuclide
concentrations.
