Interim Baseline Radiological Investigation Report
November 14, 2012
Bear Lodge Project, for Rare Element Resources, Inc.
Rev.1
6
Table 2.1. Summary of Radiological Investigation Scope
Survey Method/Endpoint
Baseline Investigation Scope
Parameters Evaluated
Gamma Survey
Scanning measurements of gamma count rates, tagged with
x- and y- geopositions, taken every second at
approximately 0.5 m above ground surface along 500 m
(Project) and 2 m (Miller Creek Road) transects at less
than 1.5 m/s.
Used to estimate exposure
rates, surface soil Ra-226
concentrations, and to identify
anomalies and/or areas for
biased sampling.
Biased Soil Sampling
Biased samples at three locations: (SS-23-081211, SS-
33-081311, and SS-35-SS-081311). (Note that these
samples were collected to determine representative
radionuclide concentrations in areas exhibiting elevated
gamma readings, shown to ERG by the RER
representative.
U-nat (ICP-MS); Ra-226 and
Ra-228 (Gamma
Spectroscopy); Th-228, Th-
230, and Th-232 (Alpha
spectroscopy)
Random Soil Sampling
Random samples at 31 locations. All random samples
were surface (0-15 cm) samples. Three duplicate
samples were collected.
U-nat (ICP-MS); Ra-226 and
Ra-228 (gamma
spectroscopy); Th-228, Th-
230, and Th-232 (alpha
spectroscopy)
Exposure Rate Monitoring
External dose rates were assessed by way of correlating
exposure rate and co-located, integrated gamma count rate
measurements. Given the strong linear correlation between
the exposure rate and associated gamma survey
measurements, ERG considers the interpolated exposure
rates documented herein to be reliable estimates.
Exposure Rates
Radon Flux Measurements
Radon flux measurements at five locations (coinciding
with random soil samples). Two duplicate measurements
were made.
Rn-222 flux from soil
Ambient Radon Measurements
Radon measurements at up to nine locations (four air
monitoring and five sediment gauging stations), using
track etch detectors. One duplicate measurement was taken
during each monitoring period.
Rn-222 concentrations in air
Airborne Radioactive Particulate
Measurements
Air sampling (total, stable rare earth elements, PM
2.5
, and
PM
10
) at four locations from November 2011 to August
2012 at various intervals.
U-nat and Th-nat (ICP-MS);
Ra-226 ( gas proportional
counting), and Th-230 (alpha
spectroscopy)
Ambient Gamma Exposure Rate
Measurements
Ambient gamma exposure rate measurements at four
locations from November, 2011 to October 2012 in four
periods, using optically stimulated luminescent detectors.
Exposure rates
Notes:
cm = centimeters
Th-228 = Thorium-228
ERG = Environmental Restoration Group
Th-230 = Thorium-230
HPIC = High Pressure Ion Chamber
Th-232 = Thorium-232
ICP-MS = Inductively Coupled Plasma-Mass Spectroscopy
U-nat = Natural Uranium
in. = inches
m = meters
m/s = meters per second
PM
2.5
= particulate matter, diameter less than 2.5 microns
PM
10
= particulate matter, diameter less than 10 microns
Ra-226 = Radium-226
Ra-228 = Radium-228
RER = Rare Element Resources
Rn-222 = Radon-222, radon
