United State Environmental Protection Agency
Aerial Radiological Surveys
Poison Canyon Uranium Mines,
Cibola and McKinley Counties, NM
National Decontamination Team
John Cardarelli II PhD CHP CIH PE
Mark Thomas, PhD
Timothy Curry MS
Paul Kudarauskas, ALM
Dynamac Contract Support:
Jeff Stapleton MS
Robert Kroutil PhD
Arrae, Inc. Contract Support:
Ray Brindle
Beorn Leger
Rich Rousseau
DYNAMAC
CQRPQRATIQN
A Subsidiary of CSS, Inc.
Office of Emergency Management
National Decontamination Team
Erlanger, Kentucky 41018
October 2011
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Table of Contents
Executive Summary iii
Acronyms and Abbreviations iii
1.0 Introduction 1
2.0 Background and Survey Area Descriptions 1
3.0 Flight Parameters 3
4.0 Data Analysis 5
5.0 Results 9
5.1 Radiological Results 9
4.2 Photographic Results 20
Appendix l:_Discussion about radiological uncertainties associated with
airborne systems 27
Background radiation 27
Secular Equilibrium Assumption 27
Atmospheric Temperature and Pressure 27
Soil moisture and Precipitation 28
Topography and vegetation cover 28
Spatial Considerations 28
Comparing ground samples and airborne measurements 29
Geo-Spatial Accuracy 29
Appendix ll:_Uranium 238 decay series 31
Appendix III: Calibration Parameters 32
Appendix IV:_Background Radiation 33
Appendix V: ASPECT Instrumentation 34
Survey Instrumentation 34
Radiation Detectors 34
Chemical Sensors 35
Camera 35
References 37
ii
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Executive Summary
From October 5 through October 8, 2011, the EPA Aerial Spectrophotometric
Environmental Collection Technology (ASPECT) program conducted aerial surveys of
approximately 20 square miles of land in the Grants, New Mexico area. This area of New
Mexico was extensively mined for Uranium ore from the 1950s until the 1980s. The aerial
survey was conducted to determine if residual contamination was present and included both
radiological and photographic surveys of areas that were formerly uranium mines. This
survey is a follow-up to a survey conducted in August of this year and is conducted with
parameters similar to those used in the August surveys. Several radiological analyses
were conducted and nearly 180 aerial photographs of the area were taken.
Roughly 5,200 one-second spectra were collected and analyzed for total count rate, exposure rate,
and equivalent uranium concentration. Radiological analysis results indicate the following:
• Approximately 30 distinct areas had exposure levels that exceeded 20
microRoentgens per hour (|iR/hr),
• Exposure rates were measured as high as 45 |xR/hr and equivalent uranium
concentrations as high as 350 pCi/g (13 Bq/g) during this survey.
The terrestrial background exposure rate in areas not associated with elevated readings on
the site ranged between 5 to 10 [xR/h. These estimates exclude cosmic radiation which is
estimated to be about 7.4 [xR/h based on the altitude of about 7000 feet. Areas associated
with elevated radiation levels ranged from 20 [xR/h to 45 [xR/h. The maximum exposure
rate measurement was located in the southern portion of the Poison Canyon Flight Block
1 (Image 4). Estimated equivalent uranium concentrations in this area are between 25
pCi/g and 30 pCi/g (1 Bq/g and 1.1 Bq/g).
Additionally, the Alluvial Watershed Flight Block 2 (Image 4) to the southwest was
flown for purposes of evaluating radiological conditions in the San Mateo Creek and
historical drainage pathways north of the Homestake Mining Company Superfund site.
San Mateo Creek was the receiving stream for the majority of the historical uranium mine
dewatering for Ambrosia Lake and Poison Canyon. The survey indicates that this area
was not significantly affected by these operations. No significant statistical deviations
from normal uranium concentrations were noted in the watershed area.
Approximately 160 downward looking and 20 oblique aerial photographs were taken
over the entire survey area. These photos are meant to record the actual conditions of the
site at the time of the survey and may indicate differences from the standard Google
Earth images. These are available for viewing in the Google Earth application.
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Acronyms and Abbreviations
AGL above ground level
ASPECT Airborne Spectral Photometric Environmental Collection Technology
Bi bismuth
Ci Curie
cps counts per second
EPA Environmental Protection Agency
214
eU Equivalent Uranium based on Bi region of interest
FOV Field of view
ft feet
FT-IR Fourier Transform Infrared detector
FWHM full width at half maximum
g gram
GEM Gamma Emergency Mapper
GPS Global Positioning System
IR Infrared
K potassium
MeV Mega electron volts
Nal(Tl) sodium iodide thallium drifted detector
NORM Naturally Occurring Radioactive Material
12
pCi picocurie (10" Curies)
R Roentgen
Ra radium
Rn radon
TENORM technologically enhanced naturally occurring radioactive material
Th thorium
T1 thallium
U uranium
|aR/hr microRoentgen per hour (10~6 R/hr)
iv
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
1.0 Introduction
The purpose of the radiological survey was to identify areas of elevated surface uranium
contamination. While subsurface concentrations of gamma-emitting isotopes can be detected by
the instrumentation, self- shielding of the ground limits its effective detection to a depth of about
30 centimeters.1
2.0 Background and Survey Area Descriptions
The Grants Mineral Belt is located in Cibola and McKinley counties of New Mexico, near the
town of Grants. This area was the site of extensive uranium mining from 1950-until the early
1980's. During this time the economy of the region changed from agriculture to uranium mining
and uranium ore processing. Most uranium mining stopped in the recession of 1982-1983.
In 2007, EPA Region 9 began a project in coordination with the Navajo Nation to investigate
residences on the Navajo Indian Reservation located in parts of Arizona, New Mexico, and Utah
for radioactive contamination caused by uranium mining on the reservation. In 2009, EPA
Region 6 initiated a similar project to investigate radioactive contamination in and around
residences near uranium mining and ore processing areas outside of the Navajo Reservation in
the Ambrosia Lake and Laguna sub-districts of the Grants Mineral Belt area of northwestern
New Mexico. These areas will include non-Navajo lands adjacent to the eastern boundary of the
Navajo Reservation with public and/or private ownership as well as lands within the Laguna
Pueblo.
The Poison Canyon Uranium Mines survey was flown on October 5 through October 8, 2011.
The mine areas are located approximately 10 miles north of Grants, NM and consist of three
parcels totaling about 20 square miles (Image 1). The area contains a number of uranium mining
areas positioned throughout the survey areas. The ASPECT aircraft was used to survey the area
in a systematic fashion using a regular altitude and line spacing. For the purpose of this survey, a
standard radiological collection altitude of 300 feet above ground level (AGL) with a line
spacing of 500 feet was used. A total of 64 flight lines were flown and required two days to
complete. Radiological survey flight lines are illustrated in Image 2.
As part of the survey, a photographic survey was also conducted over the site and consisted of
flying regularly spaced lines in a similar fashion as the radiological design. A standard altitude
of 5000 ft AGL was used with a line spacing of 3000 ft. Eight photo lines were flown and
generated about 180 digital aerial images. Photographic flight lines are illustrated in Image 3.
A summary of operational parameters and the collection schedule is provided in Table 1.
Page 1 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Image 1: Survey boundaries for Poison Canyon Uranium Mines survey.
Table 1: Poison Canyon Uranium Mines Survey Flight Details
Collection Type
Altitude
Line spacing
Air Speed
Number of Passes
Radiological
300 ft AGL
500 ft
110-120 Knots
64
Aerial Imagery
5000 ft AGL
3,000 ft
120 Knots
12
Survey Type
Date
General Location
Radiological
5 Oct 2011
Poison Canyon Uranium Mines
Radiological
6 Oct 2011
Poison Canyon Uranium Mines
Photographic
8 Oct 2011
Entire Survey Area
Page 2 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
3,0 Flight Parameters
The ASPECT aircraft used the following flight
procedures for data collection on October 5 - 8, 2011:
Altitude above the ground level (AGL):
• 300 feet for radiological survey
• 5,000 feet for photography
Target Speed: 100 knots (115 mph)
Line Spacing:
• 500 feet for radiological survey
• 3,000 feet for photographic survey
Data collection frequency:
1 per second for radiological survey
The survey area contained 49 flight lines spaced 500 feet apart and are depicted below.
Image 2: Flight lines for the October 5 - 8, 2011 radiological survey.
Flight Block 1
Flight Block 3
Flight Block 2
Page 3 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Image 3: Photographic Flight Lines - Poison Canyon Uranium Mines survey.
Page 4 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
4.0 Data Analysis
A unique feature of the ASPECT chemical and radiological technologies includes the ability to
process spectral data automatically in the aircraft with a full reach back link to the program
QA/QC program. As data is generated in the aircraft using the pattern recognition software, a
support data package is extracted by the reach back team and independently reviewed as a
confirmation to data generated on the aircraft.
Radiological spectral data are collected every second along with GPS coordinates and other data
reference information. These data are subject to quality checks
within the Radiation Solutions internal processing algorithms (e.g.
gain stabilization) to ensure a good signal. If any errors are
encountered with a specific crystal during the collection process,
an error message is generated and the data associated with that
crystal are removed from further analyses.
Prior to the survey, the RSX-4 units go through a series of internal
checks. If no problems are detected, a green indicator light notifies
the user that all systems are good. A yellow light indicates a gain
stabilization issue with a particular crystal. This can be fixed by
waiting for another automatic gain stabilization process to occur or
the user can disable the particular crystal via the RadAssist
Software application. A red light indicates another problem and
would delay the survey until it can be resolved. The data
collection process used for this survey is described below.
When powered up, the crystals go through an automated gain
stabilization process. The process uses naturally occurring
radioelements of potassium, uranium, and thorium to ensure proper
spectral data collection.
The "background data" include radiation contributions from radon,
cosmic, and aircraft sources. It does not include terrestrial
radiation. Ideally, these data are collected over water at the survey
altitude but when a large body of water does not exist, research has
shown that an acceptable alternative is to collect data 3,000 ft
above the ground (AGL). 1 At this altitude atmospheric attenuation
reduces the terrestrial radiation to a negligible level but is still low
enough that cosmic radiation is not significant.
A "test line" is flown at survey altitude (300 feet AGL) near the
survey area that is not expected to contain any elevated
concentrations of NORM or man-made radionuclides. A second
line is flown at the conclusion of the survey. If the difference
between these lines exceeds 10 percent, then the survey data are
corrected using a time-dependent linear interpolation correction
factor.
Page 5 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Two software packages were used to generate products for this survey. The first was RadAssist
Version 3.18.2.0 (Radiation Solutions. Inc.. 386 Watline Avenue, Mississauga, Ontario, Canada)
which produced contour plots of:
(1) total count rate (counts per second),
(2) exposure rate (microRoentgen per hour),
(3) concentration contours for uranium (pCi/g).
The second software package was ENVI® Version 4.8; ASPECT Version 8.6.8.0, Build
1107221901 (ITT Visual Information Solutions, Boulder, CO) which produced:
(4) excess uranium sigma point plots showing locations where21 Bi was out of balance with
the surrounding environment.
RAD Assist Method
I
Live time correction
I
Subtract cosmic and aircraft background
contribution (coefficients)
I
Radon contribution correction was
not performed using RadAssist
I
Perform stripping correction
(ASPECT specific calibration coefficients
were determined after these surveys)
I
Perform height correction (|i=0.0050 m" )
I
Perform exposure rate conversion
(determined after these surveys)
I
Create contour plots
Total Count Rate (cps)
Exposure Rate (|iR/h)
Uranium Concentration (pCi/g)
ENVI ASPECT Method
4
Live time correction
4
Subtract cosmic and aircraft background
contribution (3,000 ft AGL)
4
"Test Line" (determines "normal")
Height correction (f_i=0.0017 m"1)
Calculate 214Bi ROI K-value (median)
4
Subtract radon contribution (Test Lines)
4
Determine net count rate for 214Bi and
standard deviation (sigma value; o)
4
Determine Sigma Values
(<-6o, -6 to -4; -4 to -2; -2 to 2; 2 to 4, 4
to 6, >6o)
4
Create excess Uranium point plots
Total count rate products illustrate gamma activity from all terrestrial sources after subtracting
the "background data" contributions from radon, cosmic and aircraft sources. They can be used
to assess the wide range of radioactivity present in the environment. The calibration coefficients
... 3
were determined based on methodology published by the International Atomic Energy Agency.
Radon was accounted for by using data collected over water and then adjusting the land-based
data by the levels measured over water. The flight over water also was used to develop a site-
specific calibration correction factor for potassium, equivalent uranium/radium, and equivalent
thorium concentrations.
Page 6 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Excess uranium sigma points were determined using an algorithm published by the DOE and
incorporated into the ENVI EPA ASPECT software program. This algorithm is based on the
assumption that natural background radioisotope contributions are stable over large geographical
areas. This will result in a spectral shape that remains essentially constant over large count rate
variations (Figure 1).
70-i
0 0.5 1 1.5 2 2.5 3
Energy (MeV)
Figure 1: Typical airborne gamma ray spectrum showing positions of the conventional energy
windows. Adaptedfrom IAEA-TECDOC-1363.
214
To determine excess uranium count rate, the region-of-interest around Bi (labeled
uranium above, 1659 keV to 1860 keV) is compared to the region-of-interest (ROI) represented
by nearly the entire spectrum, called the Total Count ROI (36 keV to 3,027 keV). The count rate
ratio between these windows (e.g., Uranium ROI / Total Count Rate ROI) is relatively constant
and is referred to as the "K" value. The actual windows (ROIs) are listed in Appendix III. A Re-
value was determined from the "test line" data collected before and after each survey. The
median K-value (e.g., most common K-value) was used in the algorithm to determine excess
thorium.
K-value = Count rate in tarset region-of-interest
Count rate in "Total Count" region-of-interest
Excess activity can be estimated using the following formula:
Excess U activity = Measured U activity - Estimated U activity
Where:
Measured U activity = the measured count rate within the U ROI during the survey
Page 7 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Estimated U activity = K-value * measured count rate in Total Count ROI during the survey
The equation for excess activity becomes:
The most likely value of net "excess uranium" should be zero, and since radiological
disintegrations are randomly occurring events, the second-by-second "excess U" results are
statistically distributed about the mean in a normal Gaussian distribution (Figure 2).
Normal Gaussian Linear Distribution
P(x)
/k
11
h-
50% (PE)
- 68.27 %(|
90%
- 95.45 %(2o)
- 99.7 % (3o)
Standard deviation (a, sigma)
represents the spread of the
data about the mean. In this
survey, the mean value (net
"excess Th") was zero.
1 o = 68.27% of the data
2 g = 95.45% of the data
3 g = 99.73% of the data
4 o = 99.99366% of the data
5 o = 99.99994% of the data
6 c = 99.999999% of the data
Figure 2: Normal Gaussian Distribution and associated confidence intervals.
Every measurement was scored according to its "sigma" value and color coded according to the
ranges in Figure 3. The color code and range were arbitrarily selected to limit the risk of false
positives to 1 in about 15,800,000 samples (greater than or less than 6 sigma).
Sigma Values (Excess Bismuth-214)
Less than-6.0
^h-2.0 to +2.0 Greater than +6.0
^ -6.0 to-4.0
((§))+2.0to +4.0
^ -4.0 to-2.0
(^) +4.0 to +6.0
Figure 3: Standard Deviation Legend for Excess Uranium
Page 8 of37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
5.0 Results
5.1 Radiological Results
ASPECT collected radiological and photographic information over the Ambrosia area from
October 5-8, 2011. This survey covered nearly 22,000 acres of land consisting of about 5,200
data points. Radiological products included contour plots for total count rate, exposure rate,
uranium concentration and excess uranium sigma plots, which represent the number of standard
deviations from background (Images 4 to 15). The tables below contain the estimated areas of
the survey based on exposure rate in steps of 5 [xR/hr.
Table 1. Exposure Rate Data
for Flight Block 1
Exposure
Rate Range
(|iR/hr)
Percent of
Total Area
Approximate
Acreage
< 10
64.6%
4,431
10 to 15
26.0%
1,782
15 to 20
6.2%
427
20 to 25
2.1%
141
25 to 30
0.8%
58
30 to 35
0.2%
16
35 to 40
0.1%
5
40 to 45
0.0%
2
> 45
0.0%
1
Totals 100.0% 6,863
Page 9 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Table 2. Exposure Rate Data
for Flight Block 3
Exposure
Rate Range
(|iR/hr)
Percent of
Total Area
Approximate
Acreage
< 10
72.1%
986
10 to 15
13.4%
183
15 to 20
6.4%
88
20 to 25
3.7%
51
25 to 30
3.1%
43
30 to 35
1.2%
17
35 to 40
0.0%
1
40 to 45
0.0%
0
> 45
0.0%
0
Totals
100.0%
1,368
Approximately 20 distinct areas were identified as having exposure rates greater than 20 |jR/hr.
Additionally, the Alluvial Watershed Flight Block 2 (Image 4) to the southwest was flown for
purposes of evaluating radiological conditions in the San Mateo Creek and historical drainage
pathways north of the Homestake Mining Company Superfund site. San Mateo Creek was the
receiving stream for the majority of the historical uranium mine dewatering for Ambrosia Lake
and Poison Canyon. The survey indicates that this area was not significantly affected by these
operations. No significant statistical deviations from normal uranium concentrations were noted
in the watershed area. No significant deviations from background exposure rates were noted.
Since uranium is a naturally occurring radionuclide and is ubiquitous in nature, special analysis
is required in order to determine whether the uranium that is detected is greater than the naturally
occurring uranium concentrations. The analysis used is referred to as a sigma plot as discussed
in section 4. Areas on a sigma plot with values greater than 4 are very likely to contain uranium
or its decay products in concentrations greater than background, while values greater than 6
sigma almost certainly indicate above background levels for uranium and its decay products. Of
the 5,200 data points collected in this survey, 71 were greater than 4 sigma (standard deviations)
from the mean value and an additional 43 points were greater than 6 sigma from the mean.
Page 10 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 4: Exposure Rate Contour
Poison Canyon Uranium Mines Survey
October 5-8, 2011
Flight Block 1
m-
j-
xmrnrnm
—
S"! £'•:
Flight Block 2
¦
isqpKcrag©
Parameter ^xposure Rate (microRihr)
<5,0000
5.0000
10.000
10.000
15.000
15.000
20,000
20.000
25.000
25.000 : 30.000
30.000 : 35.000
35.000 : 40.000
40.000 : 45.000
> 45.000
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acciuisition time
Several areas in Flight Blocks 1 and 3 are identified as having exposure rates above 25 uR/hr,
Separate views of each of these flight blocks are presented below. Google Earth images are also
available so that the user can zoom in even closer to help identify the physical source of these
elevated readings.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 11 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 5: Exposure Rate Contour
Ambrosia Survey Flight Block 1
October 5-8, 2011
©2010
Area of highest
measured exposure rate
and eU concentration.
Parameter (Exposure Rate (microRrtir)
< 5.0000
25,000 : 30.000
5.0000
10,000
30.000 : 35.000
| 10,000
15,000
35.000 : 40,000
| 15,000
20,000
40,000 : 45,000
[ 20,000
25,000
> 45,000
ASPECT Program
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
Nearly two dozen areas in Flight Block 1 exhibit exposure rates which exceed 25 uR/hr. Using
the Google Earth tool, a user can zoom in more closely to help identify likely contamination
sources warranting additional survey efforts.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 12 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 6: Exposure Rate Contour
Ambrosia Survey Flight Block 3
October 5-8, 2011
Parameter ^xposure Rate (microRrtir)
<5.0000
25.000 : 30.000
5.0000
10.000
30.000 : 35.000
\\ 10.000
15,000
35.000 : 40.000
IF 15.000
20.000
¦ ! 40.000 : 45.000
20.000
25.000
> 45.000
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
Several distinct regions in Flight Block 3 exhibit exposure rates greater than 25 |iR/hr, These
yellow and orange areas on the map may warrant additional survey effort. Using the Google
Earth tool, a user can zoom in more closely to help identify likely contamination sources
warranting additional survey efforts.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 13 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 7: Equivalent Uranium Concentration Contour
Ambrosia Survey
October 5-8, 2011
Parameter
eU concentration (pCi/g)
H
¦i
<5.0000
II
5,0000 : 10,000
III
10,000 ; 15,000
¦1
15,000 : 20,000
20,000 : 25,000
25,000 : 30,000
30,000 : 35,000
35,000 : 40,000
40,000 : 45,000
>45,000
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acciuisition
The equivalent Uranium concentrations exceeding 5 pCi/g correlate well with the elevated
exposure readings. Using the Google Earth tool, a user can zoom in more closely to help
identify likely contamination sources warranting additional survey efforts.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 14 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 8: Equivalent Uranium Concentration Contour
Ambrosia Survey Flight Block 1
October 5-8, 2011
Parameter
eU concentration (pCi/g)
¦ i
<5.0000
25,000 : 30.000
¦ 1
5.0000 : 10.000
¦ I
30.000 : 35,000
I I
10.000 ; 15,000
¦ 1
35,000 : 40,000
¦ 1
15.000 : 20.000
¦1
40,000 : 45,000
1 II
20.000 : 25.000
¦ 1
> 45,000
Aspect Program
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 /second acciuisition
This image shows predicted eU concentrations in Flight Block 1. The Google Earth tool can be
used to highlight a particular region to aid in identifying any possible sources of contamination.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 15 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 9: Equivalent Uranium Concentration Contour
Ambrosia Survey Flight Block 3
October 5-8, 2011
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 /second acciuisition
The southernmost area of Flight Block 3 shows slightly elevated concentrations of uranium.
Using the Google Earth tools, one can more precisely identify areas of concern for possible
additional investigation.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Parameter eU concentration (pCi/g)
1
<5,0000
5,0000
10,000
| 10.000
15,000
r 15,000
20,000
| 20,000
25,000
25.000 : 30.000
30.000 : 35.000
35.000 : 40.000
40,000 : 45,000
> 45,000
Page 16 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 10: Excess Uranium Sigma Plot
Ambrosia Survey
October 5-8, 2011
©2010
Flight Block 1
Flight Block 3
Flight Block 2
Sigma Values (Excess Bismuth-214)
Less than -6.0
C(§))-2.0 to +2.0 Greater than +6.0
^ -5.0 to -4.0
ijiSj) +2.0 to +4.0
Q -4.0 to -2.0
(^) +4.0 to +6.0
Aspect Program'
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
Because it is ubiquitous in soils, it is sometimes helpful to do statistical analyses when assaying
for uranium in soils. These so-called sigma plots indicate that uranium is out of balance with the
background quantities in the same areas as data indicates slightly elevated exposure levels and
predicted uranium concentrations. Use of the zoom function with the Google Earth tools will
allow greater precision in locating localized sources of uranium contamination.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 17 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Image ill Excess Uranium Sigma Plot
Poison Canyon Uranium Mines Survey Flight Block 3
October 5-8, 2011
Sigma Values (Excess Bismuth-214)
Less than -6.0
^^-2.0to+2.0 A Greater than +6.0
^ -6.0 to -4.0
((§}) +2.0 to +4.0
Q -4.0 to-2.0
+4.0 to +6.0
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
This image depicts a closer view of the elevated values for eU in Flight Block 3 and shows those
areas that are statistically most different than the background levels. These areas may warrant
further investigation.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 18 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 12 - Excess Uranium Sigma Plot
Ambrosia Survey Flight Block 1
October 5-8, 2011
| Imagery Dale 6.30;2005 ' jp 1997
Sigma Values (Excess Bismuth-214)
Less than -6.0
^^-2.0 to +2.0 Greater than +6.0
^ -6.0 to -4.0
+2.0 to+4.0
^ -4.0 to-2.0
(^) +4.0 to +6.0
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acciuisition time
As depicted in this closer view of Flight Block 1, several areas have statistically significant
deviations from the background values of uranium in the area. These differences correlate
closely to the total count and exposure rate contours for the same area and may warrant further
investigation.
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 19 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 13 - Total Count Rate
Ambrosia Survey Flight Block 1
October 5-8, 2011
Imagery Date 6.30;2005 £ 1997
Parameter Total Counts (cps)
< 5500.0
27500.
¦1
5500.0
11000,
¦ 1
33000.:38500.
1 1
11000.
16500.
¦ 1
38500.:44000.
¦1
16500.
22000.
¦ 1
44000. : 49500.
¦1
22000.
27500.
¦ 1
> 49500.
33000.
o NATIONAL DEC0NTEAM
Bl
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 20 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 14 - Total Count Rate
Ambrosia Survey Flight Block 2
October 5-8, 2011
Parameter Total Counts (cps)
¦
< 5500,0
III
27500,
33000,
5500.0 : 11000,
¦ 1
33000,
38500,
¦1
11000. : 16500,
¦ 1
38500,
44000,
¦1
16500, : 22000,
¦ 1
44000,
49500.
22000.
27500.
> 49500.
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 21 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 15 - Total Count Rate
Ambrosia Survey Flight Block 3
October 5-8, 2011
Parameter Total Counts (cps)
¦
< 5500,0
III
27500,
33000,
5500.0 : 11000,
¦ 1
33000,
38500,
¦1
11000. : 16500,
¦ 1
38500,
44000,
¦1
16500, : 22000,
¦ 1
44000,
49500.
22000.
27500.
> 49500.
Flight Parameters
300 ft altitude
500 ft line spacing
110 knots
1 second acquisition time
This image should not be used independently to assess potential health risks.
Additional information is necessary to make appropriate health-related decisions.
Page 22 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
4.2 Photographic Results
Approximately 180 high resolution digital aerial photographs were taken over the entire survey
area (as depicted in Image 10). These photographs have been geo- and ortho-rectified for
geospatial applications and are available to view within Google Earth. Each aerial photo
provides coverage of about 175 acres with a pixel resolution of 7.5 inches. Image 11 is
representative of the images that were collected during the survey. Access to the photographic
imagery is available by contacting Lisa Price, Region 6.
Page 23 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 16 - Digital Photo Outlines
Poison Canyon Uranium Mines Survey
October 5-8, 2011
The above image indicates the location of the nearly 180 downward looking digital photographs
taken by the ASPECT aircraft on October 8, 2011. In addition, nearly 75 oblique photographs of
various features were also taken. Oblique and downward looking photographs can all be viewed
in the Google Earth software.
Page 24 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Image 17: Digital Images Ambrosia, New Mexico
These digital photos are intended to capture the areas as they existed at the time of the surveys.
They are available for viewing in Google Earth. For access to these photos contact Lisa Price,
Region 6.
Page 25 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Image 18 - Oblique Photo Tracks
Ambrosia Survey
October 5-8, 2011
About 50 oblique photographs were taken over the entire survey area. They have been geo-
located for incorporation into Google Earth or other geospatial software applications. Oblique
photographs were taken out the right side of the plane at an angle consistent with the direction of
the white arrows. Access to the photos is available by contacting Lisa Price, Region 6.
Page 26 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Appendix I
Discussion about radiological uncertainties associated with airborne
systems.
Ideally the airborne radiation measurements would be proportional to the average surface
concentrations of radioactive materials (mainly NORM). However, there are several factors that
can interfere with this relationship causing the results to be over- or under-estimated, as
described below. Additionally, two other sections discuss how data are interpreted and airborne
measurement data are compared to surface measurements.
Background radiation
Airborne gamma-spectroscopy systems measure radiation originating from terrestrial, radon,
aircraft, and cosmic sources. To obtain only the terrestrial contribution, all other sources need to
be accounted for (subtracted from the total counts), especially for this survey where small
differences are important. Radon gas is mobile and can escape from rocks and soil and
accumulate in the lower atmosphere. Radon concentrations vary from day to day, with time of
day, with weather conditions (e.g., inversions and stability class), and with altitude. It is the
largest contributor among background radiation and its daughter product, 214Bi, is used to
estimate radium and uranium concentration in the soil. Radon is accounted for in the processing
algorithm by flying specific test lines before and after each survey and comparing the results.
Cosmic and aircraft radiation (e.g., instrument panels and metals containing small amounts of
NORM) also provide a small contribution to the total counts. These are accounted for in the
processing algorithm by flying a "high-altitude" or "water-" test line and subtracting these
contributions for the survey data.
Secular Equilibrium Assumption
Secular equilibrium is assumed in order to estimate thorium concentrations from one of its
214
daughter products, Bi. Secular equilibrium exists when the activity of a daughter product
equals that of its parent radionuclide. This can only occur if the half-life of the daughter product
is much shorter than its parent and the daughter product stays with its parent in the environment.
214
In this case, the measurement of Bi gamma emission is used to estimate the concentration of
its parent radionuclide if one assumes all the intermediate radionuclides stay with each other.
222
However, Rn is a noble gas with a half-life of 3.8 day and may degas from soils and rocks
fissures due to changes in weather conditions. Due to the relatively long half-life and the
combined effect of radon gas mobility and environmental "chemical" migration, it is not certain
whether the secular equilibrium assumption is reasonable. In addition, human intervention in
this natural chain of events may have caused an increased uncertainty in uranium concentration
estimates.
Atmospheric Temperature and Pressure
The density of air is a function of atmospheric temperature and pressure. Density increases with
cooler temperatures and higher pressures, causing a reduction in detection of gamma-rays. This
reduction in gamma-ray detection is called attenuation and it is also a function of the gamma-ray
Page 27 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
energy. Higher energy gamma-rays are more likely to reach the detectors than lower energy
214
gamma-rays. For example, 50% of the Bi 1.76 MeV gamma-rays will reach the detector at an
40 *
altitude of 300 ft whereas only 44% of the K 1.46 MeV gamma-rays will reach the detector.
Temperature and pressure changes contribute little to the overall uncertainties associated with
airborne detection systems as compared to other factors.
Soil moisture and Precipitation
Soil moisture can be a significant source of error in gamma ray surveying. A 10% increase in
soil moisture will decrease the total count rate by about the same amount due to absorption of the
gamma rays by the water. Snow cover will cause an overall reduction in the total count rate
because it also attenuates (shields) the gamma rays from reaching the detector. About 4 inches of
fresh snow is equivalent to about 33 feet of air. There was no significant precipitation during this
survey.
Topography and vegetation cover
Topographic effect can be severe for both airborne and ground surveying. Both airborne and
ground-based detection systems are calibrated for an infinite plane source which is referred to as
271 geometry (or flat a surface). If the surface has mesas, cliffs, valleys, and large height
fluctuations, then the calibration assumptions are not met and care must be exercised in the
interpretation of the data. Vegetation can affect the radiation detected from an airborne platform
in two ways: (1) the biomass can absorb and scatter the radiation in the same way as snow
leading to a reduced signal, or (2) it can increase the signal if the biomass concentrated
radionuclides found in the soil nutrients.
Spatial Considerations
Standard ground-based environmental measurements are taken 3 ft above the ground with a field
of view of about 30 ft . The ASPECT collected data at about 300 ft above the ground with an
effective field of view of about 6.5 acres. These aerial measurements provide an average
surface activity over the effective field of view. If the ground activity varies significantly over
the field of view, then the results from ground- and aerial-based systems may not agree. It is not
unusual to have differences as much as several orders of magnitude depending on the survey
altitude and the size and intensity of the source material. For example, in the figures below, if
the "A" circle represents the detector field of view and the surrounding area had no significant
differences in surface activity, a 300 ft aerial measured could correlate to a ground-based
exposure rate of 3.5 |iR/h. However, if all the activity was contained in a small area such as a
single small structure containing thorium tailings (represented by the blue dot within the field of
view of "B"), a 300 ft aerial measurement may still provide the same exposure rate measurement
but the actual ground-based measurements could be as high as 3,150 |iR/h.
* Attenuation coefficients of 0.0077m"1 for 1.76 MeV and 0.0064m"1 for 1.46 MeV.
Page 28 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Detector Field of View
Concentration A = Concentration B
Aerial measurement is Aerial measurement
a good indicator of will not capture
average ground differences in smaller
activity. areas of intense
activity.
Illustration of aerial measurement capabilities and interpretation of the results
Comparing ground samples and airborne measurements
Aerial measurements are correlated to ground concentrations through a set of calibration
coefficients. The ASPECT calibration coefficients for exposure-rate, potassium, uranium, and
thorium concentrations were derived from a well characterized "calibration" strip of land near
Las Vegas, Nevada. In-situ gamma spectroscopy and pressurized ionization chambers
measurements were used to characterize the area. One must exercise caution when using a
laboratory to analyze soil samples to verify or validate aerial measurements because differences
will occur. In addition to local variations in radionuclide concentrations, which are likely to be
the most significant issue, differences may arise due to laboratory processing. Laboratory
processing typically includes drying, sieving and milling. These processes remove soil moisture,
rocks and vegetation, and will disrupt the equilibrium state of the decay chains due to liberation
of the noble gas radon. Thus reliance on 208T1 and 214Bi as indicators of 232Th and 238U (as is
assumed for aerial surveying) is made more complex. In addition, aerial surveys cannot remove
the effects of vegetation on gamma flux. Intercomparisons must minimize these differences and
recognize the effects of differences that cannot be eliminated.
Geo-Spatial Accuracy
All aerial measurements collected by the ASPECT aircraft are geo-coded using latitude and
longitude. The position of the aircraft at any point in time is established by interpolating
between positional data points of a non-differential global positioning system and referencing the
relevant position to the time that the measurement was made. Time of observation is derived
from the aircraft computer network which is synchronized from a master GPS receiver and has a
Page 29 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
maximum error of 1 second . Timing events based on the network running the Windows-based
operating system and the sensor timing triggers have a time resolution of 50 milliseconds, so the
controlling error in timing is the network time. If this maximum timing error is coupled to the
typical ground velocity of 55 meter/sec of the aircraft, an instantaneous error of 55 meters is
possible due to timing. In addition, geo-positional accuracy is dependent on the instantaneous
precision of the non-differential GPS system which is typically better than 30 meters for any
given observation. This results in an absolute maximum instantaneous error of about 80 meters
in the direction of travel.
For measurements dependent on aircraft attitude (photographs, IR images) three additional errors
are relevant and include the error of the inertial navigation unit (INU), the systemic errors
associated with sensor to INU mounting, and altitude errors above ground. Angular errors
associated with the INU are less than 0.5 degrees of arc. Mounting error is minimized using
detailed bore alignment of all sensors on the aircraft base plate and is less than 0.5 degrees of arc.
If the maximum error is assumed then an error of 1.0 degree of arc will result. At an altitude of
150 meters (about 500 feet) this error translates to about 10 meters. Altitude above ground is
derived from the difference in the height above the geoid (taken from the GPS) from the ground
elevation derived from a 30 meter digital elevation model. If an error of the model is assumed to
be 10 meters and the GPS shows a typical maximum error of 10 meters, this results in an altitude
maximum error of 20 meters in altitude error. If this error is combined with attitude and the
instantaneous GPS positional error (assuming no internal receiver compensation due to forward
motion) then an error of about 50 meters will result. The maximum forecasted error that should
result from the aircraft flying straight and level is +/- 130 meters in the direction of travel and +/-
50 meters perpendicular to the direction of travel. Statistical evaluation of collected ASPECT
data has shown that typical errors of +/- 22 meters in both the direction of and perpendicular to
travel are typical. Maximum errors of +/- 98 meters have been observed during high turbulence
conditions.
* The ASPECT network is synchronized to the master GPS time at system start-up. If the observed network/GPS
time difference exceeds 1 sec. at any time after synchronization, the network clock is reset.
Page 30 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Appendix II
Uranium 238 decay series
Page 31 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Appendix III
Calibration Parameters
RadAssist calibration parameters for Ambrosia Survey on October 5 - 8, 2011.
Calibration Parameters
ROI
xj
ROI
Active
Only Up
Name
Start Ch
End Ch
Det.Bg
Cosmic
Alt. Beta
Sens.Coef
~
01
YES
TotCount
137
937
14.55
1.0085
0.00702
1
02
YES
Tot Count (...
9
937
41.961
3,9698
0.00665
1
03
YES
Potassium
457
523
6.831
0.0541
0.00915
5.30216
04
YES
Uranium (Bi-...
553
620
0.8849
0.0442
0.00803
12.89833
05
YES
Thorium(Tl-2...
803
937
-0.8314
0.0505
0.00689
21.91768
06
YES
Cs-137
200
240
3.0329
0.1001
0
1
07
YES
Co-60
364
472
3.5458
0.1083
0
1
08
YES
Man-Made L...
16
465
42.487
3.5095
0
1
09
YES
Man-Made H...
466
937
0.0265
0.2592
0
1 "1
* 1
4
* rf-ft
r>
rv
..—1
<1
f
Jj
Calibration Coefficients Matrix
*
TotCount
TotCoun... 1
Potassium
Uranium
Thorium(...
Cs-137 |
Co-60
Man-Mad...
TotCount
1
0
0
0
0
0
0
(
Tot Count..,
0
1
0
0
0
0
0
t
Potassium
0
0
1
1,04984
0.7131
0
0
{
Uranium (,,,
0
0
-0.00767
1
0.51735
0
0
(
Thorium(Tl,,.
0
0
-0,0011
0,04125
1
0
0
(
Cs-137
0
0
0
0
0
1
0
(
Co-60
0
0
0
0
0
0
1
t
Man-Made...
0
0
0
0
0
0
0
Man-Made...
0
0
0
0
0
0
0
(
Cosmic
0
0
0
0
0
0
0
(
<1
1
Jj
Dose Rate computation
Dose Calibration Factor
0,042795
Dose Altitude Beta
0,005000
Scale to # xtals
Height Correction
W Enable Height Correction
Reference Altitude Altitude field
| 105.7736 [m] | Analog Input 1 (ADC 1)
Meters per unit of Altitude | 0,1506000
Fixed Altitude
I 0.0000 [m]
Cancel
OK
This screen-shot from the RadAssist Program shows the calibration coefficients used in the
determination of Uranium concentrations for this report.
Page 32 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Appendix IV
Background Radiation
Naturally occurring radioactive material (NORM) originates from cosmic radiation, cosmogenic
radioactivity, and primordial radioactive elements that were created at the beginning of the earth.
Cosmic radiation consists of very high energy particles from extraterrestrial sources such as the
sun (mainly alpha particles and protons) and galactic radiation (mainly electrons and protons).
Its intensity increases with altitude, doubling about every 6,000 ft, and with increasing latitude
north and south of the equator. The cosmic radiation level at sea level is about 3.2 |iR/h and
nearly twice this level in locations such as Denver, CO.
Cosmogenic radioactivity results from cosmic radiation interacting with the earth's upper
atmosphere. Since this is an ongoing process, a steady state has been established whereby
cosmogenic radionuclides (e.g., 3H and 14C) are decaying at the same rate as they are produced.
These sources of radioactivity were not a focus of this survey and were not included in the
processing algorithms.
Primordial radioactive elements found in significant concentrations in the crustal material of the
earth are potassium, uranium and thorium. Potassium is one of the most abundant elements in
the Earth's crust (2.4% by mass). One out of every 10,000 potassium atoms is radioactive
potassium-40 (40K) with a half-life (the time it takes to decay to one half the original amount) of
1.3 billion years. For every 100 40K atoms that decay, 11 become Argon-40 (40A) and emit a 1.46
MeV gamma-ray.
Uranium is ubiquitous in the natural environment and is found in soil at various concentrations
with an average of about 1.2 pCi/g. Natural uranium consists of three isotopes with about 99.3%
238 235
being uranium-238 ( U), about 0.7% being uranium-235 ( U), and a trace amount being
uranium-234 (234U). The tenth daughter product of 238U, bismuth-214 (214Bi), is used to estimate
the presence of radium and uranium by its 1.76 MeV gamma-ray emission.
Thorium-232 is the parent radionuclide of one of the 4 primordial decay chains. It is about four
times more abundant in nature than uranium and also decays through a series of daughter
products to a stable form of lead. The thorium content of rocks ranges between 0.9 pCi/g and 3.6
pCi/g with an average concentration of about 1.3 pCi/g. The ninth daughter product, thallium-
208
208 ( Tl), is used to estimate the presence of thorium by its 2.61 MeV gamma-ray emission.
Technologically enhanced naturally occurring radioactive material (TENORM) is NORM
processed in such a manner that its concentration has been increased. TENORM is associated
with various industries including energy production, water filtration, fertilizer production,
mining and metals production. Concentrations of radionuclides in TENORM are often orders of
magnitude greater than the naturally occurring concentrations. This survey was designed to
identify areas where the TENORM concentrations were significantly higher than the natural
background concentrations due to the mining and processing of uranium ore.
Page 33 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Appendix V: ASPECT Instrumentation
Survey Instrumentation
The ASPECT aircraft is a twin engine, high wing AeroCommander 680FL capable of cruising
speeds ranging from about 100 knots (115 mph) to 200 knots (230 mph) (Image 2). It is based in
Waxahachie, Texas and operated by two pilots and one technician. A suite of chemical,
radiological, and photographic detection technology is mounted within the airframe making it the
only aircraft in the nation with remote chemical and radiological detection capabilities.
Radiation Detectors
The radiological detection technology consisted of two RSX-4 Units (Radiation Solutions. Inc..
386 Watline Avenue, Mississauga, Ontario, Canada) (Image 9). Each unit was equipped with
four 2"x4"xl6" thallium-activated sodium iodide (NaI[Tl]) scintillation crystals for a total of 8
NaI[Tl] (16.8 L) crystals.
Detector packs for airborne spectroscopy typically consist of
clusters of NaI[Tl] crystals because they are relatively inexpensive
compared to other scintillation crystals. In addition, Nal crystals
have high sensitivity with acceptable spectral resolution
(approximately seven percent full width at half maximum
(FWHM) at 662 keV), and are easy to maintain.
The Radiation Solutions RSX-4 unit was specifically designed for
airborne detection and measurement of low-level gamma radiation
from both naturally occurring and man-made sources. It uses
advanced digital signal processing and software techniques to
produce spectral data equivalent to laboratory quality. The unit is a
fully integrated system that includes an individual high resolution
(1,024 channel) advanced digital spectrometer for each detector. A
high level of self diagnostics and performance verification routines
such as auto gain stabilization are implemented with an automatic error notification capability,
assuring that the resulting maps and products are of high quality and accuracy.
The ASPECT program calibrates it radiological instrumentation according to the International
Atomic Energy Agency specifications.3
Image 13: RSX-4 unit showing
four detector locations. The
ASPECT was equipped with 6
NaI[Tl] and 2 LaBr3:Ce
scintillating detectors.
Page 34 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
Chemical Sensors
The chemical sensors installed in the aircraft detect the
difference in infrared spectral absorption or emission of a
chemical vapor. The first sensor is a model RS-800, multi-
spectral IR-Line Scanner (Raytheon TI Systems, McKinney,
TX) (Image 4). It is a multi-spectral high spatial resolution
infrared imager that provides two-dimensional images. Data
analysis methods allow the operator to process the images
containing various spectral wavelengths into images that
indicate the presence of a particular chemical species.
The second sensor is a modified model MR254/AB (ABB,
Quebec, Quebec City, Canada). It is a high throughput Fourier
Transform Infrared Spectrometer (FT-IR) that collects higher
spectral resolution of the infrared signature from a specific
plume location. The instrument is capable of collecting spectral
signatures with a resolution selectable between 0.5 to 32 wave-
numbers.
The principle of measurement involves the detection,
identification, and quantification of a chemical vapor species
using passive infrared spectroscopy. Most vapor compounds
have unique absorption spectral bands at specific frequencies in
the infrared spectral region. Careful monitoring of the change in
total infrared radiance levels leads to concentration estimations for a particular vapor species.
Camera
The ASPECT aircraft uses a high resolution digital camera to collect visible aerial images. The
camera consists of a Nikon D2X SLR camera body with a fixed focus (infinity) 24mm F1.2
Nikor lens. The camera sensor has 12.5 million pixels (12.2 Mpixels viewable) giving a pixel
count of 4288 x 2848 in a 3:2 image ratio. An effective ground coverage area of 885 x 590
meters is obtained when operated from the standard altitude of 850 meters.
Image ortho-rectification, which corrects for optical distortion and geometric distortion due to
the three dimensional differences in the image, is accomplished using an inertial navigation unit
(pitch, roll, and heading) coupled with a dedicated 5 FIz global positioning system (GPS).
Aircraft altitude above ground is computed using the difference between the indicated GPS
altitude and a 30 meter digital elevation model (DEM). Full ortho-rectification is computed
using a camera model (lens and focal plane geometric model) and pixel specific elevation
geometry derived from the digital elevation model to minimize edge and elevation distortion.
Documented geo-location accuracy is better than 49 meters.
Image 14: View of chemical
sensors: high speed infrared
spectrometer, lower left corner;
infrared line seamier is out of view
behind the line scanner.
Page 35 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines
October 2011
Radiological spectral data are collected every second along with GPS coordinates and other data
reference information. These data are subject to quality checks within the Radiation Solutions
internal processing algorithms (e.g. gain stabilization) to ensure a good signal. If any errors are
encountered with a specific crystal during the collection process, an error message is generated
and the data associated with that crystal are removed from further analyses.
Prior to the survey, the RSX-4 units go through a series of internal checks. If no problems are
detected, a green indicator light notifies the user that all systems are good. A yellow light
indicates a gain stabilization issue with a particular crystal. This can be fixed by waiting for
another automatic gain stabilization process to occur or the user can disable the particular crystal
via the RadAssist Software application. A red light indicates another problem and would delay
the survey until it can be resolved.
Page 36 of 37
-------
Aerial Radiological Surveys Poison Canyon Uranium Mines October 2011
References
1 Bristow Q., Airborne y-ray spectrometry in Uranium Exploration. Principles and Current
Practice. International Journal of Applied Radiation and Isotopes. Vol. 34. No. 1. Pp 199-229,
1983.
2 rd
Eisenbud, M. Environmental Radioactivity; From Natural Industrial and Military Sources. 3
Edition. Academic Press, Inc., New York, NY. 1987.
3 International Atomic Energy Agency [2003], Guidelines for radioelement mapping using
gamma ray spectrometry data. Technical Report Series No. 1363. IAEA, Vienna.
Page 37 of 37
------- |