SURVEY OF THE ALBERTA INFRASTRUCTURE
TURNER VALLEY GAS PLANT
FOR EVIDENCE OF
NATURALLY OCCURRING RADIOACTIVE MATERIAL (NORM)
November 30, 2005
Report prepared
by
Stuart Hunt & Associates Ltd.
St. Albert, Alberta
for
Alberta Infrastructure and Transportation
Site and Environmental Services
SURVEY OF THE ALBERTA INFRASTRUCTURE TURNER VALLEY GAS PLANT FOR
EVIDENCE OF NATURALLY OCCURRING RADIOACTIVE MATERIAL (NORM)
November 30, 2005
REPORT INDEX
Subject
Page
Introduction ............................................................................................................................1
NORM survey instrumentation...............................................................................................2
NORM survey procedure .......................................................................................................3
Turner Valley Gas Plant buildings areas surveyed ................................................................4
Water sample analysis...........................................................................................................4
Discussion..............................................................................................................................6
Conclusion .............................................................................................................................7
Tables
Table 1. Gross alpha/beta radioactivity in Turner Valley water samples ..............................5
Table 2. Gamma spectroscopy analysis of Turner Valley water samples ............................9
Appendices
Appendix A. Chemical symbols & important characteristics of natural uranium(U-238),
Thorium (Th-232) radioactive decay series & potassium (K-40).....................11
Appendix B. NORM Screening Survey Form .......................................................................12
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Survey of the Turner Valley Gas Plant for evidence of Naturally Occurring Radioactive Material
(NORM)
Introduction
At the request of Alberta Infrastructure and Transportation, Site and Environmental Services, a
Naturally Occurring Radioactive Material (NORM) survey was carried out at the Turner Valley Gas
Plant (TVGP), Turner Valley, Alberta on November 30, 2005 by Stuart Hunt & Associates Ltd. The
purpose of the survey was to locate accumulations of naturally occurring radioactive material (NORM)
in surface production equipment and to identify those locations where the ionizing radiation1 intensity
could cause workers and/or members of the general public to receive radiation doses exceeding the
recommended dose limits defined by the Canadian Guidelines for the Management of Naturally
Occurring Radioactive Material.
The source of NORM accumulation in oil and gas production equipment is natural uranium, a
primordial radioactive isotope, encountered throughout the Earth’s crust. The decay products of
uranium are themselves radioactive and this process of radioactive decay continues until stable lead
(206Pb) is reached. Generally the concentration of NORM in the environment is low and in many cases
is only found in trace amounts. However, industries involved with mineral extraction and processing,
oil and gas production, forest products and thermal-electric production have demonstrated the ability
to enhance the specific radioactivity or concentration of NORM. NORM whose specific radioactivity
has been increased above its natural state is called technically enhanced naturally occurring
radioactive material or TENORM. Technically enhanced NORM is a condition where the potential for
radiation exposure to workers and the general public is enhanced.
In this Report there is no
distinction made between NORM and TENORM as it is common practice to use the acronym NORM
to describe both technically enhanced and NORM in its natural state.
The source of NORM accumulation in gas production facilities is radon-222 (222Rn) a noble naturally
occurring radioactive gas. Radon-222 is one of several radioactive products associated with the
natural uranium radioactive decay. Refer to Appendix A of this report for a more detailed description
of the natural uranium and thorium radioactive decay series. Radon-222 decays by alpha particle
emission which makes it impossible to detect at the exterior surface of production equipment.
However, it is possible to detect the penetrating gamma photons emitted by the radon-222 radioactive
progeny which are also known as “radon daughters.” The principal source of penetrating gamma
photons for the radon daughters is bismith-214 (214Bi). Condensate removed from gas streams can be
another source of NORM contamination although it is not always encountered in a natural gas stream.
1
Ionizing radiation – any radiation capable of displacing electrons from atoms or molecules, thereby producing
ions.
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The radioactive parent for radon-222 is radium-226 (226Ra). Radium-226, which is slightly soluble in
produced water, is the principal source of NORM contamination in oil production facilities. Radium226 sulphate is substituted for barium sulphate in barium sulphate (BaSO4) enriched produced water.
Radium-226 compared to radon-222 is a long lived radioactive isotope with a physical half life (T½p)
of 1,600 years. The physical half lives for radon-222 and bismuth-214 are 3.8 days and 19.9 minutes
respectively. Physical half life describes the amount of time required to reduce the radioactivity of a
radioactive isotope by fifty percent (50%). Physical half life frames can range form millions of years
down to fractions of a second. Since the Turner Valley Gas Plant has been out of service for a
significant number of years the TVGP NORM survey was focussed on those surface areas and
equipment where radium enriched scale or sludge was likely to be encountered. The penetrating
gamma photons associated with the radon-222 progeny will have all decayed away due to their short
physical half lives.
None of the gamma photon intensity measurements made in and around accessible Turner Valley
Gas Plant surface production and processing equipment showed any evidence of NORM
accumulation in excess of the NORM Classification/Thresholds described in Section 3 subsection
3.2.1 for the Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials
(NORM). The gross alpha/beta radioactivity for water samples collected from the Sheep River, a
TVGP water seep and, well waters from Okotoks, Black Diamond, and Turner Valley showed no
A more detailed gamma
evidence of radioactivity in excess of ambient “background”2 levels.
spectroscopy analysis of these water samples was carried out after they had reached secular
equilibrium3. Analysis of these water samples by gamma spectroscopy provided data in becquerels4
per litre (Bq/L) for the NORM radioisotopes of interest.
NORM survey instrumentation
A Ludlum Measurements, model 3-97 microR radiation survey meter was used for the TVGP NORM
survey. The internal scintillation detector for this survey meter is ideal for detecting low intensity
gamma photon radiation. This model 3-97 survey meter (serial number 157511) was last calibrated
on November 24, 2005 in accordance with Canadian Nuclear Safety Commission radiation survey
meter calibration criteria. The maximum acceptable error between the calculated radiation intensity
2
Background – radioactivity or radiation to which an individual is exposed arising from natural radiation sources
such as terrestrial radiation from radionuclides in soil, cosmic radiation from outer space and, naturally occurring
radionuclides deposited in cells from the food chain.
3
Secular equilibrium – in a radioactive decay series, the state that prevails when the rate at which the progeny
are produced is equal to the rate at which they are decaying. All members of a NORM radioactive decay series,
in equilibrium, will have the same radioctivity.
4
Becquerel – the S.I. unit for radioactivity equal to one (1) nuclear disintegration per second
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produced by a radioactive calibration standard and a measured radiation intensity is ± twenty percent
(20%). The measurement error for the model 3-97 used for the TVGP survey was zero percent for all
detection ranges and intensities except for the maximum calibrated radiation intensity. The
measurement error for a radiation intensity of 4,000 microRoentgens per hour (µR/h) was -2.5%. For
all of the gamma photon intensities measured during the TVGP NORM survey there was no correction
required for any of the measured values.
The model 3-97 was also equipped with an external model 44-9 “pancake” Geiger Mueller detector.
This primary role of this detector is the surveying of surfaces for evidence of radioactive
contamination, on accessible surfaces, from alpha, beta and gamma emitting radioactive isotopes.
Since no evidence of NORM accumulation was detected there was no requirement for the model 44-9
“pancake” Mueller detector to be used during the course of the TVGP NORM survey.
NORM survey procedure
Prior to the start of the NORM survey, an environmental radiation (background) intensity measurement
was made for the purpose of determining the incremental radiation dose5 for those areas of the TVGP
property where the NORM gamma radiation intensity exceeded the property background value.
Ambient background radiation measurements were made on contact with the ground and at waist
level at the entrance to the Turner Valley Gas Plant. A “background” radiation intensity of 6µR/h was
used for the TVGP NORM survey. Background radiation is a term used to describe radiation that
occurs naturally in the environment. Background radiation consists of cosmic radiation from outer
space, radioactive elements in rocks and soil, and radiation from radon and its decay products in the
air that we breathe.
Please note: For the remainder of this Report the Systeme International (S.I.) units for radiation dose
are used to comply with the Canadian Guidelines for the Management of Naturally Occurring
Radioactive Materials (NORM). To convert µR to microsieverts6 divide the µR value by 100. This
should be seen as a general rule for survey results. While the conversion in most instances is fairly
close they do not always correspond exactly.
All accessible surface production equipment, buildings and exterior surface areas were surveyed for
evidence of NORM accumulation. Where possible, measurements were made either on contact or
within fifty (50) centimetres of the surface being surveyed. When required, equipment or surfaces with
net gamma photon intensities exceeding 0.15 :Sv/h were subjected to a more detailed survey to
5
Incremental radiation dose – radiation dose found in excess of the local background radiation dose
microsievert – the S.I. unit of absorbed radiation dose in living organisms modified by radiation type and tissue
weighting factors. It is the unit of radiation dose for the terms “equivalent dose” and “effective dose.
(1microsievert = 1.0 E -6 sievert).
6
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identify the exact location of the NORM accumulation or accumulations. When a net measurement
exceeded 0.15 µSv/h, an additional measurement of the radiation intensity at 50 centimetres is made
to maintain conformity with the limits in the Canadian NORM Guidelines. When considered
necessary, gamma radiation intensities are made in normally occupied areas to determine the
incremental radiation dose7 for the occupied area.
Turner Valley Gas Plant buildings and areas surveyed
The following locations on the TVGP property were surveyed.
▪ Compressor Plant.
▪ Propane Plant.
▪ Gasoline Plant.
▪ Dingman #2 fence line.
▪ Oily steam condensate basin.
▪ Process water ditch and pipe canal.
▪ Sheep River flood eroded bank.
▪ Town of Turner Valley water well #7
▪ Butane/Propane tanks
▪ Propane compressor building
▪ Horton Spheres fence line
Where possible, equipment at these locations was surveyed with the Ludlum 3-97 MicroR meter.
However, for those buildings where access was not possible measurements were made around the
exterior of the building. Any measurement in excess of twice the ambient radiation background of 6
µR/h (0.06 µSv/h) would have required access to the building to identify the source of the elevated
gamma photon intensity. This additional step was not required.
A record of the NORM survey
carried out at the Turner Valley Gas Plant is included with this report as Appendix B.
Water sample analysis
Water samples from the following locations were collected for NORM contamination analysis.
•
•
•
•
ABE#1, Okotoks WTP: Raw Well Water 05SWC69031
ABE#2, Black Diamond Water Treatment Plant 05SWC69032
ABE#3, Sheep River at Black Diamond Water Treatment Plant 05SWC69033
ABE#4, Sheep River above Turner Valley 05SWC69034
7
Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM), Chapter 2,
paragraph 2.4.2, The NORM Standards – Basis and Criteria.
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•
•
•
•
•
ABE#5, Turner Valley Water Treatment Plant 05SWC69035
ABE#6, Well water, Dianne Bjornson, 622 North Royalite Way, Turner Valley
ABE#7, Seep beside road north of Plant 05SWC69037
ABE#8. Well water, L.. Abrams, Turner Valley.
SHA1117, Drinking water, 20 Rayborn Crescent, St. Albert
Forty (40) millilitres of water was taken from each sample and transferred to 45 millilitre polypropylene
plastic vials equipped leak tight flip top caps. These vials were placed in secure storage to allow the
samples to reach secular equilibrium in preparation for gamma spectroscopy analysis. A second set
of 5 millilitre samples were prepared for gross alpha/beta analysis by liquid scintillation counting on
December 2, 2005. Gross alpha/beta analysis is a technique which provides an indication of the total
amount of alpha and beta particle emitting radioactivity in the sample being analyzed. It does not,
however, provide any information on which radioisotope is the source of the radioactivity in the
sample. In Table 1 the St. Albert drinking water sample (SHA1117) is used to establish a background
value to calculate the gross alpha/beta results for samples ABE #1 to 8 , in net counts per minute
(cpm),
Table 1. Gross Alpha/Beta radioactivity in Turner Valley water samples
Sample ID
Gross cpm
Net cpm
Okotoks WTP raw well water 05SWC69031
113.60
10.0
Black Diamond WTP 05SWC69032
106.40
2.8
Sheep River at Black Diamond WTP 05SWC69033
115.20
11.6
Sheep River above Turner Valley 05SWC69034
109.00
5.4
Turner Valley WTP Raw well water 05SWC69035
106.40
2.8
Well water Dianne Bjornson 622 North Royalite Way
114.40
10.8
Seep beside road north of Plant 05SWC69037
117.60
14.0
L. Abrams well water, Turner Valley
105.20
1.6
Tap water, 20 Rayborn Crescent, St. Albert (Background)*
103.60 ±25.07
* The St. Albert tap water has been used as a background sample for comparison purposes.
Background radiation can have a significant impact on a sample analysis result especially when
samples show low levels of radioactivity. At low radioactivity levels it is important to establish the
significance of the net counts per minute (cpm) values. In other words, is there significant evidence of
radioactivity or are the net cpm values the result of random background fluctuations during the
measurement of the sample. Rather than test the validity of each individual sample measurement a
minimum cpm value is calculated to establish a cpm value that can be considered significant. In order
for the net cpm value to be considered significant it must be equal to or greater than a specified
multiple of the estimated standard deviation of the difference between the gross cpm value and
background. For example, the net difference of ±25.07 cpm for the St. Albert water sample is the
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minimum number of counts per minute that have to be recorded, above background, in order for the
net cpm value for all of the Turner Valley water samples to be considered significant at the 95%
confidence level. Since none of the net cpm values for the Turner Valley samples exceed the
minimum S-B value of ±25.07 cpm there is no evidence of measurable NORM radioactivity in the
samples.
The gamma spectroscopy analysis results for the Turner Valley water samples can be found in Table
2 on pages 9 and 10 for this Report.
Discussion
Starting in August 1995, Canadian generators of NORM relied on the guidance provided by the
Guidelines for the Handling of Naturally Occurring Radioactive Materials (NORM) in Western Canada.
Several years later the Federal-Provincial-Territorial Radiation Protection Committee (FPTRPC), a
Canadian Intergovernmental agency, decided that a national set of NORM management guidelines
was required. The Canadian Guidelines for the Management of Naturally Occurring Radioactive
Materials (NORM) came into effect during June 2001, and have now replaced the Western Canada
NORM guidelines. The Canadian Guidelines reflect changes in national and international radiation
protection practices and consensus standards for NORM classification and management that have
occurred since 1995. As with the Western Canada NORM Guidelines the assignment of NORM risk is
based on the radiation dose that workers and members of the general public may or are likely to
receive from either working with NORM contaminated materials or the disposal of such materials. The
Canadian Guidelines make use the following NORM management program classifications:
•
•
•
•
Unrestricted
NORM Management
Dose Management
Radiation Protection Management
The NORM survey carried out at the Turner Valley Gas Plant and the gross alpha/beta analysis of the
water samples described in Table 1 suggest that the NORM risk classification for the Turner Vallay
Gas Plant is Unrestricted.
The Canadian NORM Guidelines definition for the Unrestricted
classification is as follows:
“When the estimated incremental annual effective dose to the public is less than 0.3 millisieverts per
year (mSv/y) and the worker effective dose is less than 1.0 mSv/y, the NORM program classification is
Unrestricted. When this classification is in effect no preventative measures are required to control
either radiation doses or materials”.
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The effective radiation dose is the sum of all internal and external equivalent radiation doses multiplied
by the applicable tissue weighting factor (WT), for those tissues and organs that have received an
ionizing radiation dose.
H(Sv) = Σ [D(Gy) x WR ] x WT
Where Gy (gray) is the absorbed radiation dose in Joules per kilogram of irradiated material
WR is the radiation weighting factor
The 0.3 millisieverts or 300 microsievert (µSv) annual effective radiation dose when divided by 2000
hours produces an hourly radiation dose rate equal to 0.15 µSv/h. All of the gamma photon intensity
measurements made during the survey of the Turner Valley Gas Plant, the exposed bank for the
Sheep River and the Turner Valley water intake were less than 0.15 µSv/h. If a member of the
general public was to receive a radiation dose of 0.15 µSv/h eight hours a day for 365 days they would
receives an annual effective radiation dose of 438 microsieverts. For comparison purposes Table 2
describes some of the average annual radiation doses received by Canadians.
Source of Radiation Exposure
Inhalation - Radon Progeny
Radiation Dose Received
1,000 microsieverts (Canadian average)
Vancouver
200 microsieverts
Winnipeg
2,200 microsiverts
Cosmic Radiation
300 microsieverts
Gamma photons – soil & rocks
350 microsieverts
Potassium-40 inside the body
200 microsieverts
Typical chest x-ray
100 microsieverts/xray
Luminous signs, TV, smoke detectors
10 microsieverts
Dose to lungs of a pack a day smoker
80,000 microsieverts
Dose received by astronauts
Dose giving an extra 1% risk of cancer
1,.000,000 microsieverts
250,000 microsieverts
Sources: Canada; Living with Radiation; Atomic Energy Control Board, 1995.
Basic Radiation Protection Technology, 2nd Edition, Daniel A. Gollnick
Conclusion
The gamma photon survey of the Turner Valley Gas Plant and surrounding area with a hand held
Ludlum Measurements model 3-97 microR survey meter showed no evidence of technically enhanced
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naturally occurring radioactive material. The gross alpha/beta analysis results for the water samples
described in Table 1 suggest that there is no evidence of radioactivity in excess of the Canadian
NORM Guidelines unconditional derived release limits (UDRL) for radium-226 and lead-210. Analysis
of the water samples from Table 1 for long-lived radioisotopes (lead-210, radium-226, radium-228,
thorium-228 and potassium-40) by gamma spectrometry has confirmed no measurable
concentrations.
Some areas of the Turner Valley Gas Plant could not be surveyed for evidence of technically
enhanced NORM. However, there is enough data collected to state that there is no evidence of
technically enhanced NORM. The Canadian NORM Guidelines NORM risk category for the Turner
Valley Gas Plant is Unrestricted. No further radiological controls are considered necessary for this
site.
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Table 2. Gamma spectrometry analysis of Turner Valley water samples
Concentration (Bq/ml)
UDRL (NORM Guidelines)
(Bq/ml)
Lead-210
< 0.05
0.001
Radium-226
<0.005
0.005
Radium-228
<0.007
0.005
Thorium-228
<0.002
0.001
Potassium-40
<0.03
n/a
Lead-210
<0.03
0.001
Radium-226
<0.003
0.005
Radium-228
<0.005
0.005
Thorium-228
<0.002
0.001
Potassium-40
0.03 + 0.02
n/a
Lead-210
<0.03
0.001
Radium-226
<0.009
0.005
Radium-228
<0.007
0.005
Thorium-228
<0.002
0.001
Potassium-40
<0.02
n/a
Lab ID
Sample ID
Radioisotope
SHA1110
ABE #1 05SWC69031
SHA1111
SHA1112
SHA1113
SHA1114
SHA1115
SHA1116
ABE #2 05SWC69032
ABE #3 05SWC69033
ABE #4 05SWC69034
ABE #5 05SWC69035
Lead-210
<0.02
0.001
Radium-226
<0.004
0.005
Radium-228
<0.009
0.005
Thorium-228
<0.002
0.001
Potassium-40
0.04 + 0.02
n/a
Lead-210
<0.02
0.001
Radium-226
<0.004
0.005
Radium-228
<0.007
0.005
Thorium-228
<0.001
0.001
Potassium-40
0.03 + 0.02
n/a
ABE #6 Well water
Dianne Bjornson
622 North Royalite
Way
Turner Valley
Lead-210
<0.02
0.001
Radium-226
<0.005
0.005
Radium-228
<0.008
0.005
Thorium-228
<0.001
0.001
Potassium-40
<0.04
n/a
ABE #7 05SWC69037
Lead-210
<0.07
0.001
Radium-226
<0.005
0.005
Radium-228
<0.004
0.005
Thorium-228
<0.003
0.001
Potassium-40
<0.04
n/a
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SHA1117
SHA1118
ABE #8 05SWC69038
Tap water, 20 Rayborn
Crescent, St. Albert
Lead-210
<0.03
0.001
Radium-226
<0.005
0.005
Radium-228
<0.005
0.005
Thorium-228
<0.001
0.001
Potassium-40
<0.02
n/a
Lead-210
<0.005
0.001
Radium-226
<0.004
0.005
Radium-228
<0.007
0.005
Thorium-228
<0.003
0.001
Potassium-40
<0.003
n/a
Notes to Table 2
1. The UDRL is the unconditionally derived release limit found in chapter five of the Canadian
NORM Guidelines. They represent 10X the Guidelines for Canadian Drinking Water Quality
drinking water standard.
2. Lead-210 is difficult to detect at these low levels. Although both the gamma spectrometry and
liquid scintillation results provide evidence of no contamination, if further inquiry into lead-210
concentrations is required measurement using low energy gamma spectrometry (LEPS) is
suggested.
3. Measurements where the MDA of the system is greater than the UDRL have been highlighted
in italics. The standards used to calibrate the system (CANMET uranium tailings DH-1, BL-3
and UTS-2) have an error range larger than what can be measured at low level for thorium-228
and radium-228. This results in an MDA which is higher than the UDRL in some cases.
4. The MDA for a specific radioisotope is dependent on the background intensity for that
particular energy of radiation and the accuracy of the standard used to calibrate the system.
As such, variations between samples will occur.
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Appendix A
CHEMICAL SYMBOLS & IMPORTANT CHARACTERISTICS OF NATURAL URANIUM (U-238),
THORIUM (Th-232) RADIOACTIVE DECAY SERIES & POTASSIUM (K-40).
URANIUM-238 SERIES
NORM
Nuclide
Uranium-238
Half-Life
Major
Emissions
NORM Nuclide
U
4.5 x 109 y
Alpha
Thorium-232
Th
24.0 d
Symbol
238
Thorium-234
234
Protactinium-243m
234m
Uranium-234
THORIUM-232 SERIES
234
Pa
1.2 m
U
2.5 x 105 y
Beta,
Gamma
Beta,
Gamma
Alpha,
Gamma
Alpha,
Gamma
Alpha,
Gamma
Half-Life
Major
Emissions
232
Th
1.4 x 104 y
Alpha
Radium-228
228
Ra
5.7 y
Beta
Actinium-228
228
Thorium-228
Symbol
Beta,
Gamma
Alpha,
Gamma
Alpha,
Gamma
Ac
6.1 h
228
Th
1.9 y
Radium-224
224
Ra
3.7 d
Radon-220
220
Rn
55.6 s
Alpha
Alpha
Thorium-230
230
Th
7.7 x 104 y
Radium-226
226
Ra
1.6 x 103 y
Radon-222
222
Rn
3.83 d
Alpha
Polonium-216
210
Po
0.15 s
Polonium-218
218
Po
3.1 m
Alpha
Lead-212
212
Pb
10.6 h
Lead-214
214
Pb
27 m
Beta,
Gamma
Bismuth-212
212
Bismuth-214
214
Bi
20 m
Beta,
Gamma
Polonium-212
(65%)
Polonium-214
214
Po
1.6 x 10-4 s
Alpha
Thallium-208 (38%)
Lead-210
210
Pb
22.3 y
Beta,
Gamma
Lead-208
Bismuth-210
210
Bi
5.01 d
Beta
Polonium-210
210
Po
138 d
Alpha
Lead-206
206
Pb
Stable
None
Beta,
Gamma
Alpha,
Beta &,
Gamma
Bi
61 m
Po
3 x 10-7 s
Alpha
208
Th
3.1 m
Betas,
Gamma
208
Pb
Stable
None
212
POTASSIUM-40
Potassium-40
40
K
1.3 x 109 y
Beta,
Gamma
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Appendix B
Complete one for each site
NORM Screening Survey Form
Date: November 30,2005
Survey Type:
Site / Location: Turner Valley Gas Plant
NORM gamma photon survey
Survey Instrument Make/Model:
Ludlum Measurements, model 3-97 microR survey meter
Probe Make/Model: Internal NaI scintillation detector
S/N: 157511
Last Calibration Date: b November 24, 2005
S/N:
n/a
Natural Background Reading for Area (specify units):
6 microroentgens per hour (µR/h)
SURVEY LOCATION
Location / Description
READINGS
µR/h @ contact
µSv/h @ 0.5 m
(optional)
Turner Valley water intake
10.0
Not measured
Exposed river bank – Sheep River
13.0
Background
TVGP accessible production and processing
equipment
No evidence of NORM detected
TVGP accessible storage vessels
No evidence of NORM detected
Comments:
Area Sketch
Revision No.1 October 26, 2002
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