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NORM Monitor IS
User Manual
55 pgs3.36 Mb0

Tracerco NORM Monitor IS User Manual

1 MN1007-C
MN1007-P3 10/01/13
Contents
1 Introduction and Scope ...................................................................................................................................... 6
1.1Introduction ................................................................................................................................................ 6
1.2Scope ..................................................... .................................................. .................................................. 6
2 Naturally Occurring Radioactivity – an overview ................................................................................................ 6
2.1Introduction ................................................................................................................................................ 6
2.2Radioactivity in Oil and Gas Installations .................................................................................................... 7
3 Operational Options ........................................................................................................................................... 8
3.1Probe Selection .......................................................................................................................................... 8
3.2NORM assessment criteria ...................................................................................................................... 13
3.2.2 Assessment using surface activity (Bq/cm2) ..................................................................................... 13
3.3Background Measurement ....................................................................................................................... 15
4 Tracerco NORM Monitor-IS – Functional description ....................................................................................... 16
4.1Handset monitor control keys ................................................................................................................... 16
4.2Operating the instrument .......................................................................................................................... 20
4.3Measurement Modes for the Scintillator Probe. ........................................................................................ 22
4.4Modes of Operation for the Geiger Müller Probe. ..................................................................................... 24
4.4.3 Becquerels per cm squared mode (Bq/cm2) ............................................................................... ....... 25
4.5Integration Function ................................................................................................................................. 27
4.6Alarm activation in integration mode ........................................................................................................ 28
4.7Background Measurement ....................................................................................................................... 29
4.8Alarm Configuration ................................................................................................................................. 30
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5 Adjusting the integration period ........................................................................................................................ 34
6 Locking the keypad ............................................................................................................................... ........... 36
7 Using the Instrument – taking a NORM measurement ..................................................................................... 37
8 Faults /Troubleshooting .................................................................................................................................... 39
9 Display ranges – reading the screen ................................................................................................................ 40
10Maintenance and Calibration ........................................................................................................................... 41
10.1Cleaning ........................................................................ ......................................................................... .. 41
10.2Handling ............................................................... ........................................................................ ............ 41
10.3Calibration ......................................................................... ....................................................................... 41
10.4Equipment Inspection ............................................................................................................................. .. 42
10.5Repair ...................................................................................................................................................... 42
11Essential Safety Information For Hazardous Areas .......................................................................................... 43
12Contact Us ....................................................................................................................................................... 44
13Technical Specification ......................................................................................................................... ........... 46
13.1Radiological Type Tests ........................................................................................................................... 46
13.2EMC Compliance Tests .............................................................. ....................... ....................... ................ 46
13.3Battery power ................................................................................................................................ ........... 46
13.4Mechanical ............................................................... ................................................................................ 46
13.5Environmental ........................................................................................................................................ .. 47
13.6Radiological performance ......................................................................................................................... 47
13.7Hazardous area approval ......................................................................................................................... 48
14.Appendix 1 – Decay Series for Uranium and Thorium ..................................................................................... 49
14Appendix 2. - Menu diagrams .......................................................................................................................... 52
14.1Scintillator probe Menu ............................................................... ....................... ....................... ................ 52
14.2Geiger Probe Menu .................................................................................................................................. 53
14.3Alarm Menu .............................................................................................................................................. 54
15Document Revision History .............................................................................................................................. 55
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Illustrations
Figure 1 - Geiger Müller (Pancake) Probe ................................................................................................................ 9
Figure 2 - Scintillation probe ................................................................................................................................... 11
Figure 3 - Tracerco NORM Monitor–IS – key definitions ..................................... .................................................... 16
Figure 4 - Start-up sequence .................................................................................................................................. 21
Figure 5 - cps readout screen ................................................................................................................................. 22
Figure 6 - Background subtracted CPS screen ....................................................................................................... 23
Figure 7 - Dose Rate screen with SI units ............................................................................................................... 23
Figure 8 - Dose rate screen with US units ............................................................................................................... 24
Figure 9 - cps readout screen ................................................................................................................................. 24
Figure 10 - Background subtracted CPS screen ..................................................................................................... 25
Figure 11 - Radionuclide selection in Bq/cm2 mode ................................................................................................ 26
Figure 12 - Bq/cm2 mode – Reading screen with Lead-210 (wet) selected ............................................................. 26
Figure 13 - cps integration screen ........................................................................................................................... 27
Figure 14 - Integration termination .......................................................................................................................... 27
Figure 15 - Alarm operation with Integration mode ................................................................................................. 28
Figure 16 - Background measurement .................................................................................................................... 29
Figure 17 - Alarm ON/OFF selection ....................................................................................................................... 30
Figure 18 - LEVEL / FACt selection ........................................................................................................................ 31
Figure 19 - Integration period configuration ............................................................................................................ 34
Figure 20 - Keypad lock .......................................................................................................................................... 36
Figure 21 - Quick start guide to measurement ........................................................................................................ 37
Figure 22 - Display ranges ...................................................................................................................................... 40
Figure 23 - U-238 Decay chain ............................................................................................................................... 49
Figure 24 - U235 Decay Chain ................................................................................................................................ 50
Figure 25 - Thorium-232 Decay Chain .................................................................................................................... 51
Figure 26 - Complete scintillator probe menu ......................................................................................................... 52
Figure 27 - Complete Geiger probe menu ............................................................................................................... 53
Figure 28 - Complete alarm menu .......................................................................................................................... 54
Tables
Table 1 - Glossary .................................................................................................................................................... 5
Table 2 – Measurement options for probes ............................................................................................................... 8
Table 3 – Alarm options when using cps for NORM assessment ............................................................................ 13
Table 4 – Alarm options when using Bq/cm2 for NORM assessment ...................................................................... 14
Table 5 – Alarm options when using dose rate for NORM assessment .................................................................. 14
Table 6 – Complete set of alarm options ................................................................................................................. 33
Table 7 - Alarm indications ..................................................................................................................................... 33
Table 8 – Troubleshooting ...................................................................................................................................... 39
Table 9 - Radiological type test ............................................................................................................................... 46
Table 10 - EMC compliance .................................................................................................................................... 46
Table 11 - Battery power ......................................................................................................................................... 46
Table 12 - Mechanical data ..................................................................................................................................... 46
Table 13 - Environmental specification ................................................................................................................... 47
Table 14 - Scintillator probe specification ................................................................................................................ 47
Table 15 - Geiger probe specification ..................................................................................................................... 47
Table 16 - Hazardous area approval ....................................................................................................................... 48
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A
Glossary
Table 1 - Glossary
ATEX European Directive 94/9/EC applicable to equipment used in hazardous environments.
Alpha radiation Radioactive decay resulting in the emission of a helium nucleus (e.g. Ra-226 Rn-222) Background radiation The ionising radiation constantly present in the natural environment of the Earth, emitted
Baseefa A notified body for ATEX approval Beta radiation Radioactive decay resulting in emission of an electron or positron (e.g. Pb-210 Bi210) Bq/cm2 A measure of surface activity. One Becquerel is equivalent to one disintegration per
cpm cps CSA North American product approval body EMC Electromagnetic Compatibility Gamma radiation Radioactive decay in which a high energy photon occurs along with the decay particle(s)
IP rating IS
Isotope Member of an element group with the same number of protons but differing number of
LSA Low Specific Activity NaI Sodium Iodide – scintillation crystal NORM Naturally Occurring Radioactive Material Nuclide A member of the set of approx. 3100 elements and their isotopes RPA
RPS
RSO Scintillator Material which produces photons in response to incident radiation µSv/h Micro-sieverts per hour. SI units for effective dose rate µR/h Micro-roentgen per hour. Non-SI units for dose rate used in USA
From French “Appareils destinés à être utilisés en ATmosphères Explosives”
by natural and artificial sources
second.
Radiation activity measured in counts per minute Radiation activity measured in counts per second
(e.g. 47KeV γ Pb-210 Bi-210)
Level of Ingress Protection against objects and liquid Intrinsically Safe. Design concept, formally assessed and certified by a notified body,
which demonstrates that the instrument can be used safely in hazardous environments.
neutrons in its nucleus.
Radiation Protection
of Ionising radiations according to the Ionising Radiations Regulations 1999 (IRR99)
Radiation Protection Supervisor. An individual appointed to ensure compliance with local
rules and radiation regulations under IRR99
Radiation Safety Officer
dvisor. A qualified expert who advises on safe and compliant use
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1 Introduction and Scope
1.1 Introduction
The Tracerco NORM Monitor-IS is an intrinsically safe portable contamination monitor which has been developed
specifically to meet the requirements of the Oil and Gas Industry; particularly the measurement of Naturally Occurring Radioactive Material (NORM).
Its principal function is to detect and quantify naturally occurring radioactive isotopes under a wide range of operational conditions.
The monitor kit provides a single instrument platform with dual probe option to deliver optimum measurement capability under the most demanding circumstances.
Although specifically designed to overcome the technical and practical challenges of measuring NORM in the field, the monitor is also able to detect a wide range of man-made isotopes.
1.2 Scope
This manual provides detailed operational and technical information for the Tracerco NORM Monitor-IS.
In addition, an introductory guide is presented which explains the origins, radiological nature and the challenges which arise when attempting to carry out practical measurements and radiological assessments of typical Naturally Occurring Radioactive Material (NORM) deposits.
2 Naturally Occurring Radioactivity – an overview
2.1 Introduction
Radioactivity occurs naturally in the environment due to the presence of decay products from Uranium and Thorium. These isotopes have extremely long half-lives. For example:
Uranium-235: 700 million years Uranium-238: 4.5 billion years Thorium-232: 14 billion years
The parent uranium and thorium isotopes decay to produce a series of other radioactive daughter isotopes of widely differing half-lives. Eventually, through the course of time, these result in a stable isotope of Lead. A schematic of the decay chains for each nuclide series is illustrated in Appendix 1 – Decay Series for Uranium and Thorium
If the radioactive parent is undisturbed for a sufficiently long period of time, a condition of equilibrium is established in which all radioactivity levels are equal. Removal of all or an amount of a nuclide from the decay scheme will disturb this equilibrium and reduce the concentration of corresponding decay products. In a situation of true
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radioactive equilibrium, all nuclides will be present at the same level of radioactivity. The natural decay series are complex and, in theory, up to 48 separate radionuclides may exist in scales which have been derived from a mixture of the Uranium and Thorium decay products. In reality the isotopes of uranium-235, uranium-238 and thorium are rarely detected in scales themselves. This is thought to reflect the low solubility of such materials in the water within the reservoir. It is more usual to detect the more soluble decay products of each series in the form of radium isotopes and their subsequent daughter products.
The result of these processes is that NORM contains many different radionuclides which emit a complex mix of alpha, beta and gamma radiations. The relative amounts of radionuclides from the uranium and thorium decay chains can also vary depending on the history of the reservoir and chemical composition; hence scales taken from different locations often exhibit variations in radioactive composition.
Many of the isotopes in the various decay chains can be seen to have relatively short half-lives (minutes or hours) and, if present in isolation, would very quickly decay and cease to generate any further radiological hazards. These isotopes would technically be described as "unsupported" but in many cases they continue to remain present with an unchanging level of radioactivity. This occurs because they are continuously being produced by other radioisotopes in the decay chain such that there is a constant balance between production and decay leading to a constant level of radioactivity; irrespective of the actual half-life. In this situation the decay scheme would be considered to be in equilibrium and the shorter lived nuclide fully “supported” by its parent nuclide.
2.2 Radioactivity in Oil and Gas Installations
Radioactive materials from natural sources may arise in a number of forms within the oil and gas industry. A common form of the material is known as Low Specific Activity or Naturally Occurring Radioactive Material (LSA/NORM) scale. It frequently arises within oil and gas installations due to a process of selective chemical deposition. Radioactive isotopes, together with a wide variety of other chemicals, may be leached from reservoir rock and become dissolved within the reservoir formation water.
In oil and gas installations, where water injection of seawater is used to promote the recovery of oil, the presence of sulphate-rich injection waters can give rise to the deposition of barium and strontium sulphate scales. These scales may incorporate radioactive isotopes derived from the presence of uranium and thorium in the formation rock and can produce significant scaling of pipework and vessels; thereby reducing the flow of liquids and affecting the efficiency of control systems.
The laydown of radioactive scale can lead to significant external radiation levels on the outside of production equipment. This raises the possibility of exposure to personnel from contamination by ingestion of radioactive material when equipment is handled or cleaned during scale removal operations. Similarly, scale and silt may be deposited in the equipment of onshore terminals where crude oil is delivered from offshore installations via marine pipelines.
An additional problem may arise in gas production and associated handling systems from the presence of radon gas generated by radium isotopes; both in formation rock or water and in LSA/NORM scales. This radioactive gas can contaminate the production gas to significant levels and will decay to particulate-forming radioisotopes such as lead-210 and polonium-210 which can also be deposited in equipment of the gas production system.
These deposits can be radiologically significant and pose potential hazards to health when equipment is opened up. It is not uncommon for significant quantities of unsupported lead-210 or polonium-210 to be transported from a reservoir in the gaseous phase. In such circumstances the availability of these radionuclides reflects their chemical and physical properties and the historical levels of the radioactivity which over time have built up in the reservoir.
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3 Operational Options
The Tracerco NORM Monitor-IS has been designed to provide a versatile instrument which will enable the
operator to confidently detect and quantify contamination arising from NORM under most environmental conditions. In order to achieve this versatility, the instrument is provided as a single data processing unit with the choice of two types of radiation detection probes.
To realise the full capability of the instrument, it is important that the operator understands the technical advantages of each probe and the circumstances under which they should be deployed.
3.1 Probe Selection
Although, in general terms, both the Geiger Müller (GM) and Scintillator-based probes will detect the presence of NORM under most environmental conditions, there can be significant variations in detection sensitivity for different scale types.
The following table provides guidance on the selection of probe for a particular NORM measurement application. The table has been compiled on the basis that environmental background radiation is comparable to that found in an offshore facility and there are no local abnormal circumstances – for example, the presence of local scale storage containers will affect the detection capability of the scintillation probe due to a higher background radiation reading.
This guidance is based on monitoring experience and the known technical characteristics of each probe. The operator should always observe local operating procedures and, where appropriate, seek confirmation from the appointed RPS or RPA.
Type of measurement Suggested probe
Radium scale with readily accessible dry surface Geiger Müller SA-49 Radium scale with significant water, oil or sludge deposition Scintillator SA-50 Radium scale contaminated tubulars < 4” diameter (100mm) Scintillator SA-50 Radium scale deposition using external pipe surface survey measurements Lead-210 scale with readily accessible surface ( wet or dry) Geiger Müller SA-49
Table 2 – Measurement options for probes
Technology Tracerco part
ref.
Scintillator SA-50
3.1.1 Geiger Müller End Window (Pancake) Probe
The Geiger Müller probe utilises a thin window detector which, although capable of detecting gamma radiation, is particularly sensitive to the surface measurement of alpha and beta radiation.
The Geiger Müller probe’s high sensitivity to alpha and beta is ideally suited to the measurement of lead-210 and polonium-210 which are commonly found in gas producing facilities where NORM is transported in the form of the gas radon-222.
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Measurements may be taken in units of counts per second (cps) or - in the case where specific nuclides have been selected - Becquerels per square cm (Bq/cm
2
).
The Bq/cm2 measurement function is used to quantify the levels of surface activity of a particular nuclide. It is
important that the users have prior knowledge of the type of nuclides present in the deposition so that the measurements can be set up and interpreted correctly.
Contact radiation.monitors@tracerco.com for further details regarding radionuclide spectrum analysis of sample materials.
The detection sensitivity of the probe for alpha and beta emissions from scale materials may be significantly reduced if the surface is wet or obscured by oily deposits.
Although in such circumstances the probe will continue to respond to any gamma ray emissions with only a limited reduction in sensitivity, the reduced contribution from the alpha and beta particle detection will result in a significant overall loss in sensitivity relative to a dry surface.
The Geiger probe has been calibrated with a number of response factors to allow measurement of Bq/cm specific nuclides. The nuclide options which are provided includes Radium-226 in the form of wet or dry scales and Lead-210, again in the form of wet or dry scales. The operator is able to select the required nuclide through the instrument’s configuration menu [See section 0]
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Figure 1 - Geiger Müller (Pancake) Probe
2
for
The provision of a wet and dry option reflects the absorption of alpha and, to a lesser extent, beta radiation by water and oil on the surface of the scale.
The response factors have been factory set under calibration conditions where the probe is placed directly
above the scale surface at a distance of 2mm.
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3.1.2 Scintillation Probe
The scintillation probe utilises an inorganic scintillator crystal which is very sensitive to the detection of gamma radiation. It may also detect the higher energy beta radiation emitted by certain nuclides in the natural activity decay chain.
A focus on gamma radiation detection sensitivity makes the scintillation probe ideal for measuring radium nuclides and the associated decay chains. The probe has been designed to provide optimum radiation collection efficiency without significantly reducing the ruggedness of the probe.
The nature of the design provides for near 360 degree collection of radiation thus providing an extremely effective monitor for pipe internals.
High gamma radiation sensitivity is particularly suited to detecting NORM through pipe or vessel walls where internal monitoring is not possible and access limited to the external surfaces. In these situations the probe can be used in an end-on configuration to directly monitor against the surface of interest.
The potential problems associated with the Geiger Müller probe - where wet or oily surface contamination of scale limits detection of alpha and beta radiation - are largely overcome by the use of the scintillation based probe: gamma ray emissions from scale are relatively unaffected by the presence of small quantities of oil and water.
An exception to the above is where areas of known Pb-210 deposition exist. In this case the GM probe will be
more effective.
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Figure 2 - Scintillation probe
The Scintillation Probe can measure in units of cps or dose rate. The dose rate response is calibrated against a nationally traceable caesium-137 source.
The Scintillation Probe dose rate output is designed specifically for the methods of NORM screening required
by North American regulators. General dose rate surveys using the probe are not recommended.
The response of all scintillation detectors vary with radiation energy and the gamma ray energies associated with caesium-137 are significantly different to those arising from NORM.
[See calibration details in Section 10.3]
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3.2 NORM assessment criteria
There are various measures of the radiological significance of NORM. The assessment criteria favoured by local regulators regarding NORM limits can vary from region to region.
The NORM Monitor-IS is designed so that it will accommodate all current assessment criteria.
For each assessment criteria the NORM Monitor-IS provides user-configurable alarms which can be set to reflect the local rule PASS/FAIL criteria.
[See section 4.8 for alarm setting options]
The range of known assessment criteria is described in the following section.
The operator should always seek guidance from the designated RPA, RSO or RPS when selecting an
instrument for measuring NORM and observe local procedures in relation to any planned radiation monitoring operations.
3.2.1 Assessment using cps measurement
The NORM Monitor-IS may be operated in cps or cps minus background mode, with either the GM Probe or the Scintillator Probe.
The PASS/FAIL alarm criteria are summarised in the following table. These assessment methods are commonly used in the UK and Middle East oil and gas sectors.
Table 3 – Alarm options when using cps for NORM assessment
Operating mode Alarm type Description Cps Level Alarm activated when total cps exceeds user-configured level
cps - background Level Alarm activated when cps above background radiation exceeds user-
configured level
cps - background Factor Alarm activated when a multiple of background radiation is exceeded.
3.2.2 Assessment using surface activity (Bq/cm2)
Surface activity measured in Bq/cm
useful information - pr ovided the t ype of nuclide is known.
[See also Section 3.1 Probe Selection]
2
is less commonly used in NORM assessment but may offer the operator
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The NORM Monitor-IS Geiger Müller probe is calibrated with response factors for lead-210 and radium-226. Selection of the appropriate nuclide for the particular NORM samples allows the user to set PASS/FAIL criteria is summarised as follows.
Table 4 – Alarm options when using Bq/cm2 for NORM assessment
Operating mode Alarm type Description Bq/cm2 Level Alarm activated when Bq/cm2 exceeds user-configured level
3.2.3 Dose rate
Legislative requirements, typically in the US, require operators to assess NORM on the basis of the direct radiation dose rate which would be experienced by a worker at the nearest “accessible” location to the contaminated item. This requirement is satisfied with the Scintillation Probe which can take measurements in units of µSv/h or µR/h.
The NORM Monitor IS dose rate output is calibrated by Tracerco against a traceable Cs-137 source.
[See Section 10.3]
Table 5 – Alarm options when using dose rate for NORM assessment
Operating mode Alarm type Description Dose rate Level Alarm activated when total dose rate exceeds user-configured level Dose rate minus background Dose rate minus
Level Alarm activated when dose rate above background dose rate
exceeds user-configured level
Factor Alarm activated when a multiple of background dose rate is exceeded.
background
3.2.4 Specific activity
Specific activity in Bq/g is used as the fundamental measure of NORM activity. This measurement is performed by Tracerco in laboratory conditions using highly complex measurement instrumentation.
Contact radiation.monitors@tracerco.com for further details regarding radionuclide spectrum analysis of NORM samples.
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3.3 Background Measurement
An important aspect which the operator should consider when assessing the relative sensitivities of the two probes is the background radiation level.
The Geiger Probe will only be significantly affected by very local sources of radiation and will typically display a
very low and predictable background count rate - whether deployed onshore or offshore. A normal background count rate of less than 1 cps is typical.
The Scintillation Probe has a much greater environmental background count and can be significantly affected by
local geology. The lowest background values can be achieved in offshore or desert environments but can rise substantially onshore depending on the precise nature of the locality. The statistical uncertainty in background must therefore always be considered when determining the sensitivity of the probe to sample radiation in any given situation.
[See Section 4.7 for details on measuring and saving background radiation levels]
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4 Tracerco NORM Monitor-IS – Functional description
4.1 Handset monitor control keys
Figure 3 - Tracerco NORM Monitor–IS – key definitions
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Analogue / Digital Screen
Digital readout displays radiation levels detected by the probe in user selectable units. The LEDs provide operational status information.
Analogue dial representation provides an animated auto-ranging readout. The meter may be configured to show counts (cps or cpm), dose rate (µSv/h or µR/h) or Bq/cm
2
.
Instrument on/off key
Push key to turn the monitor power on or off.
Speaker / Alarm key
Press to silence audible clicking during radiation measurements. Extended press for 3 seconds provides entry to Alarm setting menu. [See Section 4.8]
The key is dual purpose and provides the means to decrease (-) the displayed value in the alarm or integration configuration menus.
Rate/Int./Stop key
This key allows the operator to select a measurement mode which gives a more statistically accurate result than that using the real-time rate method. When the key is pressed, the instrument will take a measurement over a pre-configured period of time (for example
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