1. Safety Procedures in Nuclear Gauging

2. Content Introduction Nuclear Gauging System X-ray Analyzer
Safe Handling of Nuclear Gauges and X-ray Analyzers

3. Introduction Nuclear gauging consists of:
Nuclear gauging system
X-ray analyzers
These techniques are widely used in industry and analytical laboratory.
Is used for analyzing, processing and manufacturing materials/products.

4. Nuclear Gauging System
The system involves with the use of ionizing radiation and can be hazardous.
Advantages over conventional techniques:
No contact with material being measured/ process.
Non-destructive.
Can be made on-line.
Good accuracy and long term stability.
Simple installation with minimum interruption to operating system.

5. Nuclear Gauging System
Basic principles and techniques
Nuclear gauging is a technique for:
Checking
Testing
Inspecting a system
Processing; and
Manufacturing a product
When radiation passes through a material, it loses energy and partly absorbed.
The amount absorbed depends on:
Thickness, atomic number and density of the material.
Energy of the radiation.

6. Nuclear Gauging System
The transmitted radiation is reduced in intensity and energy.
Its intensity can be calculated by:
Some portion of the radiation can also be reflected and backscattered.
The reflected and backscattered radiation also loses energy and intensity.

7. Nuclear Gauging System
The intensity of reflected and backscattered radiation can be calculated by:
The radiation can also react with a material and produce secondary radiation.
These three principles of interactions form the basic principles of a nuclear gauging operation:
Transmission gauge
Back-scattering gauge
Reactive gauge

8. Nuclear Gauging System
Transmission gauge
Backscattering gauge
Reactive gauge

9. Nuclear Gauging System
A nuclear gauge is usually addressed based on:
Its function e.g. thickness gauge, level gauge, density gauge.
Its principle of operation e.g. transmission gauge, backscattering gauge, reactive gauge.
Its source of radiation e.g. beta gauge, gamma gauge, neutron gauge.

10. Nuclear Gauging System
Application of Nuclear Gauges
Level gauge:
The most popular application in industry.
Used to check or measure the maximum and/or minimum level of liquid in containers, vessels, bunkers and pipes or the level of container filling.
It usually works on transmission principle using a gamma source with one or more detectors.
More radiation is absorbed/scattered when pass through the materials which distinguish the presence of its level.
Additional neutron source is sometimes used.
Examples are gauges used to monitor molten steel and to monitor filling of liquid into bottles or cans.

11. Nuclear Gauging System
Thickness gauge
Density gauge
Level gauge

12. Nuclear Gauging System
Basic components of a nuclear gauge
A nuclear gauging system consists of:
An electronic signal processor
A radiation detector
A radiation source
A source housing

13. Nuclear Gauging System
Radiation source:
Can be in the form of radioactive sealed source or irradiating apparatus.
Use to produce radiation required by the system.
Its choice depends on:
Availability.
Cost.
Half-life; long enough to cover useful life of device and to minimize source changes and system inaccuracy.
Type of radiation.
Energy of radiation.

14. Nuclear Gauging System
Type and energy of radiation is determined by the material to be processed:
Low energy for low density; or
Thin layer materials and vice-versa.
The most commonly used gamma sources in transmission and back-scattering gauge are:
Am-241 for low energy;
Cs-137 for medium energy; and
Co-60 for high energy.
The most commonly used beta sources are:
Ni-67 and Pm-147 for low energy;
Kr-85 for medium energy; and
Sr-90 and Ru-106 for high energy.

15. Nuclear Gauging System
The reactive gauge typically uses Fe-55, H-3, Pu-238 and Am-241.
Activity used varies as in table.
Gauges Type
Gamma Sources
Beta Sources
Neutron Sources
Transmission Gauge
Vary between GBq
Between 40 MBq - 40 GBq
Am-Be with activity within GBq
Back-scattering Gauge
Vary between GBq
Between MBq
Reactive Gauge
Utilizes sources within 200 MBq - 40 GBq
To 40

16. Nuclear Gauging System
Source housing is to provide:
Shielding to attenuate radiation from the source.
Protection and security of the source.
Enhancement of performances.
Safe handling of the source during transportation, storage, installation, source replenishment and maintenance.

17. Nuclear Gauging System
The most common detectors used are ionization chamber and GM detector:
Both are rugged, stable and relatively inexpensive.
Both can be used with practically all types of radiation sources i.e. alpha, beta, gamma, x-rays and neutrons sources.
GM detectors are good for low counting rate because of its high dead time.
Ionization chambers are good for high counting rate because of lower sensitivity.

18. Nuclear Gauging System
Radiation detector
Used to convert radiation produced by the source into a series of electronic signals.
Similar to the detector used for radiation protection.

19. Nuclear Gauging System
Should have the following characteristics:
Good stability
High efficiency
Ruggedness
Energy independence
High resolving power and low cost
Scintillation detectors and proportional counters are used for radiation spectroscopy measurements and they are more efficient in detecting gamma and x-rays.

20. Nuclear Gauging System
Electronic signal processor
Consists of:
High voltage
Preamplifier
Main amplifier
Discriminator (selector)
Scaler / ratemeter

21. Nuclear Gauging System
Electronic signal processor
It is required for:
Supplying high voltage to the detector.
Amplifying the detector’s signals to a certain level.
Registering, analyzing and presenting the detector’s signals.

22. Nuclear Gauging System
Application of nuclear gauges
Level gauge:
The most popular application in industry.
Used to check or measure the maximum and/or minimum level of liquid in containers, vessels, bunkers and pipes or the level of container filling.
It usually works on transmission principle using a gamma source with one or more detectors.

23. Nuclear Gauging System
Level gauge:
More radiation is absorbed/scattered when pass through the materials which distinguish the presence of its level.
Additional neutron source is sometimes used.
Examples are gauges used to monitor molten steel and to monitor filling of liquid into bottles or cans.

24. Nuclear Gauging System
Density gauge:
Use to measure density of materials.
Use in a broad range of industries e.g. gas/oil production, chemical and hydrocarbon processing, pulp and paper mill, mining and food industry.
It works on transmission principle utilizing a gamma (Cs-137 or Co-60) or a beta source (Sr-90) with one or more detectors.
Higher density materials attenuate more radiation and the reduction is proportional to the density.

25. Nuclear Gauging System
Thickness gauge:
Used to measure thickness of a material or a coating material.
It works on transmission principle using a gamma or a beta source.
Also works on backscattering principle using a beta source or reactive principle using a low energy gamma source.
Thicker materials attenuate or scatter more radiation and the reduction is proportional to the thickness.

26. Nuclear Gauging System
Moisture gauge:
Used to measure moisture content of bulk materials e.g. soil, sand, concrete, lime and coke.
It works on transmission or backscattering principle using a neutron source or both neutron and gamma source.
It works based on thermalization of fast neutrons by water molecules contained in the material.
Higher water content (higher moisture content) will thermalize more neutrons.

27. Nuclear Gauging System
Weighing gauge
Used to transport or measure mass flow of materials in a process line e.g. conveyor belts, screw conveyors, drag chain conveyors and apron conveyors.
It works on transmission principle using a gamma source.
Thicker materials attenuate more radiation.

28. Nuclear Gauging System
Oil logging:
Used to measure lithology, density and porosity of geological formation deep underground around prospected oil reservoir.
It works on backscattering principle of gamma or neutron radiation using one or two detectors.
The radiation is backscattered by geological formation and detected by the detector(s).

29. Nuclear Gauging System
Safety feature of a nuclear gauge:
Radiation source:
Should be properly selected in term of activity, half-life, radiation type and energy according to application.
The half-life should be as short as possible and not greater than the useful life of the system.

30. Nuclear Gauging System
Safety feature of a nuclear gauge:
Radiation source:
Should be of the lowest activity, radiotoxicity and energy.
Should be in solid form and preferably in special form to minimize leakage and contamination.
Should be designed, manufactured and tested according to recognized standards and accompanied by certificate as an evidence/proof.

31. Nuclear Gauging System
For a movable source:
It need to be placed in a source assembly to prevent loss, dislodgement or accidental removal.
The source assembly should not be capable of being physically separated from the source housing under normal operational, transport or storage conditions.
The source assembly and retraction mechanism should be designed non-fouling and jam-proof.

32. Nuclear Gauging System
Source housing:
Should be designed, manufactured and tested according to recognized standards.
Should be designed and manufactured with adequate shielding for the activity and type of source involved.
The leaked radiation should meet the dose rate criteria approved by AELB.
The design should take into consideration requirements for safe storage and transport of the source.
The shielding should be designed and manufactured to withstand all conditions encountered during use, storage and transportation.

33. Nuclear Gauging System
Source shutter:
Should be provided to the source housing.
Should be capable of cutting the radiation down to a permissible safe level.
It should be clearly and unambiguously indicated when it is OPEN/ON or CLOSE/OFF.

34. Nuclear Gauging System
Source lock:
Should be provided to the source housing and able to lock the source/source assembly when in CLOSE/OFF position.
It should be an integral part of the gauge and should not easily be tampered with.

35. Nuclear Gauging System
Warning sign and label:
The gauge should be labeled with a durable label incorporating the following information:
Name of source material
Activity of the source and date of measurement
Maximum dose rate on the surface when the source is in CLOSE/OFF position and date of measurement
Name and address of supplier/manufacturer
Identification number of the container
Radiation sign

36. X-Ray Analyzers
X-ray analysis is another technique used in modern industry and research for analyzing materials or products.
It works based on x-rays produced by an irradiating apparatus or a sealed radioactive source.
They are available either in the form of:
Enclosed devices
Partly enclosed devices or
Devices without any enclosure
Enclosed or partly enclosed devices ensure no possibility of inadvertent exposure to the X-ray beams.
Devices without enclosure should be operated in a specially designed and shielded exposure room.

37. X-Ray Analyzers Basic principles and techniques:
When X-rays interact with a material, they will be scattered, absorbed or diffracted.
The scattered X-rays can lose or change their energy after the interaction.
Diffraction is usually caused by crystal lattice and it, therefore, occurs if the material involved is of crystalline nature.

38. X-Ray Analyzers
The absorbed X-rays are potential to produce characteristics X-rays through ejection and rearrangement of electrons in the orbits.
Characteristic x-rays are unique for each element.
X-ray analyzer is used to identify unknown element present in a material or to measure thickness of an element in a material. This forms the basic principle of X-ray fluorescence (XRF).
Monochromatic X-rays can interact and be scattered by lattices of crystalline materials.

39. X-Ray Analyzers
X-rays will be diffracted by the materials only if they satisfy the following relationship:
sin  = n sin  - angle of incident to the
2d target material
d - inter-atom spacing of the lattice
 - x-rays wavelength and
n - an integer
The scattered X-rays are then measured to indicate the lattice pattern of the material and this form the basic principle of X-rays diffraction (XRD).

40. X-Ray Analyzers Basic components of an X-ray analyzer: X-ray tube:
Is the part of the device that generates x-rays.
It is similar design to x-ray tubes used in other applications except that the voltage and current applied is different and fixed according to applications.
Tube housing:
The x-ray tube is enclosed in a tube housing.
It is used to minimize leakage of the radiation and to provide protection of the x-ray tube against physical damage.
It is usually wholly or partially enclosed in interlocked barriers or shield to provide further protection.

41. X-Ray Analyzers Radiation detector:
It is used to convert the transmitted or reflected x-rays into a series of electronic signals.
Similar to the detector used for radiation protection i.e. either a GM detector, an ionization chamber or a proportional counter or a scintillation counter.
Should have the following characteristics:
Good stability
Ruggedness
Energy independence
High efficiency
High resolving power and low cost

42. X-Ray Analyzers Electronic signal processor: Consists of:
High voltage
Preamplifier
Main amplifier
Discriminator (selector)
Scaler / ratemeter
It is required for:
Supplying high voltage to the detector.
Amplifying the detector’s signals to a certain level.
Registering, analyzing and presenting the detector’s signals.

43. X-Ray Analyzers Application of X-ray analyzer:
There are two types of X-ray analyzer:
X-ray fluorescence (XRF)
X-ray diffraction (XRD)

44. X-Ray Analyzers Application of X-ray analyzer:
X-ray fluorescence (XRF):
Widely used in electronic industry, petroleum industry, cement factory, tin smelters, aircraft maintenance and research laboratories.
Used to determine or analyse thickness of platting or coating materials, chemical content and composition of a material.
Can be used on materials, such as, rock, mineral, powder, metal, paper, plastic, and petroleum products whether they are in the form of solids, liquids or thin films.

45. X-Ray Analyzers Two types of XRF: Energy-dispersive:
In energy-dispersive XRF, identification of an element is by means of its energy line.
Wavelength-dispersive:
In the wavelength-dispersive, the element is identified from its wavelength property.

46. X-Ray Analyzers XRF advantages over conventional methods of analysis:
It is non-destructive.
It requires minimum preparation with little or no pre-treatment.
It offers fast analysis of the material. Chemical composition of a material can be determined in seconds.
The device is easy to use and user friendly. It can be in portable form and easy to carry.
It has an excellent accuracy and precision of the analysis.

47. X-Ray Analyzers Disadvantages of the XRF:
It is not suitable for analysing very light elements, such as, hydrogen, helium and lithium.
It is not as sensitive as some other techniques, such as, neutron activation analysis (NAA) and inductive couple plasma (ICP). The detection limit varies according to elements (depend on atomic number).
The device is also known to have suffered from matrix effect.

48. X-Ray Analyzers X-ray diffraction (XRD):
Used in the analysis to identify and quantify crystalline materials and crystallite size of the materials.
It provides means to gather information on physical properties of metals, polymeric materials, natural products and other solids.
Used in industry to analyse ceramic materials and ores and in research laboratories for studies in geology, physics, environment, mineralogy, metallurgy and chemistry.

49. X-Ray Analyzers Safety features of X-ray analyzers: Tube housing:
Should be interlocked to the X-ray tube so that removal of one from the other or any part of the housing will immediately de-energise the X-ray tube.
Should be made of material of sufficient strength and thickness to ensure that it cannot easily be fractured or deformed under normal use, accident or misused.
The radiation dose in one hour on the surface for any permissible operation should not exceed those specified by the manufacturer and/or standards recognised by the AELB.

50. X-Ray Analyzers Tube shutter:
Should be available as part of the tube housing to cut out the radiation beam when the device is not in use.
Should be interlocked with the tube housing so that their removal will de-energise the X-ray tube.
Should be designed and constructed that the scattered and leakage radiation dose in one hour on the surface of the housing for any permissible operation should not exceed those specified by the manufacturer and/or standards recognised by the AELB.
The shutter should be fitted with a positive closing device.

51. X-Ray Analyzers Enclosure of X-ray analysers:
Should be available as an additional protection to the tube housing.
Should be attached or interlocked with the X-ray tube or the tube housing so that the device is de-energised in case of detachment.

52. X-Ray Analyzers Beam stopper:
Used to catch the primary X-ray beam if the material to be analysed is not available when the device is ON.
Should be fixed to the X-ray unit.
Should be placed close to the aperture of the tube housing to attenuate the dose to below the limit specified.
Should be interlocked with the X-ray tube so that removal of the unit immediately de-energises the X-ray tube or closes the shutter.

53. X-Ray Analyzers Warning lights, signs and labels:
The X-ray analyser should have an illuminated sign or a combination of a sign and a light, which is activated only if the X-ray tube is energised.
The sign should be legible and readily discernible for at least two metres from the analyser.
There should also be a sign to indicate the condition of shutter, which should illuminate only when the shutter is OPEN.

54. X-Ray Analyzers
Room, cubicle or area in which an x-ray analyser is operated should have at the entrance an illuminated sign or a sign combined with a light, which is activated only when the X-ray tube is energised to indicate that the X-ray tube is operating.
The lights provided to indicate operation of the X-ray tube should be fail-safe or provided with a warning to indicate its failure.
Each X-ray analyser should be clearly labelled to indicate whether it is an enclosed or a partly enclosed unit.

55. X-Ray Analyzers
Partly enclosed devices should be designed to give a clear and positive warning if the barriers or shields are incomplete or removed.
A clear and unambiguous notice should be displayed on or near the device to indicate the hazard if barriers or shields are incomplete or removed.
Partly enclosed devices should have displayed on or near them a prominent notice that warns users of the hazard of placing any part of the body inside the barriers or shields.

56. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Classification of work area:
The work area where a nuclear gauge/X-ray analyser is to be installed or operated should be classified.
It is important in the case of portable devices where the operation has to be carried out in an open field and for certain type of devices where the source has to come out of its shielded housing during operation.

57. Safe Handling of Nuclear Gauges and X-Ray Analyzers
The area should be classified into:
Clean
Supervised
controlled
The radiation level present in most of the areas around nuclear gauges/X-ray analysers is usually very low and could be classified as a supervised area.
The necessary requirements for the supervised and controlled areas e.g. warning signs, radiation signs, personal dosimeters, and control of personnel entering the area must be observed and provided accordingly.

58. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Working procedures for nuclear gauges and X-ray analyzers:
The procedures are very important to ensure that personnel involved are carrying out their work in a systematic and safe manner.
They form part of a good working practice (GWP).
The procedures should be prepared in a form and language easily understood by the workers involved and made known to all of them.

59. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Operating procedures for a nuclear gauge with a radioactive source shall cover:
Proper handling of a nuclear gauge to minimize exposure and damage during handling.
The following are typical handling procedures:
The nuclear gauge should be handled in such way that its location is known all the time through a proper inventory and records.

60. Safe Handling of Nuclear Gauges and X-Ray Analyzers
The device should be handled by authorised and trained personnel.
The device should be used or operated in a classified area.
All workers must put on protective devices and a dosimeter.
Eating, smoking and drinking should not be allowed in the classified area.
The device should be switched OFF and the shutter CLOSED and LOCKED before doing any maintenance.
The protection principles of shielding, time and distance (STD) should be applied all the time.

61. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Operating procedures for a nuclear gauge with an X-ray unit or an X-ray analyzer:
Some of the operating procedures for sealed sources can also be used for handling a nuclear gauge with an X-ray unit or an X-ray analyser.
The followings are typical procedures for safe handling of the device:

62. Safe Handling of Nuclear Gauges and X-Ray Analyzers
The device should not be operated when any part of its in-built safety system or housing is removed.
There should be an interlock system in place to prevent operation without housing.
Any changes or adjustment to be made on the materials being processed or tested should be carried out only when the device is OFF.

63. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Working procedures for field work:
A nuclear gauge should be operated and used in an established area with the necessary safety infrastructure and facilities.
Some applications requires utilisation of a portable nuclear gauge to be operated in an open field. Such operation requires more stringent set of procedures to ensure safety.

64. Safe Handling of Nuclear Gauges and X-Ray Analyzers
The followings are typical procedures for working with a portable nuclear gauge in an open field:
Identify a nuclear gauge that is going to be used in the fieldwork.
Make the necessary arrangements to record the source.
Make arrangement to transport it to the work site according to the Transport Regulations.
The device should be handled by authorised and trained personnel.

65. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Identify the type and number of safety devices and radiation protection equipment required at the work site.
The equipment should be tested for its proper functioning prior to departure to the work site.
A safety briefing should be given by the RPO to all workers involved before commencement of the work.
A controlled or supervised area should be established at the work site.

66. Safe Handling of Nuclear Gauges and X-Ray Analyzers
The border of the area should be clearly marked with rope and radiation warning signs and notices posted.
If working period has to be extended, a safe storage place should be identified and established.
All workers must put on protective equipment and a dosimeter provided to them.
The protection principles of shielding, time and distance (STD) should be applied all time.

67. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Upon completion of work, the device should be switched OFF and the shutter CLOSED and LOCKED before moving out of the work site.
Arrangements for transportation should be made according to the Transport Regulations.
Movement of the device should be recorded in the source inventory and the RPO is informed about the conclusion of the work.

68. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Storage:
The nuclear gauge should be safely and securely stored when not in use.
The source or source assembly of the gauge should be fully retracted and locked into the “CLOSE/OFF’ position.
The gauge should not be stored near regularly occupied areas, photographic films, explosives, combustible or corrosive chemicals.
The store should have the capability to protect and secure the device.
It should have radiation and warning signs displayed and should be locked and placed under the control of the RPO.

69. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Transport:
The nuclear gauge should be fully retracted and secured in the “CLOSE/OFF” position and confirmed by measurement before making any arrangement to transport.
An approval in the form of license Class D must be obtained from the AELB.
The device should be properly packed, packaged and labelled according to Transport Regulations before handing over to a carrier for transportation.

70. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Disposal:
When the useful life of the device is over, it has to be disposed off in an approved and safe manner.
An approval must be sought from the AELB before disposal can be carried out.
The device can be disposed of by sending it back to its country of origin, to Nuclear Malaysia or to other recognised waste disposal facilities.
Disposal must be recorded in the source inventory.

71. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Maintenance:
Regular maintenance:
It is important to be performed regularly on the nuclear gauge/X-ray analyser and its associated system to minimise downtime and chances of malfunction.
The nuclear gauge/X-ray analyser should be switched OFF and the shutter CLOSED and LOCKED before carrying out any maintenance.

72. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Maintenance should be carried out by authorised and trained personnel.
If the device cannot be turned off for maintenance, steps should be taken to avoid exposure of any part of the body to direct radiation.
The person doing the maintenance must have a dosimeter and survey meter.
The maintenance work, must be recorded in the maintenance record of the device.

73. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Calibration:
Calibration is needed because measurements are made in relative values.
It is important to use good accuracy and sensitivity instruments for measurement of radiation and personnel exposure.
The instrument should be calibrated at a recognised calibration centre.
It is important to check on validity of the calibration certificate before using the instrument.
The instrument should be sent for re-calibration once it is expired.
The calibration factor should be used in order to get the actual reading of exposure or dose of the radiation measured.

74. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Leak test of a sealed source:
It is required by the Basic Safety Standard Regulations to be performed regularly.
A sealed source shall be considered leaking if the removable activity of the test is greater than 185 Bq (5 nCi).

75. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Leak test is recommended:
before initial use;
within an interval approved by the AELB;
whenever damage is suspected; and
whenever contamination is detected.
It is conducted annually or during maintenance by an authorized and trained person.
The person must be provided with appropriate protective and monitoring devices.
Care must be taken not to damage the source while doing a leak test.

76. Safe Handling of Nuclear Gauges and X-Ray Analyzers
A sealed source of a nuclear gauge can be tested for leakage using any one of the following methods:
Wet wipe (smear) test;
Dry wipe test;
Immersion or boiling-immersion test;
Gaseous emanation test; and
Liquid scintillation emanation test.
Results of the test should be recorded in the source inventory/registry.

77. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Leak test of an irradiating apparatus:
It shall be tested for radiation leakage on the outside of tube housing, shutter and enclosure.
The radiation level measured shall meet the standards specified by the manufacturer or AELB.
The test should be carried out regularly and results are recorded in the maintenance record of the device.

78. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Radiation monitoring:
Work area monitoring:
Areas around a nuclear gauge should be checked for radiation.
Measurements can be carried out either weekly or a few times in a month.
Monitoring results should be recorded and kept for inspection by the AELB.
For portable nuclear gauge, radiation measurements must be carried out to classify the area and to ensure compliance.

79. Safe Handling of Nuclear Gauges and X-Ray Analyzers
Personnel monitoring:
Personnel involved with operation and maintenance of the device should wear a suitable personnel dosimeter.
The dosimeter and record of its results should be properly kept.

80. Summary

81. THANKS YOU FOR YOUR ATTENTION