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IAEAInternational Atomic Energy Agency
Types of Exposure Devices
Day 5 – Lecture 4
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To gain an overview of the types, designs and usage of the various types of industrial radiographic equipment including devices, sealed sources and ancillary equipment.
Objective
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• Gamma radiography devices, sources and ancillary equipment
• X-ray equipment• Pipe crawler equipment• Real time radiography systems• Accelerators (linear accelerators and Betatrons)• Neutron radiography equipment
Contents
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Category I
• the source is not removed from the exposure device and a shutter or other mechanism is used to expose the source.
Types of Operation
Category II
• the source is projected outside the shielded source container (via a wind out cable, pneumatic device, etc) through a projection sheath to the exposure position.
Category X
• special applications
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• The source does not leave the device.
Category I Devices
• It has a shutter mechanism.• The source may be moved to the
expose position by vacuum or air pressure.
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• The source is projected out of the source container.
• Remote controls are used.
• The source is unshielded during the exposure (but should be collimated when practicable).
• Manual or automatic operation.
Category II Devices
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• Are used for special applications i.e. gamma crawlers in pipelines.
• Their design and test requirements are dependent on the specific device application.
Category X Devices
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Gamma Radiography – Projector Type Equipment
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• are shielded with depleted uranium or lead;• contain the sealed radioactive sealed source in a holder;• use ancillary equipment to control the source movement;• exposes the radioactive source to produce the radiograph.
Gamma Radiography - Principles of Use
Gamma radiography source containers:
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• can be carried by one person; < 50 kg;
• are the most common type used;
• typically contain 192Ir in activities up to 3.7 TBq
Portable Devices
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• ISO1 3999 for devices and some ancillary equipment• ISO 2919 for sealed sources• IAEA SSR-6 for transport of radioactive packages
1 International Standards Organization
Gamma Radiography Equipment Standards
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• usually on a cart or trolley for ease of movement;
• typically contain 60Co
Mobile Devices
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• used in one location;• are heavy;• may use 8.5 - 37 TBq 60Co
Fixed Devices
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• Radiation levels (for user safety, particularly with portable devices, and transport).
General Design Requirements
• Lock (and source) security.
• Resistant to ingress of water, mud, sand (minimize the risk of failure of the source movement and lock mechanisms, minimize wear of the source guide tube, etc.
• Able to withstand extremes of temperature (to minimize risk of the source jamming).
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“General” ConditionsThe device is to be fully operational after each test
• shielding efficiency test;• vertical shock test;• horizontal shock test;• endurance test.
Tests for Source Containers
“Accident” ConditionsThe device need not be operational after test
• 9m drop test;• 1m puncture bar drop test.
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Shielding Efficiency
Dose Rates (µSv/h) at the Device’s Maximum Rated Capacity
Device Type at 1 m at surface at 5 cm
Portable 20AND
EITHER
2000
OR
500
Mobile 50 2000 1000
Fixed 100 2000 1000
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Sealed Source Construction
• Sealed capsule.• ISO 2919 design and tests.• Special form design and
test.• Leak test by user.
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Source Assemblies
• Source capsule crimped on wire.
• Wire can be teleflex, aircraft or shielded links.
• Connector styles.• Endurance and
tensile tests.
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Properties of Typical Sources
Isotope T1/2
Typical Activity
µGy h-1 GBq-1 at 1m
Usable Steel Thickness
(mm)
Dose rate mGy/h at
1m
192Ir 74 days 3.7 TBq 130 10 – 70 480
60Co 5.2 years 1.8 – 3.7 TBq 351 50 – 150 1300*
169Yb 32 days 0.185 TBq 34 2.5 – 15 6.3
75Se 120 days 1.48 TBq 55 4 – 28 100
* dose rate for 3.7 TBq source
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Control cables Typical length 7.6 m
Projection sheaths Typical length 2.1 m
Collimators 4-7 HVLs typical
Specialized source stops Detachable, probes
Magnetic clamps for large tanks, vessels
Ancillary Equipment
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• ISO 3999.• Typical construction and
lengths.• Stop spring at end.• Other types of construction
that do not meet ISO 3999.
Remote Controls
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• Typical construction• ISO 3999 tests.• Other types of sheaths.• Source stops.• Specialized source stops,
i.e. jet engine probes.
Projection Sheaths and Stops
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• Usage.• General types.• Construction of lead,
tungsten or uranium.• Directional or panoramic.• Application of ALARA.
Collimators
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• are used to allow field transfers of an old (decayed) source for a new source;
Source Changers
Source changers:
• typically have a depleted uranium shield;
• have a locking system to prevent the source from accidentally coming out during the transfer;
• have two or more storage cavities or tubes.
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Source Changers (cont)
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X-ray Equipment
May be panoramic or directional
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Control panel
• interlocks.
• warning systems.
• key switch to operate; removed when not in operation.
X-ray Equipment Controls
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• Pipe Crawler devices.
• Accelerators, cyclotrons and betatrons.
• Neutron radiography.
Less Common Equipment
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• meet national requirements for electrical safety;
X-ray Equipment
X-ray equipment must:
• have an appropriately labeled control panel;
• have cables (between the x-ray tube assembly and the control panel) of sufficient length. e.g. >20 m.
• have a control panel that is key operated to prevent inadvertent use.
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• Used to radiograph pipe welds with the x-ray equipment inside the pipe.
• Travels under its own power
Pipe Crawler X-ray Equipment
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• Utilizes an external radiation source to provide stop / go information.
Pipe Crawler X-ray Equipment (cont)
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Pipe Crawler X-ray Equipment (cont)
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• Use high energy x-rays.
• Can be used in large shielded enclosure for large components.
• Portable units can be brought to temporary job sites
• Additional safety precautions are necessary due to the high energy radiation produced.
Accelerators, Cyclotrons
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Accelerators – mobile or fixed
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Accelerators – mobile or fixed (cont)
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Accelerators, Cyclotrons
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• Can be portable.
• New safety considerations.
Betatrons
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• Neutrons either source or accelerator produced.
• Will penetrate heavy metals and hydrogenous materials.
• Mostly used in research applications.
• Typical isotope is 252Cf.
Neutron Radiography
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• Image from radiation is measured in real time by film, detection instrumentation or computer display.
• Used in conjunction with conveyer systems to move product.
• Typically large 60Co source or x-rays.
Real Time Radiography
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