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