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Types of Exposure Devices

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1 Types of Exposure Devices
Day 5 – Lecture 4

2 Objective 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.

3 Contents 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

4 Types of Operation Category I
the source is not removed from the exposure device and a shutter or other mechanism is used to expose the source. 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

5 Category I Devices The source does not leave the device.
It has a shutter mechanism. The source may be moved to the expose position by vacuum or air pressure.

6 Category II Devices 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.

7 Category X Devices Are used for special applications i.e. gamma crawlers in pipelines. Their design and test requirements are dependent on the specific device application.

8 Gamma Radiography – Projector Type Equipment
Simple drawing of an example of the principals of projector type equipment

9 Gamma Radiography - Principles of Use
Gamma radiography source containers: 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.

10 Portable Devices can be carried by one person; < 50 kg;
are the most common type used; typically contain 192Ir in activities up to 3.7 TBq

11 Gamma Radiography Equipment Standards
ISO for devices and some ancillary equipment ISO 2919 for sealed sources IAEA SSR-6 for transport of radioactive packages 1 International Standards Organization

12 Mobile Devices usually on a cart or trolley for ease of movement;
typically contain 60Co

13 Fixed Devices used in one location; are heavy;
may use TBq 60Co

14 General Design Requirements
Radiation levels (for user safety, particularly with portable devices, and transport). 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).

15 Tests for Source Containers
“General” Conditions The device is to be fully operational after each test shielding efficiency test; vertical shock test; horizontal shock test; endurance test. “Accident” Conditions The device need not be operational after test 9m drop test; 1m puncture bar drop test.

16 Maximum Rated Capacity
Shielding Efficiency Dose Rates (µSv/h) at the Device’s Maximum Rated Capacity Device Type at 1 m at surface at 5 cm Portable 20 AND EITHER 2000 OR 500 Mobile 50 1000 Fixed 100

17 Sealed Source Construction
Sealed capsule. ISO 2919 design and tests. Special form design and test. Leak test by user.

18 Source Assemblies Source capsule crimped on wire.
Wire can be teleflex, aircraft or shielded links. Connector styles. Endurance and tensile tests.

19 Usable Steel Thickness (mm)
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

20 Ancillary Equipment Control cables Typical length 7.6 m
Projection sheaths Typical length 2.1 m Collimators HVLs typical Specialized source stops Detachable, probes Magnetic clamps for large tanks, vessels

21 Remote Controls ISO 3999. Typical construction and lengths.
Stop spring at end. Other types of construction that do not meet ISO 3999.

22 Projection Sheaths and Stops
Typical construction ISO 3999 tests. Other types of sheaths. Source stops. Specialized source stops, i.e. jet engine probes.

23 Collimators Usage. General types.
Construction of lead, tungsten or uranium. Directional or panoramic. Application of ALARA.

24 Source Changers Source changers:
are used to allow field transfers of an old (decayed) source for a new source; 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.

25 Source Changers (cont)

26 X-ray Equipment May be panoramic or directional

27 X-ray Equipment Controls
Control panel interlocks. warning systems. key switch to operate; removed when not in operation.

28 Less Common Equipment Pipe Crawler devices.
Accelerators, cyclotrons and betatrons. Neutron radiography.

29 X-ray Equipment X-ray equipment must:
meet national requirements for electrical safety; 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.

30 Pipe Crawler X-ray Equipment
Used to radiograph pipe welds with the x-ray equipment inside the pipe. Travels under its own power

31 Pipe Crawler X-ray Equipment (cont)
Utilizes an external radiation source to provide stop / go information.

32 Pipe Crawler X-ray Equipment (cont)

33 Accelerators, Cyclotrons
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.

34 Accelerators – mobile or fixed

35 Accelerators – mobile or fixed (cont)

36 Accelerators, Cyclotrons

37 Betatrons Can be portable. New safety considerations.

38 Neutron Radiography Neutrons either source or accelerator produced.
Will penetrate heavy metals and hydrogenous materials. Mostly used in research applications. Typical isotope is 252Cf.

39 Real Time Radiography 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.

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