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Industrial radiography


Industrial radiography entails the use of powerful radiation sources, often in open industrial premises or outdoors. Undertakings engaged in industrial radiography are therefore subject to specific requirements and official approval in accordance with the Regulations on Radiation Protection, §5.

Non-destructive test methods
Industrial radiography is  a method for Non Destructive Testing, or NDT; that is, the material qualities of an object can be examined and studied without destroying the object.

Photographing the object with the help of x-rays or gamma radiation makes it possible to discover different material defects such as poor welding seams or cracks. The method resembles medical use of x-rays to discover bone fractures.

The picture below shows a typical situation in radiography where a gamma source is being used to inspect a welded seam on a pipe. There are about 100 companies in Norway authorised to carry out industrial radiography.
Illustration of industrial radiography.
Radioactive sources and physical protection
In gamma radiography, the radiation comes from a radioactive source, such as Iridium-192, for example. The radioactive source is placed in a portable protective container during storage and transport, as shown in the picture. When in use, the source can be pushed forward to the radiating position with the help of a mechanical crank. After use, the source is then returned to its shielded position.

Industrial radiography usually has to be carried out outdoors or within shielded enclosures, as shown in the figure. The surrounding area must then be cordoned off and the dose rate outside the barred area should not exceed 7.5 µSv/hour. The dose rate is controlled by the operators through the use of a hand monitor. In order to meet the barrier requirements, it is essential that the primary beam from the radioactive source or x-ray machine is shielded, because of the high radiation intensity in the beam. There will be radiation also in the area immediately outside the primary beam, and this is known as scattered radiation or secondary radiation. However, the intensity of this radiation is much lower, on the order of 1/1000 the intensity of the primary beam.

A radioactive source can never be turned off; hence, upon the completion of exposure, the source must be redrawn into its shielded container. The operator must them check with the hand monitor that the source is safely back in its shielded position. An x-ray machine on the other hand ceases to emit radiation once the power has been shut off, and hence does not need any kind of protective shielding.

Gamma radiography equipment. Photo: NRPA.

Requirements for approval and certification
Industrial radiography entails the use of powerful radiation sources, often in open industrial premises or outdoors. Undertakings engaged in industrial radiography are therefore subject to specific requirements and official approval in accordance with the Regulations on Radiation Protection, §5. The standard application form for approval of industrial radiography activities may be downloaded from NRPA’s web pages. Note that section 1 and section 2 must both be filled out and sent in.

The letter of approval may also contain additional concrete requirements and specific conditions concerning equipment, competence, reporting, and so on, as specified in the regulations. See the following for the concrete requirements that are usually set in the letter of approval:
  • Requirement of two (2) certified operators for industrial radiography carried out outside shielded enclosures. This means that the operators must be in possession of a radiation protection certificate issued by NRPA (old system), or by an accredited personnel licensing agency (new system).
  • Requirement of annual maintenance of gamma radiography equipment, to be carried out by an authorised dealer or servicing company. 
  • Requirement of maximum source activity limits as follows:
    Co-60:  400 GBq
    Ir-192: 1500 GBq
    Se-75:  3000 GBq