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Industrial radiography is a method of testing for hidden flaws and defects in various types of materials with X-ray or gamma radiation. Industrial radiography is similar to medical X-ray technology in that a film records an image of an item placed between it and a radiation source. The penetrative nature of the radiation produces a clear image of the internal structure of the material with any density anomalies such as cracks being clearly visible. This "hidden view" characteristic of industrial radiography makes it a nondestructive testing vehicle to check working parts for wear and newly produced items for uniformity and possible defects. Although the radiation sources used in radiography generally pose no health risks, relevant safety measures should always be adhered to.
Hidden flaws and defects within the structure of any item are impossible to detect without invasive or destructive testing techniques or X-ray imaging. As sawing up newly welded parts to check weld integrity is somewhat counterproductive, for example, industrial radiography is an attractive choice for nondestructive diagnostics. The technology can also be used in the construction industry to locate rebar or pipes in concrete structures prior to chasing or cutting. It is even used as a security aid to scan closed containers for contraband, weapons, or stowaways.
The basic principle of the process is fairly simple and common to all radiography applications. The radiation from a controlled source is allowed to penetrate the test item and expose a specially formulated film. As the radiation passes through the item, a portion of it is absorbed by the molecular structure of the material. The amount of radiation absorbed depends on the density and composition of the material. Simply put, the amount of radiation that passes through the item to expose the film depends on the density of the material.
As cracks, fissures, and pockets in the material obviously have different densities, they will be characterized by different exposure values as more or less radiation penetrates at those points during exposure. This creates a very accurate image of the internal structure of the item. Objects placed within a closed space will also show up as anomalies when exposed to the radiation, thereby making investigative scans possible without opening a container. Industrial radiography can be used to scan a wide range of materials in this way including metals, ceramics, concrete, masonry, plastics, wood, and organic fibers.
The sources of radiation for industrial radiography depend on the process used. Betatrons and linear accelerators are typically employed for X-ray photon generation and radioactive isotopes such as caesium-137, cobalt-60, and iridium-192 are used to generate gamma radiation. Although these radiation sources are considered safe, operators should always strictly adhere to all safety measures specific to the equipment used.