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Industry : Gamma - Radiography
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Another application of radioisotopes in the manufacturing process is called gamma-radiography. This process uses gamma-ray radioisotopes to test materials for flaws such as invisible cracks, defects and occlusions in welds, etc. The advantage of gamma radiography compared to non-nuclear technologies is that gamma radiography can be done thoroughly and non-invasively (one does not have to cut the material open), as well as more rapidly and cheaply. It can even be done continuously as objects pass by on a conveyor belt.
The process is very similar to x-ray radiography in a hospital or x-ray screening of luggage at an airport. The difference is that instead of using x-rays, gamma radiography uses a source that is more penetrating, such as cobalt-60, and that is portable and easy to use. X-ray sets can only be used when electric power is available and when the object to be x-rayed can be taken to the x-ray source and radiographed. Radioisotopes have the supreme advantage in that they can be taken to the site when an examination is required, and no electric power is needed. All that is needed to produce effective gamma rays is a small pellet of radioactive material in a sealed titanium capsule. The capsule is placed on one side of the object being screened, and some photographic film is placed on the other side. The gamma rays, like x-rays, pass through the object and create an image on the film. Just as x-rays show a break in a bone, gamma rays show flaws in metal castings or welded joints. The technique allows critical components to be inspected for internal defects without damage and in place.
Because isotopes can be transported easily, gamma radiography is particularly useful in remote areas where, for example, it has been used to check welds in pipelines that carry natural gas or oil. Where a weld has been made, special film is taped over the weld around the outside of the pipe. A machine called a "pipe crawler" carries a shielded radioactive source down the inside of the pipe to the position of the weld. There, the radioactive source is remotely exposed and a radiographic image of the weld is produced on the film. This film is later developed and examined for signs of flaws in the weld.
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