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Radioactive Tracers

Radioactive isotopes or radio – isotopes can be made by bombarding materials inside a nuclear reactor. They have many uses.

  • Radioactive fertiliser can be fed to plants. As the fertliser is used by the plant, the radioactivity can be traced. The data is used to make better fertilisers.

  • People may be given tracers to find the sites of blockages in the body. If it is suspected that a patient has a blocked kidney, a small amount of iodine – 123 is injected into the patient. The iodine should be extracted from the bloodstream within five minutes and appear in the bladder within twenty minutes. The most common tracer is Technetium – 99. It only emits gamma rays, which almost all escape from the body, and this, together with its half life of only six hours, makes it a safe radioisotope. The gamma rays can produce an image using a gamma camera.

  • Tracers can be used to test for engine wear. The pistons are made from radioactive material. When the engine is run, if there is excessive wear, the oil will be made radioactive as it circulates through the engine. Different designs of piston, different oils, different running temperatures... a whole range of materials and conditions can be tested to find the optimum combination.

  • Buried pipelines can be tested for leaks using a diluted solution of the isotope. If the pipeline has a crack, some of the solution will leak into the surrounding soil and this will lead to an enhanced level of radioactivity. This technique can save the expense of digging up miles of pipeline. An isotope is chosen that has a short lifetime and that emits beta rays. If an alpha emitter were used, the particles would all be absorbed by the soil, and if a gamma emitter were used, they rays would virtuall all pass through the metal, so there would be no difference in the strength of the signal between the region of a crack and the surrounding areas. The isotope is chosen to have a short half life, so that no radioactivity remains after the leak has been investigated.

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