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Industry : Use of Tracers
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Radioisotopes can also be used as tracers not just in medicine, but also in industry. These radiotracers emit gamma rays and/or beta particles that can be detected and measured by a variety of different counters -- either in situ or from samples in labs. By proper analysis the quantity of the tracer can be determined at any point in a pathway through which it is traveling. The tracers used are specific to the use.
For example, one wouldn't want a long-lived tracer to measure pollution in a stream that only took a day to empty into the river. On the other hand, one might be interested in longer-lived species if one was also interested in how plants along the way took in the fluids and in what happened to them as a consequence. The activity selected would also depend on the decay time because you still need to take accurate measurements later in time. Then from a combination of the original characteristics of the tracer and its dilution and elapsed time and quantity of the measured sample, the absolute origin and time-of-passage are easily identifiable.
The radiotracers can be applied in different ways:
- Mixing efficiency of industrial blenders can be measured: radiotracers are added to various solutions that are to be mixed together to allow the manufacturer to determine when his mixture has reached uniformity.
- Radiotracers are used to trace down sources of pollution. For example, if one injects a known amount of radioactive tracer at a source of pollution (say at an outflow from an industrial plant or even a point of soil wash into a stream), its pathway downstream can be identified. In this way, it might be found that the industrial plant was the culprit for pollution washed ashore miles away, or (equally likely) that that particular pollutant came from a different source. Similarly, looking at soil washed into streams, it would be possible to determine which farmer (or even which cows) where the culprits by using different tracers. In the old days a colored dye might be used as an indicator, but no accurate measurements could be taken.
- Small leaks can be detected in complex systems such as power station heat exchangers or oil pipelines in a refinery.
- Flow rates of liquids and gases in pipelines can be measured accurately, as can the flow rates of large rivers.
- The extent of termite infestation in a structure can be found by feeding the insects radioactive wood substitute, then measuring the extent of the radioactivity spread by the insects. This measurement can be made without damaging any structure as the radiation is easily detected through building materials.
- Using tracers, research is conducted to examine the impact of human activities. The age of water obtained from underground bores can be estimated from the level of naturally occurring radioisotopes in the water. This information can indicate if groundwater is being used faster than it is being replenished. Tracer radioactive fallout from nuclear weapons' testing in the 1950s and 1960s is now being used to measure soil movement and degradation. This is assuming greater importance in environmental studies of the impact of agriculture.
- Radioisotopes are used to test material parts and products such as metals, tire rubber, and engine oil for wear. Radioisotopes are added to these products, and then with the use of sensitive radiation detectors, the location and amount of wear of these products is determined. These tests help the manufacturer to produce the best quality and most reliable products.
- In agricultural laboratories, radioisotopes are used to determine how plants take up nutritional materials or fertilizers to improve the efficiency. In the past, the improvement of plant species took several plant generation times as those with good characteristics (say, disease resistance, or nutritional value, or smell -- in herbs) were weeded out and propagated in favor of those with poor characteristics. Now by use of radioactive labeling, it is possible to shorten the time considerably and even arrange that a plant be generated with all the desirable characteristics (both disease resistance and oil flavor in the case of the peppermint plant).
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