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Tracing How Radioactive Materials Are Used in Research

Betsy Ullrich
Sr. Health Physicist
Region I

scientistScientists have been using radioactive materials in research nearly as long as they’ve known there were radioactive materials.

Most radioactive materials are used in research as “tracers.” A radioactive element is attached to a compound in order to see what happens to the compound. In other words, the radioactive material is used to “trace” what happens to the compound. Making the compound with the radiotracer is referred to as “labeling” or “tagging” the compound.

Let’s suppose a scientist is developing a new pesticide for treating crops. In order to understand what happens to that pesticide, the scientist uses tritium to label the compound. The atom of tritium will replace one of the normal hydrogen atoms on that compound. Then the pesticide labeled with the tritium tracer will be applied to a plant in a greenhouse. Samples of the leaves, roots and soil will be collected periodically and tested to see whether there is tritium in the samples.

Then the scientist will know whether the pesticide stays on the leaves, is absorbed into the plant, or gets into the soil from the plant roots or from being washed off the leaves during watering (in a laboratory setting).  

By far, the most frequently used radionuclides for research are carbon‑14 (C14), tritium (H3), iodine‑125 (I125), phosphorus‑32 (P32) and sulfur‑35 (S35), which have low enough energies to be easily shielded with thin plastic. I125 emits low-energy gamma radiation which also is easily shielded by plastic or glass.

Only very small quantities of these radionuclides are used, usually measured in microcuries or nanocuries. Because it’s gotten more expensive to use and dispose of radioactive materials, scientists have developed alternate testing methods for many studies. However, some research still requires radioactive materials because they’re the best way to label and trace a compound.

The use of radioactive materials in research requires a license from the NRC or an Agreement State, and scientists who use radioactive materials are trained in radiation safety and their research methods.

One response to “Tracing How Radioactive Materials Are Used in Research

  1. CaptD July 1, 2014 at 1:01 pm

    “Tracing” radioactive tracers is probably what the NRC does best, since it creates a paper trail that can be examined and verified as being accurate. As detectors get more sensitive, I look for the use of ever smaller amounts of radioactive tracers being used, especially in medicine, which will mean that even less is washed down the drain and/or listed as wasted.

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