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The Bad Stuff: Ingested Radionuclides

The information given above would seem to indicate that medical X-rays were the worst radiation hazard around, except for natural sources we can't do much about. Unfortunately this is a distortion based on the difficulty of measuring the most dangerous kind of radiation: $\alpha$-emitting radionuclides (radioactive isotopes). Many heavy elements have isotopes which naturally fission into lighter elements plus a helium nucleus, with the latter being emitted with a substantial kinetic energy as an alpha ``ray.'' The range of most $\alpha$ particles is only a few cm in air and less than a mm in tissue, so the damage they cause is localized. While this may be reassuring when the isotopes are at arm's length, it can be bad news if you have breathed them into your lungs or swallowed them so that they can collect in your bones, where they can do the most damage! Since there is such a wide variety of radioactive elements with assorted chemical properties, it is wise to be aware of the specific hazards associated with each. I have neither the expertise nor the space to provide a comprehensive survey here, but I can mention a few of the most common culprits.

It is important to note that the food chain may serve to concentrate ``harmless'' levels of radionuclides in (e.g.) sea water to a level which is worthy of our concern. Were it not for this effect, and the fact that the waste products of nuclear fission include a large variety of radionuclides with various chemical properties that naturally occurring isotopes do not exhibit, it would be a sensible strategy to dispose of radioactive waste by diluting it and spreading it far and wide in the oceans - since the net radioactivity of reactor fuel actually decreases in the process of digging up the uranium, burning it in a reactor and storing the spent fuel rods for 10 years until the short-lived isotopes decay away. Because of the biological concentration effect, however, it is wiser to seek safe long-term containments for radioactive waste.


next up previous
Next: Protection Against Radiation Up: Radiation Hazards Previous: Sources of Radiation
Jess H. Brewer
1999-11-05