Answer to Question #608 Submitted to "Ask the Experts"

Products that contain radioactive material (radionuclides):

Just about everything that you can imagine is radioactive—the question is "how radioactive." One possible way to answer your question is to restrict the answer to commonly encountered products that are radioactive enough to produce an audible response with a simple survey instrument (such as a hand-held Geiger Mueller detector). The background count rate of a survey instrument usually has to double before the increase is easily discernible. Note that the use of licensed radioactive sources is very common in industry but we will only consider "radioactive" products used by the public that are commonly available and are being manufactured today.

Smoke Detectors—Many smoke detector designs utilize an americium (²⁴¹Am) source. The alpha radiation from the americium ionizes the air inside the device and makes the air conductive so that a current will flow between two electrodes. Smoke reduces the conductivity of the air and the resulting decreased current sets off the alarm.

Gas Lantern Mantles—Many gas lantern mantles of the sort used by campers contain thorium (²³²Th). When heated by the gas flame, the thorium emits light.

Welding Rods—Some welding rods include radioactive thorium (up to a few percent). The addition of the thorium produces a better weld between certain types of metals.

Products that contain high levels of potassium (potassium is naturally radioactive) are often easily detectable, e.g., many types of glass, low-sodium salt (e.g., Nu Salt), fertilizer, de-icers, etc.

Wristwatches—Some wristwatches contain a radioluminescent source such as tritium (³H) or promethium (¹⁴⁷Pm). The tritium cannot produce a detector response but the ¹⁴⁷Pm can to some degree. If the watch is using a radioactive material as the light source, the intensity of the glow will remain constant overnight.

In the past, many more consumer products were available that were measurably radioactive (e.g., ceramic dishes such as Fiesta red, false teeth, camera lenses, static eliminators). A special category of such products were the radioactive quack cures that were primarily sold in the first half of the 20^th century—many were extremely radioactive. Examples of these can be seen at the Radioactive Quack Cures Web page.

Products that emit electronically generated x rays:

At one time, television sets emitted enough radiation to be easily detected. Modern designs do emit x rays but to a much lesser extent. There is very little published information about this subject that is easily obtainable. Perhaps the most comprehensive single source is a publication written by Bill Kolb, with a little assistance from me. Ordering information can be found at the Atomic Rocks Collectables Web page. Perhaps the best, and most easily available, "official" source of information is NCRP Report 95 "Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources." Ordering Information can be found at the Instructions for Purchasing NCRP Publications Web page.

Paul Frame, CHP, PhD