Everyday radioactive sources

Please note that all radioactive materials are potentially dangerous and must be handled with some care and expertise. Please read the Safety Hints.

Radium dials

Radium dials found on old clocks/watches, and sometimes old meters. The luminous paint used on these dials contains radium to make it glow even after a long time of darkness. The use of radium in such paints was banned some deca des ago, mainly because of the danger for the workers handling it. Radium and its decay products emit alpha-, beta- and gamma radiation. The alpha part won't penetrate the frontglass. The rest is easily absorbed by a few mm metal or 2cm paper, for example. The activity of radium dials can be astonishingly high.

Luminous plastic

Some modern luminous plastics contain tritium in tiny vials. As tritium is a very weak beta emitter, this radiation is probably completely absorbed by the plastic. On the other hand, the amounts used are quite high (several MBq).

Lantern mantles

Thorium doped lantern mantles are still sold in camping supply stores, but there are also newer ones that are not active, so check before you buy. Activity and penetration power are comparable to radium dials, both alpha and beta radiation is emitted.

Smoke detectors

Ionisation smoke detectors. These contain Americium-241 (an alpha emitter), for home purposes usually 1uCi or 37kBq, which is quite a lot. Industrial units may contain even more. However, the radiation is nearly pure alpha, and so is not easily detected by cheap (non-window type) geiger counter tubes.

Voltage regulation tubes

Some old voltage regulation tubes contain radioactive crypton to lower the breakdown voltage. Single tubes may radiate too weakly to detect, but a whole box full is quite detectable.

Radioactive chemicals

Thorium and Uranium salts can be bought in chemical supply stores. Certain maximum quantities are usually freely available. Both are not very active substances, some 1000 Bq/gm. Uranium is expensive, thorium-nitrate is reasonable. Thorium emits very penetrating gamma radiation, that is easily detected even through relatively thick metal (some mm), or 10cm water.

Fiesta ware

"Fiesta ware" and certain other (cheap...) kinds of orange glazed ceramic . The orange glaze used to contain uranium, but is not sold nowadays. Also some antique greenish glass contains uranium. This glass also fluoresces under UV light.

Rocks and minerals

Of course, there are several kinds radiactive rocks and minerals. Some are really hot (pitchblende, monazite), some are just slightly active, such as e.g. lava from the Vesuvius.

Thorium doped optics

Thorium increases the index of refraction of glass and was used extensively in WW II era optics. Look for glass which is slightly browned.

Cesium doped spark gaps

These can be found surplus and are labelled as containing cesium-137. Cesium puts out high energy gamma rays, which is nice for some experiments. The spark gaps contain only trace amounts of the material, but they are still neat and measurable.

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Jochen Kronjaeger
Kronjaeg@stud-mailer.uni-marburg.de