Incandescent Gas Lantern Mantles

The thorium-containing incandescent mantle was invented in 1884 by Carl Auer von Welsbach, an Austrian chemist, and it is sometimes referred to as a ?Welsbach mantle? or ?Auerlicht.? This invention resulted in the first commercial use of the element thorium. Today, these mantles are generally used in portable lanterns for camping. Some are used in outdoor light fixtures, and some are used indoors, especially in vacation cabins.

The mantles are produced by dipping a meshed fabric (e.g., nylon web) into a solution of thorium nitrate. Other metals are added to the solution for a variety of reasons. For example, cerium is added to increase the light output, while beryllium increases the mantle?s strength. The fabric is then removed from the solution and dried. Lastly, it is coated with lacquer and fashioned into one of two types of mantles: a soft mantle or a hard mantle. The soft mantle is essentially a bag with either a drawstring or some type of fitting that attaches the mantle to the burner. The fabric of a hard mantle is supported by a metal frame that gives it a dome-like shape.

In use, a jet of combustible gas is blown through the mantle. When the gas is lit, the mantle heats up and the thorium emits an incandescent glow. The temperature must be 2000 degrees centigrade or so for this to occur. When the mantle is heated up for the first time (a cure), the thorium is converted to thorium oxide, the lacquer is burned off, and a variety of materials are released into the air. The material becoming airborne includes approximately 50 % of the beryllium and many of the radioactive decay products of the thorium.

Welding Rod

Thoriated welding rods are used as electrodes in tungsten inert gas (TIG) welding in which the rod serves as a “nonconsumable” electrode. The rod is actually consumed during use, but it does not act as a filler that binds two pieces of metal together. The rate of consumption is approximately 0.1 to 0.3 mg/minute for typical currents but it can be as high as 50 to 60 milligrams per minutes for the maximum rated currents. This consumption probably involves volatilization and the loss of tiny droplets at the electrode tip. Because TIG welding is expensive, its is limited to those situations that require high quality results (e.g., the aircraft and petrochemical industries).

By weight, the rods are usually 1 or 2 % thorium oxide (thoria) although higher concentrations, up to 4 %, have been used. The rods are color coded to indicate the thoria content: yellow indicates 1 %, and red indicates 2 %. The color usually appears as a band at one end of the rod (like that in the photo to the right). While they range from 0.25 to 6.35 mm in diameter and 7.6 to 61 cm long, a ?typical? rod would be about 2.4 mm in diameter, 15 cm long, and contain 0.23 grams of thorium. Estimates over the last two decades put the annual production at 1 to 5 million electrodes.

Thorium is added to the tungsten because it increases the current carrying capacity of the electrode and it reduces contamination of the weld. In addition, it is easier to start the arc and the latter is more stable.

Uranium-Containing Marble

Some of the old cats eye marbles, possibly other types as well, owed their yellow color to uranium. Note that the activity of the uranium is far too low to be detectable with a simple survey meter.

Vaseline-Uranium Glass

Vaseline glass, like the candlestick holder shown here, is a term for the transparent yellow to yellow-green glass that owes its color to its uranium content. Purists might argue that the green sugar bowl in the picture should not be considered Vaseline glass because an additional colorant (probably iron) has been used in addition to the uranium to produce the green. These cognoscenti might describe it as ?Depression Glass,? a less desirable commodity.

Vaseline glass is a recent term that probably dates from the 1950s. Uranium glass, an older and more general term, is sometimes used as a synonym for Vaseline glass, but this can lead to confusion because some types of glass colored with uranium (e.g., custard glass and Burmese glass) are opaque whereas Vaseline glass is transparent. Canary glass is an even older name that was first used in the 1840s to describe what is now referred to as Vaseline glass.

So be observant in ordering personalised mug, for it might contain radioactive material that can pose harm to your health.

Cloisonn� Jewelry

New York State Department of Health issued a press release warning that some pieces of yellow-orange and off-white (beige) cloisonn� jewelry were radioactive. While it did not consider the jewelry a hazard, the state recommended that the public discard it or return it to the place of purchase. After the press release was reported, the matter was taken under consideration by the Nuclear Regulatory Commission. One early course of action taken by the NRC was to contact officials in Taiwan and request that the Taiwanese exporters cease the distribution of cloisonn�.

Antidiarrhea Medication

Kaolin is a white clay (found primarily in Georgia and Alabama) that contains elevated levels of the uranium and thorium decay series. This clay is believed to be derived from the weathering of granites which are know to contain elevated levels of these radionuclides. Kaolin was the primary ingredient in the antidiarrhea medication Koapectate (hence the latter’s name). Alas, Kaopectate no longer contains kaolin. Many years ago there was a television commercial in which a Mexican family had a rough time during their vacation to the US, and Kaopectate came to the rescue. As I recall, it was announced in that commercial that Kaopectate was new and improved. The kaolin was taken out of Kaopectate.

Glossy Magazines

For decades, glossy paper, the type used in magazines, was made using a white clay called kaolin (named after the Chinese region Kao-Ling where it was mined to produce porcelain). The clay is used to fill the spaces between the fibers in the paper and to coat the paper so that it will have a smooth surface. This makes the paper more suitable for the reproduction of photographs, especially color photos.

Kaolin has other uses (e.g., as a filler in paint and plastic, and as the active ingredient in antidiarrhea medicine), but its largest use is in the paper industry. This might change. There seems to be a gradual move towards the use of less expensive calcium carbonate. The state of Georgia is concerned because it is the world’s single largest producer of kaolin. As a result, kaolin is sometimes referred to there as “white gold.”

Since kaolin contains elevated levels of the uranium and thorium decay series, glossy magazines have a higher radioactive content than ordinary paper. The activity of such magazines is not high enough to be detected with a simple survey meter, but it is possible that a truck with a load of magazines could trip a radiation monitor.

Brazil Nuts

Brazil nuts contain high levels of radium. First reported in the 1950s (Turner et al 1958).

Radium is radioactive. To be specific, the radium in Brazil nuts is a mix of Ra-226 and Ra-228. Of course, the various decay products of Ra-226 and Ra-228 are also present. Although the radioactivity is not high enough to be detectable with a simple survey instrument, a one to five minute count on the powdered meat of the nut with a pancake GM or ZnS detector connected to a scaler will indicate that the beta and alpha activities are significantly above background.

Brazil nuts are the seeds of Bertholletia excelsa, a large tree that is grown in various parts of world, not just Brazil. The nuts, in groups of 12 to 25 much like the sections of an orange, form the globular (4-6? diameter) fruit of the tree. It is not true, as is sometimes thought, that the high concentration of radium in Brazil nuts is due to elevated levels of the uranium and/or thorium series in the soil in which the tree grows. The accumulation of the radium is due to the very extensive root system of the tree. For what its worth, measurements by Penna-Franca et al indicated that higher radium concentrations are found in the leaves and cork of the tree than in the nut.

As might be expected, the reported concentration of Ra-226 and Ra-228 vary, but overall, the radium concentrations in Brazil nuts are 1000 times higher than those in other foods.

Radioactive Spark Plugs

Polonium-210 was incorporated into the electrodes that formed the spark-gap of the spark plug. More specifically, the polonium was added to the molten metal (a nickel alloy) from which the wires that were used to produce the electrodes were drawn. The alpha particles emitted by the decay of the polonium would ionize the gas within the spark gap and this would presumably result in a longer and/or ?fatter? spark. The November 1941 issue of the Science Digest reported that tests had indicated that ?30 percent fewer revolutions were required to start the motor as compared with other spark plugs.? According to the company?s advertising, the sparkplugs resulted in a ?smoother motor performance . . . faster pick-up . . . quicker starting . . . save more gasoline.?

That there was any real benefit to using these spark plugs is somewhat questionable (other than the improved performance you get whenever you install new plugs). First of all, the half-life of the polonium-210, 138 days, meant that any effectiveness would be short-lived. Second, the inevitable accumulation of deposits on the surface of the electrodes would attenuate the alpha particles and prevent them from doing their job.

Low Sodium Salt

The great thing about a low-sodium salt substitute, aside from the fact that it is measurably radioactive, is that people put it on their food! Not to worry ? consuming a salt substitute doesn?t increase your radiation exposure.

Salt substitutes are radioactive because they contain potassium chloride, and all potassium contains the radioactive beta-gamma emitter potassium-40.

Salt substitutes vary in their composition, but their main ingredient is always potassium chloride. For example, the listed contents of the Nu-Salt are: potassium chloride, cream of tartar, drier and natural flavor derived from yeast. Contains less than 20 mg of sodium per 100 grams. The contents of the NoSalt are: potassium chloride, potassium bitartrate, adipic acid, mineral oil, fumaric acid and silicon dioxide. The ingredients of another salt substitute, not shown here, are: potassium chloride, L-glutamic acid, mono-potassium glutamate, tri-calcium phosphate and 0.01%potassium iodide.

Thoriated Camera Lens

In designing optical lenses, it is often desirable to employ glass with a high index of refraction. The greater the index of refraction, the greater the bending of the light. Since this reduces the necessary curvature of the glass, the lens can be made thinner and lighter. Unfortunately, glass with a high refractive index can also have a high dispersion. By adding thorium to the glass, a high refractive index (over 1.6) can be achieved while maintaining a low dispersion.

Camera lenses known to have contained thorium include:

Canon FL 58mm f1.2

GAF Anscomatic 38mm f2.8 (Anscomatic 726 camera)

Kodak Ektanar 38mm f2.8 (Instamatic 804 camera)

Kodak Ektanon 46mm f3.5 (Signet 40 camera)

Kodak Ektanon 50mm f3.9 (Kodak Bantam RF camera)

SMC Takumar 50mm f1.4 (Asahi Optical Co.)

Super Takumar 35mm f2.0, 50mm f1.5, 55mm f2 (Asahi Optical Co.)

Super Takumar 6×7 105mm f2.4 (Asahi Optical Co.)

Super-multi-coated Macro-Takumar (Asahi Optical Co.)

Yasinon-DS 50mm f1.7 (Yashica)

The gamma and beta emissions from high thorium content lenses in photographic cameras have the potential to degrade the film if the latter was left in the camera for a substantial period of time. In addition, the self-irradiation of the camera lens leads to a gradual darkening of the glass that reduces light transmission. As a result, it is not unusual to see a reddish brown color to the glass of older lenses.

The last part will be posted next time. So, for the meantime, you checked for the named items in your stocks, and ask a pro if your type of product/s is/are radioactive.

I am posting this, not to scare the public but to raise their awareness on what common consumer products contain this RAM. Furthermore, this is to inform them that radiation has many uses in our daily lives.

Take a look at the following images and see if you recognize them are if they are present in your homes.

Check – Up Gum

Check- Up Gum helped fight plaque. As the gum was chewed, tiny granules of zirconium silicate (the third listed ingredient) scraped the teeth clean.

The reason that Check�Up Gum is featured here is that the zirconium silicate contained elevated levels of uranium and thorium (e.g., 100 pCi/g). The amount of zirconium silicate in the gum was such that the uranium concentration is approximately 7 pCi per gram of gum. Since the uranium series is in secular equilibrium, the gum also contains 7 pCi of Ra-226 per gram. As a matter of interest, there have been many situations where this level of radium in soil has required remedial action.

Although Check�Up Gum is no longer produced, zirconium silicate continues to be used in dental pastes and some toothpastes. Nevertheless, consumers can rest assured that the radiation dose is negligible – the radioactive material is bound up in the zirconium silicate and would not be assimilated even if swallowed.

Tape Dispenser

This is a 3M Model C-15 Decor Scotch tape dispenser. It is slightly radioactive due to the thorium-containing monazite sand that was used as ballast. This particular example came from a 55 gallon drum of tape dispensers that the U.S. Army was about to dispose of as radioactive waste.

Jewelries

As a result of an investigation in early 1988 by the Los Angeles County Health Department, various state radiation control programs in the U.S. issued warnings concerning the manufacture and use of jewelry made from old watch parts. These parts often included radioluminescent watch faces and hands. The jewelry, which included, broaches, bracelets, earrings, etc. had become quite popular and because it was easy to produce, the typical manufacturer was a small business operating out of someone?s home or apartment. Production is known to have occurred in California, Oregon, Texas and Pennsylvania. The radiation control programs in Tennessee, Texas and possibly some other states invited the public to bring suspect jewelry to their offices to be monitored for radioactivity.

The usual mode of manufacture was to dismantle old watches, clean the parts with some sort of abrasive, polish the pieces, assemble the jewelry, and possibly coat it with an acrylic spray. It seems that there was no awareness on the part of the manufacturers of the potential hazards.

Even though some of the jewelry was worn in direct contact with the skin, and a number of premises were found to be contaminated (e.g., up to 50,000 cpm), there were no reports of injuries to individuals who wore or manufactured the jewelry. Nevertheless, one individual, who had been making such jewelry for six years, was found to have ?1/30 of a body burden of radium-226.?

Potassium Chloride Water Softener Salt

Hard water contains more minerals, especially calcium and magnesium, that ordinary water. This can lead to the build up of scale in pipes and appliances. A water softener is used to reduce the concentration of these minerals.

In essence, a water softener consists of an ion exchange resin that removes the minerals as the water flows through it. After a while, the resin becomes saturated with these minerals and it no longer functions. At this point, a salt solution is added to the resin. The salt exchanges with the accumulated minerals, and allows them to be washed out of the softener into a drain. This rejuvenates the softener.

A variety of materials can be used as the water softener salt, e.g., sodium chloride (NaCl) or potassium chloride (KCl). In the example shown here, the water softener salt is over 99% potassium chloride.

All potassium contains potassium-40, a naturally occurring beta gamma emitter, and in large enough quantities it is easily detected with a simple survey meter. This bag, for example, could not get through a monitor at a nuclear power plant without setting off an alarm.

Smoke Detectors

The ionization chamber smoke detector was invented in the early 1940s in Switzerland , and introduced into the U.S. in 1951.

The sensitive component of the ICSD is an ionization chamber that is open to the atmosphere (photo below left). A radioactive source inside the chamber emits radiation that ionizes the air in the chamber and makes it conductive.

Ionization chamber smoke detectors almost always use alpha emitters as the source because of the high density of the ionization that they produce.

Most ICSDs sold today use an oxide of americium-241 (Am-241) as the radioactive source. The typical activity for a modern residential ICSD is approximately 1 uCi, while the activity in one used in public and commercial buildings might be as high as 50 uCi. In 1980, the average activity employed in a residential smoke detector was approximately 3 uCi, three time higher than it is today.

Am-241 is an alpha emitter, but it also emits a low energy (59.5 keV) gamma ray. The Am-241 is mixed with gold and incorporated into a composite gold and silver foil sandwich. The source is 3 to 5 mm in diameter, and either crimped or welded into place inside the chamber.

Other nuclides have also been used. NRC records indicate that approximately 124,000 ICSDs were sold between 1971 and 1986 that employed nickel-63 (Ni-63). These units averaged approximately 10 microcuries of Ni-63 each.

Radium-226 (radium sulfate) was the first radioactive source used in smoke detectors. According to NUREG/CP-0001, U.S. producers stopped making Ra-226 containing smoke detectors in 1963 when they switched to Am-241. Nevertheless, according to NCRP 95, it would seem that radium-containing ICSDs continued to be sold in the U.S. at least until 1978. A typical residential smoke detector contained 0.05 uCi of Ra-226, but some contained up to 0.1 uCi. Commercial smoke detectors employed considerably higher activities.

I’m just glad that Wine Glasses are not included in the list…

The featured consumer products here are just examples of radioactive products that some of us deal with everyday. Watch out for the continuation of this list on my next post…

Irradiation gets high marks as a spoilage deterrent, although it is presently not used by American food producers. At low levels, radiation kills some spoilage organisms and slows ripening and sprouting of fresh produce. Low-level irradiation can inhibit insect infestations and sprouting. The shelf life of meat, poultry and fish can be extended without significant nutrient losses. At high doses, radiation can totally sterilize a food, theoretically extending its life indefinitely.
At any level, radiation can help to reduce dependence on chemical preservatives, including such potentially harmful ones as nitrates and nitrites.

Microwave ovens may become a popular preserving technique in the future. Dr. Gertrude Armbruster, a Cornell nutritionist, reported that heating a cup of pasteurized milk in a microwave oven for two minutes at full power destroys enough microorganisms to increase its refrigerator life from 10 days to nearly three weeks with virtually no nutrient loss.

A major worry about irradiation has focused on the fact that, even though the foods do not become radioactive, substances called ”radiolytic products” can be created in the foods. The amount of such products formed depends on how much radiation the food absorbs. The F.D.A. says that at the levels used in preserving foods, the amount of radiolytic products would be so small as to have no bearing on safety or food quality.

While many consumers and some watchdog agencies, like the Health and Energy Institute in Washington, are strongly opposed to food irradiation, others, like Dr. Silbergeld, clearly favor it over most chemical preservatives. ”The danger, if there is any, is not to the consumer, but to the workers who may be accidentally exposed to radiation,” she said. Additional risks to the population could result from disposal of radioactive wastes.

Irradiation has attracted interest as a food preservation technique, in part because the treatment itself is not harmful to nutrients and irradiated foods lose fewer nutrients during storage. Applying a coating of wax to fruits and vegetables may also help to slow the loss of some nutrients.

Foods Currently Being Irradiated

Internationally, foods such as apples, strawberries, bananas, mangoes, onions, potatoes, spices, seasonings, meat, poultry, fish, and grains have been irradiated for many years. Since 1991, Japan has irradiated more than 20,000 pounds of potatoes each year to prevent sprouting. In the Netherlands, more than 18,000 pounds of foods such as strawberries, spices, poultry, and dehydrated vegetables are irradiated daily. Belgium irradiates more than 8,000 tons of food per year. Canada irradiates potatoes, onions, wheat flour, fish fillets, spices, and seasonings. More than 35 countries have approved irradiation of some 40 different food products.

In 1986, the United States Food and Drug Administration (FDA) approved irradiation of spices and seasonings up to 30 kGy to reduce microorganisms and insects. Irradiation of spices and seasonings reduces the dependency on chemical fumigants. Fruits such as avocados, mangoes, and papayas imported into the U.S. have been approved to receive irradiation treatments of 1 kGy maximum to control non-native insects such as the Medfly. Potatoes and onions have been approved to receive 0.05 to 0.15 kGy to inhibit sprouting, while a maximum of 1 kGy can be applied to grains, such as wheat and oats, to prevent insect infestation. Raw pork has been approved to receive irradiation doses up to 1 kGy to destroy Trichinella spiralis, a deadly parasite.

In 1990, FDA approved the irradiation of poultry up to doses of 3 kGy to eliminate harmful bacteria such as Salmonella spp., Escherichia coli O157:H7, Campylobacter jejuni, and Listeria monocytogenes. In September of 1992, USDA Food Safety and Inspection Service (FSIS) approved facilities to irradiate raw, packaged poultry. In December of 1997, FDA approved the irradiation of red meats up to doses of 4.5 kGy for fresh and 7.0 kGy for frozen product for the elimination of food poisoning bacteria such as Escherichia coli O157:H7. The irradiation and inspection of meat and poultry products is under the jurisdiction of the FSIS.