Radiation Tidbits - Radiation in Consumer Goods
Radiation Tidbits - Radiation in Consumer Goods
Written by: Yeung Siu-wai
Talking about radiation, people may immediately think of some high technology facilities, such as X-rays, nuclear power stations, nuclear weapons etc. However, there are consumer goods that give out radiation or make use of radiation. Radiation is also widely applied in some industrial processes.
(1) The following are examples of consumer goods containing radioactive materials:
- Luminous watch and clock
- Smoke Detector
- Ceramic Ware and Ornament
- Cigarette
Luminous watch and clock utilize radiation from small amounts of radium-226, tritium or promethium-147 to produce light. Clock hands and graduations are painted with a mixture of radioactive materials and phosphor. The radioactive emissions energize the phosphor which in turn radiates visible light. The radioactivity is only of trace amount and the effect on health is minimal. However, people should avoid wearing watches or placing the clocks nearby the bed while sleeping. Staying too close to luminous watch or clock over a prolonged period will increase the absorbed dose.
Smoke detectors are used in public places, offices or factory buildings for fire detection. The commonly used smoke detectors are of the ionizing type and utilize a low-level radioactive source of americium-241. Americium-241 emits alpha particles which ionize the air in the detector, i.e. atoms in air dissociate into electrically charged ions and electrons, forming an electric current flowing through two electrodes in the detector. When a fire occurs, the smoke entering the detector will block the ions and cause a sudden drop in the electric current, thus triggering the alarm. Since the radioactivity of americium-241 in the smoke detector is extremely low, and alpha particles are easily blocked outside the detector because of their very weak penetrating power, properly installed smoke detectors will not affect people's health.
Ceramic ware and ornament contain quartz particles, in which some radioactive materials, such as uranium-238, thorium-232 and potassium-40 are present. In general, the more beautiful and brilliant the glazed ceramic ware and ornament, the more radiation will be given out. Consumers should beware of the radiation arising from ceramic ware and ornament and avoid close contact with them for prolonged period.
The radioactive materials in cigarette come from the phosphorus fertilizer used in the growing of tobacco. Lead-210 and polonium-210 are present in the fine tobacco hairs. When tobacco is burnt during smoking, the fine hairs are inhaled. As they tend to stay in the lung for a long time, they may cause damage to the lung tissue by virtue of the radiation emitted.
(2) Radiation is usefully applied in some industrial processes. Some examples are:
- Sterilization of Medical Utensils and Cosmetics
- X-ray and gamma ray are highly penetrating. They can evenly and thoroughly disinfect a large amount of materials in a very effective way;
- The process is applied at room temperature, which is suitable for plastic products, organic materials and medicine which cannot endure high temperatures;
- X-ray and gamma ray are electromagnetic waves, hence they leave no residual poisonous substances.
- Food Preservation
- Quality Control
Radiation sterilization of medical utensils and cosmetics utilizes X-ray and gamma ray to control the growth of microorganism or even kill them. Radioactive sources commonly used are cobalt-60 and cesium-137.
The advantages of using radiation for sterilization are:
Food preservation by radiation is a food processing technology using gamma rays to lengthen the shelf-life of food. Cobalt-60 is the most commonly used radioactive source. The process has the effect of killing worms, sterilization, suppressing sprouting and delaying ripening, which reduce the wastage in storage and transportation of food, as well as improve the hygiene. There is no residual poisonous material and the food after the irradiation process contains no radioactivity.
Industries such as paper making, plastic processing and steel rolling use radiation in quality control processes to monitor the weight, thickness and density of the products. Depending on the processes, radiation with a wide range of penetrating power is employed. An example of this is that soft drink factories use medium-power gamma ray to irradiate aluminum cans to check the liquid volume inside.
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