Radionuclides
Radioactive isotopes (often referred to as radioisotopes) play an important part in the technologies that provide us with food, water and good health. Radioisotopes consist of unstable atoms with an unusual number of neutrons. This causes them to decay radioactively, during which they give off energy and subatomic particles. Radioisotopes do occur naturally, but are also artificially produced by bombarding particular elements with neutrons (usually emitted from a nuclear reactor). Radioisotopes are used in two major ways: for their chemical properties and as sources of radiation.
Trace radioisotopes are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives that are significantly shorter than the age of the Earth. Synthetic isotopes are not naturally occurring on Earth, but they can be created by nuclear reactions.
Uses
Radioactive isotopes of familiar elements such as carbon can serve as tracers because they are chemically very similar to the non-radioactive isotopes, so most chemical, biological, and ecological processes treat them in an identical way. One can then examine the result with a geiger counter to determine where the atoms one has provided have ended up. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive.
In medicine, radioisotopes are used for diagnosis and research. Radioactive chemical tracers emit gamma rays which provides diagnostic information about a person's anatomy and the functioning of specific organs. Radiotherapy also uses radiation in the treatment of some illnesses, such as cancer. More powerful gamma sources are used to sterilise syringes and other medical equipment. About one in two people in Western countries are likely to experience the benefits of nuclear medicine in their lifetime.
In food preservation, radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables.
In agriculture and animal husbandry, radioisotopes also play an important role. They are used to produce high intake of crops, disease and weather resistant varieties of crops, to study how fertilisers and insecticides work, and to improve the production and health of domestic animals.
Industrially, and in mining, they are used to examine welds, to detect leaks, to study the rate of wear of metals, and for on-stream analysis of a wide range of minerals and fuels.
Most household smoke detectors use radioisotopes containing americium formed in nuclear reactors, saving many lives.
Environmentally, radioisotopes are used to trace and analyse pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.
Natural radioisotopes can be used in archaeology and in paleontology to measure ages. When radioactive carbon, for example, is in the atmosphere, it rapidly becomes separated from its decay products. Once it is bound up in a solid, such as wood or paper, its decay products must remain in place. So by measuring how much of these decay products has accumulated, one can estimate the time when the carbon was captured into solid form.
Dangers
If radioisotopes are released into the environment, through accident, poor disposal, or other means, they can constitute dangerous radioactive contamination.
See also
