Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to normal levels of background radiation. The term irradiation usually excludes the exposure to non-ionizing radiation, such as infrared, visible light, microwaves from cellular phones or electromagnetic waves emitted by radio and TV receivers and power supplies.
Applications
Sterilization
If administered at appropriate levels, all forms of ionizing radiation can sterilize objects, including medical instruments, disposables such as syringes, and sterilize food. Ionizing radiation may be used to kill bacteria in food or other organic material, including blood. Food irradiation, while effective, is seldom used due to problems with public acceptance.
Ion irradiation is routinely used to implant impurities atoms into materials, especially semiconductors, to modify their properties. This process, usually known as ion implantation, is an important step in the manufacture of silicon integrated circuits.
Irradiation can be used to cross-linkplastics or to improve material qualities of semi-precious stones. Due to its efficiency, electron beam processing is often used in the irradiation treatment of polymer-based products to improve their mechanical, thermal, and chemical properties, and often to add unique properties. Cross-linked polyethylene pipe, high-temperature products such as tubing and gaskets, wire and cable jacket curing, curing of composite materials, and crosslinking of tires are a few examples.
After its discovery by Lewis Stadler at the University of Missouri, irradiation of seed and plant germplasm has resulted in creating many widely-grown cultivars of food crops worldwide. The process, which consists of striking plant seeds or germplasm with radiation in the form of X-rays, UV waves, heavy-ion beams, or gamma rays, essentially "mixes" the genes already existing in the genome. The UN has been an active participant through the International Atomic Energy Agency. Irradiation is also employed to prevent the sprouting of certain cereals, onions, potatoes and garlic. Appropriate irradiation doses are also used to produce insects for use in the sterile insect technique of pest control. The U.S. Department of Agriculture's Food Safety and Inspection Service recognizes irradiation as an important technology to protect consumers. Fresh meat and poultry including whole or cut up birds, skinless poultry, pork chops, roasts, stew meat, liver, hamburgers, ground meat, and ground poultry are approved for irradiation.
Assassination
Some claim that Gheorghe Gheorghiu-Dej, who died of lung cancer in Bucharest on March 19, 1965, was intentionally irradiated during a visit to Moscow, due to his political stance. In 1999, an article in Der Spiegel alleged that the East GermanMfS intentionally irradiated political prisoners with high-dose radiation, possibly to provoke cancer. Alexander Litvinenko, a secret serviceman who was tackling organized crime in Russia, was intentionally poisoned with Po-210; the very large internal doses of radiation he received caused his death.
