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Most people are aware of the important contribution nuclear energy makes in providing 16% of the world's electricity. Not so well known are the many other ways nuclear technologies enhances our lives. Radioisotopes (radioactive forms of elements) and radiation have many applications in agriculture, medicine, industry and research and these benefit all of us.
Radioisotopes and radiation used in food and agriculture are helping some of the 800 million people who are chronically malnourished, and tens of thousands who die daily from hunger and hunger-related causes.
Insects are estimated to cause the loss of 25-35% of crops in developing countries. Chemical insecticides have used for many years , but they have not always been effective.
The Sterile Insect Technique (SIT) involves rearing large numbers of insects then irradiating them with gamma radiation before hatching, to sterilize them. The sterile males are then released in large numbers in the infested areas. When they mate with females, no offspring are produced. With repeated releases of sterilized males, the population of the insect pest in a given area is drastically reduced.
Successful SIT campaigns have been carried out against the screwworm in southern USA , Mexico, Libya, Jamaica and Central America. SIT has also been used to tackle the tsetse fly in Zanzibar, which was declared tsetse-free in 1997, and Nigeria has also benefited. In southern Ethiopia a major tsetse SIT program is under way.
Some 25-30% of the food harvested is lost as a result of spoilage by microbes and pests. In all parts of the world there is growing use of irradiation technology to preserve food.
Food irradiation works by exposing raw foods to high levels of gamma radiation which kills bacteria and other harmful organisms without affecting the nutritional value of food itself or leaving any residue. It is the only means of killing bacterial pathogens in raw and frozen food. Of course, irradiation of food does not make it radioactive.
Radioisotopes are an essential part of diagnostic treatment. An advantage over x-ray techniques is that both bone and soft tissue can be imaged very successfully.
A major use of radioisotopes for diagnosis is in radio-immunoassays for biochemical analysis. Very low concentrations of hormones, enzymes, hepatitis virus, some drugs and a range of other substances in a sample of the patient's blood can be measured with these techniques. The patient never comes in contact with the radioisotopes used in the diagnostic tests. In the USA alone it is estimated that some 40 million such tests are carried out each year.
Many medical products today are sterilized by gamma rays. It is safer and cheaper because it can be done after the item is packaged. Medical products sterilized by radiation include syringes, cotton wool, burn dressings, surgical gloves, heart valves, bandages, plastic and rubber sheets and surgical instruments.
One of the commonest uses of radioisotopes today is in household smoke detectors. These contain a small amount of americium-241 which is a decay product of plutonium-241 originating in nuclear reactors. The Am-241 emits alpha particles which ionize the air and allow a current between two electrodes. If smoke enters the detector it absorbs the alpha particles and interrupts the current, setting off the alarm.
Radioisotopes also play an important role in detecting and analyzing pollutants, since even very small amounts of a radioisotope can easily be detected, and the decay of short-lived isotopes means that no residues remain in the environment.
Nuclear techniques have been applied to a range of pollution problems including smog formation, sulphur dioxide contamination of the atmosphere, sewage dispersal from ocean outfalls and oil spills.
Radioisotopes which emit gamma rays which can be used to check welds of new gas and oil pipeline systems, with the radioactive source being placed inside the pipe and the film outside the welds. This is more convenient than employing X-ray equipment.
Some radioisotopes emit a lot of energy as they decay. Such energy can be harnessed for heart pacemakers and to power navigation beacons and satellites. The decay heat of plutonium-238 has powered many space vehicles, such as the Cassini space probe now orbiting Saturn and the New Horizons probe that will reach Pluto in 2015.
Analysis of radioisotopes is of vital importance in determining the age of rocks and other materials that are of interest to geologists, anthropologists and archaeologists.
The use of radiation can help kill cancerous growths. Iodine-131 is commonly used to treat thyroid cancer, probably the most successful kind of cancer treatment, and also for non-malignant thyroid disorders. Iridium-192 wire implants are used especially in the head and breast to give precise doses of beta rays to limited areas, then removed. A new treatment uses samarium-153 to relieve the pain of secondary cancers lodged in bone.